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Journal articles on the topic 'Myosin Regulatory Light chain (RLC20)'

Author: Grafiati

Published: 7 September 2023

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1

Artamonov, Mykhaylo V., Swapnil K. Sonkusare, Miranda E. Good, Ko Momotani, Masumi Eto, Brant E. Isakson, Thu H. Le, et al. "RSK2 contributes to myogenic vasoconstriction of resistance arteries by activating smooth muscle myosin and the Na+/H+ exchanger." Science Signaling 11, no. 554 (October 30, 2018): eaar3924. http://dx.doi.org/10.1126/scisignal.aar3924.

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Smooth muscle contraction is triggered when Ca2+/calmodulin-dependent myosin light chain kinase (MLCK) phosphorylates the regulatory light chain of myosin (RLC20). However, blood vessels from Mlck-deficient mouse embryos retain the ability to contract, suggesting the existence of additional regulatory mechanisms. We showed that the p90 ribosomal S6 kinase 2 (RSK2) also phosphorylated RLC20 to promote smooth muscle contractility. Active, phosphorylated RSK2 was present in mouse resistance arteries under normal basal tone, and phosphorylation of RSK2 increased with myogenic vasoconstriction or agonist stimulation. Resistance arteries from Rsk2-deficient mice were dilated and showed reduced myogenic tone and RLC20 phosphorylation. RSK2 phosphorylated Ser19 in RLC in vitro. In addition, RSK2 phosphorylated an activating site in the Na+/H+ exchanger (NHE-1), resulting in cytosolic alkalinization and an increase in intracellular Ca2+ that promotes vasoconstriction. NHE-1 activity increased upon myogenic constriction, and the increase in intracellular pH was suppressed in Rsk2-deficient mice. In pressured arteries, RSK2-dependent activation of NHE-1 was associated with increased intracellular Ca2+ transients, which would be expected to increase MLCK activity, thereby contributing to basal tone and myogenic responses. Accordingly, Rsk2-deficient mice had lower blood pressure than normal littermates. Thus, RSK2 mediates a procontractile signaling pathway that contributes to the regulation of basal vascular tone, myogenic vasoconstriction, and blood pressure and may be a potential therapeutic target in smooth muscle contractility disorders.

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2

Ihara, Eikichi, Elena Edwards, Meredith A. Borman, David P. Wilson, Michael P. Walsh, and Justin A. MacDonald. "Inhibition of zipper-interacting protein kinase function in smooth muscle by a myosin light chain kinase pseudosubstrate peptide." American Journal of Physiology-Cell Physiology 292, no. 5 (May 2007): C1951—C1959. http://dx.doi.org/10.1152/ajpcell.00434.2006.

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As a regulator of smooth muscle contractility, zipper-interacting protein kinase (ZIPK) appears to phosphorylate the regulatory myosin light chain (RLC20), directly or indirectly, at Ser19 and Thr18 in a Ca2+-independent manner. The calmodulin-binding and autoinhibitory domain of myosin light chain kinase (MLCK) shares similarity to a sequence found in ZIPK. This similarity in sequence prompted an investigation of the SM1 peptide, which is derived from the autoinhibitory region of MLCK, as a potential inhibitor of ZIPK. In vitro studies showed that SM1 is a competitive inhibitor of a constitutively active 32-kDa form of ZIPK with an apparent Ki value of 3.4 μM. Experiments confirmed that the SM1 peptide is also active against full-length ZIPK. In addition, ZIPK autophosphorylation was reduced by SM1. ZIPK activity is independent of calmodulin; however, calmodulin suppressed the in vitro inhibitory potential of SM1, likely as a result of nonspecific binding of the peptide to calmodulin. Treatment of ileal smooth muscle with exogenous ZIPK was accompanied by an increase in RLC20 diphosphorylation, distinguishing between ZIPK [and integrin-linked kinase (ILK)] and MLCK actions. Administration of SM1 suppressed steady-state muscle tension developed by the addition of exogenous ZIPK to Triton-skinned rat ileal muscle strips with or without calmodulin depletion by trifluoperazine. The decrease in contractile force was associated with decreases in both RLC20 mono- and diphosphorylation. In summary, we present the SM1 peptide as a novel inhibitor of ZIPK. We also conclude that the SM1 peptide, which has no effect on ILK, can be used to distinguish between ZIPK and ILK effects in smooth muscle tissues.

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3

Tsuji, Masayuki, Takao Ojima, and Kiyoyoshi Nishita. "Exchange of DTNB light chain with molluscan myosin regulatory light chain in rabbit myosin." NIPPON SUISAN GAKKAISHI 55, no. 4 (1989): 681–87. http://dx.doi.org/10.2331/suisan.55.681.

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4

Takashima, Seiji. "Phosphorylation of Myosin Regulatory Light Chain by Myosin Light Chain Kinase, and Muscle Contraction." Circulation Journal 73, no. 2 (2009): 208–13. http://dx.doi.org/10.1253/circj.cj-08-1041.

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5

Akiyama, K., G. Akopian, P. Jinadasa, T. L. Gluckman, A. Terhakopian, B. Massey, and R. J. Bing. "Myocardial Infarction and Regulatory Myosin Light Chain." Journal of Molecular and Cellular Cardiology 29, no. 10 (October 1997): 2641–52. http://dx.doi.org/10.1006/jmcc.1997.0493.

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6

Sevrieva, Ivanka R., Birgit Brandmeier, Saraswathi Ponnam, Mathias Gautel, Malcolm Irving, Kenneth S. Campbell, Yin-Biao Sun, and Thomas Kampourakis. "Cardiac myosin regulatory light chain kinase modulates cardiac contractility by phosphorylating both myosin regulatory light chain and troponin I." Journal of Biological Chemistry 295, no. 14 (February 21, 2020): 4398–410. http://dx.doi.org/10.1074/jbc.ra119.011945.

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Heart muscle contractility and performance are controlled by posttranslational modifications of sarcomeric proteins. Although myosin regulatory light chain (RLC) phosphorylation has been studied extensively in vitro and in vivo, the precise role of cardiac myosin light chain kinase (cMLCK), the primary kinase acting upon RLC, in the regulation of cardiomyocyte contractility remains poorly understood. In this study, using recombinantly expressed and purified proteins, various analytical methods, in vitro and in situ kinase assays, and mechanical measurements in isolated ventricular trabeculae, we demonstrate that human cMLCK is not a dedicated kinase for RLC but can phosphorylate other sarcomeric proteins with well-characterized regulatory functions. We show that cMLCK specifically monophosphorylates Ser23 of human cardiac troponin I (cTnI) in isolation and in the trimeric troponin complex in vitro and in situ in the native environment of the muscle myofilament lattice. Moreover, we observed that human cMLCK phosphorylates rodent cTnI to a much smaller extent in vitro and in situ, suggesting species-specific adaptation of cMLCK. Although cMLCK treatment of ventricular trabeculae exchanged with rat or human troponin increased their cross-bridge kinetics, the increase in sensitivity of myofilaments to calcium was significantly blunted by human TnI, suggesting that human cTnI phosphorylation by cMLCK modifies the functional consequences of RLC phosphorylation. We propose that cMLCK-mediated phosphorylation of TnI is functionally significant and represents a critical signaling pathway that coordinates the regulatory states of thick and thin filaments in both physiological and potentially pathophysiological conditions of the heart.

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7

Kamm, Kristine E., and James T. Stull. "Signaling to Myosin Regulatory Light Chain in Sarcomeres." Journal of Biological Chemistry 286, no. 12 (January 21, 2011): 9941–47. http://dx.doi.org/10.1074/jbc.r110.198697.

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Myosin regulatory light chain (RLC) phosphorylation in skeletal and cardiac muscles modulates Ca2+-dependent troponin regulation of contraction. RLC is phosphorylated by a dedicated Ca2+-dependent myosin light chain kinase in fast skeletal muscle, where biochemical properties of RLC kinase and phosphatase converge to provide a biochemical memory for RLC phosphorylation and post-activation potentiation of force development. The recent identification of cardiac-specific myosin light chain kinase necessary for basal RLC phosphorylation and another potential RLC kinase (zipper-interacting protein kinase) provides opportunities for new approaches to study signaling pathways related to the physiological function of RLC phosphorylation and its importance in cardiac muscle disease.

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8

Josephson, Matthew P., Laura A. Sikkink, Alan R. Penheiter, Thomas P. Burghardt, and Katalin Ajtai. "Smooth muscle myosin light chain kinase efficiently phosphorylates serine 15 of cardiac myosin regulatory light chain." Biochemical and Biophysical Research Communications 416, no. 3-4 (December 2011): 367–71. http://dx.doi.org/10.1016/j.bbrc.2011.11.044.

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9

Chaudoir, B. M., P. A. Kowalczyk, and R. L. Chisholm. "Regulatory light chain mutations affect myosin motor function and kinetics." Journal of Cell Science 112, no. 10 (May 15, 1999): 1611–20. http://dx.doi.org/10.1242/jcs.112.10.1611.

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The actin-based motor protein myosin II plays a critical role in many cellular processes in both muscle and non-muscle cells. Targeted disruption of the Dictyostelium regulatory light chain (RLC) caused defects in cytokinesis and multicellular morphogenesis. In contrast, a myosin heavy chain mutant lacking the RLC binding site, and therefore bound RLC, showed normal cytokinesis and development. One interpretation of these apparently contradictory results is that the phenotypic defects in the RLC null mutant results from mislocalization of myosin caused by aggregation of RLC null myosin. To distinguish this from the alternative explanation that the RLC can directly influence myosin activity, we expressed three RLC point mutations (E12T, G18K and N94A) in a Dictyostelium RLC null mutant. The position of these mutations corresponds to the position of mutations that have been shown to result in familial hypertrophic cardiomyopathy in humans. Analysis of purified Dictyostelium myosin showed that while these mutations did not affect binding of the RLC to the MHC, its phosphorylation by myosin light chain kinase or regulation of its activity by phosphorylation, they resulted in decreased myosin function. All three mutants showed impaired cytokinesis in suspension, and one produced defective fruiting bodies with short stalks and decreased spore formation. The abnormal myosin localization seen in the RLC null mutant was restored to wild-type localization by expression of all three RLC mutants. Although two of the mutant myosins had wild-type actin-activated ATPase, they produced in vitro motility rates half that of wild type. N94A myosin showed a fivefold decrease in actin-ATPase and a similar decrease in the rate at which it moved actin in vitro. These results indicate that the RLC can play a direct role in determining the force transmission and kinetic properties of myosin.

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10

Cummins, C., and P. Anderson. "Regulatory myosin light-chain genes of Caenorhabditis elegans." Molecular and Cellular Biology 8, no. 12 (December 1988): 5339–49. http://dx.doi.org/10.1128/mcb.8.12.5339-5349.1988.

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We have cloned and analyzed the Caenorhabditis elegans regulatory myosin light-chain genes. C. elegans contains two such genes, which we have designated mlc-1 and mlc-2. The two genes are separated by 2.6 kilobases and are divergently transcribed. We determined the complete nucleotide sequences of both mlc-1 and mlc-2. A single, conservative amino acid substitution distinguishes the sequences of the two proteins. The C. elegans proteins are strongly homologous to regulatory myosin light chains of Drosophila melanogaster and vertebrates and weakly homologous to a superfamily of eucaryotic calcium-binding proteins. Both mlc-1 and mlc-2 encode abundant mRNAs. We mapped the 5' termini of these transcripts by using primer extension sequencing of mRNA templates. mlc-1 mRNAs initiate within conserved hexanucleotides at two different positions, located at -28 and -38 relative to the start of translation. The 5' terminus of mlc-2 mRNA is not encoded in the 4.8-kilobase genomic region upstream of mlc-2. Rather, mlc-2 mRNA contains at its 5' end a short, untranslated leader sequence that is identical to the trans-spliced leader sequence of three C. elegans actin genes.

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11

Cummins, C., and P. Anderson. "Regulatory myosin light-chain genes of Caenorhabditis elegans." Molecular and Cellular Biology 8, no. 12 (December 1988): 5339–49. http://dx.doi.org/10.1128/mcb.8.12.5339.

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We have cloned and analyzed the Caenorhabditis elegans regulatory myosin light-chain genes. C. elegans contains two such genes, which we have designated mlc-1 and mlc-2. The two genes are separated by 2.6 kilobases and are divergently transcribed. We determined the complete nucleotide sequences of both mlc-1 and mlc-2. A single, conservative amino acid substitution distinguishes the sequences of the two proteins. The C. elegans proteins are strongly homologous to regulatory myosin light chains of Drosophila melanogaster and vertebrates and weakly homologous to a superfamily of eucaryotic calcium-binding proteins. Both mlc-1 and mlc-2 encode abundant mRNAs. We mapped the 5' termini of these transcripts by using primer extension sequencing of mRNA templates. mlc-1 mRNAs initiate within conserved hexanucleotides at two different positions, located at -28 and -38 relative to the start of translation. The 5' terminus of mlc-2 mRNA is not encoded in the 4.8-kilobase genomic region upstream of mlc-2. Rather, mlc-2 mRNA contains at its 5' end a short, untranslated leader sequence that is identical to the trans-spliced leader sequence of three C. elegans actin genes.

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12

Huang, Jian, John M. Shelton, James A. Richardson, Kristine E. Kamm, and James T. Stull. "Myosin Regulatory Light Chain Phosphorylation Attenuates Cardiac Hypertrophy." Journal of Biological Chemistry 283, no. 28 (May 12, 2008): 19748–56. http://dx.doi.org/10.1074/jbc.m802605200.

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13

Donato, Megan E., Jonathan Schiavi, Alexis D. Ulerich, Frances E. Weaver, and David J. Coughlin. "Myosin regulatory light chain expression in trout muscle." Journal of Experimental Zoology Part A: Ecological Genetics and Physiology 309A, no. 2 (2008): 64–72. http://dx.doi.org/10.1002/jez.433.

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14

Breithaupt, Jason J., Hannah C. Pulcastro, Peter O. Awinda, David C. DeWitt, and Bertrand C. W. Tanner. "Regulatory light chain phosphorylation augments length-dependent contraction in PTU-treated rats." Journal of General Physiology 151, no. 1 (December 6, 2018): 66–76. http://dx.doi.org/10.1085/jgp.201812158.

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Force production by actin–myosin cross-bridges in cardiac muscle is regulated by thin-filament proteins and sarcomere length (SL) throughout the heartbeat. Prior work has shown that myosin regulatory light chain (RLC), which binds to the neck of myosin heavy chain, increases cardiac contractility when phosphorylated. We recently showed that cross-bridge kinetics slow with increasing SLs, and that RLC phosphorylation amplifies this effect, using skinned rat myocardial strips predominantly composed of the faster α-cardiac myosin heavy chain isoform. In the present study, to assess how RLC phosphorylation influences length-dependent myosin function as myosin motor speed varies, we used a propylthiouracil (PTU) diet to induce >95% expression of the slower β-myosin heavy chain isoform in rat cardiac ventricles. We measured the effect of RLC phosphorylation on Ca2+-activated isometric contraction and myosin cross-bridge kinetics (via stochastic length perturbation analysis) in skinned rat papillary muscle strips at 1.9- and 2.2-µm SL. Maximum tension and Ca2+ sensitivity increased with SL, and RLC phosphorylation augmented this response at 2.2-µm SL. Subtle increases in viscoelastic myocardial stiffness occurred with RLC phosphorylation at 2.2-µm SL, but not at 1.9-µm SL, thereby suggesting that RLC phosphorylation increases β-myosin heavy chain binding or stiffness at longer SLs. The cross-bridge detachment rate slowed as SL increased, providing a potential mechanism for prolonged cross-bridge attachment to augment length-dependent activation of contraction at longer SLs. Length-dependent slowing of β-myosin heavy chain detachment rate was not affected by RLC phosphorylation. Together with our previous studies, these data suggest that both α- and β-myosin heavy chain isoforms show a length-dependent activation response and prolonged myosin attachment as SL increases in rat myocardial strips, and that RLC phosphorylation augments length-dependent activation at longer SLs. In comparing cardiac isoforms, however, we found that β-myosin heavy chain consistently showed greater length-dependent sensitivity than α-myosin heavy chain. Our work suggests that RLC phosphorylation is a vital contributor to the regulation of myocardial contractility in both cardiac myosin heavy chain isoforms.

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15

Post, P. L., R. L. DeBiasio, and D. L. Taylor. "A fluorescent protein biosensor of myosin II regulatory light chain phosphorylation reports a gradient of phosphorylated myosin II in migrating cells." Molecular Biology of the Cell 6, no. 12 (December 1995): 1755–68. http://dx.doi.org/10.1091/mbc.6.12.1755.

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Phosphorylation of the regulatory light chain by myosin light chain kinase (MLCK) regulates the motor activity of smooth muscle and nonmuscle myosin II. We have designed reagents to detect this phosphorylation event in living cells. A new fluorescent protein biosensor of myosin II regulatory light chain phosphorylation (FRLC-Rmyosin II) is described here. The biosensor depends upon energy transfer from fluorescein-labeled regulatory light chains to rhodamine-labeled essential and/or heavy chains. The energy transfer ratio increases by up to 26% when the regulatory light chain is phosphorylated by MLCK. The majority of the change in energy transfer is from regulatory light chain phosphorylation by MLCK (versus phosphorylation by protein kinase C). Folding/unfolding, filament assembly, and actin binding do not have a large effect on the energy transfer ratio. FRLC-Rmyosin II has been microinjected into living cells, where it incorporates into stress fibers and transverse fibers. Treatment of fibroblasts containing FRLC-Rmyosin II with the kinase inhibitor staurosporine produced a lower ratio of rhodamine/fluorescein emission, which corresponds to a lower level of myosin II regulatory light chain phosphorylation. Locomoting fibroblasts containing FRLC-Rmyosin II showed a gradient of myosin II phosphorylation that was lowest near the leading edge and highest in the tail region of these cells, which correlates with previously observed gradients of free calcium and calmodulin activation. Maximal myosin II motor force in the tail may contribute to help cells maintain their polarized shape, retract the tail as the cell moves forward, and deliver disassembled subunits to the leading edge for incorporation into new fibers.

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16

Naqvi, Naweed I., Kelvin C. Y. Wong, Xie Tang, and Mohan K. Balasubramanian. "Type II myosin regulatory light chain relieves auto-inhibition of myosin-heavy-chain function." Nature Cell Biology 2, no. 11 (October 17, 2000): 855–58. http://dx.doi.org/10.1038/35041107.

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17

Greenberg, Michael J., Tanya R. Mealy, James D. Watt, Michelle Jones, Danuta Szczesna-Cordary, and Jeffrey R. Moore. "The molecular effects of skeletal muscle myosin regulatory light chain phosphorylation." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 297, no. 2 (August 2009): R265—R274. http://dx.doi.org/10.1152/ajpregu.00171.2009.

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Phosphorylation of the myosin regulatory light chain (RLC) in skeletal muscle has been proposed to act as a molecular memory of recent activation by increasing the rate of force development, ATPase activity, and isometric force at submaximal activation in fibers. It has been proposed that these effects stem from phosphorylation-induced movement of myosin heads away from the thick filament backbone. In this study, we examined the molecular effects of skeletal muscle myosin RLC phosphorylation using in vitro motility assays. We showed that, independently of the thick filament backbone, the velocity of skeletal muscle myosin is decreased upon phosphorylation due to an increase in the myosin duty cycle. Furthermore, we did not observe a phosphorylation-dependent shift in calcium sensitivity in the absence of the myosin thick filament. These data suggest that phosphorylation-induced movement of myosin heads away from the thick filament backbone explains only part of the observed phosphorylation-induced changes in myosin mechanics. Last, we showed that the duty cycle of skeletal muscle myosin is strain dependent, consistent with the notion that strain slows the rate of ADP release in striated muscle.

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18

Chen, Chen, Tao Tao, Cheng Wen, Wei-Qi He, Yan-Ning Qiao, Yun-Qian Gao, Xin Chen, et al. "Myosin Light Chain Kinase (MLCK) Regulates Cell Migration in a Myosin Regulatory Light Chain Phosphorylation-independent Mechanism." Journal of Biological Chemistry 289, no. 41 (August 13, 2014): 28478–88. http://dx.doi.org/10.1074/jbc.m114.567446.

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19

Ding, Peiguo, Jian Huang, Pavan K. Battiprolu, Joseph A. Hill, Kristine E. Kamm, and James T. Stull. "Cardiac Myosin Light Chain Kinase Is Necessary for Myosin Regulatory Light Chain Phosphorylation and Cardiac Performancein Vivo." Journal of Biological Chemistry 285, no. 52 (October 13, 2010): 40819–29. http://dx.doi.org/10.1074/jbc.m110.160499.

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20

McDaniel, Nancy L., Christopher M. Rembold, and Richard A. Murphy. "Cyclic nucleotide dependent relaxation in vascular smooth muscle." Canadian Journal of Physiology and Pharmacology 72, no. 11 (November 1, 1994): 1380–85. http://dx.doi.org/10.1139/y94-199.

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Although not without controversy, the mechanisms inducing contraction of vascular smooth muscle are relatively well defined. There is a stimulus-induced increase in myoplasmic [Ca2+] with activation of myosin light chain kinase by the Ca2+–calmodulin complex, phosphorylation of the 20-kDa regulatory light chain of myosin, with subsequent cross-bridge cycling and force development. Ca2+-dependent phosphorylation of the myosin regulatory light chain appears to be the primary mechanism responsible for regulating stress in vascular smooth muscle. The relationship between myoplasmic [Ca2+] and myosin phosphorylation (i.e., the calcium sensitivity of phosphorylation) is regulated. It is higher with agonist stimulation than in tissues depolarized with high potassium solutions or after skinning procedures. The relationship between myosin phosphorylation and stress appears to be invariant with physiologic stimulation. This suggests that cross-bridge phosphorylation normally determines contraction. The mechanisms of relaxation are less well defined. In the most simple scheme, reduction of myoplasmic [Ca2+] with a fall in myosin light chain kinase activity would suffice to account for dephosphorylation of the regulatory light chain and relaxation. However, other mechanisms have been implicated in cyclic nucleotide dependent relaxation in vascular and other smooth muscle tissues. The current hypotheses of the mechanism of cyclic nucleotide dependent relaxation in vascular smooth muscle are reviewed.Key words: calcium, cyclic adenosine 3′,5′-monophosphate, cyclic guanosine 3′,5′-monophosphate, myosin light chain phosphorylation, vasodilation.

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21

Bennett, A. J., and C. R. Bagshaw. "The mechanism of regulatory light chain dissociation from scallop myosin." Biochemical Journal 233, no. 1 (January 1, 1986): 179–86. http://dx.doi.org/10.1042/bj2330179.

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The dissociation of the regulatory light chains from scallop myosin subfragments, on addition of EDTA, was investigated by using the fluorophore 8-anilinonaphthalene-1-sulphonate as a probe. The rate of this process (0.014 s-1) was partially limited by the rate of Mg2+ dissociation (0.058 s-1) from the non-specific high-affinity site. The dissociation of the regulatory light chain subfragment 1 was less extensive than from heavy meromyosin. Reassociation of the scallop regulatory light chain was induced on addition of Mg2+, but it appeared to be limited by a first-order step. The nature of this step was revealed by the kinetics of Mercenaria regulatory light chain association. Scallop heavy meromyosin, denuded of its regulatory light chains, exists in a refractory state, whose reversal to the nascent state limits the rate of light chain association (0.006 s-1). The formation of the refractory state is the driving force for the net dissociation of regulatory light chains from scallop heavy meromyosin. This mechanism is discussed with reference to existing structural information on light-chain-denuded myosin.

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22

Ishibashi, K., A. Evans, T. Shingu, K. Bian, and R. D. Bukoski. "Differential expression and effect of 1,25-dihydroxyvitamin D3 on myosin in arterial tree of rats." American Journal of Physiology-Cell Physiology 269, no. 2 (August 1, 1995): C443—C450. http://dx.doi.org/10.1152/ajpcell.1995.269.2.c443.

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The hypothesis that 1,25-dihydroxyvitamin D3 [1,25(OH)2D3, also known as calcitriol] modulates myosin expression in vascular smooth muscle was tested. Wistar-Kyoto or spontaneously hypertensive rats given intraperitoneal injections of 25 ng 1,25(OH)2D3/100 g body weight for varying periods of time showed a greater than twofold increase in aortic mRNA encoding the myosin regulatory light chain relative to 18S rRNA (P < 0.05). 1,25(OH)2D3 administration to Wistar rats caused a significant increase in the aortic content of total myosin regulatory light chain and total myosin heavy chain. The increase in myosin light chain was the result of a specific increase in expression of its smooth muscle isoform [control = 65.2 +/- 3.4% vs. 1,25(OH)2D3 = 78.7 +/- 3.6%, P = 0.020]. 1,25(OH)2D3 had no effect on total myosin light chain or heavy chain in the superior mesenteric artery. The hormone did, however, increase the proportion of the smooth muscle isoform of the light chain in this vessel [control = 81.4 +/- 2.6% vs. 1,25(OH)2D3 = 88.8 +/- 2.1%, P = 0.048]. In branch II and III mesenteric resistance arteries, 1,25(OH)2D3 significantly increased the active stress response to 10 mumol/l norepinephrine but was without effect on total myosin light chain or heavy chain content or on the relative expression of the myosin light chain isoforms [control = 94.0 +/- 1.4% vs. 1,25(OH)2D3 = 95.8 +/- 1.1%, P = 0.33].(ABSTRACT TRUNCATED AT 250 WORDS)

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23

Greenberg, M. J., K. Kazmierczak, D. Szczesna-Cordary, and J. R. Moore. "Cardiomyopathy-linked myosin regulatory light chain mutations disrupt myosin strain-dependent biochemistry." Proceedings of the National Academy of Sciences 107, no. 40 (September 20, 2010): 17403–8. http://dx.doi.org/10.1073/pnas.1009619107.

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24

Cao, Lichuang, Chengli Hou, Qingwu Shen, Dequan Zhang, and Zhenyu Wang. "Phosphorylation of myosin regulatory light chain affects actomyosin dissociation and myosin degradation." International Journal of Food Science & Technology 54, no. 6 (February 22, 2019): 2246–55. http://dx.doi.org/10.1111/ijfs.14138.

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25

SATTERWHITE, LISA, LARS CISEK, JEFFRY CORDEN, and THOMAS POLLARD. "A p34cdc2-Containing Kinase Phosphorylates Myosin Regulatory Light Chain." Annals of the New York Academy of Sciences 582, no. 1 Cytokinesis (April 1990): 307. http://dx.doi.org/10.1111/j.1749-6632.1990.tb21692.x.

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26

Grant, James W., Rui Q. Zhong, Pat M. McEwen, and Susan L. Church. "Human nonsarcomeric 20,000 Da myosin regulatory light chain cDNA." Nucleic Acids Research 18, no. 19 (1990): 5892. http://dx.doi.org/10.1093/nar/18.19.5892.

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27

Wang, Lu, Isabel J. Sobieszek, Chun Y. Seow, and Apolinary Sobieszek. "Purification of Myosin from Bovine Tracheal Smooth Muscle, Filament Formation and Endogenous Association of Its Regulatory Complex." Cells 12, no. 3 (February 3, 2023): 514. http://dx.doi.org/10.3390/cells12030514.

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Dynamic regulation of myosin filaments is a crucial factor in the ability of airway smooth muscle (ASM) to adapt to a wide length range. Increased stability or robustness of myosin filaments may play a role in the pathophysiology of asthmatic airways. Biochemical techniques for the purification of myosin and associated regulatory proteins could help elucidate potential alterations in myosin filament properties of asthmatic ASM. An effective myosin purification approach was originally developed for chicken gizzard smooth muscle myosin. More recently, we successfully adapted the procedure to bovine tracheal smooth muscle. This method yields purified myosin with or without the endogenous regulatory complex of myosin light chain kinase and myosin light chain phosphatase. The tight association of the regulatory complex with the assembled myosin filaments can be valuable in functional experiments. The purification protocol discussed here allows for enzymatic comparisons of myosin regulatory proteins. Furthermore, we detail the methodology for quantification and removal of the co-purified regulatory enzymes as a tool for exploring potentially altered phenotypes of the contractile apparatus in diseases such as asthma.

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28

Ikebe, M., S. Reardon, J. P. Schwonek, C. R. Sanders, and R. Ikebe. "Structural requirement of the regulatory light chain of smooth muscle myosin as a substrate for myosin light chain kinase." Journal of Biological Chemistry 269, no. 45 (November 1994): 28165–72. http://dx.doi.org/10.1016/s0021-9258(18)46909-8.

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29

Ding, Peiguo, Jian Huang, Pavan K. Battiprolu, Joseph A. Hill, Kristine E. Kamm, and James T. Stull. "Cardiac Myosin Light Chain Kinase is Essential for Myosin Regulatory Light Chain Phosphorylation and Normal Cardiac Function in vivo." Biophysical Journal 100, no. 3 (February 2011): 369a. http://dx.doi.org/10.1016/j.bpj.2010.12.2203.

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30

Duggal, D., J. Nagwekar, R. Rich, W. Huang, K. Midde, R. Fudala, H. Das, I. Gryczynski, D. Szczesna-Cordary, and J. Borejdo. "Effect of a myosin regulatory light chain mutation K104E on actin-myosin interactions." American Journal of Physiology-Heart and Circulatory Physiology 308, no. 10 (May 15, 2015): H1248—H1257. http://dx.doi.org/10.1152/ajpheart.00834.2014.

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Familial hypertrophic cardiomyopathy (FHC) is the most common cause of sudden cardiac death in young individuals. Molecular mechanisms underlying this disorder are largely unknown; this study aims at revealing how disruptions in actin-myosin interactions can play a role in this disorder. Cross-bridge (XB) kinetics and the degree of order were examined in contracting myofibrils from the ex vivo left ventricles of transgenic (Tg) mice expressing FHC regulatory light chain (RLC) mutation K104E. Because the degree of order and the kinetics are best studied when an individual XB makes a significant contribution to the overall signal, the number of observed XBs in an ex vivo ventricle was minimized to ∼20. Autofluorescence and photobleaching were minimized by labeling the myosin lever arm with a relatively long-lived red-emitting dye containing a chromophore system encapsulated in a cyclic macromolecule. Mutated XBs were significantly better ordered during steady-state contraction and during rigor, but the mutation had no effect on the degree of order in relaxed myofibrils. The K104E mutation increased the rate of XB binding to thin filaments and the rate of execution of the power stroke. The stopped-flow experiments revealed a significantly faster observed dissociation rate in Tg-K104E vs. Tg-wild-type (WT) myosin and a smaller second-order ATP-binding rate for the K104E compared with WT myosin. Collectively, our data indicate that the mutation-induced changes in the interaction of myosin with actin during the contraction-relaxation cycle may contribute to altered contractility and the development of FHC.

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31

Kampourakis, Thomas, and Malcolm Irving. "Phosphorylation of myosin regulatory light chain controls myosin head conformation in cardiac muscle." Journal of Molecular and Cellular Cardiology 85 (August 2015): 199–206. http://dx.doi.org/10.1016/j.yjmcc.2015.06.002.

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32

Karabina, Anastasia, Priya Muthu, Katarzyna Kazmierczak, Danuta Szczesna-Cordary, and Jeffrey Moore. "The Effect of Myosin Regulatory Light Chain Phosphorylation on N47K Mutant Myosin Mechanics." Biophysical Journal 106, no. 2 (January 2014): 563a. http://dx.doi.org/10.1016/j.bpj.2013.11.3126.

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33

Mackenzie, L. W., R. A. Word, M. L. Casey, and J. T. Stull. "Myosin light chain phosphorylation in human myometrial smooth muscle cells." American Journal of Physiology-Cell Physiology 258, no. 1 (January 1, 1990): C92—C98. http://dx.doi.org/10.1152/ajpcell.1990.258.1.c92.

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Ca2+/calmodulin-dependent phosphorylation of the 20-kDa regulatory light chain of myosin is of signal importance in the initiation of contraction in a number of smooth muscle tissues. In this investigation, we evaluated the relationship between intracellular free Ca2+/concentration [( Ca2+]i) and the extent of myosin light chain phosphorylation in cultured human myometrial smooth muscle cells. Treatment of myometrial cells with ionomycin caused a concentration- and time-dependent increase in [Ca2+]i and phosphorylation of myosin light chain. Temporally, the increases in light chain phosphorylation and [Ca2+]i in response to ionomycin were similar. In myometrial cells treated with ionomycin (10(-5) M) for 10 s, [Ca2+]i increased from 138 to 800 nM; in these same cells, myosin light chain phosphorylation increased from 5% to a maximum value of 54%. Half-maximal phosphorylation of myosin light chain was attained at 300 nM [Ca2+]i. Treatment of myometrial smooth muscle cells with prostaglandin (PG) F2 alpha (10(-8) M) and PGE2 (10(-8) M) caused a proportionate increase in [Ca2+]i and myosin light chain phosphorylation. In addition, [Ca2+]i and myosin light chain phosphorylation increased in response to oxytocin and angiotensin II. These findings indicate that a number of uterotonic agents effect an increase in [Ca2+]i, which in turn causes phosphorylation of myosin light chain. Furthermore, the concentration of Ca2+ in the cytoplasm is a primary determinant for myosin light chain phosphorylation in human myometrial smooth muscle cells.

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34

Ichikawa, Hisashi, and Kiyoyoshi Nishita. "Binding ability of regulatory light chain in akazara hybridized myosin." NIPPON SUISAN GAKKAISHI 54, no. 10 (1988): 1823–28. http://dx.doi.org/10.2331/suisan.54.1823.

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35

Gnanasekar, Munirathinam, Ashok M. Salunkhe, A. Krishna Mallia, Yi Xun He, and Ramaswamy Kalyanasundaram. "Praziquantel Affects the Regulatory Myosin Light Chain of Schistosoma mansoni." Antimicrobial Agents and Chemotherapy 53, no. 3 (December 22, 2008): 1054–60. http://dx.doi.org/10.1128/aac.01222-08.

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ABSTRACT Praziquantel (PZQ) is the drug of choice for schistosomiasis and probably is the only highly effective drug currently available for treating schistosomiasis-infected individuals. The mode of action of PZQ involves increasing the calcium uptake of the parasite, resulting in tegumental damage and death of the parasite. Despite its remarkable function, the target of PZQ has not been identified yet. To begin to understand where PZQ acts, in this study we expressed the cDNA library of Schistosoma mansoni on the surface of T7 bacteriophages and screened this library with labeled PZQ. This procedure identified a clone that strongly bound to PZQ. Subsequent DNA analysis of inserts showed that the clone coded for regulatory myosin light chain protein. The gene was then cloned, and recombinant S. mansoni myosin light chain (SmMLC) was expressed. Immunoblot analysis using antibodies raised to recombinant SmMLC (rSmMLC) showed that SmMLC is abundantly expressed in schistosomula and adult stages compared to the amount in cercarial stages. In vitro analyses also confirmed that PZQ strongly binds to rSmMLC. Further, peptide mapping studies showed that PZQ binds to amino acids 46 to 76 of SmMLC. Immunoprecipitation analysis confirmed that SmMLC is phosphorylated in vivo upon exposure to PZQ. Interestingly, significant levels of anti-SmMLC antibodies were present in vaccinated mice compared to the amount in infected mice, suggesting that SmMLC may be a potential target for protective immunity in schistosomiasis. These findings suggest that PZQ affects SmMLC function, and this may have a role in PZQ action.

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36

Li, Hua-Shan, Qian Lin, Jia Wu, Zhi-Hui Jiang, Jia-Bi Zhao, Jian Pan, Wei-Qi He, and Juan-Min Zha. "Myosin regulatory light chain phosphorylation is associated with leiomyosarcoma development." Biomedicine & Pharmacotherapy 92 (August 2017): 810–18. http://dx.doi.org/10.1016/j.biopha.2017.05.139.

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37

Pauly, Daniel F. "The Slow Cardiac Myosin Regulatory Light Chain in Heart Failure." Clinical Cardiology 34, no. 1 (January 2011): 10–11. http://dx.doi.org/10.1002/clc.20867.

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38

Walker, John S., Lori A. Walker, Elaine F. Etter, and Richard A. Murphy. "A Dilution Immunoassay to Measure Myosin Regulatory Light Chain Phosphorylation." Analytical Biochemistry 284, no. 2 (September 2000): 173–82. http://dx.doi.org/10.1006/abio.2000.4704.

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39

COLEGRAVE, Melanie, Hitesh PATEL, Gerald OFFER, and Peter D. CHANTLER. "Evaluation of the symmetric model for myosin-linked regulation: effect of site-directed mutations in the regulatory light chain on scallop myosin." Biochemical Journal 374, no. 1 (August 15, 2003): 89–96. http://dx.doi.org/10.1042/bj20030404.

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Regulatory myosins are controlled through mechanisms intrinsic to their structures and can alternate between activated and inhibited states. However, the structural difference between these two states is unclear. Scallop (Pecten maximus) striated adductor myosin is activated directly by calcium. It has been proposed that the two heads of scallop myosin are symmetrically arranged and interact through their regulatory light chains [Offer and Knight (1996) J. Mol. Biol. 256, 407–416], the interface being strengthened in the inhibited state. By contrast, vertebrate smooth-muscle myosin is activated by phosphorylation. Its structure in the inhibited state has been determined from two-dimensional crystalline arrays [Wendt, Taylor, Trybus and Taylor (2001) Proc. Natl. Acad. Sci. U.S.A. 98, 4361–4366] and is asymmetric, requiring no interaction between regulatory light chains. Using site-directed mutagenesis of the scallop regulatory light chain, we have tested the symmetric model for scallop adductor muscle myosin. Specifically, we have made myosin hybrid molecules from scallop (P. maximus) myosin, in which the normal regulatory light chains have been replaced by expressed light chains containing mutations in three residues proposed to participate in the interaction between regulatory light chains. The mutations were R126A (Arg126→Ala), K130A and E131A; made singly, in pairs or all three together, these mutations were designed to eliminate hydrogen bonding or salt linkages between heads, which are key features of this model. Functional assays to address the competence of these hybrid myosins to bind calcium specifically, to exhibit a calcium-regulated myofibrillar Mg-ATPase and to display calcium-dependent actin sliding were performed. We conclude that the symmetrical model does not describe the inhibited state of scallop regulatory myosin and that an asymmetric structure is a plausible alternative.

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40

Liu, G., and P. C. Newell. "Regulation of myosin regulatory light chain phosphorylation via cyclic GMP during chemotaxis of Dictyostelium." Journal of Cell Science 107, no. 7 (July 1, 1994): 1737–43. http://dx.doi.org/10.1242/jcs.107.7.1737.

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Previous studies on the chemotactic movement of Dictyostelium have indicated a role for cyclic GMP in regulating the association of myosin II with the cytoskeleton. In this study we have examined the part played by phosphorylation of the 18 kDa myosin regulatory light chain in this event. Using streamer F mutant NP368 (which is deficient in the structural gene for cyclic GMP-specific phosphodiesterase) we find that, for the regulatory light chain kinase, the major peak of phosphorylation is delayed compared to the parental control strain XP55, occurring at 80 seconds rather than about 30 seconds in XP55. In two independently derived mutants that are unable to increase their cellular concentration of cyclic GMP (above basal levels) in response to a chemotactic stimulus of cyclic AMP (KI-10 and SA219), no increase in the phosphorylation of the light chain occurred, or movement of myosin II to the cytoskeleton. We also find a smaller peak of light chain phosphorylation that occurs within 10 seconds of cyclic AMP stimulation of the amoebae, and which is absent in the cyclic GMP-unresponsive strains. We conclude that cyclic GMP is involved in regulating light chain phosphorylation in this system. The possible significance of these findings is discussed and a model that relates these findings to published data on cytoskeletal myosin changes during chemotaxis is presented.

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41

Gao, Xing, Xin Li, Zheng Li, Manting Du, and Dequan Zhang. "Dephosphorylation of myosin regulatory light chain modulates actin-myosin interaction adverse to meat tenderness." International Journal of Food Science & Technology 52, no. 6 (May 16, 2017): 1400–1407. http://dx.doi.org/10.1111/ijfs.13343.

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42

Greenberg, Michael J., Katarzyna Kazmierczak, Danuta Szczesna-Cordary, and Jeffrey R. Moore. "Familial Hypertrophic Cardiomyopathy Mutations of the Myosin Regulatory Light Chain Remove Myosin Load Sensitivity." Biophysical Journal 98, no. 3 (January 2010): 215a—216a. http://dx.doi.org/10.1016/j.bpj.2009.12.1163.

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43

Karabina, Anastasia, Katarzyna Kazmierczak, Danuta Szczesna-Cordary, and Jeffrey R. Moore. "Myosin regulatory light chain phosphorylation enhances cardiac β-myosin in vitro motility under load." Archives of Biochemistry and Biophysics 580 (August 2015): 14–21. http://dx.doi.org/10.1016/j.abb.2015.06.014.

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44

Lorenz, Robert R., David O. Warner, and Keith A. Jones. "Hydrogen peroxide decreases Ca2+ sensitivity in airway smooth muscle by inhibiting rMLC phosphorylation." American Journal of Physiology-Lung Cellular and Molecular Physiology 277, no. 4 (October 1, 1999): L816—L822. http://dx.doi.org/10.1152/ajplung.1999.277.4.l816.

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The purpose of this study was to determine the mechanism by which hydrogen peroxide (H2O2), an important inflammatory mediator, relaxes canine tracheal smooth muscle (CTSM). H2O2caused concentration-dependent relaxations of CTSM strips contracted with ACh or isotonic KCl [EC50 of 0.24 ± 0.04 (SE) and 0.23 ± 0.04 mM, respectively]. Indomethacin (10 μM) decreased the sensitivity of both KCl- and ACh-contracted strips to H2O2. H2O2increased intracellular cAMP levels, an increase that was abolished by indomethacin. H2O2did not affect intracellular cGMP levels. In strips treated with indomethacin and contracted with ACh or isotonic KCl, H2O2-evoked relaxations were accompanied by increases in intracellular Ca2+ concentration and decreases in regulatory myosin light chain phosphorylation. We conclude that H2O2decreases Ca2+ sensitivity in CTSM by decreasing regulatory myosin light chain phosphorylation through inhibition of myosin light chain kinase and/or activation of smooth muscle protein phosphatases.

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45

Nayak, Arnab, Tianbang Wang, Peter Franz, Walter Steffen, Igor Chizhov, Georgios Tsiavaliaris, and Mamta Amrute-Nayak. "Single-molecule analysis reveals that regulatory light chains fine-tune skeletal myosin II function." Journal of Biological Chemistry 295, no. 20 (April 9, 2020): 7046–59. http://dx.doi.org/10.1074/jbc.ra120.012774.

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Myosin II is the main force-generating motor during muscle contraction. Myosin II exists as different isoforms that are involved in diverse physiological functions. One outstanding question is whether the myosin heavy chain (MHC) isoforms alone account for these distinct physiological properties. Unique sets of essential and regulatory light chains (RLCs) are known to assemble with specific MHCs, raising the intriguing possibility that light chains contribute to specialized myosin functions. Here, we asked whether different RLCs contribute to this functional diversification. To this end, we generated chimeric motors by reconstituting the MHC fast isoform (MyHC-IId) and slow isoform (MHC-I) with different light-chain variants. As a result of the RLC swapping, actin filament sliding velocity increased by ∼10-fold for the slow myosin and decreased by >3-fold for the fast myosin. Results from ensemble molecule solution kinetics and single-molecule optical trapping measurements provided in-depth insights into altered chemo-mechanical properties of the myosin motors that affect the sliding speed. Notably, we found that the mechanical output of both slow and fast myosins is sensitive to the RLC isoform. We therefore propose that RLCs are crucial for fine-tuning the myosin function.

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46

Ikebe, Reiko, Sheila Reardon, Toshiaki Mitsui, and Mitsuo Ikebe. "Role of the N-terminal Region of the Regulatory Light Chain in the Dephosphorylation of Myosin by Myosin Light Chain Phosphatase." Journal of Biological Chemistry 274, no. 42 (October 15, 1999): 30122–26. http://dx.doi.org/10.1074/jbc.274.42.30122.

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47

Tafuri, S. R., A. M. Rushforth, E. R. Kuczmarski, and R. L. Chisholm. "Dictyostelium discoideum myosin: isolation and characterization of cDNAs encoding the regulatory light chain." Molecular and Cellular Biology 9, no. 7 (July 1989): 3073–80. http://dx.doi.org/10.1128/mcb.9.7.3073-3080.1989.

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Phosphorylation of the regulatory light chains (RMLC) of nonmuscle myosin can increase the actin-activated ATPase activity and filament formation. Little is known about these regulatory mechanisms and how the RMLC are involved in ATP hydrolysis. To better characterize the nonmuscle RMLC, we isolated cDNAs encoding the Dictyostelium RMLC. Using an antibody specific for the RMLC, we screened a lambda gt11 expression library and obtained a 200-base-pair clone that encoded a portion of the RMLC. The remainder of the sequence was obtained from two clones identified by DNA hybridization, using the 200-base-pair cDNA. The composite RMLC cDNA was 645 nucleotides long. It contained 60 base pairs of 5' untranslated, 483 bases of coding, and 102 base pairs of 3' untranslated sequence. The amino acid sequence predicted an 18,300-dalton protein that shares 42% amino acid identity with Dictyostelium calmodulin and 30% identity with the chicken skeletal myosin RMLC. This sequence contained three regions that were similar to the E-F hand calcium-binding domains found in calmodulin, troponin C, and other myosin light chains. A sequence similar to the phosphorylation sequence found in chicken gizzard and skeletal myosin light chains was found at the amino terminus. Genomic Southern blot analysis suggested that the Dictyostelium genome contains a single gene encoding the RMLC. Analysis of RMLC expression patterns during Dictyostelium development indicated that accumulation of this mRNA increases just before aggregation and again during culmination. This pattern is similar to that obtained for the Dictyostelium essential myosin light chain and suggests that expression of the two light chains is coordinated during development.

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48

Tafuri, S. R., A. M. Rushforth, E. R. Kuczmarski, and R. L. Chisholm. "Dictyostelium discoideum myosin: isolation and characterization of cDNAs encoding the regulatory light chain." Molecular and Cellular Biology 9, no. 7 (July 1989): 3073–80. http://dx.doi.org/10.1128/mcb.9.7.3073.

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Phosphorylation of the regulatory light chains (RMLC) of nonmuscle myosin can increase the actin-activated ATPase activity and filament formation. Little is known about these regulatory mechanisms and how the RMLC are involved in ATP hydrolysis. To better characterize the nonmuscle RMLC, we isolated cDNAs encoding the Dictyostelium RMLC. Using an antibody specific for the RMLC, we screened a lambda gt11 expression library and obtained a 200-base-pair clone that encoded a portion of the RMLC. The remainder of the sequence was obtained from two clones identified by DNA hybridization, using the 200-base-pair cDNA. The composite RMLC cDNA was 645 nucleotides long. It contained 60 base pairs of 5' untranslated, 483 bases of coding, and 102 base pairs of 3' untranslated sequence. The amino acid sequence predicted an 18,300-dalton protein that shares 42% amino acid identity with Dictyostelium calmodulin and 30% identity with the chicken skeletal myosin RMLC. This sequence contained three regions that were similar to the E-F hand calcium-binding domains found in calmodulin, troponin C, and other myosin light chains. A sequence similar to the phosphorylation sequence found in chicken gizzard and skeletal myosin light chains was found at the amino terminus. Genomic Southern blot analysis suggested that the Dictyostelium genome contains a single gene encoding the RMLC. Analysis of RMLC expression patterns during Dictyostelium development indicated that accumulation of this mRNA increases just before aggregation and again during culmination. This pattern is similar to that obtained for the Dictyostelium essential myosin light chain and suggests that expression of the two light chains is coordinated during development.

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49

Ostrow, B. D., P. Chen, and R. L. Chisholm. "Expression of a myosin regulatory light chain phosphorylation site mutant complements the cytokinesis and developmental defects of Dictyostelium RMLC null cells." Journal of Cell Biology 127, no. 6 (December 15, 1994): 1945–55. http://dx.doi.org/10.1083/jcb.127.6.1945.

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In a number of systems phosphorylation of the regulatory light chain (RMLC) of myosin regulates the activity of myosin. In smooth muscle and vertebrate nonmuscle systems RMLC phosphorylation is required for contractile activity. In Dictyostelium discoideum phosphorylation of the RMLC regulates both ATPase activity and motor function. We have determined the site of phosphorylation on the Dictyostelium RMLC and used site-directed mutagenesis to replace the phosphorylated serine with an alanine. The mutant light chain was then expressed in RMLC null Dictyostelium cells (mLCR-) from an actin promoter on an integrating vector. The mutant RMLC was expressed at high levels and associated with the myosin heavy chain. RMLC bearing a ser13ala substitution was not phosphorylated in vitro by purified myosin light chain kinase, nor could phosphate be detected on the mutant RMLC in vivo. The mutant myosin had reduced actin-activated ATPase activity, comparable to fully dephosphorylated myosin. Unexpectedly, expression of the mutant RMLC rescued the primary phenotypic defects of the mlcR- cells to the same extent as did expression of wild-type RMLC. These results suggest that while phosphorylation of the Dictyostelium RMLC appears to be tightly regulated in vivo, it is not essential for myosin-dependent cellular functions.

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Cao, Lichuang, Zhenyu Wang, Dequan Zhang, Xin Li, Chengli Hou, and Chi Ren. "Phosphorylation of myosin regulatory light chain at Ser17 regulates actomyosin dissociation." Food Chemistry 356 (September 2021): 129655. http://dx.doi.org/10.1016/j.foodchem.2021.129655.

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