Relevant bibliographies by topics / AP-4 Complex

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Academic literature on the topic 'AP-4 Complex'

Author: Grafiati
Published: 14 March 2023

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Journal articles on the topic "AP-4 Complex"

1

Hirst, Jennifer, Nicholas A. Bright, Brian Rous, and Margaret S. Robinson. "Characterization of a Fourth Adaptor-related Protein Complex." Molecular Biology of the Cell 10, no. 8 (1999): 2787–802. http://dx.doi.org/10.1091/mbc.10.8.2787.

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Adaptor protein complexes (APs) function as vesicle coat components in different membrane traffic pathways; however, there are a number of pathways for which there is still no candidate coat. To find novel coat components related to AP complexes, we have searched the expressed sequence tag database and have identified, cloned, and sequenced a new member of each of the four AP subunit families. We have shown by a combination of coimmunoprecipitation and yeast two-hybrid analysis that these four proteins (ε, β4, μ4, and ς4) are components of a novel adaptor-like heterotetrameric complex, which we are calling AP-4. Immunofluorescence reveals that AP-4 is localized to ∼10–20 discrete dots in the perinuclear region of the cell. This pattern is disrupted by treating the cells with brefeldin A, indicating that, like other coat proteins, the association of AP-4 with membranes is regulated by the small GTPase ARF. Immunogold electron microscopy indicates that AP-4 is associated with nonclathrin-coated vesicles in the region of the trans-Golgi network. The μ4 subunit of the complex specifically interacts with a tyrosine-based sorting signal, indicating that, like the other three AP complexes, AP-4 is involved in the recognition and sorting of cargo proteins with tyrosine-based motifs. AP-4 is of relatively low abundance, but it is expressed ubiquitously, suggesting that it participates in a specialized trafficking pathway but one that is required in all cell types.
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2

Salazar, G., B. Craige, M. L. Styers, et al. "BLOC-1 Complex Deficiency Alters the Targeting of Adaptor Protein Complex-3 Cargoes." Molecular Biology of the Cell 17, no. 9 (2006): 4014–26. http://dx.doi.org/10.1091/mbc.e06-02-0103.

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Mutational analyses have revealed many genes that are required for proper biogenesis of lysosomes and lysosome-related organelles. The proteins encoded by these genes assemble into five distinct complexes (AP-3, BLOC-1-3, and HOPS) that either sort membrane proteins or interact with SNAREs. Several of these seemingly distinct complexes cause similar phenotypic defects when they are rendered defective by mutation, but the underlying cellular mechanism is not understood. Here, we show that the BLOC-1 complex resides on microvesicles that also contain AP-3 subunits and membrane proteins that are known AP-3 cargoes. Mouse mutants that cause BLOC-1 or AP-3 deficiencies affected the targeting of LAMP1, phosphatidylinositol-4-kinase type II alpha, and VAMP7-TI. VAMP7-TI is an R-SNARE involved in vesicle fusion with late endosomes/lysosomes, and its cellular levels were selectively decreased in cells that were either AP-3- or BLOC-1–deficient. Furthermore, BLOC-1 deficiency selectively altered the subcellular distribution of VAMP7-TI cognate SNAREs. These results indicate that the BLOC-1 and AP-3 protein complexes affect the targeting of SNARE and non-SNARE AP-3 cargoes and suggest a function of the BLOC-1 complex in membrane protein sorting.
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3

Dell’Angelica, Esteban C., Chris Mullins, and Juan S. Bonifacino. "AP-4, a Novel Protein Complex Related to Clathrin Adaptors." Journal of Biological Chemistry 274, no. 11 (1999): 7278–85. http://dx.doi.org/10.1074/jbc.274.11.7278.

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4

Ponsankarar, Lalitha, A. Sinthiya, and V. Rashmi. "Hydrogen-bonding interaction of 4-AP metal complex with proteins." Acta Crystallographica Section A Foundations and Advances 73, a2 (2017): C402. http://dx.doi.org/10.1107/s2053273317091719.

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5

Behne, Robert, Julian Teinert, Miriam Wimmer, et al. "Adaptor protein complex 4 deficiency: a paradigm of childhood-onset hereditary spastic paraplegia caused by defective protein trafficking." Human Molecular Genetics 29, no. 2 (2020): 320–34. http://dx.doi.org/10.1093/hmg/ddz310.

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Abstract Deficiency of the adaptor protein complex 4 (AP-4) leads to childhood-onset hereditary spastic paraplegia (AP-4-HSP): SPG47 (AP4B1), SPG50 (AP4M1), SPG51 (AP4E1) and SPG52 (AP4S1). This study aims to evaluate the impact of loss-of-function variants in AP-4 subunits on intracellular protein trafficking using patient-derived cells. We investigated 15 patient-derived fibroblast lines and generated six lines of induced pluripotent stem cell (iPSC)-derived neurons covering a wide range of AP-4 variants. All patient-derived fibroblasts showed reduced levels of the AP4E1 subunit, a surrogate for levels of the AP-4 complex. The autophagy protein ATG9A accumulated in the trans-Golgi network and was depleted from peripheral compartments. Western blot analysis demonstrated a 3–5-fold increase in ATG9A expression in patient lines. ATG9A was redistributed upon re-expression of AP4B1 arguing that mistrafficking of ATG9A is AP-4-dependent. Examining the downstream effects of ATG9A mislocalization, we found that autophagic flux was intact in patient-derived fibroblasts both under nutrient-rich conditions and when autophagy is stimulated. Mitochondrial metabolism and intracellular iron content remained unchanged. In iPSC-derived cortical neurons from patients with AP4B1-associated SPG47, AP-4 subunit levels were reduced while ATG9A accumulated in the trans-Golgi network. Levels of the autophagy marker LC3-II were reduced, suggesting a neuron-specific alteration in autophagosome turnover. Neurite outgrowth and branching were reduced in AP-4-HSP neurons pointing to a role of AP-4-mediated protein trafficking in neuronal development. Collectively, our results establish ATG9A mislocalization as a key marker of AP-4 deficiency in patient-derived cells, including the first human neuron model of AP-4-HSP, which will aid diagnostic and therapeutic studies.
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6

BAROIS, Nicolas, and Oddmund BAKKE. "The adaptor protein AP-4 as a component of the clathrin coat machinery: a morphological study." Biochemical Journal 385, no. 2 (2005): 503–10. http://dx.doi.org/10.1042/bj20041010.

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The four members of the AP (adaptor protein) family are heterotetrameric cytosolic complexes that are involved in the intracellular trafficking of cargo proteins between different organelles. They interact with motifs present in the cytoplasmic tails of their specific cargo proteins at different intracellular locations. While AP-1, AP-2 and AP-3 have been investigated extensively, very few studies have focused on the fourth member, AP-4. In the present study, we report on the intracellular localization of AP-4 in the MDCK (Madin–Darby canine kidney) and MelJuSo cell lines after immunogold labelling of ultrathin cryosections. We find that AP-4 is localized mainly in the Golgi complex, as well as on endosomes and transport vesicles. Interestingly, we show for the first time that AP-4 is localized with the clathrin coat machinery in the Golgi complex and in the endocytic pathway. Furthermore, we find that AP-4 is localized with the CI-MPR (cation-independent mannose 6-phosphate receptor), but not with the transferrin receptor, LAMP-2 (lysosomal-associated membrane protein-2) or invariant chain. The difference in morphology between CI-MPR/AP-4-positive vesicles and CI-MPR/AP-1-positive vesicles raises the possibility that AP-4 acts at a location different from that of AP-1 in the intracellular trafficking pathway of CI-MPR.
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7

Mattera, Rafael, Chad D. Williamson, Xuefeng Ren, and Juan S. Bonifacino. "The FTS-Hook-FHIP (FHF) complex interacts with AP-4 to mediate perinuclear distribution of AP-4 and its cargo ATG9A." Molecular Biology of the Cell 31, no. 9 (2020): 963–79. http://dx.doi.org/10.1091/mbc.e19-11-0658.

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In this study, we identify the dynein–dynactin adaptor FTS-Hook-FHIP (FHF) complex as an accessory factor for the TGN-associated adaptor protein 4 (AP-4) coat. We show that FHF is required for distribution of AP-4 and its cargo ATG9A to the perinuclear area, highlighting a novel mechanism for coupling of transport vesicles to microtubule motors.
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8

Schneider, Helga, Margarita Martin, Fernando A. Agarraberes та ін. "Cytolytic T Lymphocyte-Associated Antigen-4 and the TCRζ/CD3 Complex, But Not CD28, Interact with Clathrin Adaptor Complexes AP-1 and AP-2". Journal of Immunology 163, № 4 (1999): 1868–79. http://dx.doi.org/10.4049/jimmunol.163.4.1868.

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Abstract The negative signaling receptor cytolytic T lymphocyte-associated Ag-4 (CTLA-4) resides primarily in intracellular compartments such as the Golgi apparatus of T cells. However, little is known regarding the molecular mechanisms that influence this accumulation. In this study, we demonstrate binding of the clathrin adaptor complex AP-1 with the GVYVKM motif of the cytoplasmic domain of CTLA-4. Binding occurred primarily in the Golgi compartment of T cells, unlike with AP-2 binding that occurs mostly with cell surface CTLA-4. Although evidence was not found to implicate AP-1 binding in the retention of CTLA-4 in the Golgi, AP-1 appears to play a role in shuttling of excess receptor from the Golgi to the lysosomal compartments for degradation. In support of this, increased CTLA-4 synthesis resulted in an increase in CTLA-4/AP-1 binding and a concomitant increase in the appearance of CTLA-4 in the lysosomal compartment. At the same time, the level of intracellular receptor was maintained at a constant level, suggesting that CTLA-4/AP-1 binding represents one mechanism to ensure steady state levels of intracellular CTLA-4 in T cells. Finally, we demonstrate that the TCRζ/CD3 complex (but not CD28) also binds to AP-1 and AP-2 complexes, thus providing a possible link between these two receptors in the regulation of T cell function.
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9

Mattera, Rafael, Sang Yoon Park, Raffaella De Pace, Carlos M. Guardia, and Juan S. Bonifacino. "AP-4 mediates export of ATG9A from the trans-Golgi network to promote autophagosome formation." Proceedings of the National Academy of Sciences 114, no. 50 (2017): E10697—E10706. http://dx.doi.org/10.1073/pnas.1717327114.

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AP-4 is a member of the heterotetrameric adaptor protein (AP) complex family involved in protein sorting in the endomembrane system of eukaryotic cells. Interest in AP-4 has recently risen with the discovery that mutations in any of its four subunits cause a form of hereditary spastic paraplegia (HSP) with intellectual disability. The critical sorting events mediated by AP-4 and the pathogenesis of AP-4 deficiency, however, remain poorly understood. Here we report the identification of ATG9A, the only multispanning membrane component of the core autophagy machinery, as a specific AP-4 cargo. AP-4 promotes signal-mediated export of ATG9A from the trans-Golgi network to the peripheral cytoplasm, contributing to lipidation of the autophagy protein LC3B and maturation of preautophagosomal structures. These findings implicate AP-4 as a regulator of autophagy and altered autophagy as a possible defect in AP-4–deficient HSP.
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10

Szurmak, Blanka, Aleksandra Wysłouch-Cieszyńska, Małgorzata Wszelaka-Rylik, Wojciech Bal, and Marta Dobrzańska. "A diadenosine 5',5''-P1P4 tetraphosphate (Ap4A) hydrolase from Arabidopsis thaliana that is activated preferentially by Mn2+ ions." Acta Biochimica Polonica 55, no. 1 (2008): 151–60. http://dx.doi.org/10.18388/abp.2008_3173.

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Asymmetrical diadenosine 5',5''-P(1)P(4) tetraphosphate (Ap(4)A) hydrolases are key enzymes controlling the in vivo concentration of Ap(4)A--an important signaling molecule involved in regulation of DNA replication and repair, signaling in stress response and apoptosis. Sequence homologies indicate that the genome of the model plant Arabidopsis thaliana contains at least three open reading frames encoding presumptive Ap(4)A hydrolases: At1g30110, At3g10620, and At5g06340. In this work we present efficient overexpression and detailed biochemical characteristics of the AtNUDX25 protein encoded by the At1g30110 gene. Aided by the determination of the binding constants of Mn(Ap(4)A) and Mg(Ap(4)A) complexes using isothermal titration calorimetry (ITC) we show that AtNUDX25 preferentially hydrolyzes Ap(4)A in the form of a Mn(2+) complex.
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