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AP-1 binding to sorting signals and release from clathrin-coated vesicles is regulated by phosphorylation

The adaptor protein complex-1 (AP-1) sorts and packages membrane proteins into clathrin-coated vesicles (CCVs) at the TGN and endosomes. Here we show that this process is highly regulated by phosphorylation of AP-1 subunits. Cell fractionation studies revealed that membrane-associated AP-1 differs f...

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Autores principales: Ghosh, Pradipta, Kornfeld, Stuart
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 2003
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2173368/
https://www.ncbi.nlm.nih.gov/pubmed/12604586
http://dx.doi.org/10.1083/jcb.200211080
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author Ghosh, Pradipta
Kornfeld, Stuart
author_facet Ghosh, Pradipta
Kornfeld, Stuart
author_sort Ghosh, Pradipta
collection PubMed
description The adaptor protein complex-1 (AP-1) sorts and packages membrane proteins into clathrin-coated vesicles (CCVs) at the TGN and endosomes. Here we show that this process is highly regulated by phosphorylation of AP-1 subunits. Cell fractionation studies revealed that membrane-associated AP-1 differs from cytosolic AP-1 in the phosphorylation status of its β1 and μ1 subunits. AP-1 recruitment onto the membrane is associated with protein phosphatase 2A (PP2A)–mediated dephosphorylation of its β1 subunit, which enables clathrin assembly. This Golgi-associated isoform of PP2A exhibits specificity for phosphorylated β1 compared with phosphorylated μ1. Once on the membrane, the μ1 subunit undergoes phosphorylation, which results in a conformation change, as revealed by increased sensitivity to trypsin. This conformational change is associated with increased binding to sorting signals on the cytoplasmic tails of cargo molecules. Dephosphorylation of μ1 (and μ2) by another PP2A-like phosphatase reversed the effect and resulted in adaptor release from CCVs. Immunodepletion and okadaic acid inhibition studies demonstrate that PP2A is the cytosolic cofactor for Hsc-70–mediated adaptor uncoating. A model is proposed where cyclical phosphorylation/dephosphorylation of the subunits of AP-1 regulate its function from membrane recruitment until its release into cytosol.
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spelling pubmed-21733682008-05-01 AP-1 binding to sorting signals and release from clathrin-coated vesicles is regulated by phosphorylation Ghosh, Pradipta Kornfeld, Stuart J Cell Biol Article The adaptor protein complex-1 (AP-1) sorts and packages membrane proteins into clathrin-coated vesicles (CCVs) at the TGN and endosomes. Here we show that this process is highly regulated by phosphorylation of AP-1 subunits. Cell fractionation studies revealed that membrane-associated AP-1 differs from cytosolic AP-1 in the phosphorylation status of its β1 and μ1 subunits. AP-1 recruitment onto the membrane is associated with protein phosphatase 2A (PP2A)–mediated dephosphorylation of its β1 subunit, which enables clathrin assembly. This Golgi-associated isoform of PP2A exhibits specificity for phosphorylated β1 compared with phosphorylated μ1. Once on the membrane, the μ1 subunit undergoes phosphorylation, which results in a conformation change, as revealed by increased sensitivity to trypsin. This conformational change is associated with increased binding to sorting signals on the cytoplasmic tails of cargo molecules. Dephosphorylation of μ1 (and μ2) by another PP2A-like phosphatase reversed the effect and resulted in adaptor release from CCVs. Immunodepletion and okadaic acid inhibition studies demonstrate that PP2A is the cytosolic cofactor for Hsc-70–mediated adaptor uncoating. A model is proposed where cyclical phosphorylation/dephosphorylation of the subunits of AP-1 regulate its function from membrane recruitment until its release into cytosol. The Rockefeller University Press 2003-03-03 /pmc/articles/PMC2173368/ /pubmed/12604586 http://dx.doi.org/10.1083/jcb.200211080 Text en Copyright © 2003, The Rockefeller University Press This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
spellingShingle Article
Ghosh, Pradipta
Kornfeld, Stuart
AP-1 binding to sorting signals and release from clathrin-coated vesicles is regulated by phosphorylation
title AP-1 binding to sorting signals and release from clathrin-coated vesicles is regulated by phosphorylation
title_full AP-1 binding to sorting signals and release from clathrin-coated vesicles is regulated by phosphorylation
title_fullStr AP-1 binding to sorting signals and release from clathrin-coated vesicles is regulated by phosphorylation
title_full_unstemmed AP-1 binding to sorting signals and release from clathrin-coated vesicles is regulated by phosphorylation
title_short AP-1 binding to sorting signals and release from clathrin-coated vesicles is regulated by phosphorylation
title_sort ap-1 binding to sorting signals and release from clathrin-coated vesicles is regulated by phosphorylation
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2173368/
https://www.ncbi.nlm.nih.gov/pubmed/12604586
http://dx.doi.org/10.1083/jcb.200211080
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