EpsinR: an ENTH Domain-containing Protein that Interacts with AP-1

Jennifer Hirst, Alison Motley, Kouki Harasaki, Sew Y. Peak Chew, Margaret S. Robinson

doi:10.1091/mbc.e02-09-0552

<jats:p>We have used GST pulldowns from A431 cell cytosol to identify three new binding partners for the γ-adaptin appendage: Snx9, ARF GAP1, and a novel ENTH domain-containing protein, epsinR. EpsinR is a highly conserved protein that colocalizes with AP-1 and is enriched in purified clathrin-coated vesicles. However, it does not require AP-1 to get onto membranes and remains membrane-associated in AP-1–deficient cells. Moreover, although epsinR binds AP-1 via its COOH-terminal domain, its NH<jats:sub>2</jats:sub>-terminal ENTH domain can be independently recruited onto membranes, both in vivo and in vitro. Brefeldin A causes epsinR to redistribute into the cytosol, and recruitment of the ENTH domain requires GTPγS, indicating that membrane association is ARF dependent. In protein-lipid overlay assays, the epsinR ENTH domain binds to PtdIns(4)P, suggesting a possible mechanism for ARF-dependent recruitment onto TGN membranes. When epsinR is depleted from cells by RNAi, cathepsin D is still correctly processed intracellularly to the mature form. This indicates that although epsinR is likely to be an important component of the AP-1 network, it is not necessary for the sorting of lysosomal enzymes.</jats:p>

EpsinR: an ENTH Domain-containing Protein that Interacts with AP-1

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EpsinR: an ENTH Domain-containing Protein that Interacts with AP-1

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