Identification of an adaptor-associated kinase, AAK1, as a regulator of clathrin-mediated endocytosis

Sean D. Conner, Sandra L. Schmid

Research output: Contribution to journalArticle

185 Scopus citations

Abstract

The μ2 subunit of the AP2 complex is known to be phosphorylated in vitro by a copurifying kinase, and it has been demonstrated recently that μ2 phosphorylation is required for transferrin endocytosis (Olusanya, O., P.D. Andrews, J.R. Swedlow, and E. Smythe, 2001. Curr. Biol. 11:896-900). However, the identity of the endogenous kinase responsible for this phosphorylation is unknown. Here we identify and characterize a novel member of the Prk/Ark family of serine/threonine kinases, adaptor-associated kinase (AAK)1. We find that AAK1 copurifies with adaptor protein (AP)2 and that it directly binds the ear domain of α-adaptin in vivo and in vitro. In neuronal cells, AAK1 is enriched at presynaptic terminals, whereas in nonneuronal cells it colocalizes with clathrin and AP2 in clathrin-coated pits and at the leading edge of migrating cells. AAK1 specifically phosphorylates the μ subunit in vitro, and stage-specific assays for endocytosis show that μ phosphorylation by AAK1 results in a decrease in AP2-stimulated transferrin internalization. Together, these results provide strong evidence that AAK1 is the endogenous μ2 kinase and plays a regulatory role in clathrin-mediated endocytosis. These results also lend support to the idea that clathrin-mediated endocytosis is controlled by cycles of phosphorylation/desphosphorylation.

Original languageEnglish (US)
Pages (from-to)921-929
Number of pages9
JournalJournal of Cell Biology
Volume156
Issue number5
DOIs
StatePublished - Mar 4 2002

Keywords

  • AAK1
  • AP2
  • Clathrin
  • Endocytosis
  • Kinase

ASJC Scopus subject areas

  • Cell Biology

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