Developmental Cell
Volume 10, Issue 3, March 2006, Pages 329-342
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Article
Molecular Switches Involving the AP-2 β2 Appendage Regulate Endocytic Cargo Selection and Clathrin Coat Assembly

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Summary

Clathrin-associated sorting proteins (CLASPs) expand the repertoire of endocytic cargo sorted into clathrin-coated vesicles beyond the transmembrane proteins that bind physically to the AP-2 adaptor. LDL and GPCRs are internalized by ARH and β-arrestin, respectively. We show that these two CLASPs bind selectively to the AP-2 β2 appendage platform via an α-helical [DE]nX1–2FXX[FL]XXXR motif, and that this motif also occurs and is functional in the epsins. In β-arrestin, this motif maintains the endocytosis-incompetent state by binding back on the folded core of the protein in a β strand conformation. Triggered via a β-arrestin/GPCR interaction, the motif must be displaced and must undergo a strand to helix transition to enable the β2 appendage binding that drives GPCR-β-arrestin complexes into clathrin coats. Another interaction surface on the β2 appendage sandwich is identified for proteins such as eps15 and clathrin, suggesting a mechanism by which clathrin displaces eps15 to lattice edges during assembly.

CELLBIO
SIGNALING

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