科研之友
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摘要
The AP-2 clathrin adaptor complex oversees endocytic cargo selection in two parallel but independent manners. First, by physically engaging peptide-based endocytic sorting signals, a subset of clathrin-dependent transmembrane cargo is directly collected into assembling buds. Synchronously, by interacting with an assortment of clathrin-associated sorting proteins (CLASPs) that independently select different integral membrane cargo for inclusion within the incipient bud, AP-2 handles additional cargo capture indirectly. The distal platform subdomain of the AP-2 beta 2 subunit appendage is a privileged CLASP-binding surface that recognizes a cognate, short alpha-helical interaction motif. This signal, found in the CLASPs beta-arrestin and the autosomal recessive hypercholesterolemia (ARH) protein, docks into an elongated groove on the beta 2 appendage platform. Tyr-888 is a critical constituent of this spatially confined beta 2 appendage contact interface and is phosphorylated in numerous high-throughput proteomic studies. We find that a phosphomimetic Y888E substitution does not interfere with incorporation of expressed beta 2-YFP subunit into AP-2 or alter AP-2 deposition at surface clathrin-coated structures. The Y888E mutation does not affect interactions involving the sandwich subdomain of the beta 2 appendage, indicating that the mutated appendage is folded and operational. However, the Y888E, but not Y888F, switch selectively uncouples interactions with ARH and beta-arrestin. Phyogenetic conservation of Tyr-888 suggests that this residue can reversibly control occupancy of the beta 2 platform-binding site and, hence, cargo sorting.
- 出版日期2014-6-20
