Clathrin regulates the association of PIPKIγ661 with the AP-2 adaptor β2 Appendage

James R. Thieman, Sanjay K. Mishra, Kun Ling, Balraj Doray, Richard A. Anderson, Linton M. Traub

Research output: Contribution to journalArticlepeer-review

42 Scopus citations


The AP-2 clathrin adaptor differs fundamentally from the related AP-1, AP-3, and AP-4 sorting complexes because membrane deposition does not depend directly on an Arf family GTPase. Instead phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) appears to act as the principal compartmental cue for AP-2 placement at the plasma membrane as well as for the docking of numerous other important clathrin coat components at the nascent bud site. This PtdIns(4,5)P2 dependence makes type I phosphatidylinositol 4-phosphate 5-kinases (PIPKIs) lynchpin enzymes in the assembly of clathrin-coated structures at the cell surface. PIPKIγ is the chief 5-kinase at nerve terminals, and here we show that the 26-amino acid, alternatively spliced C terminus of PIPKIγ661 is an intrinsically unstructured polypeptide that binds directly to the sandwich subdomain of the AP-2 β2 subunit appendage. An aromatic side chain-based, extended interaction motif that also includes the two bulky C-terminal residues of the short PIPKIγ635 variant is necessary for β2 appendage engagement. The clathrin heavy chain accesses the same contact surface on the AP-2b2 appendage, but because of additional clathrin binding sites located within the unstructured hinge segment of the β2 subunit, clathrin binds the β2 chain with a higher apparent affinity than PIPKIγ661. A clathrin-regulated interaction with AP-2 could allow PIPKIγ661 to be strategically positioned for regional PtdIns(4,5)P2 generation during clathrin-coated vesicle assembly at the synapse.

Original languageEnglish
Pages (from-to)13924-13939
Number of pages16
JournalJournal of Biological Chemistry
Issue number20
StatePublished - May 15 2009


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