Phosphatidylinositol-(4,5)-bisphosphate regulates sorting signal recognition by the clathrin-associated adaptor complex AP2

摘要

The α,β 2,μ 2,σ 2 heterotetrameric AP2 complex is recruited exclusively to the phosphatidylinositol-4,5-bisphosphate (PtdIns4,5P(2))-rich plasma membrane where, amongst other roles, it selects motif-containing cargo proteins for incorporation into clathrin-coated vesicles. Unphosphorylated and μ 2Thr156-monophosphorylated AP2 mutated in their α PtdIns4,5P2, μ 2PtdIns4,5P(2), and μ 2Yxxφ binding sites were produced, and their interactions with membranes of different phospholipid and cargo composition were measured by surface plasmon resonance. We demonstrate that recognition of Yxxφ and acidic dileucine motifs is dependent on corecognition with PtdIns4,5P2, explaining the selective recruitment of AP2 to the plasma membrane. The interaction of AP2 with PtdIns4,5P(2)/Yxxφ-containing membranes is two step: initial recruitment via the aPtdIns4,5P2 site and then stabilization through the binding of μ 2Yxxφ and μ 2PtdIns4,5P2 sites to their ligands. The second step is facilitated by a conformational change favored by μ 2Thr156 phosphorylation. The binding of AP2 to acidic-dileucine motifs occurs at a different site from Yxxφ binding and is not enhanced by μ 2Thr156 phosphorylation.