title: Clathrin adaptors. AP2 controls clathrin polymerization with a membrane-activated switch.
abstract: Clathrin-mediated endocytosis (CME) is vital for the internalization of most cell-surface proteins. In CME, plasma membrane-binding clathrin adaptors recruit and polymerize clathrin to form clathrin-coated pits into which cargo is sorted. Assembly polypeptide 2 (AP2) is the most abundant adaptor and is pivotal to CME. Here, we determined a structure of AP2 that includes the clathrin-binding β2 hinge and developed an AP2-dependent budding assay. Our findings suggest that an autoinhibitory mechanism prevents clathrin recruitment by cytosolic AP2. A large-scale conformational change driven by the plasma membrane phosphoinositide phosphatidylinositol 4,5-bisphosphate and cargo relieves this autoinhibition, triggering clathrin recruitment and hence clathrin-coated bud formation. This molecular switching mechanism can couple AP2's membrane recruitment to its key functions of cargo and clathrin binding.
authors: Cambridge Institute for Medical Research (CIMR), Department of Clinical Biochemistry, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK. btk1000@cam.ac.uk djo30@cam.ac.uk.
authors: Bernard T
authors: BT
authors: Kelly
authors: Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
authors: Stephen C
authors: SC
authors: Graham
authors: Cambridge Institute for Medical Research (CIMR), Department of Clinical Biochemistry, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK.
authors: Nicole
authors: N
authors: Liska
authors: Department of Cell Biology, Center of Anatomy, Hannover Medical School, Carl-Neuberg Strasse 1, D-30625 Hannover, Germany.
authors: Philip N
authors: PN
authors: Dannhauser
authors: Institute of Biochemistry I and Center for Molecular Medicine Cologne, University of Cologne, Joseph-Stelzmann-Strasse 52, 50931 Cologne, Germany.
authors: Stefan
authors: S
authors: Höning
authors: Department of Cell Biology, Center of Anatomy, Hannover Medical School, Carl-Neuberg Strasse 1, D-30625 Hannover, Germany.
authors: Ernst J
authors: EJ
authors: Ungewickell
authors: Cambridge Institute for Medical Research (CIMR), Department of Clinical Biochemistry, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK. btk1000@cam.ac.uk djo30@cam.ac.uk.
authors: David J
authors: DJ
authors: Owen
mesh_terms: D033962:Adaptor Protein Complex 2 / Q000737:chemistry*; D033966:Adaptor Protein Complex beta Subunits / Q000737:chemistry*; D002462:Cell Membrane / Q000737:chemistry*; D002966:Clathrin / Q000737:chemistry*; D004705:Endocytosis; D006801:Humans; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000737:chemistry; D058105:Polymerization
chemical_list: D033962:Adaptor Protein Complex 2; D033966:Adaptor Protein Complex beta Subunits; D002966:Clathrin; D019269:Phosphatidylinositol 4,5-Diphosphate