title: The membrane-associated proteins FCHo and SGIP are allosteric activators of the AP2 clathrin adaptor complex.
abstract: The AP2 clathrin adaptor complex links protein cargo to the endocytic machinery but it is unclear how AP2 is activated on the plasma membrane. Here we demonstrate that the membrane-associated proteins FCHo and SGIP1 convert AP2 into an open, active conformation. We screened for Caenorhabditis elegans mutants that phenocopy the loss of AP2 subunits and found that AP2 remains inactive in fcho-1 mutants. A subsequent screen for bypass suppressors of fcho-1 nulls identified 71 compensatory mutations in all four AP2 subunits. Using a protease-sensitivity assay we show that these mutations restore the open conformation in vivo. The domain of FCHo that induces this rearrangement is not the F-BAR domain or the µ-homology domain, but rather is an uncharacterized 90 amino acid motif, found in both FCHo and SGIP proteins, that directly binds AP2. Thus, these proteins stabilize nascent endocytic pits by exposing membrane and cargo binding sites on AP2.
authors.affiliation: Stowers Institute for Medical Research, Kansas City, United States.
authors.forename: Gunther
authors.initials: G
authors.lastname: Hollopeter
authors.affiliation: Stowers Institute for Medical Research, Kansas City, United States.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Lange
authors.affiliation: Stowers Institute for Medical Research, Kansas City, United States.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Biology, Howard Hughes Medical Institute, University of Utah, Salt Lake City, United States.
authors.forename: Thien N
authors.initials: TN
authors.lastname: Vu
authors.affiliation: Department of Biology, Howard Hughes Medical Institute, University of Utah, Salt Lake City, United States.
authors.forename: Mingyu
authors.initials: M
authors.lastname: Gu
authors.affiliation: Department of Biology, Howard Hughes Medical Institute, University of Utah, Salt Lake City, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Ailion
authors.affiliation: Department of Cell and Developmental Biology, Ludwig-Maximilians-University, Munich, Germany.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Lambie
authors.affiliation: Stowers Institute for Medical Research, Kansas City, United States.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Slaughter
authors.affiliation: Stowers Institute for Medical Research, Kansas City, United States.
authors.forename: Jay R
authors.initials: JR
authors.lastname: Unruh
authors.affiliation: Stowers Institute for Medical Research, Kansas City, United States.
authors.forename: Laurence
authors.initials: L
authors.lastname: Florens
authors.affiliation: Department of Biology, Howard Hughes Medical Institute, University of Utah, Salt Lake City, United States.
authors.forename: Erik M
authors.initials: EM
authors.lastname: Jorgensen
mesh_terms: D033962:Adaptor Protein Complex 2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000494:Allosteric Regulation; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D022163:Clathrin-Coated Vesicles / Q000378:metabolism / Q000648:ultrastructure; D003034:Coated Pits, Cell-Membrane / Q000378:metabolism / Q000648:ultrastructure; D004705:Endocytosis / Q000235:genetics*; D005786:Gene Expression Regulation; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction
chemical_list: D033962:Adaptor Protein Complex 2; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D008565:Membrane Proteins; D021122:Protein Subunits
keywords: AP2; FCHo proteins; SGIP1; cell biology; clathrin adaptor complex; elegans; endocytosis; protein conformation