title: Molecular machinery for insertion of tail-anchored membrane proteins into the endoplasmic reticulum membrane in mammalian cells.
abstract: Tail-anchored (TA) membrane proteins destined for the secretory pathway are posttranslationally inserted into the endoplasmic reticulum (ER) membrane, but the molecular machinery for this insertion in mammalian cells remains elusive. Here we reveal a mammalian protein complex that drives the membrane insertion. We identify calcium-modulating cyclophilin ligand (CAML) as a mammal-specific receptor for TRC40, an ATPase targeting newly synthesized TA proteins, and show that CAML mediates membrane insertion of TA proteins. We show that CAML binds to WRB, an evolutionarily conserved TRC40 receptor, through the transmembrane domains and that CAML and WRB synergistically insert TA proteins into the membrane. Mutagenesis of CAML demonstrates that binding of TRC40 to CAML is required to ensure synergistic membrane insertion. Thus, identification of CAML and WRB as components of the TRC40 receptor complex represents a crucial mechanism for driving ER membrane insertion of TA proteins in mammalian cells.
authors.affiliation: Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Sakisaka
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D053501:Arsenite Transporting ATPases / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D034622:RNA Interference; D051381:Rats; D017386:Sequence Homology, Amino Acid
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C089404:CAMLG protein, human; C111546:GET1 protein, human; C489667:GET3 protein, human; D008565:Membrane Proteins; D009687:Nuclear Proteins; D053501:Arsenite Transporting ATPases