title: TRP and Rhodopsin Transport Depends on Dual XPORT ER Chaperones Encoded by an Operon.
abstract: TRP channels and G protein-coupled receptors (GPCRs) play critical roles in sensory reception. However, the identities of the chaperones that assist GPCRs in translocating from the endoplasmic reticulum (ER) are limited, and TRP ER chaperones are virtually unknown. The one exception for TRPs is Drosophila XPORT. Here, we show that the xport locus is bicistronic and encodes unrelated transmembrane proteins, which enable the signaling proteins that initiate and culminate phototransduction, rhodopsin 1 (Rh1) and TRP, to traffic to the plasma membrane. XPORT-A and XPORT-B are ER proteins, and loss of either has a profound impact on TRP and Rh1 targeting to the light-sensing compartment of photoreceptor cells. XPORT-B complexed in vivo with the Drosophila homolog of the mammalian HSP70 protein, GRP78/BiP, which, in turn, associated with Rh1. Our work highlights a coordinated network of chaperones required for the biosynthesis of the TRP channel and rhodopsin in Drosophila photoreceptor cells.
authors.affiliation: Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA; Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
authors.forename: Zijing
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA; Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
authors.forename: Hsiang-Chin
authors.initials: HC
authors.lastname: Chen
authors.affiliation: Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USA; Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA. Electronic address: craig.montell@lifesci.ucsb.edu.
authors.forename: Craig
authors.initials: C
authors.lastname: Montell
mesh_terms: D000818:Animals; D004330:Drosophila / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D009876:Operon; D011485:Protein Binding; D021381:Protein Transport; D012243:Rhodopsin / Q000378:metabolism*; D050051:Transient Receptor Potential Channels / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D018840:HSP70 Heat-Shock Proteins; D018832:Molecular Chaperones; D050051:Transient Receptor Potential Channels; C569221:Xport-A protein, Drosophila; D012243:Rhodopsin