title: TRP1 interacting PDZ-domain protein GIPC forms oligomers and is localized to intracellular vesicles in human melanocytes.
abstract: PDZ proteins coordinate assembly of protein complexes that participate in diverse biological processes. GIPC is a multifunctional PDZ protein that interacts with several soluble and membrane proteins. Unlike most PDZ proteins, GIPC contains single PDZ domain and the mechanisms by which GIPC mediates its actions remain unclear. We investigated the possibility that in lieu of multiple PDZ domains, GIPC forms multimers. Here, we demonstrate that GIPC can bind to itself and that the PDZ domain is involved in GIPC-GIPC interaction. Gel filtration, sucrose gradient centrifugation and chemical cross-linking showed that whereas bulk of cytosolic GIPC was present as monomer, oligomers with an estimated molecular mass corresponding to GIPC homotrimer were readily detectable in the membrane fraction. Modeling of GIPC PDZ domain showed feasibility of trimerization. Immunogold electron microscopy showed that GIPC is present in clusters near vesicles. Our data suggest that oligomers of GIPC mediate its functions in melanocytes.
authors.affiliation: Department of Dermatology, University of Wisconsin, Madison, WI 53706, USA.
authors.forename: Rajendra H
authors.initials: RH
authors.lastname: Kedlaya
authors.forename: Kumar M R
authors.initials: KM
authors.lastname: Bhat
authors.forename: Julie
authors.initials: J
authors.lastname: Mitchell
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Darnell
authors.forename: Vijayasaradhi
authors.initials: V
authors.lastname: Setaluri
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D001704:Biopolymers; D045744:Cell Line, Tumor; D003001:Cloning, Molecular; D003432:Cross-Linking Reagents / Q000737:chemistry; D003545:Cysteine / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008544:Melanocytes / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D022161:Transport Vesicles / Q000378:metabolism*; D014357:Trypsin; D014362:Trypsinogen / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D001704:Biopolymers; D003432:Cross-Linking Reagents; C492009:GIPC1 protein, human; D014362:Trypsinogen; C489303:PRSS1 protein, human; D014357:Trypsin; D003545:Cysteine