title: Heterotrimeric Galphaq11 co-immunoprecipitates with surface-anchored GRP78 from plasma membranes of alpha2M*-stimulated macrophages.
abstract: We have previously shown that a fraction of newly expressed GRP78 is translocated to the cell surface in association with the co-chaperone MTJ-1. Proteinase and methylamine-activated alpha(2)M (alpha(2)M*) bind to cell surface-associated GRP78 activating phosphoinositide-specific phospholipase C coupled to a pertussis toxin-insensitive heterotrimeric G protein, generating IP(3)/calcium signaling. We have now studied the association of pertussis toxin-insensitive Galphaq11, with GRP78/MTJ-1 complexes in the plasma membranes of alpha(2)M*-stimulated macrophages. When GRP78 was immunoprecipitated from plasma membranes of macrophages stimulated with alpha(2)M*, Galphaq11, and MTJ-1 were co-precipitated. Likewise Galphaq11 and GRP78 co-immunoprecipitated with MTJ-1 while GRP78 and MTJ-1 co-immunoprecipitated with Galphaq11. Silencing GRP78 expression with GRP78 dsRNA or MTJ-1 with MTJ-1 dsRNA greatly reduced the levels of Galphaq11 co-precipitated with GRP78 or MTJ-1. In conclusion, we show here that plasma membrane-associated GRP78 is coupled to pertussis toxin-insensitive Galphaq11 and forms a ternary signaling complex with MTJ-1.
authors.affiliation: Department of Pathology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: Uma Kant
authors.initials: UK
authors.lastname: Misra
authors.forename: Salvatore Vincent
authors.initials: SV
authors.lastname: Pizzo
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000737:chemistry*; D000091342:Endoplasmic Reticulum Chaperone BiP; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism*; D050956:HSP40 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism*; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D047468:Immunoprecipitation; D008262:Macrophage Activation; D008264:Macrophages / Q000737:chemistry*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D018832:Molecular Chaperones / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: C485368:DNAJC1 protein, human; D000091342:Endoplasmic Reticulum Chaperone BiP; D050956:HSP40 Heat-Shock Proteins; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D008565:Membrane Proteins; D018832:Molecular Chaperones; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020962:Heterotrimeric GTP-Binding Proteins