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Heterotrimeric Gαq11 co‐immunoprecipitates with surface‐anchored GRP78 from plasma membranes of α 2 M*‐stimulated macrophages
Author(s) -
Misra Uma Kant,
Pizzo Salvatore Vincent
Publication year - 2008
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.21607
Subject(s) - heterotrimeric g protein , microbiology and biotechnology , membrane , chemistry , g protein , biology , signal transduction , biochemistry
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 α 2 M (α 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 Gαq11, with GRP78/MTJ‐1 complexes in the plasma membranes of α 2 M*‐stimulated macrophages. When GRP78 was immunoprecipitated from plasma membranes of macrophages stimulated with α 2 M*, Gαq11, and MTJ‐1 were co‐precipitated. Likewise Gαq11 and GRP78 co‐immunoprecipitated with MTJ‐1 while GRP78 and MTJ‐1 co‐immunoprecipitated with Gαq11. Silencing GRP78 expression with GRP78 dsRNA or MTJ‐1 with MTJ‐1 dsRNA greatly reduced the levels of Gαq11 co‐precipitated with GRP78 or MTJ‐1. In conclusion, we show here that plasma membrane‐associated GRP78 is coupled to pertussis toxin‐insensitive Gαq11 and forms a ternary signaling complex with MTJ‐1. J. Cell. Biochem. 104: 96–104, 2008. © 2008 Wiley‐Liss, Inc.