G protein mediated signal transduction: membrane immunoglobulin associated phosphoproteins identified in octyl-beta-glucoside lysates of normal B cells.
Several recent studies have shown that the antigen receptors (mIgM and mIgD) on normal B cell surfaces are part of larger multimolecular complexes, as each is noncovalently coupled to at least two other proteins whose phosphorylation is inducible upon G protein activation. However, B cell receptor complexes appear to be extremely labile, so that extraction of membrane immunoglobulin (mIg) from cell lysates in physical association with noncovalently coupled proteins has been shown to be highly dependent on the choice of detergent. Recent progress has to a large extent been dependent upon the introduction of digitonin, a detergent in which B cell receptor complexes are at least partially stable, as an agent to solubilize B cell membranes. Studies presented here demonstrate that if another well known detergent, octyl-beta-D-glucopyranoside (octyl glucoside), is utilized in place of digitonin, mIg receptors are immunoprecipitated from B cell lysates in association with several newly identified proteins, whose phosphorylation is also G protein dependent. In particular we find three to four mIg associated phosphoproteins in the molecular weight range of 47 to 57 kDa, and at least two others at 82 and 112 kDa. Some of these proteins may correspond to polypeptides that have been functionally linked to mIg dependent signal transduction, but have not as yet been shown to be physically coupled to the receptor.
Chang
C C
CC
Department of Biological Sciences, Wayne State University, Detroit, MI 48202.
Alhasan
S
S
Rosenspire
A J
AJ
D000818:Animals; D001402:B-Lymphocytes / Q000737:chemistry; D002462:Cell Membrane / Q000737:chemistry*; D004072:Digitonin; D019204:GTP-Binding Proteins / Q000737:chemistry*; D005960:Glucosides; D051379:Mice; D010750:Phosphoproteins / Q000737:chemistry*; D010766:Phosphorylation; D011947:Receptors, Antigen, B-Cell / Q000737:chemistry*; D015398:Signal Transduction; D013154:Spleen / Q000166:cytology
D005960:Glucosides; D010750:Phosphoproteins; D011947:Receptors, Antigen, B-Cell; C018619:octyl-beta-D-glucoside; D019204:GTP-Binding Proteins; D004072:Digitonin