Distribution and relative levels of expression of the phosphoinositidase-C-linked G-proteins Gq alpha and G11 alpha: absence of G11 alpha in human platelets and haemopoietically derived cell lines.

Membranes of a variety of clonal cell lines, including neuroblastoma x glioma hybrid NG108-15, glioma C6, Rat 1 and CHO fibroblasts and the pituitary-derived cell lines alpha T3 and GH3 were immunoblotted with an antiserum (CQ) raised against a synthetic peptide corresponding to the C-terminal decapeptide of the alpha subunits of the phosphoinositidase-C-linked G-proteins Gq and G11. In SDS-PAGE conditions able to resolve these two polypeptides, direct evidence was obtained for co-expression of these two G-proteins in all of the above cell lines. The ratio of these two G-proteins varied substantially (alpha 11/alpha q = 0.25-2.5) between the cell lines. In human platelets and in a range of haemopoietically derived human cell lines including U937 (monoblasts), Raji (Burkitts lymphoma) and Jurkat (mature T cell) expression of G11 alpha was not detected. This was not due to the inability of the antiserum to identify human G11 alpha as other human cell lines co-expressed both G-proteins. A third, unidentified CQ reactive polypeptide of similar mobility was resolved and present in all cell lines examined.