ANTIBODIES RAISED AGAINST A PEPTIDE CORRESPONDING TO A G(S-ALPHA) DOMAIN REVEAL A VIMENTIN-ASSOCIATED PROTEIN

In an attempt to localize the guanine nucleotide binding protein G(salpha) by immunocytochemistry, we synthetized peptides corresponding to several stretches of residues deduced from the published cDNA sequence of G(salpha) and raised antibodies against them. Among the peptides, one corresponding to residues 367-381 elicited antibodies that immunocytochemically detected, at the optical level, what appeared to be vimentin in several cells and tissues. Studies at the ultrastructural level confirmed this observation and also showed weak staining of some areas of plasma membranes of glial and nerve cells. Analysis by Western blots of rat brain subcellular fractions indicated that: (a) the protein stained by the anti-peptide antibodies was associated with the cystoskeleton; and (b) it was not vimentin but a protein of higher molecular weight, 65 KD. We accordingly suggest that the G(salpha)-derived peptide elicited two types of antibodies, one recognizing G(salpha), in fixed tissues, the other recognizing an epitope located in a vimentin-associated protein. This study emphasizes the caution that is needed when conclusions are drawn on the basis of immunocytochemical studies using anti-peptide antibodies.