MOLECULAR CHARACTERIZATION OF ANTIPEPTIDE ANTIBODIES AGAINST THE 5-HT1A RECEPTOR - EVIDENCE FOR STATE-DEPENDENT ANTIBODY-BINDING

Differential immunohistochemical labeling is often observed using diff erent antibodies against the same protein. Two polyclonal antipeptide antibodies against the 5-HT1A receptor have been generated by our grou p. The S1A-170 (aa 170-186) and 258 (aa 258-274) are specific for site s in the second extracellular loop and third intracellular loop, respe ctively [E.C. Azmtia, I. Yu, H.M. Akbari, N. Kheck, P.M. Whitaker-Azmi tia and D.R. Marshak, Antipeptide antibodies against the 5-HT1A recept or, J. Chem. Neuroanat., 5 (1992) 289-298]. Comparison of the labeling patterns of these two antibodies and other antipeptide antibodies aga inst the 5-HT1A receptor revealed that although similar populations of cells were labeled, individual antibodies favor certain staining patt erns. Immunocytochemistry and western blotting results of transfected cell lines and brain tissue revealed the following: (1) both the S1A-1 70 and S1A-258 are specific for the 5-HT1A receptor when used for immu nocytochemistry in transfected HEK-293 and COS-1 cells; (2) when expre ssed in cultured cell lines, the 5-HT1A receptor is differentially gly cosylated dependent on cell type, and the S1A-258 is specific for only certain species on immunoblots; and (3) the S1A-258 and L5B7 [M. Riad , S. El Mestikawy, D. Derge, H. Gozlan, and M. Hamon, Visualization an d quantification of central 5-HT1A receptors with specific antibodies, Neurochem. Int., 4 (1991) 413-423] label common bands at 40 and 70 kD a on immunoblots of hippocampal proteins, but show opposite staining i ntensities. These results provide evidence for the immunocytochemical specificity of both the S1A-170 and S1A-258 and suggest that the discr epancies noted in immunohistochemistry may be due in part to different molecular conformations. (C) 1997 Elsevier Science B.V.