Identification and subcellular localization of a 21-kilodalton molecule using affinity-purified antibodies against .alpha.-transforming growth factor

Abstract

Monospecific antibodies were generated against each of six different peptide sequences derived from rat and human .alpha.-transforming growth factor (.alpha.-TGF). The affinity-purified antibody to the 17 amino acid carboxyl-terminal portion of the molecule proved most useful in detecting .alpha.-TGF. When used in a peptide-based radioimmunoassay, it was possible to measure nanogram quantities of native .alpha.-TGF in conditioned cell culture media. When used to analyze cell lysate, these antibodies specifically recognized a 21-kilodalton protein species. Indirect immunofluorescence localization procedures revealed a high concentration of .alpha.-TGF in a perinuclear ring with a diffuse cytoplasmic distribution. These results suggest that a precursor form of .alpha.-TGF has a cellular role beyond that of an autocrine growth factor.