IDENTIFICATION OF A NOVEL SECRETOGRANIN II-DERIVED PEPTIDE (SGII(187-252)) IN ADULT AND FETAL HUMAN ADRENAL-GLANDS USING ANTIBODIES RAISED AGAINST THE HUMAN RECOMBINANT PEPTIDE

Molecular cloning of secretogranin II (SgII) in phylogenetically dista nt species has recently revealed the existence of a highly conserved 6 6-amino acid peptide flanked by preserved pairs of basic residues. Thi s observation suggested that this peptide, named EM66, which had not b een described to date, could be an important processing product of SgI I. The aim of the present study was to investigate the possible occurr ence of EM66 in the human adrenal gland. The EM66 peptide was generate d in Escherichia coli, which was programmed to make a fusion protein c ontaining the human EM66 sequence. The affinity-purified fusion protei n was used to raise polyclonal antibodies in rabbits. The free EM66 pe ptide was obtained by cleavage of the fusion protein followed by high performance liquid chromatography purification. Immunohistochemical an alysis using the EM66 antibodies revealed intense labeling of adrenoch romaffin cells in the adult adrenal medulla and the fetal adrenal glan d. A sensitive and specific RIA was developed and applied to the detec tion of EM66-like immunoreactivity in extracts of adult adrenal medull a and whole fetal adrenal gland after high performance liquid chromato graphic analysis. A major immunoreactive species exhibiting the same r etention time as recombinant EM66 was detected in both adult and fetal adrenal extracts. Taken together, these data demonstrate that posttra nslational processing of SgII actually generates EM66 in the adrenal g land. The strong conservation of the amino acid sequence bf EM66 in th e vertebrate phylum and the occurrence of the mature peptide in both f etal and adult chromaffin cells suggest that EM66 could play an import ant physiological role in the human adrenal gland.