The spectrum of endogenous human chromogranin A-derived peptides identified using a modified proteomic strategy.
The hypothesis that chromogranin A (CgA), a protein of neuroendocrine cell secretory granules, may be a precursor of biologically active peptides, rests on observed activities of peptide fragments largely produced by exogenous protease digestion of the bovine protein. Here we have adopted a modified proteomic strategy to isolate and characterise human CgA-derived peptides produced by endogenous prohormone convertases. Initial focus was on an insulinoma as previous studies have shown that CgA is rapidly processed in pancreatic beta cells and that tumours arising from these express appropriate prohormone convertases. Eleven novel peptides were identified arising from processing at both monobasic and dibasic sites and processing was most evident in the C-terminal domain of the protein. Some of these peptides were identified in endocrine tumours, such as mid-gut carcinoid and phaeochromocytoma, which arise from endocrine cells of different phenotype and in different anatomical sites. Two of the most interesting peptides, GR-44 and ER-37, representing the C-terminal region of CgA, were found to be amidated. These data would imply that the intact protein is C-terminally amidated and that these peptides are probably biologically active. The spectrum of novel CgA-derived peptides, described in the present study, should provide a basis for biological evaluation of authentic entities.
Orr
David F
DF
School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland. df.orr@ulst.ac.uk
Chen
Tianbao
T
Johnsen
Anders H
AH
Chalk
Rod
R
Buchanan
Keith D
KD
Sloan
James M
JM
Rao
Pingfan
P
Shaw
Chris
C
D000595:Amino Acid Sequence; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D053379:Chromogranin A; D002864:Chromogranins / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D007340:Insulinoma / Q000737:chemistry / Q000378:metabolism; D008099:Liver / Q000473:pathology; D008297:Male; D013058:Mass Spectrometry; D008875:Middle Aged; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D040901:Proteomics / Q000379:methods*; D015203:Reproducibility of Results
C506150:CHGA protein, human; D053379:Chromogranin A; D002864:Chromogranins; D010446:Peptide Fragments