AJP - Endocrinology and Metabolism, Vol 251, Issue 6 707-E714, Copyright © 1986 by American Physiological Society
Expression of a cholecystokinin precursor-related peptide in vertebrate and invertebrate tissues
B. S. Schneider, J. Maimon and J. Friedman
We have developed a radioimmunoassay for the nonapeptide predicted by cDNA
sequence analysis to reside at the extreme C-terminus of the mouse
cholecystokinin (CCK) precursor. Sensitivity of the assay is 1 pg synthetic
CCK precursor-related peptide (CCK-PRP)/ml. The antibody has no
cross-reactivity with cholecystokinin, gastrin, or a variety of other known
neuropeptides. We have employed this assay to demonstrate the presence, in
rodent brain, gut, and peripheral plasma, of peptides with immunological
properties that are identical to, and gel filtration characteristics that
are very similar to, those of the synthetic CCK-PRP. We have also detected
a similar peptide in the culture media of a human CCK-producing tumor. The
molar ratios of immunoreactive CCK-PRP/CCK vary widely among tissues of
origin and during ontogeny, suggesting regional and developmental
differences in the turnover rates or in posttranslational modification of
the two peptides. Our studies suggest that peptides very similar to intact
CCK-PRP are posttranslationally liberated from the cholecystokinin
precursor in a variety of tissues and may have neurotransmitter and/or
hormonal functions distinct from those of CCK. Relatively high quantities
of material immunologically indistinguishable from CCK-PRP were also found
in several coelenterate species, indicating that this epitope arose as
early in evolution as did CCK.
