CHROMOGRANIN &THE NEUROENDOCRINE SYSTEM

The protein chromogranin, which was originally isolated from adrenal
chromaffin granules has been found to be a pan-marker for neuroendocrine
cells. The proposed experiments aim toward understanding the nature of
chromogranin structure and expression. Using cDNA for chromogranin, the
number of mRNAs coding for chromogranin will be assessed. The peptide
fragments of the various forms of chromogranin will be compared in order to
further understand their interrelationships, and to determine the location
of proteolytic cleavage sites. Heterogeneity in chromogranin
immunostaining, both in tissue sections and in cultured cells will be
studied. The relationship of functional status to chromogranin
immunoreactivity will also be explored. The time of appearance of
chromogranin in development of neuroendocrine tissues will be studied by
immunohistochemistry and in situ hybridization. The extent of
phosphorylation of membrane and soluble chromogranin will be compared.
Incorporation of 32P in chromaffin granules will be measured. The position
of phosphorylation sites will be located.