The somatostatins constitute a family of structurally related small peptides synthesized as large precursors within multiple organs, including the islets, intestine and central and peripheral nervous systems. They serve both hormonal and paracrine functions in the regulation of secretions and probably as neurotransmitters and/or neuromodulators; their actions are essential for metabolic homeostasis. The production of the somatostatins is, in turn, regulated by hormonal and paracrine influences. We plan to investigate at a molecular level the cellular mechanisms involved in the expression of the somatostatin gene.
Aims of this proposal are: 1) To determine the aspects of the primary structure of prosomatostatin required for accurate post-translational processing to somatostatin-28 and somatostatin-14 utilizing site-specific mutagenesis of the somatostatin coding sequence in a recombinant fusion gene introduced and expressed in foreign cell lines; 2) To analyze the patterns of somatostatin gene expression in various organs and tissues of transgenic mice in which the somatostatin fusion gene has been integrated in the germ line of the mice. These studies will involve analyses of the patterns of integration of the somatostatin gene in mouse genome, qualitative levels of somatostatin transcripts, the efficiency and fidelity of processing of prosomatostatin to somatostatin-14 and somatostatin-28, immunocytochemical and histohybridizational localization of cell types expressing the somatostatin gene and the effects of prolonged, excessive levels of somatostatin on the production of growth hormone, growh hormone-releasing hormone, thyrotropin, glucagon, and insulin. 3) Analyses in pancreas and pancreatic islets of somatostatin mRNA, along with corresponding levels of mRNAs encoding glucagon and insulin in response to physiologic (dietary) manipulations of rats in both normal and diabetic animals; 4) Studies in hypothalamic explants and dispersed cell cultures of the effects of known regulators of somatostatin secretion on the production of mRNA encoding somatostatin. The results of these studies may provide information relevant to the pathogenesis of diabetes mellitus and other disorders of hormone deficiencies, as well as insights into the functions of the somatostatins in the central and as well as insights into the functions of the somatostatins in the central and peripheral nervous systems.
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