Juvenile-onset diabetes mellitus is characterized by a severe insulin deficiency. Epidemiological studies and investigations using mice and human pancreatic cells suggest that the disease may be caused by certain viruses. However, the molecular mechanism which produces this insulin deficiency has not been established. The long-term goals of the proposed research are: (1) To ascertain whether the insulin deficiency virus-induced diabetes is the consequence of destruction of pancreatic beta cells or of survival of infected beta cells with impaired function affecting the synthesis or secretion of insulin. (2) To examine whether the virus strain and the host strain influence the mechanism of insulin synthesis inhibition. Using diabetes-prone and resistant mice and diabetogenic and nondiabetogenic variants of coxsackievirus B4, the specific aims for the grant period are: (1) Protein studies to correlate virus-induced diabetogenic activity with beta cell survival, insulin synthesis and its secretion; (2) mRNA studies to correlate insulin synthesis with the amount of mRNA; and (3) receptor studies to determine whether the unique susceptibility of beta cells from certain mouse strains to virus infection is controlled by the cell surface receptors. Various techniques of molecular biology (such as, cell-free protein synthesis, high resolution gel electrophoresis, cloning, hybridization, etc.) and immunology (such as, immunoprecipitation, indirect immunofluorescence assay) will be used to analyze the number of insulin-containing beta cells, proportion of beta cells actively infected with the virus, synthesis and cleavage of insulin precursors, release of nascent insulin, production and availability of insulin mRNA for translation and binding of virus to beta cell receptors. The study will further assess the role of viral etiology in juvenile onset diabetes, define the mechanism which produces insulin deficiency and may lead to a better understanding of virus-inuced cell death.
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