M.S. (Master of Science)
Department of Biological Sciences
Pancreatic acinar cells; Cellular signal transduction; Pancreas--Cytology
This thesis has outlined several parallel pathways leading to the activation of ERK in the pancreatic acinar cell. The objectives of this thesis were: (1) to demonstrate that CCK can promote both secretion and ERK activation, (2) to identify which PKC isoforms lead to the activation of ERK, (3) to determine whether the pancreatic ERK pathway operates through the Shc-Grb2-SOS-Ras complex, (4) to identify the signaling proteins that form a complex with She, and (5) to establish the role of Ca2+ in the activation of ERK. Acinar cells were isolated from the rat pancreas and treated with agonists and/or inhibitors of the ERK signaling pathway. Protein activation was monitored by the level of tyrosyl phosphorylation, immunoprecipitation, Western blotting, and densitometry. The results show that PKC 0 is necessary to promote She phosphorylation, likely through activation of a Src tyrosine kinase. JAK and PI3K were shown to coprecipitate with She, although the exact role of this interaction remains to be elucidated. Furthermore, PKC e and/or 8 appear(s) to directly phosphorylate Raf, based on differential levels of ERK and She phosphorylation after treatment with GF109203X, a selective inhibitor of a, e, and 8 PKC isoforms. The results also show that Ca2+ decreases ERK phosphorylation. BAPTA-AM chelation of intracellular Ca2+caused a 60% increase in CCKpromoted ERK phosphorylation, while increases in Ca2+caused an 80% decrease in CCK phosphorylation of ERK. However, results also show that Ca2+ is an absolute requirement for the exocytotic branch of CCK stimulation in the exocrine pancreas. CCK stimulation promotes both exocytosis and synthesis, and Ca2+ may likely serve as a coordinator of these two aspects, ensuring that protein synthesis levels correlate with the rate of enzyme release during secretion. Taken together, the results demonstrate that ERK activation requires different PKC isoforms at various stages, PI3K and JAK contribute to the activation, and Ca2+down regulates all aspects of the ERK pathway.
Kein, Heidi Marie, "Signal transduction in pancreatic acinar cells" (2000). Graduate Research Theses & Dissertations. 4914.
vii, 86 pages
Northern Illinois University
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Includes bibliographical references (pages -86)