The recruitment of ERK, Cortactin, and WASP in the process of enzymatic secretion of Zymogen granules following CCK stimulation
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Cellular secretion has been extensively studied in physiology. It is the process whereby cellular products are released outside the cell for with the pancreatic secretion of digestive enzymes being the best example. The secretory vesicles are thought to move by cytoskeletal rearrangements in the cell to reach the plasma membrane. The goal of this research was to identify proteins that might contribute to cytoskeletal rearrangement and determine whether they assemble at zymogen granules during secretion. These protein integral components include extracellular signal-regulated protein kinase (ERK), Wiskott-Aldrich Syndrome protein (WASP), and cortactin. This research indeed confirmed the presence of all three protiens on the zymogen granule following stimulation with CCK (2nM). ERK became apparent on the zymogen granule during a time course after stimulation with 2nM CCK. The ERK phosphorylation at the zymogen granule was also shown to be dependent on protein kinase C (PKC) and phosphatidyl inositol 4,5 bisphosphate (PI3K). The presence of cortactin and WASP was observed on the zymogen granule and provides a potential role in the cytoskeletal rearrangement necessary to traffic the vesicles to the plasma membrane. It is proposed, through this research, that ERK phosphorylates cortactin at the zymogen granule. Cortactin will subsequently activate WASP, which then stimulates cytoskeletal rearrangements through the Arp2/3 complex. These changes in the cytoskeleton are likely necessary to move the vesicle to the plasma membrane for secretion.