The performance of the mammalian brain is dependent on a continuous supply of oxygen and glucose. When brain cells are deprived of these nutritive substances present in blood, neuronal function and viability are endangered. Little is known regarding the mechanisms that operate during such ischemic insult or the factors that favor recovery. It is recognized however, that ischemic brain cells rapidly synthesize and release unsaturated fatty acids and platelet activating factor (PAF), both of which act to release calcium from its intracellular site of storage known as the endoplasmic reticulum (ER). Dr. Brostom has provided evidence that calcium mobilization from the ER provokes rapid shutdown of the synthesis of all cellular proteins. Upon continued incubation, recovery of protein synthesis is observed immediately when preceded by an increase in a glucose-related protein, GRP78, a resident of the ER. GRP78 is hypothesized to function in protein processing, the last stage of protein synthesis. This research will investigate the importance of this protein in the functioning of neurons with depleted calcium stores. Neuronal cells in culture will constitute the primary model system. Gene expression for GRP78 will be modulated to prove that an increase in this ER protein is required for the recovery phase. Efforts will be made to determine the importance of GRP78 content in the processing of proteins by neurons with inadequate ER calcium. Experiments using free fatty acids and PAF will be performed to test for the capacity of influencing protein synthesis, protein processing and GRP78 content under conditions that prevail during brain ischemia. Results from this study will provide insight on the role of GRP78 during the regulation of protein synthesis in neuronal ischemia.
