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Date of Award
Thesis - Pacific Access Restricted
Master of Science (M.S.)
Pharmaceutical and Chemical Sciences
First Committee Member
Second Committee Member
The versatility of Ca2+ as a messenger regulating a myriad of signalling events requires that the concentration of Ca2+ ions in the cytoplasm be highly regulated. Capacitative Ca2+ entry (CCE) or store-operated Ca2+ (SOC) entry, whereby the depletion of intracellular Ca2+ stores induces the influx of Ca2+ across the plasma membrane, plays a crucial role in Ca2+ signalling. Despite the recent advances in elucidating the entry pathway, its molecular identity, biophysical properties and store-depletion signal remains undefined. Thapsigargin (TG), a sarcoplasmic/endoplasmic reticulum Ca2+ A TPase pump (SERCA), inhibitor induces passive depletion of the internal Ca2+ stores and triggers CCE. The universality of this signal has been widely accepted and TG has proven to be a valuable tool in studying CCE. The neuronal cell line NG 115 -401 L lacks the TG activated Ca2+ influx pathway. Agonists of the ryanodine receptor (RyR); chlorom- cresol (CMC), polychlorinated biphenyl 95 (PCB), ryanodine, caffeine, and that of the inositol-1 ,4 ,5-trisphosphate receptor (IP3R), bradykinin, effectively couple to the activation of Ca2+ influx in these cells. The Ca2+ influx signal due to these agonists can be inhibited by SOC blockers such as La3+, Zn2+, Ni2+ and SF&F 96365. Thapsigargin, CMC and PCB95 share the same Ca2+ releasable pools in the 401 L cells. Our data thus suggests that the channels present in the 401 L cells are likely to be receptor-activated channels rather than the store-depletion activated channels. Cell viability studies show that thapsigargin (25 nM) can decrease viability by 75% within 24 hrs and the RyR agonist caffeine decreased viability to <60% within 24hrs. CMC, PCB95 and ryanodine also were cytotoxic at higher doses. Nuclear fragmentation patterns and activation of caspase-3 in thapsigargin and caffeine-treated cells suggest the induction of apoptosis within 12 hrs of treatment. The treated cells were shown to generate nitric oxide, a potential apoptosis inducing agent.
Bose, Diptiman Dipen. (2002). Role of ryanodine receptors in neuronal calcium signalling and growth control. University of the Pacific, Thesis - Pacific Access Restricted. https://scholarlycommons.pacific.edu/uop_etds/566
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