Campus Access Only

All rights reserved. This publication is intended for use solely by faculty, students, and staff of University of the Pacific. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, now known or later developed, including but not limited to photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author or the publisher.

Role of ryanodine receptors in neuronal calcium signalling and growth control

Author

Diptiman Dipen Bose, University of the Pacific

Date of Award

2002

Document Type

Thesis - Pacific Access Restricted

Degree Name

Master of Science (M.S.)

Department

Pharmaceutical and Chemical Sciences

First Advisor

David Thomas

First Committee Member

Roshanak Rahimiam

Second Committee Member

James Uchizono

Abstract

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.

Pages

144

Recommended Citation

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