Purchase this article with an account.
Y. Tamada, E. Nakajima, M. Azuma, T.R. Shearer; Activation of Downstream Pathways after Calpain-induced Proteolysis in the Hypoxic Rat Retina . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3567.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: In our previous studies with rats, calpain-induced proteolysis was an important mid-stage event in retinal cell death induced in vivo by ischemia-reperfusion injury or by hypoxic cell culture. The purpose of present study was to identify the downstream pathways activated after calpain-induced proteolysis in hypoxic rat retinas. Methods: To induce hypoxia, rat retinas were incubated in RPMI medium without glucose under 95 % N2/5 % CO2. Leakage of LDH into the medium measured retinal cell death. Activation of calpain and proteolysis of calpain substrates were analyzed by casein zymography and immunoblotting. Results: LDH leaked into the medium from retinas under hypoxic conditions. Caseinolytic activity of calpains decreased with hypoxia, suggesting calpain activation followed by autolytic degradation. Caspase-3, previously identified as a executor of apoptosis, was cleaved by calpain to a 29 kDa fragment. This initial cleavage of caspase-3 is thought to facilitate subsequent cleavage into active caspase. αB-crystallin, whose interaction with caspase-3 prevents apoptosis, was degraded in retina with hypoxia. Cytoskeletal proteins such as α-spectrin and tau, required for the maintenance of proper membrane order and integrity, were proteolyzed in hypoxic retina. Conclusions: These results suggested that activation of caspase-3, reduction of the anti-apoptotic effect of αB-crystallin, and proteolysis of α-spectrin and tau after calpain activation contributed to retinal cell death induced by hypoxia in vitro. Dr. Shearer has a significant financial interest (research contract and consulting fee) in Senju Pharmaceutical Co., Ltd.
This PDF is available to Subscribers Only