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J.P. Alexander, V. Currie, A. Park, T. Acott; Calpains in the Trabecular Meshwork . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1144.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To characterize the calpain enzymes in the trabecular meshwork. Methods: Porcine trabecular meshwork (TM) cells were dissected from fresh tissue, enzymatically dispersed, and grown in DMEM with 10% FCS to passage three. Confluent cells were made serum free for 24 hours, then treated with agonists (PMA, IL-1α, IL-1ß, TNF-α, Retinoic acid) for 24 hours. Cells were lysed in SDS PAGE sample buffer with proteinase inhibitors, and lysates were electrophoresed in 10% SDS PAGE gels. Gels were blotted onto PVDF, blocked with 3% non-fat dry milk in PBS, then incubated with antibodies to calpains. After secondary antibody incubation and washes, bands were visualized by BCIP/NBT. Results: Porcine trabecular meshwork cells in culture produce a number of calpain enzymes, including calpain-1, 2, 3, 5, 6, 7, 9, 10, 11, 12, 13, and 15, as well as calpain small subunit-1. Treatment with agonists did not markedly change calpain levels, but did increase processing of calpains. Conclusions: Trabecular meshwork cells produce both "classical" calpains (calpain-1 and calpain-2) and "novel" calpains. Calpain-1 and calpain-2 are ubiquiteously expressed, and differ in their sensitivity to calcium, while the novel calpains are thought to be more tissue specific, and regulated differently. Trabecular meshwork cells are phagocytically active, and the calpains may play a role in degredation of ECM components. Calpains are also thought to play a role in signal transduction, cleaving protein kinase-C to produce a constituitevly active form. Apoptosis is also a target, and calpains are thought to cleave caspase-3. The diverse mix of calpains in the TM suggests a wide variety of roles, and a need for further study.
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