Purchase this article with an account.
A. Anderssohn, K.A. Cox, S.C. Dees, M. Hosseini, T.S. Acott; The Function of Myocilin as a Molecular Chaperone . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1360.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Myocilin is the gene product of the GLC1A region of chromosome 1, and is known to be associated with certain forms of primary open angle glaucoma. Myocilin is located within both ocular and nonocular tissues, and its levels have been observed to increase upon various conditions associated with stress. The function of myocilin is poorly understood. This study investigated the possible function of myocilin as a molecular chaperone. Methods: Myocilin was isolated and purified from tissue culture media of porcine trabecular meshwork cells that were previously treated with 10 µM dexamethasone. The ability of myocilin to protect against the thermal inactivation and thermal aggregation of citrate synthase activity was assessed using UV–Vis spectroscopy and light scattering experiments, respectively. Agarose gel electrophoresis was employed in order to examine the ability of myocilin to protect against the thermal inactivation of restriction endonucleases. Results: Citrate synthase activity at 55oC exhibits strict time dependence with respect to heat inactivation. The protection of citrate synthase activity by myocilin is distinctly concentration dependent, with the optimal protection of 1.5 uM citrate synthase afforded by approximately 0.65 µM myocilin. Full restoration of activity was observed after five minutes of thermal inactivation at 55oC, with slight difference noted in initial rates of reaction. Furthermore, 0.65 µM myocilin is capable of partially restoring citrate synthase activity after 10 minutes of heat inactivation (values = 50% of controls). In comparison, 0.65 µM bovine serum albumin (BSA) was much less effective at protecting the activity of citrate synthase, while maximum protection was observed with 60 µM BSA (12.3% and 75.3% of controls, respectively). The presence of approximately 0.22 uM myocilin significantly reduces the thermal aggregation of 0.50 µM citrate synthase by 57% – 80%. In addition, myocilin is able to partially protect against the thermal inactivation of the restriction endonuclease Drd I at 58oC. Conclusions: Myocilin appears to serve as a molecular chaperone for several enzymes.
This PDF is available to Subscribers Only