Role of Myocilin Proteolytical Processing in Myocilin-Myocilin Interactions

Abstract

Purpose: : Myocilin is a matricellular glycoprotein that is mutated in some forms of glaucoma. This protein is present in ocular tissues as large molecular aggregates and consists of an N-terminal leucine-zipper-like domain, a central linker region, and a C-terminal olfactomedin-like domain. Recently we have described that myocilin can be proteolitically cleaved in the middle of the polypeptide chain splitting the N- and C-terminal domains in cells in culture. There are evidences indicating that this processing also occurs in ocular tissues. The purpose of this work was to explore the possible effect of this proteolytical processing in myocilin-myocilin interactions.

Methods: : Human recombinant myocilin was produced in 293-T cells under different culture conditions and the aggregates were analyzed by western blot. Molecular interactions of full-length myocilin and its N- and C-terminal fragments, purificated by Ni-chelating chromatography, were analyzed by solid phase binding assays in ELISA plates.

Results: : Activation of myocilin processing reduced the amount of myocilin homo-aggregates. Solid phase binding assays indicate that the cleaved fragments of myocilin also interact with the full-length protein, although with lower affinity.

Conclusions: : Altogether these results indicate that the proteolytical processing of myocilin reduces its aggregation and could regulate myocilin-myocilin interactions.

Keywords: protein purification and characterization • extracellular matrix • proteolysis