SUMO-Conjugated RanGAP1 Is A Major Lens Protein Regulating MAP Kinase Pathway and MicroRNA Distribution

Abstract

Purpose: The nuclear Ras-related protein Ran binds guanine nucleotide (called RanGAP1) and is involved in cell cycle regulation. Whether RanGAP1 is expressed in lens and plays a role during lens differentiation remains unknown. The present study reports our initial identification of RanGAP1 as a major lens protein with important functions in regulation both signaling pathways and microRNA distribution.

Methods: Mass Spectrometry was used to identify and purify RanGAP1. Immuno-fluorescence and Western blot analysis were used to detect the expression patterns of RanGAP1 in developing mouse lens and lens epithelial cells. In vitro and in vivo experiments were used to confirm the SUMOylation regulation of RanGAP1. Lens epithelial cell differentiation and viability were analyzed in the presence or knockdown of RanGAP1. Various signal transduction pathways and microRNA distribution were analyzed in the presence or knockdown of RanGAP1.

Results: In lens systems, RanGAP1 is highly expressed in the ocular lens and lens epithelial cells. Changes in the level of RanGAP1 expression cause altered viability and differentiation pattern of lens epithelial cells. RanGAP1 is also involved in regulating MAP kinase pathway and distribution of over a dozens of microRNAs.

Conclusions: RanGAP1 is a major lens protein that executes important functions in different biological processes. Its functions is highly regulated by SUMOylation.

Keywords: 497 development • 714 signal transduction • 533 gene/expression