Rho guanine nucleotide exchange factor (RGNEF) is a prosurvival factor under stress conditions

Rho guanine nucleotide exchange factor (RGNEF) is a 190kDa RNA binding protein (RBP) that also contains a Dbl/PH domain capable of RhoA activation. Consistent with a key role in the pathogenesis of amyotrophic lateral sclerosis (ALS), RGNEF forms pathological neuronal cytoplasmic inclusions in degenerating spinal motor neurons. To further understand the role of RGNEF in the stress response, we first observed that the expression of RGNEF is upregulated in murine spinal motor neurons following distal sciatic nerve injury. Secondly, in response to in vitro cellular stress (500μM sodium arsenite for 1h; or 400mM sorbitol 1 hour exposure; as an oxidative or osmotic stress, respectively), we observed a significant survival benefit in RGNEF-transfected HEK293T cells. Using deletion constructs, we found that the NH₂-terminus domain is essential for this protective effect. Interestingly, we observed that under stress conditions RGNEF associates with Staufen1 positive granules but not TIA-1-positive stress granules. These findings support the hypothesis that RGNEF plays a critical role both in RNA homeostasis and in the response to cell stress.