RASGRP1 and rheumatoid arthritis: With this regard, converging findings have indicated that the gene coding for the guanine-nucleotide-exchange factor 1 (RASGRP1), an enzyme that catalyzes the exchange of a G-protein bound guanosine diphosphate (GDP) to guanosine triphosphate (GTP) in manifold biochemical processes [15] and whose locus is genome-wide associated with SCZ and RA [16], is a putative link between SCZ and alteration of the immune system.