Rac1 is a novel interactor of Drosophila guanine nucleotide exchange factor GEFmeso.

Guanine nucleotide exchange factors (GEF) are proteins that regulate the activity of GTPases by catalysing the exchange of GDP for GTP. In this work, we studied the interaction of various Rho family GTPases CDC42, Rac1 and RhoA with GEFmeso, a GEF expressed in Drosophila melanogaster (fruit fly). The interaction of GEFmeso with Rho family GTPases was studied by means of guanine nucleotide exchange assays. Our results suggest that GEFmeso interacts with Rac1 in addition to its interaction with CDC42 and Ral, which was reported earlier. We propose that the guanine nucleotide exchange factor GEFmeso is involved in a developmental process that requires the synergistic action of CDC42 and Rac1 during Drosophila development.