Rho GTPases control a complex network of intracellular signalling pathways. Whereas progress has been made in identifying downstream signalling partners for these proteins, the characterization of Rho upstream regulatory guanine-nucleotide exchange factors (GEFs) has been hampered by a lack of suitable research tools. Here we use small interfering RNAs (siRNAs) to examine the cellular regulation of the RhoB GTPase, and show that RhoB is activated downstream of the epidermal-growth-factor receptor through the Vav2 exchange factor. These studies demonstrate that siRNAs are an ideal research tool for the assignment of Rho GEF function in vivo.

Abbreviations used: DMEM, Dulbecco's modified Eagle's medium; EGF, epidermal growth-factor; GEF, guanine-nucleotide exchange factor; GST, glutathione S-transferase; LPA, lysophosphatidic acid; siRNA, small interfering RNA.

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