title: Homo- and hetero-oligomerization of PDZ-RhoGEF, LARG and p115RhoGEF by their C-terminal region regulates their in vivo Rho GEF activity and transforming potential.
abstract: PDZ-RhoGEF, LARG, and p115RhoGEF are members of a newly identified family of Rho-guanine nucleotide exchange factors (GEFs) exhibiting a unique structural feature consisting of the presence of an area of similarity to regulators of G protein signaling (RGS). This RGS-like (RGL) domain provides a functional motif by which Galpha(12) and Galpha(13) can bind and regulate the activity of these RhoGEFs, thus providing a direct link from these heterotrimeric G proteins to Rho. PDZ-RhoGEF and LARG can also be phosphorylated by tyrosine kinases, including FAK, and associate with Plexin B, a semaphorin receptor, which controls axon guidance during development, through their PDZ domain, thereby stimulating Rho. Interestingly, while characterizing a PDZ-RhoGEF antiserum, we found that a transfected PDZ-RhoGEF construct associated with the endogenous PDZ-RhoGEF. Indeed, we observed that PDZ-RhoGEF and LARG can form homo- and hetero-oligomers, whereas p115RhoGEF can only homo-oligomerize, and that this intermolecular interaction was mediated by their unique C-terminal regions. Deletion of the C-terminal tail of PDZ-RhoGEF had no significant effect on the GEF catalytic activity towards Rho in vitro, but resulted in a drastic increase in the ability to stimulate a serum response element reporter and the accumulation of the GTP-bound Rho in vivo. Furthermore, removal of the C-termini of each of the three RGL-containing GEFs unleashed their full transforming potential. Together, these findings suggest the existence of a novel mechanism controlling the activity of PDZ-RhoGEF, LARG, and p115RhoGEF, which involves homo- and hetero-oligomerization through their inhibitory C-terminal region.
authors.affiliation: Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892-4340, USA.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Chikumi
authors.forename: Ana
authors.initials: A
authors.lastname: Barac
authors.forename: Babak
authors.initials: B
authors.lastname: Behbahani
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gao
authors.forename: Hidemi
authors.initials: H
authors.lastname: Teramoto
authors.forename: Yi
authors.initials: Y
authors.lastname: Zheng
authors.forename: J Silvio
authors.initials: JS
authors.lastname: Gutkind
mesh_terms: D000818:Animals; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry* / Q000502:physiology; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D017470:Receptors, Glutamate / Q000737:chemistry* / Q000502:physiology; D064067:Rho Guanine Nucleotide Exchange Factors; D013329:Structure-Activity Relationship
chemical_list: C577234:ARHGEF11 protein, human; C577222:ARHGEF12 protein, human; C577223:Arhgef12 protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D017470:Receptors, Glutamate; D064067:Rho Guanine Nucleotide Exchange Factors