p63RhoGEF and GEFT are Rho-specific guanine nucleotide exchange factors encoded by the same gene

Abstract

Activation of Rho GTPases, which play pivotal roles in diverse cellular functions, is catalysed by specific guanine nucleotide exchange factors (GEFs). We and others (Souchet et al. (2002)) independently cloned a human cDNA encoding a 580 aa protein (p63RhoGEF), which contains a tandem of Dbl homology and pleckstrin homology domains typical for RhoGEFs. In accordance with Souchet et al., recombinant p63RhoGEF interacted with and catalysed GDP/GTP exchange at RhoA, but not Rac1 or Cdc42. Recently, an N-terminally truncated form of p63RhoGEF, termed GEFT, was described as a Rac/Cdc42-specific GEF (Guo et al. 2003). As judged by RT-PCR with specific primers, we were able to detect mRNA variants encoding p63RhoGEF and GEFT within several tissues and cell lines. Apparently, they co-exist within one cell and are derived from the same gene. When expressed in human embryonic kidney cells, both p63RhoGEF and GEFT caused activation of RhoA, but not Rac1 or Cdc42, and induced serum response factor-mediated gene transcription, which was fully blunted by the Rho-inactivating C3 transferase. In line with these data, expression of either p63RhoGEF or GEFT in J82 human bladder carcinoma cells induced the formation of actin stress fibres. We therefore conclude that p63RhoGEF and GEFT are apparently isoforms derived from the same gene and that GEFT, similar to p63RhoGEF, activates RhoA in several cell types.

Gαq Directly Activates p63RhoGEF and Trio via a Conserved Extension of the Dbl Homology-associated Pleckstrin Homology Domain

“…To generate a soluble p63RhoGEF DH fragment, we used a TEV-cleavable MBP fusion at the N terminus; both MBP fusion and TEV-treated DH constructs retained similar activity toward RhoA. Whereas there is conflicting literature regarding the regulatory role of the PH domain of p63RhoGEF, our results are in accordance with previous studies that suggest an autoinhibitory role (43,44).…”

“…Previous studies have demonstrated that the DH domain of p63RhoGEF activated serum response factor-dependent gene transcription more robustly than full-length protein (44). Previous work has also shown that the PH domain functioned in trans as a dominant-negative by reducing serum response factor-dependent gene transcription mediated by full-length (43) or isolated DH domains (44). However, conflicting reports also suggest the PH domain is essential for induction of stress fibers (49); additional studies may be needed to explore the membrane-targeting capacity of the PH domain and other associated in vivo roles.…”

Comparative pharmacological analysis of Rho-kinase inhibitors and identification of molecular components of Ca2+ sensitization in the rat lower urinary tract

“…Leukemia-associated RhoGEF (LARG) and its homologs PDZ-RhoGEF and p115RhoGEF make up a subgroup of RhoGEFs, known as regulators of G protein signaling (RGS) domain-containing RhoGEFs. To our knowledge, the present report represents the first demonstration of the expression of these RhoGEFs in the lower urinary tract at both gene and protein levels, although another GEF, namely p63RhoGEF, is expressed and binds to RhoA in J82 human bladder carcinoma cells [48]. Because the activation of RhoA comes from an increased activity of RhoGEF or decreased RhoGDI, the lower expression level of PDZ-RhoGEF may explain the lack of effect of Rho-kinase inhibitors to reduce baseline tension in the urethra, given the centrality of RhoGEFs for RhoA activation, notwithstanding that RhoA levels were not different among detrusor, trigonal and urethral strips.…”

GEFT, A Rho Family Guanine Nucleotide Exchange Factor, Regulates Neurite Outgrowth and Dendritic Spine Formation

“…Although GEFT expression induces neuronal outgrowth, a process attributed to the activation of both Rac1 and Cdc42 and inhibited by RhoA, GEFT shows no specificity in catalyzing the GDP-to GTP-bound state for any Rho-GTPase in the N2A cells. It has previously been demonstrated that GEFT is most specific for Rac1 and Cdc42 in NIH3T3 cells, and multiple studies suggest that GEFT could regulate RhoA in a cell-type specific manner (22,24,25).…”

“…Expression of GEFT has been shown to promote the formation of lamellipodia, actin microspikes, and filopodia in NIH3T3 cells via activation of the Rho family of small GTPases (22). A potential splice variant of GEFT, encoding the gene for p63RhoGEF, has also been identified and shown to be highly expressed in both the brain and heart, and it induces a RhoAdependent stress fiber formation in several cell types (24,25). Using primary hippocampal neurons and Neuro2a (N2A) neuroblastoma cell lines, we examined the role that GEFT plays in the regulation of dendritic spine morphogenesis and neurite outgrowth.…”