Disease relevance of Rhoa

• Enteropathogenic Escherichia coli activates the RhoA signaling pathway via the stimulation of GEF-H1 [1].
• Rac1/Cdc42 and RhoA GTPases antagonistically regulate chondrocyte proliferation, hypertrophy, and apoptosis [2].
• Deleted in liver cancer 2 (DLC2) suppresses cell transformation by means of inhibition of RhoA activity [3].
• We previously showed that RhoA played an important role in the proliferation of murine We prostate cancer (TRAMP) cells (P. M. Ghosh et al., Oncogene, 18: 4120-4130, 1999) [4].
• The overall pathway to primitive endoderm formation was shown to be inhibited by treatment with Clostridium botulinum C3 exotoxin, a specific inactivator of RhoA family members [5].

High impact information on Rhoa

• YpkA inhibits nucleotide exchange in Rac1 and RhoA, and mutations that disrupt the YpkA-GTPase interface abolish this activity in vitro and impair in vivo YpkA-induced cytoskeletal disruption [6].
• Activated alleles of Cdc42 and Rac1, but not RhoA, stimulate pp70S6k activity in multiple cell types [7].
• Analysis by mass spectrometry and amino-acid sequencing of proteolytic peptides derived from CNF1-treated RhoA indicate that CNF1 induces deamidation of a glutamine residue at position 63 (Gln 63) to give constitutively active Rho protein [8].
• Overexpression of RhoA or activated RhoA in NIH 3T3 cells increased phosphorylation of MBS and MLC [9].
• In lymphoid cells transfected with formyl peptide or interleukin-8 receptors, agonist stimulation activated nucleotide exchange on the small guanosine triphosphate-binding protein RhoA in seconds [10].

Chemical compound and disease context of Rhoa

• We now report the isolation of a rat cDNA encoding a 150-kDa protein, which specifically binds RhoA in its GTP form and contains an N-terminal serine/threonine kinase domain highly related to the human myotonic dystrophy kinase and a cysteine-rich domain toward the C terminus [11].
• Potential targets of therapeutic intervention include the cytoplasmic phosphatase calcineurin and small guanosine triphosphate-binding proteins, such as Rac1 and RhoA, all of which have been implicated in maladaptive hypertrophy [12].
• Western blotting showed that protein expression of RhoA, RhoB and Cdc42 RhoGTPases dramatically increased, in a programmed manner, during neuronal differentiation of P19 mouse embryonal carcinoma cells with retinoic acid [13].
• Overexpression of p116Rip in neuroblastoma cells inhibits RhoA-mediated cell contraction induced by lysophosphatidic acid (LPA); so far, however, the function of p116Rip is unknown [14].
• OBJECTIVE: To investigate the role of Rho A and Rho-kinase in acute myocardial ischemia/reperfusion injury and the protective effect of Rho-kinase inhibitor, Y-27632 [(R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)cyclohexanecarboxamide] [15].

Biological context of Rhoa

• Our results obtained from gene-targeted primary MEFs indicate that Rac1 is essential not only for lamellipodia induction but also for the RhoA-regulated actin stress fiber and focal adhesion complex formation and that Rac1 is involved in cell survival regulation through anoikis-dependent as well as -independent mechanisms [16].
• Here we show that the small GTPases, Rac1 and Cdc42, accelerate the rate of chondrocyte differentiation and apoptosis, thereby antagonizing the activity of RhoA [2].
• Inhibition of RhoA by Tat-C3 blocked phosphorylation of p47(PHOX) [17].
• Downstream components of RhoA required for signal pathway of superoxide formation during phagocytosis of serum opsonized zymosans in macrophages [17].
• Tat-C3 blocked superoxide production, suggesting that RhoA is essentially involved in superoxide formation during phagocytosis of SOZ [17].
• RhoA is activated at the leading edge of fibroblasts during wound healing migration and active RhoA colocalizes with mDia1 at the wound edge [18]

Anatomical context of Rhoa

• A recent study showed that microtubule-bound GEF-H1, a RhoA-specific guanine nucleotide exchange factor, was converted to its active form by microtubule destabilization, and this sequence of events resulted in RhoA stimulation [1].
• Unexpectedly, deletion of Rac1 also abolished actin stress fibers in the cells without detectable alteration of endogenous RhoA activity [16].
• Dendrite development in neurons is one of the bases for the formation of a complex neuronal network in the nervous system, and involvement of the Rho family GTPases, including Rac1, Cdc42, and RhoA, in dendrite formation has been demonstrated [19].
• RhoA GTPase regulates L-type Ca2+ currents in cardiac myocytes [20].
• RhoA GTPase regulates B cell receptor signaling [21].

Associations of Rhoa with chemical compounds

• Inhibition of RhoA-activated kinase (ROCK), an important downstream effector of RhoA, by Y27632 and myosin light chain kinase (MLCK) by ML-7 abrogated superoxide production by SOZ [17].
• The RhoA-specific inhibitor, C3 toxin, inhibited both BCR-dependent calcium flux and cell proliferation [21].
• RhoA is important for BCR-dependent synthesis of IP(3) by PLCgamma2, but is not required for tyrosine phosphorylation of PLCgamma2 [21].
• BCR-dependent synthesis of phosphatidylinositol-4,5-bisphosphate (PtdIns-4,5-P(2)) is inhibited in the absence of RhoA function [21].
• The RhoA and RhoC proteins regulate numerous effector proteins, with a central and vital signaling role mediated by the ROCK I and ROCK II serine/threonine kinases [22].

Physical interactions of Rhoa

• Leukemia-associated Rho guanine nucleotide exchange factor promotes G alpha q-coupled activation of RhoA [23].
• The RhoA/RhoGDI complex, purified to greater than 98% at high yield from the yeast cytosolic fraction, could be stoichiometrically ADP-ribosylated by Clostridium botulinum C3 exoenzyme, contained stoichiometric GDP, and could be nucleotide exchanged fully with [3H]GDP or partially with GTP in the presence of submicromolar Mg2+ [24].
• We have developed a Rho activation assay that is based on the specific binding of active RhoA to its downstream effector Rho-kinase (ROK) [25].

Regulatory relationships of Rhoa

• In the present study, using NIH3T3 cells stably transfected with CCK-A receptors as a model cell, we demonstrate that CCK can induce actin stress fibers through a G13- and RhoA-dependent mechanism [26].
• CCK-A receptor activates RhoA through G alpha 12/13 in NIH3T3 cells [26].
• RhoA/ROCK signaling regulates Sox9 expression and actin organization during chondrogenesis [27].
• Thus, mNET1 can activate signalling pathways in addition to those directly controlled by activated RhoA [28].
• RhoA signaling was activated as early as 5 min following TGF-beta addition [29].
• Foxj1 expression coincided with actin web formation, activated RhoA and RhoB, and persisted despite RhoA inhibition, suggesting that Foxj1 promoted RhoA during ciliogenesis [30].

Other interactions of Rhoa

• By contrast, Galpha(13)Q226L activated RhoA but not Rac1 or Cdc42 [31].
• Our data clearly show that G12/G13 as well as Gq/G11 alone can couple GPCRs to the rapid activation of RhoA [32].
• The central nervous system abnormalities of Jip3-/- mice may be accounted for in part by a reduction in signal transduction by RhoA and its effector ROCK [33].
• Finally, EphB-mediated RhoA activation is disrupted by FAK knock-down [34].
• Expression of the constitutively active mutant form of p115RhoGEF (guanine nucleotide exchange factor) was found to activate RhoA and JNK1 activities [5].

Analytical, diagnostic and therapeutic context of Rhoa

• Actin stress fibers and translocation of active v-Src to focal adhesions in quiescent Swiss 3T3 cells were restored by microinjection of activated Rho A and by serum [35].
• Immunohistochemistry, immunoblotting, and reverse transcriptase-PCR indicated that RhoA, a small GTPase signaling protein, is abundant in undifferentiated embryonic mesenchymal cells and that its levels decrease along with SM myogenesis [36].
• Using immunoblot analysis and the PCR, we found evidence that RhoA, Rac1, and Cdc42 all are expressed in NG108-15 cells [37].
• Here, we report that FAK interacts with p190RhoGEF, a RhoA-specific GDP/GTP exchange factor, in neuronal cells and in brain tissue extracts by co-immunoprecipitation and co-localization analyses [38].
• Protein levels of RhoA and RhoC in ESCC cell lines were visualised by Western blotting, and showed highest expression in TE-2 cells [39].

References