Disease relevance of RHOA

• In this report, we have isolated several RHOA cDNAs from a multidrug-resistant MCF-7 human breast cancer cell line [1].
• Immunohistochemistry and immunoblotting were used to determine RHOA and RND protein expression and localization in nonpregnant, pregnant nonlaboring, and laboring patients at term and patients in spontaneous preterm labor [2].
• In addition, overexpression of NF-kappaB p50 induced RhoA activity and Rock-mediated formation of stress fiber in melanoma cells [3].
• Although the RhoA and RhoC proteins comprise an important subset of the Rho GTPase family that have been implicated in invasive breast carcinomas, attributing specific functions to these individual members has been difficult [4].
• Cell lysates from Sf9 insect cells infected with recombinant baculovirus encoding myr 5 exhibited increased GAP activity for RhoA but not for Cdc42Hs or Rac1 [5].

Psychiatry related information on RHOA

• We suggest that high expression of RhoA contributes, through RhoA-mediated Ca(2+) sensitization, to the flaccid state of CC that can be reversed by a water-soluble, orally active Rho kinase inhibitor suitable for therapy of erectile dysfunction [6].

High impact information on RHOA

• Members of the Rho family of small Ras-like GTPases--including RhoA, -B, and -C, Rac1 and -2, and Cdc42--exhibit guanine nucleotide-binding activity and function as molecular switches, cycling between an inactive GDP-bound state and an active GTP-bound state [7].
• RhoA and hence to ROK through a mechanism involving association of GEF, RhoA, and ROK in multimolecular complexes at the lipid cell membrane [8].
• We suggest that the RhoA/ROK pathway is constitutively active in a number of organs under physiological conditions; its aberrations play major roles in several disease states, particularly impacting on Ca2+ sensitization of smooth muscle in hypertension and possibly asthma and on cancer neoangiogenesis and cancer progression [8].
• The effector IpgB2 stimulates cellular responses analogous to GTP-active RhoA, whereas IpgB1 and Map function as the active forms of Rac1 and Cdc42, respectively [9].
• Furthermore, in 293 cells expressing Kv1.2 and ml muscarinic acetylcholine receptors, inactivating RhoA using C3 exoenzyme blocked the ability of ml receptors to suppress Kv1.2 current [10].

Chemical compound and disease context of RHOA

• We also found that lovastatin-induced cell cycle arrest resulted in increased RHOA RNA expression in breast cancer cell lines.(ABSTRACT TRUNCATED AT 250 WORDS)[1]
• We investigated in intact (human adenocarcinoma A549 cells) the role of RhoA and ARF in activation of PLD by phorbol 12-myristate 13-acetate, bradykinin, and/or sphingosine 1-phosphate [11].
• Importantly, preincubation of cells with the toxin C3, which inhibits RhoA, reduced HIF-1alpha protein accumulation by 84% during hypoxia [12].
• Caki-1 cells were exposed to hypoxia (1% O2) and exhibited increased Cdc42, Rac1 and RhoA protein expression [12].
• Role of direct RhoA-phospholipase D1 interaction in mediating adenosine-induced protection from cardiac ischemia [13].

Biological context of RHOA

• Utilization of multiple polyadenylation signals in the human RHOA protooncogene [1].
• RNase-protection analysis demonstrated that all three polyadenylation signals are utilized in breast cancer cell lines and RNA stability studies demonstrated that RHOA RNA species with different 3' ends have equivalent stability [1].
• Synaptopodin orchestrates actin organization and cell motility via regulation of RhoA signalling [14].
• The Rho family of small GTPases (RhoA, Rac1 and Cdc42) controls signal-transduction pathways that influence many aspects of cell behaviour, including cytoskeletal dynamics [14].
• We show here that N-terminal effector site mutations in the Rac protein do not compromise its interaction with RhoGDI and that, whilst geranylgeranylation and -AAX proteolysis of the C-terminal CAAX motif of Rac1 and RhoA are required for efficient interaction with RhoGDI, methylesterification of the C-terminal cysteine residue is not required [15].

Anatomical context of RHOA

• Thus, in neutrophils, beta(2) integrin-induced activation of p190RhoGAP requires a signal from a Src family tyrosine kinase, but it does not occur via the signaling pathway responsible for activation of RHOA:[16]
• On the contrary, RhoA promotes the formation of contractile actin-myosin-containing stress fibres in the cell body and at the rear [14].
• Here, we identify synaptopodin, an actin-associated protein, as a novel regulator of RhoA signalling and cell migration in kidney podocytes [14].
• In cells, it potently blocked serum or platelet-derived growth factor-induced Rac1 activation and lamellipodia formation without affecting the activity of endogenous Cdc42 or RhoA [17].
• In conclusion, G2A represents a family of GPCRs expressed in lymphocytes that may link diverse stimuli to cytoskeletal reorganization and transcriptional activation through a pathway involving G alpha 13 and RhoA [18].

Associations of RHOA with chemical compounds

• We determined the crystal structure of a small GTPase RHOA complexed with GDP in the absence of Mg(2+) at 2.0-A resolution [19].
• However, in intact PMNs stimulated with N-formyl-1-methionyl-1-leucyl-1-phenylalamine (FMLP) or permeabilized PMNs stimulated with GTP gamma S, C2-ceramide did not inhibit RhoA translocation [20].
• Exogenous RhoA did not restore ceramide-inhibited PLD activity but bound to membranes despite ceramide treatment [20].
• Herein, we use protein transduction to identify novel, opposing anti- and pro-cytokine-inducing roles for RhoA in the resting and lipopolysaccharide (LPS)-stimulated human PMN, respectively [21].
• These observations suggest that, although ceramide may affect RhoA in some systems, ceramide inhibits PLD through another mechanism, perhaps related to the ability of ceramide to inhibit phosphatidylinositol-bisphosphate (PIP2) interaction with PLD [20].

Physical interactions of RHOA

• Here we report the 2.2 A crystal structure of RhoA bound to an effector domain of protein kinase PKN/PRK1 [22].
• These results conclusively demonstrate that the C-terminal region of PLD1 contains the RhoA-binding site and suggest that the ARF and PKC interactions occur elsewhere in the protein [23].
• Herein we describe the atomic structures of the catalytic Dbl homology (DH) and pleckstrin homology (PH) domains of LARG alone and in complex with RhoA [24].
• Glutathione S-transferase-capture experiments revealed that Rhophilin-1 and Rhophilin-2 interacted with both GDP- and GTP-bound RhoA in vitro [25].
• An adjacent domain of M-RIP directly binds RhoA in a nucleotide-independent manner [26].

Enzymatic interactions of RHOA

• Localized suppression of RhoA activity by Tyr31/118-phosphorylated paxillin in cell adhesion and migration [27].
• Owing to the molecular activity of CNF1, we have investigated the relationship between permanent activation of RhoA catalyzed by CNF1 and subsequent ubiquitylation of RhoA by Smurf1 [28].
• First, TGF-beta1 phosphorylated RhoA via protein kinase A, leading to inactivation of RhoA [29].

Co-localisations of RHOA

• Nir2 colocalizes with the small GTPase RhoA in the cleavage furrow and the midbody, and it associates with RhoA in mitotic cells [30].

Regulatory relationships of RHOA

• In the resting cell, RhoA suppresses Cdc42 activation, IkappaBalpha degradation, nuclear factor-kappaB (NF-kappaB) activation, and induction of TNFalpha and NF-kappaB-dependent chemokines [21].
• PRK1 (PKN) is a serine/threonine kinase that has been shown to be activated by RhoA (Amano, M., Mukai, H., Ono, Y., Chihara, K., Matsui, T., Hamajima, Y., Okawa, K., Iwamatsu, A., and Kaibuchi, K. (1996) Science 271, 648-650) [31].
• In this study, we have investigated the proximal events in TNF-alpha-induced RhoA activation [32].
• In addition, we show that ligand-induced dimerization of Plexin B is sufficient to stimulate endogenous RhoA potently and to induce the reorganization of the cytoskeleton [33].
• These results suggest that CB2 might play a role in regulating excessive inflammatory response by controlling RhoA activation, thereby suppressing neutrophil migration [34].
• We also demonstrate that NEP inhibits neuropeptide activation of RhoA [35].

Other interactions of RHOA

• We show that RhoG(GTP) specifically interacts with the central domain of kinectin, which also contains a RhoA binding domain in its C terminus [36].
• Instead, IQGAP2 binds Cdc42 and Racl but not RhoA [37].
• In active R-Ras (38V) cells, the activity of RhoA is increased and accompanied with translocation to plasma membrane, but not that of Rac1 or Cdc42 [38].
• We have reported that the transient expression of the endogenous RhoB protein is regulated during the cell cycle, contrasting with the permanent RhoA protein expression () [39].
• The effect of ARF was greater than that of RhoA, although the concentrations for half-maximal stimulation (0.08-0.2 microM) were similar [40].
• TRPC6-mediated RhoA activity was shown to be dependent on PKCalpha activation [41].

Analytical, diagnostic and therapeutic context of RHOA

• Sequence analyses of these RHOA cDNA clones indicate that multiple polyadenylation signals are used to terminate RHOA transcripts [1].
• Membrane Arf and RhoA contents were assessed by Western immunoblot analyses [42].
• RT-PCR analysis indicated that the increase in RhoA protein expression was also reflected at the mRNA level [12].
• Immunoprecipitation of metabolically labelled RhoA showed that overexpression was at least due to neo-synthesis [12].
• Immunocytochemistry was performed to study the effects on the actin cytoskeleton and RhoA localization [43].

References