G Protein βγ Subunits Stimulate p114RhoGEF, a Guanine Nucleotide Exchange Factor for RhoA and Rac1

Niu, Jiaxin; Profirovic, Jasmina; Pan, Haiyun; Vaiškunaite, Rita; Voyno-Yasenetskaya, Tatyana A.

doi:10.1161/01.res.0000097607.14733.0c

Cited by 110 publications

(94 citation statements)

References 28 publications

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“…Signaling through the SRE Pathway-Transcriptional regulation through the SRE pathway has been proposed to be stimulated by various G protein systems, including G␣ 13 , G␣ I , and G␤␥ (32)(33)(34)(35).…”

Section: Resultsmentioning

confidence: 99%

Common Structural Basis for Constitutive Activity of the Ghrelin Receptor Family

Holst

Holliday

Bach

et al. 2004

Journal of Biological Chemistry

309

305

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Three members of the ghrelin receptor family were characterized in parallel: the ghrelin receptor, the neurotensin receptor 2 and the orphan receptor GPR39. In transiently transfected COS-7 and human embryonic kidney 293 cells, all three receptors displayed a high degree of ligand-independent signaling activity. The structurally homologous motilin receptor served as a constitutively silent control; upon agonist stimulation, however, it signaled with a similar efficacy to the three related receptors. The constitutive activity of the ghrelin receptor and of neurotensin receptor 2 through the G q , phospholipase C pathway was ϳ50% of their maximal capacity as determined through inositol phosphate accumulation. These two receptors also showed very high constitutive activity in activation of cAMP response element-driven transcription. GPR39 displayed a clear but lower degree of constitutive activity through the inositol phosphate and cAMP response element pathways. In contrast, GPR39 signaled with the highest constitutive activity in respect of activation of serum response element-dependent transcription, in part, possibly, through G 12/13 and Rho kinase. Antibody feeding experiments demonstrated that the epitope-tagged ghrelin receptor was constitutively internalized but could be trapped at the cell surface by an inverse agonist, whereas GPR39 remained at the cell surface. Mutational analysis showed that the constitutive activity of both the ghrelin receptor and GPR39 could systematically be tuned up and down depending on the size and hydrophobicity of the side chain in position VI:16 in the context of an aromatic residue at VII:09 and a large hydrophobic residue at VII:06. It is concluded that the three ghrelin-like receptors display an unusually high degree of constitutive activity, the structural basis for which is determined by an aromatic cluster on the inner face of the extracellular ends of TMs VI and VII.

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Section: Resultsmentioning

confidence: 99%

Common Structural Basis for Constitutive Activity of the Ghrelin Receptor Family

Holst

Holliday

Bach

et al. 2004

Journal of Biological Chemistry

309

305

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“…This is an issue that needs to be addressed in the future. In recent studies, calcium and PKC-dependent phosphorylation of RhoGDI have been proposed to promote the release of bound Rac and RhoA and subsequent translocation to the plasma membrane (8,(51)(52)(53)(54)(55)(56) RhoGDI for Rac may be a common feature preceding its translocation. Our data suggest that ICMT regulates the association of RhoGDI with Rac1; however, whether ICMT can reduce the affinity of RhoGDI for Rac1 remains to be demonstrated.…”

Section: Discussionmentioning

confidence: 99%

Tumor Necrosis Factor α Stimulation of Rac1 Activity

Papaharalambus

Sajjad

Syed

et al. 2005

Journal of Biological Chemistry

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We have previously demonstrated that both isoprenylcysteine carboxylmethyltransferase (ICMT) and one of its substrates, the RhoGTPase Rac1, are critical for the tumor necrosis factor ␣ (TNF␣) stimulation of vascular cell adhesion molecule-1 expression in endothelial cells (EC). Here, we have shown that ICMT regulates TNF␣ stimulation of Rac1 activity. TNF␣ stimulation of EC increased the membrane association of Rac1, an event that is essential for Rac1 activity. ICMT inhibitor Nacetyl-S-farnesyl-L-cysteine (AFC) blocked the accumulation of Rac1 into the membrane both in resting and TNF␣-stimulated conditions. Similarly, the membraneassociated Rac1 was lower in Icmt-deficient versus wildtype mouse embryonic fibroblasts (MEFs). TNF␣ also increased the level of GTP-Rac1, the active form of Rac1, in EC. AFC completely suppressed the TNF␣ stimulation of increase in GTP-Rac1 levels. Confocal microscopy revealed resting EC Rac1 was present in the plasma membrane and also in the perinuclear region. AFC mislocalized Rac1, both from the plasma membrane and the perinuclear region. Mislocalization of Rac1 was also observed in Icmt-deficient versus wild-type MEFs. To determine the consequences of ICMT inhibition, we investigated the effect of AFC on p38 mitogen-activated protein (MAP) kinase phosphorylation, which is downstream of Rac1. AFC inhibited the TNF␣ stimulation of p38 MAP kinase phosphorylation in EC. TNF␣ stimulation of p38 MAP kinase phosphorylation was also significantly attenuated in Icmt-deficient versus wild-type MEFs. To understand the mechanism of inhibition of Rac1 activity, we examined the effect of ICMT inhibition on the interaction of Rac1 with its inhibitor, Rho guanine nucleotide dissociation inhibitor (RhoGDI). The association of Rac1 with its inhibitor RhoGDI was dramatically increased in the Icmt-deficient versus wild-type MEFs both in resting as well as in TNF␣-stimulated conditions, suggesting that RhoGDI was involved in inhibiting Rac1 activity under the conditions of ICMT inhibition. These results suggest that ICMT regulates Rac1 activity by controlling the interaction of Rac1 with RhoGDI. We hypothesize that ICMT regulates the release of Rac1 from RhoGDI.Some signaling proteins, such as small GTPases and the ␥ subunits of heterotrimeric G proteins, end with a CAAX (C for cysteine, A for aliphatic amino acids, and X for almost any other amino acid) sequence, which is post-translationally modified in three ways (1). Isoprenylation (farnesylation or geranylgeranylation) at cysteine is followed by cleavage of the last three amino acids (AAX) (1-3). Finally, the isoprenylated cysteine is carboxyl methylated by an endoplasmic reticulum resident enzyme (4, 5) isoprenylcysteine carboxylmethyltransferase (ICMT) 1 (5). This carboxyl methylation provides additional hydrophobicity to the isoprenylated proteins. Carboxyl methylation is dependent on the first two modifications and is potentially reversible.We demonstrated that ICMT and one of its substrates, the RhoGTPase Rac1, regulate in endothelial cells...

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“…Direct activation of Rho proteins was determined by using a pull-down assay (Niu et al, 2003). pGEX expression vectors encoding glutathione S-transferase (GST) fusion proteins that contain the isolated GTP-dependent binding domains of the Rac1 and Cdc42 effector p21-activated kinase 1 (PAK1) [amino acids 70 -132 of PAK1; PAK Rac-binding domain (RBD)] or the RhoA effector rhotekin (amino acids 7-89 of rhotekin; rhotekin RBD) were used for the bacterial expression of GST fusion proteins.…”

Section: Methodsmentioning

confidence: 99%

5-HT₇Receptor Is Coupled to Gα Subunits of Heterotrimeric G12-Protein to Regulate Gene Transcription and Neuronal Morphology

Kvachnina¹,

Liu²,

Dityatev³

et al. 2005

J. Neurosci.

180

220

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The neurotransmitter serotonin (5-HT) plays an important role in the regulation of multiple events in the CNS. We demonstrated recently a coupling between the 5-HT 4 receptor and the heterotrimeric G13-protein resulting in RhoA-dependent neurite retraction and cell rounding (Ponimaskin et al., 2002). In the present study, we identified G12 as an additional G-protein that can be activated by another member of serotonin receptors, the 5-HT 7 receptor. Expression of 5-HT 7 receptor induced constitutive and agonist-dependent activation of a serum response element-mediated gene transcription through G12-mediated activation of small GTPases. In NIH3T3 cells, activation of the 5-HT 7 receptor induced filopodia formation via a Cdc42-mediated pathway correlating with RhoA-dependent cell rounding. In mouse hippocampal neurons, activation of the endogenous 5-HT 7 receptors significantly increased neurite length, whereas stimulation of 5-HT 4 receptors led to a decrease in the length and number of neurites. These data demonstrate distinct roles for 5-HT 7 R/G12 and 5-HT 4 R/G13 signaling pathways in neurite outgrowth and retraction, suggesting that serotonin plays a prominent role in regulating the neuronal cytoarchitecture in addition to its classical role as neurotransmitter.

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G Protein βγ Subunits Stimulate p114RhoGEF, a Guanine Nucleotide Exchange Factor for RhoA and Rac1

Cited by 110 publications

References 28 publications

Common Structural Basis for Constitutive Activity of the Ghrelin Receptor Family

Common Structural Basis for Constitutive Activity of the Ghrelin Receptor Family

Tumor Necrosis Factor α Stimulation of Rac1 Activity

5-HT₇Receptor Is Coupled to Gα Subunits of Heterotrimeric G12-Protein to Regulate Gene Transcription and Neuronal Morphology

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G Protein βγ Subunits Stimulate p114RhoGEF, a Guanine Nucleotide Exchange Factor for RhoA and Rac1

Cited by 110 publications

References 28 publications

Common Structural Basis for Constitutive Activity of the Ghrelin Receptor Family

Common Structural Basis for Constitutive Activity of the Ghrelin Receptor Family

Tumor Necrosis Factor α Stimulation of Rac1 Activity

5-HT7Receptor Is Coupled to Gα Subunits of Heterotrimeric G12-Protein to Regulate Gene Transcription and Neuronal Morphology

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5-HT₇Receptor Is Coupled to Gα Subunits of Heterotrimeric G12-Protein to Regulate Gene Transcription and Neuronal Morphology