A Rho Exchange Factor Mediates Thrombin and Gα12-induced Cytoskeletal Responses

Majumdar, Mousumi; Seasholtz, Tammy M.; Buckmaster, Carolan; Toksoz, Deniz; Brown, Joan Heller

doi:10.1074/jbc.274.38.26815

Cited by 94 publications

(90 citation statements)

References 44 publications

(97 reference statements)

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“…Reduced TXA 2 -induced actin polymerization in Lsc -/-thymocytes Lsc regulates actin cytoskeleton dynamics in cells stimulated with thrombin [23], and Rho is a wellknown regulator of actin reorganization [24]. Since previous studies have demonstrated that actin reorganization is central to apoptosis and that the Rho effector ROCK (Rho kinase) can influence apoptosis [25,26], we examined the requirement for Lsc and ROCK in actin reorganization.…”

Section: Lsc Is Required For Txa 2 -Mediated Rho Activationmentioning

confidence: 99%

The Lsc RhoGEF mediates signaling from thromboxane A2 to actin polymerization and apoptosis in thymocytes

et al. 2005

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Section: Lsc Is Required For Txa 2 -Mediated Rho Activationmentioning

confidence: 99%

The Lsc RhoGEF mediates signaling from thromboxane A2 to actin polymerization and apoptosis in thymocytes

et al. 2005

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“…Although MLC kinase can be regulated by [Ca 2ϩ ] i (78,79), the MLC phosphatases are regulated by Rho kinase (80). Hence, activation of Rho in HMEC-1 could result in the inactivation of MLC phosphatases, favoring the phosphorylated state of MLC (30,81,82), making the pathway calcium-independent.…”

Section: Figmentioning

confidence: 99%

Functional Selectivity of G Protein Signaling by Agonist Peptides and Thrombin for the Protease-activated Receptor-1

McLaughlin

Shen

Holinstat

et al. 2005

Journal of Biological Chemistry

179

182

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Thrombin activates protease-activated receptor-1 (PAR-1) by cleavage of the amino terminus to unmask a tethered ligand. Although peptide analogs can activate PAR-1, we show that the functional responses mediated via PAR-1 differ between the agonists. Thrombin caused endothelial monolayer permeability and mobilized intracellular calcium with EC 50 values of 0.1 and 1.7 nM, respectively. The opposite order of activation was observed for agonist peptide (SFLLRN-CONH 2 or TFLL-RNKPDK) activation. The addition of inactivated thrombin did not affect agonist peptide signaling, suggesting that the differences in activation mechanisms are intramolecular in origin. Although activation of PAR-1 or PAR-2 by agonist peptides induced calcium mobilization, only PAR-1 activation affected barrier function. Induced barrier permeability is likely to be G␣ 12/13 -mediated as chelation of G␣ q -mediated intracellular calcium with BAPTA-AM, pertussis toxin inhibition of G␣ i/o , or GM6001 inhibition of matrix metalloproteinase had no effect, whereas Y-27632 inhibition of the G␣ 12/13 -mediated Rho kinase abrogated the response. Similarly, calcium mobilization is G␣ q -mediated and independent of G␣ i/o and G␣ 12/13 because pertussis toxin and Y-27632 had no effect, whereas U-73122 inhibition of phospholipase C-␤ blocked the response. It is therefore likely that changes in permeability reflect G␣ 12/13 activation, and changes in calcium reflect G␣ q activation, implying that the pharmacological differences between agonists are likely caused by the ability of the receptor to activate G␣ 12/13 or G␣ q . This functional selectivity was characterized quantitatively by a mathematical model describing each step leading to Rho activation and/or calcium mobilization. This model provides an estimate that peptide activation alters receptor/G protein binding to favor G␣ q activation over G␣ 12/13 by ϳ800-fold.

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“…This correlation suggests that IIA is specifically required for contractile events downstream of the Rho-ROCK signaling pathway in a way that is consistent with the classically described functions of myosin II. To characterize this more carefully, we examined the specific contributions of IIA and IIB to another process in which myosin II contractility is required downstream of Rho-ROCK signaling, namely thrombin-induced cell rounding (5,38,39). Serumstarved MDA-MB-231 cells display a flattened morphology; however, after thrombin treatment the cells round up and undertake a spherical shape (Fig.…”

Section: Sirna Depletion Of Iia or Iib Has Opposing Effects On Epithementioning

confidence: 99%

Rho Kinase Differentially Regulates Phosphorylation of Nonmuscle Myosin II Isoforms A and B during Cell Rounding and Migration

Sandquist

Swenson

DeMali

et al. 2006

Journal of Biological Chemistry

179

156

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The actin-myosin cytoskeleton is generally accepted to produce the contractile forces necessary for cellular processes such as cell rounding and migration. All vertebrates examined to date are known to express at least two isoforms of non-muscle myosin II, referred to as myosin IIA and myosin IIB. Studies of myosin IIA and IIB in cultured cells and null mice suggest that these isoforms perform distinct functions. However, how each myosin II isoform contributes individually to all the cellular functions attributed to "myosin II" has yet to be fully characterized. Using isoform-specific small-interfering RNAs, we found that depletion of either isoform resulted in opposing migration phenotypes, with myosin IIA-and IIB-depleted cells exhibiting higher and lower wound healing migration rates, respectively. In addition, myosin IIA-depleted cells demonstrated impaired thrombin-induced cell rounding and undertook a more motile morphology, exhibiting decreased amounts of stress fibers and focal adhesions, with concomitant increases in cellular protrusions. Cells depleted of myosin IIB, however, were efficient in thrombin-induced cell rounding, displayed a more retractile phenotype, and maintained focal adhesions but only in the periphery. Last, we present evidence that Rho kinase preferentially regulates phosphorylation of the regulatory light chain associated with myosin IIA. Our data suggest that the myosin IIA and IIB isoforms are regulated by different signaling pathways to perform distinct cellular activities and that myosin IIA is preferentially required for Rho-mediated contractile functions.

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A Rho Exchange Factor Mediates Thrombin and Gα12-induced Cytoskeletal Responses

Cited by 94 publications

References 44 publications

The Lsc RhoGEF mediates signaling from thromboxane A2 to actin polymerization and apoptosis in thymocytes

The Lsc RhoGEF mediates signaling from thromboxane A2 to actin polymerization and apoptosis in thymocytes

Functional Selectivity of G Protein Signaling by Agonist Peptides and Thrombin for the Protease-activated Receptor-1

Rho Kinase Differentially Regulates Phosphorylation of Nonmuscle Myosin II Isoforms A and B during Cell Rounding and Migration

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