RhoA GTPase regulates B cell receptor signaling
ABSTRACT The RhoA GTPase controls many cellular functions, including gene transcription and actin polymerization. Several lines of evidence suggest that Rho GTPases are required for B cell receptor (BCR) signaling, but whether RhoA is necessary has not been investigated. Here, we show that RhoA is activated, downstream of PI3K, in response to BCR stimulation and is important for BCR-dependent calcium flux and cell proliferation. A RhoA dominant-negative mutant strongly inhibited BCR-dependent calcium mobilization. The RhoA-specific inhibitor, C3 toxin, inhibited both BCR-dependent calcium flux and cell proliferation. RhoA is important for BCR-dependent synthesis of IP(3) by PLCgamma2, but is not required for tyrosine phosphorylation of PLCgamma2. BCR-dependent synthesis of phosphatidylinositol-4,5-bisphosphate (PtdIns-4,5-P(2)) is inhibited in the absence of RhoA function. Providing exogenous PtdIns-4,5-P(2) restores BCR-dependent calcium flux in cells lacking functional RhoA. Our findings support a function for RhoA in BCR-dependent PtdIns-4,5-P(2) synthesis, PLCgamma2 activation, calcium mobilization, and cell proliferation.
- SourceAvailable from: Richard A Lang
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- "ROCK and mDia) to modulate actin cytoskeleton organization, adhesion, migration, proliferation, and survival in mammalian cells –. In B cells, RhoA transduces signals from the B cell receptor (BCR) to regulate phosphatidylinositol-4, 5-bisphosphate synthesis, PLCγ2 activation, calcium influx, protein kinase D activation, and B cell proliferation , . RhoA also plays a role in CCL19- and CCL21-induced migration of B-chronic lymphocytic leukemia cells . "
ABSTRACT: RhoA is a member of the Rho family small GTPases that are implicated in various cell functions including proliferation and survival. However, the physiological role of RhoA in vivo remains largely unknown. Here, we deleted RhoA in the B cell and hematopoietic stem cell (HSC) populations in RhoA(flox/flox) mice with CD19 and Mx promoter-driven Cre expression, respectively. Deletion of RhoA by CD19(Cre/+) significantly blocked B cell development in spleen, leading to a marked reduction in the number of transitional, marginal zone, and follicular B cells. Surprisingly, neither B cell proliferation in response to either LPS or B cell receptor (BCR) engagement nor B cell survival rate in vivo was affected by RhoA deletion. Furthermore, RhoA(-/-) B cells, like control cells, were rescued from apoptosis by BCR crosslinking in vitro. In contrast, RhoA deficiency led to a defect in B cell activating factor (BAFF)-mediated B cell survival that was associated with a dampened expression of BAFF receptor and a loss of BAFF-mediated Akt activation. Finally, HSC deletion of RhoA by Mx-Cre severely reduced proB/preB and immature B cell populations in bone marrow while common lymphoid progenitors were increased, indicating that RhoA is also required for B cell progenitor/precursor differentiation. Taken together, our results uncover an important role for RhoA at multiple stages of B cell development.PLoS ONE 03/2012; 7(3):e33773. DOI:10.1371/journal.pone.0033773 · 3.23 Impact Factor
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- "RhoA-PI4P5K-PIP 2 pathway mediates CD146-induced ERM activation At the downstream of RhoA, Ser/Thr kinases Rhoassociated coiled-coil protein kinase (ROCK) and phosphatidylinositol-4-phosphate-5-kinase (PI4P5K) have been shown to regulate ERM phosphorylation and its interactions (Shibasaki et al., 1997; Matsui et al., 1999; Saci and Carpenter, 2005). Moreover, Rho- PI4P5K-PIP 2 pathway is responsible for continuous activation of ERM proteins. "
ABSTRACT: Tumor cell migration is a well-orchestrated multistep process that drives cancer development and metastasis. Previous data indicated that CD146 expression correlates with malignant progression and metastatic potential of human melanoma cells. However, the exact molecular mechanism of how CD146 promotes melanoma cell migration still remains poorly understood. Here, we report that CD146 physically interacts with actin-linking ezrin-radixin-moesin (ERM) proteins and recruits ERM proteins to cell protrusions, promoting the formation and elongation of microvilli. Moreover, CD146-promoted melanoma cell migration is linked to RhoA activation and ERM phosphorylation. CD146 recruits Rho guanine nucleotide dissociation inhibitory factors 1 (RhoGDI1) through ERM proteins and thus sequesters RhoGDI1 from RhoA, which leads to upregulated RhoA activity and increased melanoma cell motility. CD146-activated RhoA also promotes further ERM phosphorylation and activation through Rho-phosphatidylinositol-4-phosphate-5-kinase-phosphatidylinositol 4,5-biphosphate pathway, which reinforces CD146/ERM association. Thus, our results provide a mechanistic basis to understand the role of CD146 in regulating human melanoma cell motility.Oncogene 07/2011; 31(3):306-21. DOI:10.1038/onc.2011.244 · 8.56 Impact Factor
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- "This ultimately leads to the activation of RhoA and ROCK-2 and, finally, of moesin. It is possible that when engaged by MPA, PRs may be driven to form a functional signaling module with Src and PI3K, where activated PI3K would lead to recruitment of RhoA, as shown in other cells . In analogy, ER, Src and PI3K are reportedly organized into a similar complex to mediate rapid signaling of estrogens in endothelial cells . "
ABSTRACT: Progesterone plays a role in breast cancer development and progression but the effects on breast cancer cell movement or invasion have not been fully explored. In this study, we investigate the actions of natural progesterone and of the synthetic progestin medroxyprogesterone acetate (MPA) on actin cytoskeleton remodeling and on breast cancer cell movement and invasion. In particular, we characterize the nongenomic signaling cascades implicated in these actions. T47-D breast cancer cells display enhanced horizontal migration and invasion of three-dimensional matrices in the presence of both progestins. Exposure to the hormones triggers a rapid remodeling of the actin cytoskeleton and the formation of membrane ruffles required for cell movement, which are dependent on the rapid phosphorylation of the actin-regulatory protein moesin. The extra-cellular small GTPase RhoA/Rho-associated kinase (ROCK-2) cascade plays central role in progesterone- and MPA-induced moesin activation, cell migration and invasion. In the presence of progesterone, progesterone receptor A (PRA) interacts with the G protein G alpha(13), while MPA drives PR to interact with tyrosine kinase c-Src and to activate phosphatidylinositol-3 kinase, leading to the activation of RhoA/ROCK-2. In conclusion, our findings manifest that progesterone and MPA promote breast cancer cell movement via rapid actin cytoskeleton remodeling, which are mediated by moesin activation. These events are triggered by RhoA/ROCK-2 cascade through partially differing pathways by the two compounds. These results provide original mechanistic explanations for the effects of progestins on breast cancer progression and highlight potential targets to treat endocrine-sensitive breast cancers.PLoS ONE 02/2008; 3(7):e2790. DOI:10.1371/journal.pone.0002790 · 3.23 Impact Factor