Inhibition of RhoA GTPase activity enhances hematopoietic stem and progenitor cell proliferation and engraftment

Ghiaur, Gabriel; Lee, Andrew; Bailey, Jeff; Cancelas, José A.; Zheng, Yi; Williams, David A.

doi:10.1182/blood-2006-02-001560

Cited by 74 publications

(63 citation statements)

References 57 publications

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“…Thus, our results indicate that at least a part of the toxin-induced effects on HPC are attributable to G3BP. Similar effects have been observed by inhibition of Rac or RhoA in primary HPC [22]. Furthermore, deletion of both Rac1 and Rac2 causes massive defects in stem cell proliferation and survival in vitro and Rac1-deficient stem cells have reduced homing efficiency to the BM and fail to engraft [23,24].…”

Section: Discussionsupporting

confidence: 54%

Novel Role of Ras-GTPase Activating Protein SH3 Domain-Binding Protein G3BP in Adhesion and Migration of 32D Myeloid Progenitor Cells

Schwarz¹,

Aschenbrenner²,

Rüster³

et al. 2012

TOHJ

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Rho GTPases are involved in homing and mobilization of hematopoietic stem and progenitor cells due to their impact on cytoskeleton remodeling. We have previously shown that inhibition of Rho, Rac and Cdc42 clearly impairs adhesion of normal and leukemic hematopoietic progenitor cells (HPC) to fibronectin and migration in a three-dimensional stromal cell model. Here, we identified the Ras GTPase-Activating Protein SH3 Domain-Binding Protein (G3BP) as a target gene of Rho GTPases and analysed its role in regulating HPC motility. Overexpression of G3BP significantly enhanced adhesion of murine 32D HPC to fibronectin and human umbilical vein endothelial cells, increased the proportion of adherent cells in a flow chamber assay and promoted cell migration in a transwell assay and a three-dimensional stromal cell model suggesting a strong impact on the cytoskeleton. Immunofluorescent staining of G3BP-overexpressing fibroblasts revealed a Rho-like phenotype characterized by formation of actin stress fibers in contrast to the Rac-like phenotype of control fibroblasts. This is the first report implicating a role for G3BP in Rho GTPase-mediated signalling towards adhesion and migration of HPC. Our results may be of clinical importance, since G3BP was found overexpressed in human cancers.

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Section: Discussionsupporting

confidence: 54%

Novel Role of Ras-GTPase Activating Protein SH3 Domain-Binding Protein G3BP in Adhesion and Migration of 32D Myeloid Progenitor Cells

Schwarz¹,

Aschenbrenner²,

Rüster³

et al. 2012

TOHJ

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“…Whether these phenotypes reflect the functions of Cdc42 in normal HSCs remains uncertain, because all mice deficient in Cdc42 die because of progressive myeloproliferative disease [31]. Also reported is that the inhibition of RhoA, another Rho GTPase, by a dominant negative mutation enhances engraftment and longterm repopulation by HSPCs [32]. As all these Rho family members affect HSC functions, it will be fascinating to elucidate how their downstream signaling molecules, including WAVE2, work coordinately for proper execution of HSC functions, especially in close association with the BM microenvironment.…”

Section: Discussionmentioning

confidence: 99%

The Actin Polymerization Regulator WAVE2 Is Required for Early Bone Marrow Repopulation by Hematopoietic Stem Cells

et al. 2009

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The Rho GTPase family members play essential roles in hematopoiesis. Of these, Rac1 is thought to be required for the appropriate spatial localization of hematopoietic stem and/or progenitor cells (HSPCs) within the bone marrow (BM), whereas Rac2 likely plays a role in BM retention of HSPCs. To elucidate the molecular mechanisms underlying Rac-mediated functions in hematopoietic stem cells (HSCs), we studied Wiskott-Aldrich syndrome protein family verprolin-homologous proteins (WAVEs), the specific effectors downstream of the Rac GTPases in actin polymerization. We here showed that CD34 2/low cKit 1 Sca-1 1 lineage 2 HSCs (CD34 2 KSL HSCs) express WAVE2 but neither WAVE1 nor WAVE3. Because WAVE2 knockout mice are embryonic-lethal, we utilized HSCs in which the expression of WAVE2 was reduced by small interfering RNA. We found that knockdown (KD) of WAVE2 in HSCs affected neither in vitro colony formation nor cell proliferation but did impair in vivo long-term reconstitution. Interestingly, WAVE2 KD HSCs exhibited unaltered homing but showed poor BM repopulation detected as early as day 5 after transplantation. The mechanistic studies on WAVE2 KD HSCs revealed modest but significant impairment in both cobblestone-like area-forming on stromal layers and actin polymerization upon integrin ligation by fibronectin. These results suggested that WAVE2-mediated actin polymerization, potentially downstream of Rac1, plays an important role in intramarrow mobilization and proliferation of HSCs, which are believed to be crucial steps for long-term marrow reconstitution after transplantation.

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“…The reduced retention in the microenvironment, resulting from actin structure and adhesion defects coupled with altered expression of cell cycle regulatory proteins, such as p21 Cip1 and c-Myc, propels Cdc42 Ϫ/Ϫ LT-HSCs to enter into an active cell cycle, giving rise to increased short-term repopulating HSCs and progenitors. These effects appear to be uniquely regulated by Cdc42, because Rac1 and Rac2, two closely related Rho GTPases, are important in HSC retention in the BM niche and for HSC survival and cell cycle progression but are not involved in the maintenance of HSC quiescent state (18,26), whereas RhoA, another related Rho GTPase, may be involved in HSC engraftment but not retention in the BM niche (12,27). Whether Cdc42 plays a role in HSC differentiation into various blood cell lineages will be an important question to address in future studies.…”

Section: Resultsmentioning

confidence: 99%

Rho GTPase Cdc42 coordinates hematopoietic stem cell quiescence and niche interaction in the bone marrow

Yang¹,

Wang²,

Geiger³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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167

164

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Adult hematopoietic stem cells (HSCs) exist in a relatively quiescent state in the bone marrow (BM) microenvironment to fulfill longterm self-renewal and multilineage differentiation functions, an event that is tightly regulated by extrinsic and intrinsic cues. However, the mechanism coordinating the quiescent state of HSCs and their retention in the BM microenvironment remains poorly understood. In a conditional-knockout mouse model, we show that Cdc42 ؊/؊ HSCs enter the active cell cycle, resulting in significantly increased number and frequency of the stem/progenitor cells in the BM. Cdc42 deficiency also causes impaired adhesion, homing, lodging, and retention of HSCs, leading to massive egress of HSCs from BM to distal organs and peripheral blood and to an engraftment failure. These effects are intrinsic to the HSCs and are associated with deregulated c-Myc, p21 Cip1 , ␤1-integrin, and Ncadherin expressions and defective actin organization. Thus, Cdc42 is a critical coordinator of HSC quiescence maintenance and interaction with the BM niche.bone marrow microenvironment ͉ cell cycle ͉ adhesion A dult hematopoietic stem cells (HSCs) exist in a relatively quiescent state in the bone marrow (BM) microenvironment to execute long-term self-renewal and multilineage differentiation functions (1-3). The maintenance of HSC quiescence involves both extrinsic and intrinsic mechanisms. A number of genes that encode cell cycle or transcriptional regulators, including p21 Cip1 , p27 Kip1 , ␤-catenin/axin, cyclin D1, and c-Myc (4, 5), have been shown to regulate the intrinsic programs of HSCs in this process. In addition, interactions of HSCs with the BM microenvironment in specific anatomical and functional areas, referred to as niches, in the maintenance of HSC quiescence have also gained increasing recognition (6). One hypothesis is that the intrinsic and extrinsic cues, such as bone morphogenic proteins, Ca 2ϩ , Notch ligands, and/or Ang-1/Tie2 (7-10), in the BM microenvironment may coordinately regulate the HSC quiescent state.Despite of the identification of these molecular factors in HSCs and in BM that may collectively contribute to the maintenance of quiescence (7), the mechanism coordinating HSC cell cycle regulation and niche interaction remains unclear. Cdc42 is a ubiquitously expressed member of the Rho GTPase family involved in the regulation of multiple cell functions, including actin polymerization, cell-to-cell or cell-to-extracellular matrix adhesion, and gene transcription (11). Although its function has been extensively studied in various cell systems by expression of dominant negative or constitutively active mutants (12), the physiological roles of Cdc42 in most primary cell lineages, particularly in HSCs, remain unclear. Previously, in a gain-of-Cdc42 activity, Cdc42GAP Ϫ/Ϫ mouse model, we have found that constitutively increased Cdc42-GTP species cause increased hematopoietic progenitor apoptosis, disorganized actin structure, and defective engraftment without affecting the cell cycle status (13). T...

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Inhibition of RhoA GTPase activity enhances hematopoietic stem and progenitor cell proliferation and engraftment

Abstract: Ras-related

Cited by 74 publications

References 57 publications

Novel Role of Ras-GTPase Activating Protein SH3 Domain-Binding Protein G3BP in Adhesion and Migration of 32D Myeloid Progenitor Cells

Novel Role of Ras-GTPase Activating Protein SH3 Domain-Binding Protein G3BP in Adhesion and Migration of 32D Myeloid Progenitor Cells

The Actin Polymerization Regulator WAVE2 Is Required for Early Bone Marrow Repopulation by Hematopoietic Stem Cells

Rho GTPase Cdc42 coordinates hematopoietic stem cell quiescence and niche interaction in the bone marrow

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