RhoA and ROCK Promote Migration by Limiting Membrane Protrusions

Previously, we and others have shown that RhoA and ROCK signaling are required for negatively regulating integrin-mediated adhesion and for tail retraction of migrating leukocytes. This study continues our investigation into the molecular mechanisms underlying RhoA/ROCK-regulated integrin adhesion. We show that inhibition of ROCK up-regulates integrin-mediated adhesion, which is accompanied by both increased phosphotyrosine signaling through Pyk-2 and paxillin and inappropriate membrane protrusions. We provide evidence that inhibition of ROCK induces integrin adhesion by promoting remodeling of the actin cytoskeleton. Furthermore, we find that ROCK regulates membrane activity through a pathway involving cofilin. Inhibition of RhoA signaling allows the formation of multiple competing lamellipodia that disrupt productive migration of monocytes. Together, our results show that RhoA/ROCK signaling promotes migration by restricting integrin activity and membrane protrusions to the leading edge. Previously, we and others have shown that RhoA and ROCK signaling are required for negatively regulating integrin-mediated adhesion and for tail retraction of migrating leukocytes. This study continues our investigation into the molecular mechanisms underlying RhoA/ROCK-regulated integrin adhesion. We show that inhibition of ROCK up-regulates integrin-mediated adhesion, which is accompanied by both increased phosphotyrosine signaling through Pyk-2 and paxillin and inappropriate membrane protrusions. We provide evidence that inhibition of ROCK induces integrin adhesion by promoting remodeling of the actin cytoskeleton. Furthermore, we find that ROCK regulates membrane activity through a pathway involving cofilin. Inhibition of RhoA signaling allows the formation of multiple competing lamellipodia that disrupt productive migration of monocytes. Together, our results show that RhoA/ROCK signaling promotes migration by restricting integrin activity and membrane protrusions to the leading edge. RhoA-activated kinase proline-rich tyrosine kinase 2 induced cell adhesion molecule vascular cell adhesion molecule glutathione S-transferase macrophage chemotactic protein 1 Circulating leukocytes respond to infection or injury by dramatically altering cell shape and adhesive properties to facilitate migration from the bloodstream to the affected tissue (1Springer T.A. Cell. 1994; 76: 301-314Abstract Full Text PDF PubMed Scopus (6426) Google Scholar, 2Brown E.J. Trends Cell Biol. 1997; 7: 289-295Abstract Full Text PDF PubMed Scopus (56) Google Scholar). Leukocytes follow biochemical cues to guide the timing and location of activation (3Worthylake R.A. Burridge K. Curr. Opin. Cell Biol. 2001; 13: 569-577Crossref PubMed Scopus (248) Google Scholar, 4Johnson-Leger C. Aurrand-Lions M. Imhof B.A. J. Cell Sci. 2000; 113: 921-933PubMed Google Scholar). These cues include soluble inflammatory cytokines and chemokines as well as stationary adhesion molecules. Both types of signals initiate immune system responses from resting leukocytes and provide directional information for appropriate migration. The process of cell migration can be described as the result of coordination between membrane protrusive activity at a leading edge, movement of the cell body, and retraction of the rear of the cell (5Stossel T.P. Science. 1993; 260: 1086-1094Crossref PubMed Scopus (908) Google Scholar,6Lauffenburger D.A. Horwitz A.F. Cell. 1996; 84: 359-369Abstract Full Text Full Text PDF PubMed Scopus (3302) Google Scholar). New membrane extensions at the leading edge are stabilized by adhesive interactions between integrins and stationary adhesion molecules located on another cell or deposited as an extracellular matrix. Conversely, the retraction of membrane at the rear of the cell requires the disruption of the adhesive interaction either by disengagement between the ligand and receptor or dissociation of the links between the integrin and the internal cytoskeleton (7Palecek S.P. Huttenlocher A. Horwitz A.F. Lauffenburger D.A. J. Cell Sci. 1998; 111: 929-940Crossref PubMed Google Scholar). The actin cytoskeleton plays an important role in regulating both cell shape and adhesive properties. Actin polymerization at the leading edge can physically drive membrane protrusion (8Borisy G.G. Svitkina T.M. Curr. Opin. Cell Biol. 2000; 12: 104-112Crossref PubMed Scopus (404) Google Scholar). Interactions between the actin cytoskeleton and integrins regulate integrin activity (9Sastry S.K. Burridge K. Exp. Cell Res. 2000; 261: 25-36Crossref PubMed Scopus (432) Google Scholar, 10Schoenwaelder S.M. Burridge K. Curr. Opin. Cell Biol. 1999; 11: 274-286Crossref PubMed Scopus (653) Google Scholar). The links between the actin cytoskeleton and integrins can either promote or restrain integrin adhesiveness depending on the cell type and environmental context. Early investigations of integrin-actin linkages in stationary fibroblasts demonstrated that actomyosin-dependent integrin clustering was required for strong integrin adhesions (11Burridge K., M. Chzanowska-Wodnicka M. Zhong C. Trends Cell Biol. 1997; 7: 342-347Abstract Full Text PDF PubMed Scopus (199) Google Scholar). More recently, a study of highly motile leukocytes and lymphocytes have revealed that when these cells are circulating, interactions between integrins and cortical actin can restrain integrin activity until the appropriate signals are received (12Zhou X. Li J. J. Biol. Chem. 2000; 275: 20217-20222Abstract Full Text Full Text PDF PubMed Scopus (52) Google Scholar, 13Hogg N. Henderson R. Leitinger B. McDowall A. Porter J. Stanley P. Immunol. Rev. 2002; 186: 164-171Crossref PubMed Scopus (145) Google Scholar, 14Kucik D.F. Dustin M.L. Miller J.M. Brown E.J. J. Clin. Invest. 1996; 97: 2139-2144Crossref PubMed Scopus (295) Google Scholar, 15van Kooyk Y. van Vliet S.J. Figdor C.G. J. Biol. Chem. 1999; 274: 26869-26877Abstract Full Text Full Text PDF PubMed Scopus (131) Google Scholar). Upon activation, the restraining integrin-actin linkage is broken, resulting in increased integrin mobility to allow clustering and the formation of new integrin-actin interactions that promote adhesion and signaling (16Lub M. van Kooyk Y. van Vliet S.J. Figdor C.G. Mol. Biol. Cell. 1997; 8: 341-351Crossref PubMed Scopus (147) Google Scholar, 17Sampath R. Gallagher P.J. Pavalko F.M. J. Biol. Chem. 1998; 273: 33588-33594Abstract Full Text Full Text PDF PubMed Scopus (199) Google Scholar). The Rho family of small GTPases regulates many facets of cytoskeletal dynamics that underlie changes in cell shape and adhesion during migration (18Schmitz A.A. Govek E.E. Bottner B. Van Aelst L. Exp. Cell Res. 2000; 261: 1-12Crossref PubMed Scopus (512) Google Scholar, 19Ridley A.J. Trends Cell Biol. 2001; 11: 471-477Abstract Full Text Full Text PDF PubMed Scopus (645) Google Scholar, 20Sanchez-Madrid F. del Pozo M.A. EMBO J. 1999; 18: 501-511Crossref PubMed Scopus (523) Google Scholar, 21Schwartz M. Shattil S. Trends Biochem. Sci. 2000; 25: 388-391Abstract Full Text Full Text PDF PubMed Scopus (262) Google Scholar, 22Dharmawardhane S. Bokoch G.M. Curr. Opin. Hematol. 1997; 4: 12-18Crossref PubMed Scopus (31) Google Scholar, 23Nobes C.D. Hall A. J. Cell Biol. 1999; 144: 1235-1244Crossref PubMed Scopus (1216) Google Scholar, 24Cox E.A. Sastry S.K. Huttenlocher A. Mol. Biol. Cell. 2001; 12: 265-277Crossref PubMed Scopus (250) Google Scholar). These signaling proteins act as molecular switches that are responsive to a range of extracellular signals that influence cell migration including those transduced by tyrosine kinase receptors, G-protein coupled receptors, and integrin adhesion molecule receptors (25Van Aelst L. D'Souza-Schorey C. Genes Dev. 1997; 11: 2295-2322Crossref PubMed Scopus (2102) Google Scholar, 26Bishop A.L. Hall A. Biochem. J. 2000; 348: 241-255Crossref PubMed Scopus (1686) Google Scholar, 27Kjoller L. Hall A. Exp. Cell Res. 1999; 253: 166-179Crossref PubMed Scopus (344) Google Scholar). The targets of Rho GTPase signaling pathways modulate actomyosin contractility through regulation of myosin phosphorylation and actin dynamics by either promoting polymerization or by stimulating depolymerization and severing of existing F-actin filaments (28Somlyo A.P. Somlyo A.V. J Physiol. (Lond.). 2000; 522: 177-185Crossref Scopus (1082) Google Scholar, 29Kuhn T.B. Meberg P.J. Brown M.D. Bernstein B.W. Minamide L.S. Jensen J.R. Okada K. Soda E.A. Bamburg J.R. J Neurobiol. 2000; 44: 126-144Crossref PubMed Scopus (160) Google Scholar, 30Pollard T.D. Blanchoin L. Mullins R.D. Annu. Rev. Biophys. Biomol. Struct. 2000; 29: 545-576Crossref PubMed Scopus (1190) Google Scholar, 31Fukata Y. Amano M. Kaibuchi K. Trends Pharmacol. Sci. 2001; 22: 32-39Abstract Full Text Full Text PDF PubMed Scopus (668) Google Scholar). Previously, we have investigated the role of RhoA in regulating cell shape and migration properties. In fibroblasts, we have shown that down-regulation of RhoA by p190RhoGAP is necessary for cell spreading and directed migration into a wound (32Arthur W.T. Burridge K. Mol. Biol. Cell. 2001; 12: 2711-2720Crossref PubMed Scopus (384) Google Scholar). In leukocytes, we have shown that RhoA signaling to a serine/threonine kinase, ROCK,1 regulates the retraction of the tail of migrating monocytes and negatively influences integrin adhesion at the cell rear (33Alblas J. Ulfman L. Hordijk P. Koenderman L. Mol. Biol. Cell. 2001; 12: 2137-2145Crossref PubMed Scopus (217) Google Scholar, 34Worthylake R.A. Lemoine S. Watson J.M. Burridge K. J. Cell Biol. 2001; 154: 147-160Crossref PubMed Scopus (413) Google Scholar). This role for RhoA and ROCK in negative regulation of integrin adhesion was initially unexpected based on previous findings that RhoA promotes the formation of large integrin-based focal adhesions in fibroblasts. However, these large focal adhesions are a characteristic of stationary cells and are absent from leukocytes. Instead, leukocytes form small focal complexes of tethering and signaling molecules surrounding ligand-engaged integrins. These focal complexes coordinate integrin signaling during migration and are present both in leukocytes and the leading edge of migrating fibroblasts. In both cases, membrane protrusions and their accompanying focal complexes have been shown to be dependent on Rac or Cdc42 and negatively regulated by RhoA and ROCK activity (33Alblas J. Ulfman L. Hordijk P. Koenderman L. Mol. Biol. Cell. 2001; 12: 2137-2145Crossref PubMed Scopus (217) Google Scholar, 34Worthylake R.A. Lemoine S. Watson J.M. Burridge K. J. Cell Biol. 2001; 154: 147-160Crossref PubMed Scopus (413) Google Scholar, 35Allen W.E. Jones G.E. Pollard J.W. Ridley A.J. J. Cell Sci. 1997; 110: 707-720Crossref PubMed Google Scholar, 36Rottner K. Hall A. Small J.V. Curr. Biol. 1999; 9: 640-648Abstract Full Text Full Text PDF PubMed Scopus (515) Google Scholar, 37D'Souza-Schorey C. Boettner B. Van Aelst L. Mol. Cell. Biol. 1998; 18: 3936-3946Crossref PubMed Scopus (140) Google Scholar, 38Liu L. Schwartz B.R. Lin N. Winn R.K. Harlan J.M. J. Immunol. 2002; 169: 2330-2336Crossref PubMed Scopus (60) Google Scholar). In our current study, we have further investigated the RhoA/ROCK signaling pathway in regulating integrin activity. We find that ROCK negatively regulates two integrin-mediated functions: phosphytyrosine signaling and membrane protrusion. We present evidence suggesting that ROCK regulates integrin adhesion and membrane activity by suppressing cytoskeletal remodeling. Finally, we show that a biological consequence of RhoA/ROCK signaling is to promote migration by limiting membrane protrusions to the leading edge. THP-1 monocytes were routinely cultured in Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum and antibiotics. Transfections were carried out with 15 μl of LipofectAMINE 2000 (Invitrogen) and 1 μg of DNA in 100 μl of Dulbecco's modified Eagle's medium in 24-well plates containing 3 × 105 cells for 24 h. Primary monocytes were isolated and electroporated as described previously (24Cox E.A. Sastry S.K. Huttenlocher A. Mol. Biol. Cell. 2001; 12: 265-277Crossref PubMed Scopus (250) Google Scholar). Myc-wild type and were from and The were by and into a for the of proteins were isolated a to and were a from and were into an protein by and proteins were as described previously R.A. Lemoine S. Watson J.M. Burridge K. J. Cell Biol. 2001; 154: 147-160Crossref PubMed Scopus (413) Google Scholar). and were from of and are in the was either at 1 or was at and were from was from and from were to was from and the was a from to or was as described previously R.A. Lemoine S. Watson J.M. Burridge K. J. Cell Biol. 2001; 154: 147-160Crossref PubMed Scopus (413) Google Scholar). Cell was by F-actin with or by a with either a or were with a and in and was to cell cells on or a of cells from was with were by and those to be of were for the of cell were from were with were for 15 to cell at a of were further in were by the membrane with a of and 3 previously shown to promote C. R. B. T.A. J. Cell Biol. 1996; PubMed Scopus Google in the and in the to migration. Primary monocytes were to 1 THP-1 cell migration was 3 h. to the of the were with a and the of cells to the of the was by shown that ROCK negatively influences integrin-mediated adhesion in and (33Alblas J. Ulfman L. Hordijk P. Koenderman L. Mol. Biol. Cell. 2001; 12: 2137-2145Crossref PubMed Scopus (217) Google Scholar, 34Worthylake R.A. Lemoine S. Watson J.M. Burridge K. J. Cell Biol. 2001; 154: 147-160Crossref PubMed Scopus (413) Google Scholar, 38Liu L. Schwartz B.R. Lin N. Winn R.K. Harlan J.M. J. Immunol. 2002; 169: 2330-2336Crossref PubMed Scopus (60) Google Scholar). the molecular underlying we the THP-1 cell to study the of ROCK on integrin adhesion, membrane and migration. THP-1 cells in in with the integrin or induces adhesion that is in the of the ROCK This that integrin adhesion of the THP-1 cell is regulated in the as adhesion was with a in cell spreading in we the of THP-1 cells with these we F-actin to the shape of THP-1 cells to integrin an extracellular present in that and are cell adhesion molecules by cells to leukocytes through and THP-1 cells to or a the cells on extensions and characteristic of the role of ROCK on we the cells to the in the of The by THP-1 cells was and the results are in The inhibition of ROCK cell spreading in to integrin when on In to a in cell the F-actin in that inhibition of ROCK membrane activity as by F-actin and lamellipodia the of the The protrusions were dependent on the integrin cells to a were and with lamellipodia or membrane as by the and of F-actin These findings to integrin signaling was by the inhibition of ROCK with tyrosine are of integrin we the of tyrosine kinase signaling in THP-1 cells to integrin of phosphotyrosine in the leading edge of cells to or THP-1 cells to integrin in the of multiple membrane extensions on the with a of The phosphotyrosine of cells to was that the integrin the phosphotyrosine the increased membrane protrusions were accompanied by phosphotyrosine signaling by integrin further the of ROCK on tyrosine phosphorylation we cell for the of tyrosine phosphorylation by that when THP-1 cells to is an in proteins in the of and This phosphotyrosine signaling is further when the cells are to in the of We to the of proteins that increased tyrosine phosphorylation when ROCK is with on the molecular of the in we the phosphorylation of the tyrosine kinase Pyk-2 and and which have molecular of and THP-1 cells were to to for by of Pyk-2 or paxillin and to of phosphotyrosine by In Pyk-2 tyrosine suggesting that signaling to Pyk-2 requires ROCK We that the of tyrosine phosphorylation for both Pyk-2 and paxillin in cells to in the of that inhibition of ROCK with increased integrin adhesion that is accompanied by in membrane protrusions and phosphotyrosine we investigated the molecular for increased integrin adhesion. of integrin is an important of integrin adhesion in leukocytes Kooyk Y. Figdor C.G. Cell Biol. 2000; 12: PubMed Scopus (295) Google Scholar). is that the cells integrins by tethering to the of cortical actin until appropriate signals are Upon activation, integrins are from their cytoskeletal and to with the actin cytoskeleton for signaling and migration. both for and the of cytoskeletal been we to with our cell system two that the and A. adhesion of THP-1 cells to either or when the cells are in the of or A. results the cytoskeletal both adhesion to integrin at cytoskeletal promotes adhesion, F-actin allow the formation of the cytoskeletal linkages to be required for productive integrin clustering and This is further by the that cells in the of a well those in 1 were small and We the role of in promoting integrin be to a of the cortical actin we another which F-actin actin remodeling. that the of on THP-1 cell as the cells with both and are those with In and have and on THP-1 cells adhesion. adhesion, promotes adhesion, and cells in the of both show an of adhesion These results are with a in which ROCK negatively regulates integrin by the cortical actin that integrins. was to signaling pathways from ROCK that integrin in a dependent cytoskeletal remodeling. The small GTPase plays an important role in integrin adhesion, in leukocytes J. Rev. Mol. Cell. Biol. 2001; PubMed Scopus Google Scholar, K. M. N. S. K. Mol. Cell. Biol. 2000; PubMed Scopus Google Scholar, A.J. Hall A. Curr. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar, A. Y. K. N. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). between of the small GTPase is a we ROCK through by the of on THP-1 cell membrane protrusions. is to integrin with the a negative the on that these have on the cell with or In we that the of when cells were on These results that is a of ROCK signaling that integrin from ROCK is the kinase to signaling ROCK and kinase, which and cofilin. both and F-actin actin remodeling J.R. Annu. Rev. Cell Dev. Biol. 1999; PubMed Scopus Google Scholar). In ROCK activity to that to the existing F-actin to that promote actin remodeling. However, kinase and are regulated by pathways the of ROCK signaling in regulation in our cell we the of on phosphorylation We an that that is on 3 to show that in THP-1 cells on is a of cofilin. cells are to to in the of the of phosphorylation are This that ROCK plays an important role in regulating the phosphorylation and activation, the of in to THP-1 cell adhesion. We an of that be and to the of activity in cell shape and membrane protrusions. In THP-1 cells with we that of to a in cell spreading In cells of F-actin are leading to cells with a small This is with our previous and that strong on integrin We the of on the of monocytes. In these cells were with either type or proteins by as described previously R.A. Lemoine S. Watson J.M. Burridge K. J. Cell Biol. 2001; 154: 147-160Crossref PubMed Scopus (413) Google Scholar). Previously, we have demonstrated that ROCK in monocytes increased membrane protrusive and the cells are highly ROCK inhibition results in cells with R.A. Lemoine S. Watson J.M. Burridge K. J. Cell Biol. 2001; 154: 147-160Crossref PubMed Scopus (413) Google Scholar). that of type to a small in the of cells with in with type the cells with results in a of cells with The of monocytes with is to the with Together, these results that is from which to the of membrane protrusions and inhibition of tail This study the molecular mechanisms underlying of membrane protrusions induced by inhibition of was to the biological consequence of RhoA/ROCK-regulated membrane protrusions. study we our system in which cells were with a of and ROCK activity. The monocytes were and their migration was by cells with a migration in which the membrane at the leading edge the cell and the rear of the cell This results in a cell with a the between protrusions at the of the cells and retraction of membrane at the rear of the the out a in an and the leading edge and In monocytes with competing membrane the cell in at the activity is to a leading edge, resulting in an cell with protrusions the of the RhoA activity is required to membrane protrusions at the rear of a migrating in which RhoA or ROCK is have a to promote migration. the monocytes to be to monocytes ROCK signaling to productive we a migration Primary monocytes or THP-1 cells were in the of a and to the in the The membrane was with the to integrin by monocytes for migration. The of cells that to the was by and the results are in induced of migration for the migration was in the of the ROCK migration was to Together, these results that RhoA/ROCK signaling is required to protrusions at the rear of migrating monocytes to allow productive migration. In study, we have results from previous the of RhoA and ROCK signaling in migration. We that RhoA and ROCK signaling are required to membrane protrusions to a leading edge. ROCK signaling was with we increased integrin adhesion accompanied by increased membrane activity and phosphotyrosine We described an important role for cytoskeletal remodeling in regulating integrin adhesion in either actin or investigation into the signaling pathways that influence cytoskeletal remodeling to regulate integrin activity revealed that both ROCK and to regulating membrane protrusions. Finally, we that in the of RhoA/ROCK monocytes out competing lamellipodia that with productive migration. We a strong increased integrin adhesion, increased phosphotyrosine and inappropriate protrusions. We that the integrin phosphotyrosine which promotes membrane protrusion. for a between integrin signaling and lamellipodia formation from our of Pyk-2 and paxillin as two proteins tyrosine phosphorylation are by ROCK activity. Both Pyk-2 and paxillin have been in promoting protrusive activity in leukocytes and fibroblasts Cell 2000; PubMed Scopus Google Scholar, J.M. Li X. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, Ridley A.J. J. Immunol. 2000; PubMed Scopus Google Scholar, K. Horwitz A.F. J. Cell Biol. 2001; PubMed Scopus Google Scholar, J.M. M.D. J. Biol. Chem. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). This is further by from the that increased Pyk-2 signaling in with was from integrin clustering L. M. M. S. J. F. C. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). a previously role for ROCK signaling in suppressing integrin adhesion, and membrane protrusions from the leading edge. Circulating leukocytes regulation the of integrin Leukocytes integrin in the resting to inflammatory responses integrin adhesion in to infection or of cortical actin the shape of leukocytes, and been that cortical actin integrin to with integrins D.F. Dustin M.L. Miller J.M. Brown E.J. J. Clin. Invest. 1996; 97: 2139-2144Crossref PubMed Scopus (295) Google Scholar, Kooyk Y. Figdor C.G. Cell Biol. 2000; 12: PubMed Scopus (295) Google Scholar). the for cytoskeletal remodeling as a molecular that regulates integrin adhesion in leukocytes. We that of two actin and promote integrin adhesion, the a F-actin adhesion. the evidence for the role of actin remodeling in integrin activation, the in signaling pathways that regulate actin dynamics have been well we ROCK in actin inhibition of ROCK the as of actin on integrin adhesion. In the of the ROCK with an actin on adhesion and membrane protrusion. investigation of signaling pathways from ROCK that the actin remodeling is in regulating membrane protrusions in THP-1 cells and tail retraction in monocytes. is to promote actin remodeling by of actin severing and activity J.R. Annu. Rev. Cell Dev. Biol. 1999; PubMed Scopus Google Scholar). Furthermore, activity been in promoting protrusions in to N. M. S. J. Cell Biol. 2000; PubMed Scopus Google Scholar, M. N. J. Cell Biol. 2000; PubMed Scopus Google Scholar). The of were as as those with inhibition of which a role for signaling molecules. These results that regulation of integrin by actin remodeling was regulated by ROCK signaling through a pathway involving of cofilin. the biological consequence of RhoA and ROCK regulation of integrin we the of monocytes in to THP-1 we that inhibition of RhoA signaling to the formation of multiple competing These monocytes to be to a leading edge and to membrane protrusive activity. We the of the monocytes to in a which demonstrated the ROCK of migration. This is with results by N. M. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google that show that migration of THP-1 results those findings and by two phosphotyrosine signaling and membrane as molecular mechanisms underlying the in directed migration. from the present with that from many and we a in which regulation of RhoA activity is required for productive migration. In RhoA be at the leading edge to allow protrusions. This is by in fibroblasts that show that the inhibition of RhoA/ROCK signaling with or of p190RhoGAP promotes cell and (32Arthur W.T. Burridge K. Mol. Biol. Cell. 2001; 12: 2711-2720Crossref PubMed Scopus (384) Google Scholar, 36Rottner K. Hall A. Small J.V. Curr. Biol. 1999; 9: 640-648Abstract Full Text Full Text PDF PubMed Scopus (515) Google Scholar). Furthermore, p190RhoGAP is to of membrane protrusions and M. Y. Y. W.T. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar, J. J. 2000; Google Scholar). RhoA be at the leading edge, our that RhoA be at the rear of the cell to promote migration. contractility previously been in the tail retraction of migrating F. J. Cell Sci. 2000; 113: PubMed Google and the RhoA/ROCK signaling pathway is to regulate myosin However, our previous in migrating monocytes a role for myosin contractility in tail current an that RhoA and ROCK are required to lamellipodia formation from the leading edge and that to membrane activity productive migration. We and Bamburg for was by We and for during the of and with the activity