title: Mouse macrophages completely lacking Rho subfamily GTPases (RhoA, RhoB, and RhoC) have severe lamellipodial retraction defects, but robust chemotactic navigation and altered motility.
abstract: RhoA is thought to be essential for coordination of the membrane protrusions and retractions required for immune cell motility and directed migration. Whether the subfamily of Rho (Ras homolog) GTPases (RhoA, RhoB, and RhoC) is actually required for the directed migration of primary cells is difficult to predict. Macrophages isolated from myeloid-restricted RhoA/RhoB (conditional) double knock-out (dKO) mice did not express RhoC and were essentially "pan-Rho"-deficient. Using real-time chemotaxis assays, we found that retraction of the trailing edge was dissociated from the advance of the cell body in dKO cells, which developed extremely elongated tails. Surprisingly, velocity (of the cell body) was increased, whereas chemotactic efficiency was preserved, when compared with WT macrophages. Randomly migrating RhoA/RhoB dKO macrophages exhibited multiple small protrusions and developed large "branches" due to impaired lamellipodial retraction. A mouse model of peritonitis indicated that monocyte/macrophage recruitment was, surprisingly, more rapid in RhoA/RhoB dKO mice than in WT mice. In comparison with dKO cells, the phenotypes of single RhoA- or RhoB-deficient macrophages were mild due to mutual compensation. Furthermore, genetic deletion of RhoB partially reversed the motility defect of macrophages lacking the RhoGAP (Rho GTPase-activating protein) myosin IXb (Myo9b). In conclusion, the Rho subfamily is not required for "front end" functions (motility and chemotaxis), although both RhoA and RhoB are involved in pulling up the "back end" and resorbing lamellipodial membrane protrusions. Macrophages lacking Rho proteins migrate faster in vitro, which, in the case of the peritoneum, translates to more rapid in vivo monocyte/macrophage recruitment.
authors.affiliation: Institut für Molekulare Zellbiologie, Wilhelms-Universität Münster, 48149 Münster, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Königs
authors.affiliation: Conway Institute, University College Dublin, Dublin, Ireland.
authors.forename: Richard
authors.initials: R
authors.lastname: Jennings
authors.affiliation: Institut für Immunologie, Wilhelms-Universität Münster, 48149 Münster, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Vogl
authors.affiliation: Institut für Molekulare Zellbiologie, Wilhelms-Universität Münster, 48149 Münster, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Horsthemke
authors.affiliation: Institut für Molekulare Zellbiologie, Wilhelms-Universität Münster, 48149 Münster, Germany.
authors.forename: Anne C
authors.initials: AC
authors.lastname: Bachg
authors.affiliation: Institut für Molekulare Zellbiologie, Wilhelms-Universität Münster, 48149 Münster, Germany.
authors.forename: Yan
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Institut für Physiologische Chemie und Pathobiochemie, and Wilhelms-Universität Münster, 48149 Münster, Germany.
authors.forename: Kay
authors.initials: K
authors.lastname: Grobe
authors.affiliation: Biotech Research and Innovation Centre (BRIC), University of Copenhagen, 2200 Copenhagen, Denmark.
authors.forename: Cord
authors.initials: C
authors.lastname: Brakebusch
authors.affiliation: Institut für Physiologie II, Wilhelms-Universität Münster, 48149 Münster, Germany, and.
authors.forename: Albrecht
authors.initials: A
authors.lastname: Schwab
authors.affiliation: Institut für Molekulare Zellbiologie, Wilhelms-Universität Münster, 48149 Münster, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Bähler
authors.affiliation: Conway Institute, University College Dublin, Dublin, Ireland.
authors.forename: Ulla G
authors.initials: UG
authors.lastname: Knaus
authors.affiliation: Institut für Molekulare Zellbiologie, Wilhelms-Universität Münster, 48149 Münster, Germany,. Electronic address: hanley@uni-muenster.de.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Hanley
mesh_terms: D000818:Animals; D016764:Cell Polarity; D002478:Cells, Cultured; D002633:Chemotaxis; D005260:Female; D015870:Gene Expression; D017737:Macrophages, Peritoneal / Q000201:enzymology* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D009218:Myosins / Q000235:genetics; D010538:Peritonitis / Q000201:enzymology / Q000473:pathology; D011554:Pseudopodia / Q000201:enzymology / Q000473:pathology*; D018631:ras Proteins / Q000235:genetics* / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D020742:rhoA GTP-Binding Protein; D020743:rhoB GTP-Binding Protein / Q000235:genetics* / Q000378:metabolism; D000075024:rhoC GTP-Binding Protein
chemical_list: C113469:myosin IXB; D009218:Myosins; C526380:RhoA protein, mouse; C512911:Rhoc protein, mouse; D018631:ras Proteins; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; D020743:rhoB GTP-Binding Protein; D000075024:rhoC GTP-Binding Protein
keywords: Cell Migration; Cell Motility; Cell Polarity; Chemotaxis; Macrophage; Mouse; Myosin; Ras Homolog Gene Family, Member A (RhoA); Rho (Rho GTPase); Rho GTPases