scholarly journals The small G-protein MglA connects to the MreB actin cytoskeleton at bacterial focal adhesions

2015 ◽  
Vol 210 (2) ◽  
pp. 243-256 ◽  
Author(s):  
Anke Treuner-Lange ◽  
Eric Macia ◽  
Mathilde Guzzo ◽  
Edina Hot ◽  
Laura M. Faure ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
G Protein ◽  
Myxococcus Xanthus ◽  
Focal Adhesions ◽  
Gliding Motility ◽  
Guanosine Triphosphate ◽  
Cell Pole ◽  
Peptidoglycan Synthesis ◽  
Small G Protein ◽  
Guanosine Triphosphatase

In Myxococcus xanthus the gliding motility machinery is assembled at the leading cell pole to form focal adhesions, translocated rearward to propel the cell, and disassembled at the lagging pole. We show that MglA, a Ras-like small G-protein, is an integral part of this machinery. In this function, MglA stimulates the assembly of the motility complex by directly connecting it to the MreB actin cytoskeleton. Because the nucleotide state of MglA is regulated spatially and MglA only binds MreB in the guanosine triphosphate–bound form, the motility complexes are assembled at the leading pole and dispersed at the lagging pole where the guanosine triphosphatase activating protein MglB disrupts the MglA–MreB interaction. Thus, MglA acts as a nucleotide-dependent molecular switch to regulate the motility machinery spatially. The function of MreB in motility is independent of its function in peptidoglycan synthesis, representing a coopted function. Our findings highlight a new function for the MreB cytoskeleton and suggest that G-protein–cytoskeleton interactions are a universally conserved feature.

scholarly journals The actin cytoskeleton and small G protein RhoA are not involved in flow-dependent activation of ENaC

2010 ◽  
Vol 3 (1) ◽  
Author(s):  
Alexey V Karpushev ◽  
Daria V Ilatovskaya ◽  
Alexander Staruschenko
Keyword(s):  
Actin Cytoskeleton ◽  
G Protein ◽  
Small G Protein

scholarly journals The actin nucleation factors JMY and WHAMM enable a rapid p53-dependent pathway of apoptosis

2020 ◽  
Author(s):  
Virginia L. King ◽  
Nathan K. Leclair ◽  
Kenneth G. Campellone
Keyword(s):  
Gene Expression ◽  
Cell Death ◽  
Programmed Cell Death ◽  
Actin Cytoskeleton ◽  
Cell Survival ◽  
G Protein ◽  
Actin Nucleation ◽  
Caspase Cleavage ◽  
Cell Death Pathways ◽  
Small G Protein

AbstractThe actin cytoskeleton is a well-known player in most vital cellular processes, but comparably little is understood about how the actin assembly machinery impacts programmed cell death pathways. In the current study, we explored roles for the human Wiskott-Aldrich Syndrome Protein (WASP) family of actin nucleation factors in DNA damage-induced apoptosis. Inactivation of each WASP-family gene revealed that two, JMY and WHAMM, are required for rapid apoptotic responses. JMY and WHAMM enable p53-dependent cell death by enhancing mitochondrial permeabilization, initiator caspase cleavage, and executioner caspase activation. The loss of JMY additionally results in significant changes in gene expression, including upregulation of the small G-protein RhoD. Depletion or deletion of RHOD increases cell death, suggesting that RhoD normally plays a key role in cell survival. These results give rise to a model in which JMY and WHAMM promote intrinsic cell death responses that can be opposed by RhoD.Author SummaryThe actin cytoskeleton is a collection of protein polymers that assemble and disassemble within cells at specific times and locations. Cytoskeletal regulators called nucleation-promoting factors ensure that actin polymerizes when and where it is needed, and many of these factors are members of the Wiskott-Aldrich Syndrome Protein (WASP) family. Humans express 8 WASP-family proteins, but whether the different factors function in programmed cell death pathways is not well understood. In this study, we explored roles for each WASP-family member in apoptosis and found that a subfamily consisting of JMY and WHAMM are critical for a rapid pathway of cell death. Furthermore, the loss of JMY results in changes in gene expression, including a dramatic upregulation of the small G-protein RhoD, which appears to be crucial for cell survival. Collectively, our results point to the importance of JMY and WHAMM in driving intrinsic cell death responses plus a distinct function for RhoD in maintaining cell viability.

scholarly journals Association of Frabin with the Actin Cytoskeleton Is Essential for Microspike Formation through Activation of Cdc42 Small G Protein

1999 ◽  
Vol 274 (36) ◽  
pp. 25197-25200 ◽  
Author(s):  
Masato Umikawa ◽  
Hiroshi Obaishi ◽  
Hiroyuki Nakanishi ◽  
Keiko Satoh-Horikawa ◽  
Kenichi Takahashi ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
G Protein ◽  
Small G Protein

scholarly journals Rho and Rab Small G Proteins Coordinately Reorganize Stress Fibers and Focal Adhesions in MDCK Cells

1998 ◽  
Vol 9 (9) ◽  
pp. 2561-2575 ◽  
Author(s):  
Hiroshi Imamura ◽  
Kenji Takaishi ◽  
Katsutoshi Nakano ◽  
Atsuko Kodama ◽  
Hideto Oishi ◽  
...  
Keyword(s):  
Cell Motility ◽  
G Protein ◽  
Cultured Cells ◽  
Mdck Cells ◽  
Family Members ◽  
Focal Adhesions ◽  
Protein Family ◽  
Stress Fibers ◽  
Small G Protein ◽  
Rab Family

The Rho subfamily of the Rho small G protein family (Rho) regulates formation of stress fibers and focal adhesions in many types of cultured cells. In moving cells, dynamic and coordinate disassembly and reassembly of stress fibers and focal adhesions are observed, but the precise mechanisms in the regulation of these processes are poorly understood. We previously showed that 12-O-tetradecanoylphorbol-13-acetate (TPA) first induced disassembly of stress fibers and focal adhesions followed by their reassembly in MDCK cells. The reassembled stress fibers showed radial-like morphology that was apparently different from the original. We analyzed here the mechanisms of these TPA-induced processes. Rho inactivation and activation were necessary for the TPA-induced disassembly and reassembly, respectively, of stress fibers and focal adhesions. Both inactivation and activation of the Rac subfamily of the Rho family (Rac) inhibited the TPA-induced reassembly of stress fibers and focal adhesions but not their TPA-induced disassembly. Moreover, microinjection or transient expression of Rab GDI, a regulator of all the Rab small G protein family members, inhibited the TPA-induced reassembly of stress fibers and focal adhesions but not their TPA-induced disassembly, indicating that, furthermore, activation of some Rab family members is necessary for their TPA-induced reassembly. Of the Rab family members, at least Rab5 activation was necessary for the TPA-induced reassembly of stress fibers and focal adhesions. The TPA-induced, small G protein-mediated reorganization of stress fibers and focal adhesions was closely related to the TPA-induced cell motility. These results indicate that the Rho and Rab family members coordinately regulate the TPA-induced reorganization of stress fibers and focal adhesions that may cause cell motility.

scholarly journals Distinct Actions and Cooperative Roles of ROCK and mDia in Rho Small G Protein-induced Reorganization of the Actin Cytoskeleton in Madin–Darby Canine Kidney Cells

1999 ◽  
Vol 10 (8) ◽  
pp. 2481-2491 ◽  
Author(s):  
Katsutoshi Nakano ◽  
Kenji Takaishi ◽  
Atsuko Kodama ◽  
Akiko Mammoto ◽  
Hitoshi Shiozaki ◽  
...  
Keyword(s):  
Actin Cytoskeleton ◽  
Focal Adhesions ◽  
Stress Fibers ◽  
Kidney Cells ◽  
Madin Darby Canine Kidney ◽  
Downstream Target ◽  
Small G Protein ◽  
Target Molecules ◽  
Darby Canine Kidney ◽  
Canine Kidney

Rho, a member of the Rho small G protein family, regulates the formation of stress fibers and focal adhesions in various types of cultured cells. We investigated here the actions of ROCK and mDia, both of which have been identified to be putative downstream target molecules of Rho, in Madin–Darby canine kidney cells. The dominant active mutant of RhoA induced the formation of parallel stress fibers and focal adhesions, whereas the dominant active mutant of ROCK induced the formation of stellate stress fibers and focal adhesions, and the dominant active mutant of mDia induced the weak formation of parallel stress fibers without affecting the formation of focal adhesions. In the presence of C3 ADP-ribosyltransferase for Rho, the dominant active mutant of ROCK induced the formation of stellate stress fibers and focal adhesions, whereas the dominant active mutant of mDia induced only the diffuse localization of actin filaments. These results indicate that ROCK and mDia show distinct actions in reorganization of the actin cytoskeleton. The dominant negative mutant of either ROCK or mDia inhibited the formation of stress fibers and focal adhesions, indicating that both ROCK and mDia are necessary for the formation of stress fibers and focal adhesions. Moreover, inactivation and reactivation of both ROCK and mDia were necessary for the 12-O-tetradecanoylphorbol-13-acetate–induced disassembly and reassembly, respectively, of stress fibers and focal adhesions. The morphologies of stress fibers and focal adhesions in the cells expressing both the dominant active mutants of ROCK and mDia were not identical to those induced by the dominant active mutant of Rho. These results indicate that at least ROCK and mDia cooperatively act as downstream target molecules of Rho in the Rho-induced reorganization of the actin cytoskeleton.

scholarly journals CglB adhesins secreted at bacterial focal adhesions mediate gliding motility

2020 ◽  
Author(s):  
Salim T. Islam ◽  
Laetitia My ◽  
Nicolas Y. Jolivet ◽  
Akeisha M. Belgrave ◽  
Betty Fleuchot ◽  
...  
Keyword(s):  
Cell Surface ◽  
Focal Adhesion ◽  
Cell Envelope ◽  
Myxococcus Xanthus ◽  
Focal Adhesions ◽  
Gliding Motility ◽  
Bacterial Motility ◽  
Force Microscopy ◽  
Coupling Protein ◽  
Novel Protein

AbstractThe predatory deltaproteobacterium Myxococcus xanthus uses a helically-trafficked motor at bacterial focal adhesion (bFA) sites to power gliding motility. Using TIRF and force microscopy, we herein identify the integrin αI-domain-like outer-membrane (OM) lipoprotein CglB as an essential substratum-coupling protein of the gliding motility complex. Similar to most known OM lipoproteins, CglB is anchored on the periplasmic side of the OM and thus a mechanism must exist to secrete it to the cell surface in order for it to interact with the underlying substratum. We reveal this process to be mediated by a predicted OM β-barrel structure of the gliding complex. This OM platform was found to regulate the conformational activation and secretion of CglB across the OM. These data suggest that the gliding complex promotes surface exposure of CglB at bFAs, thus explaining the manner by which forces exerted by inner-membrane motors are transduced across the cell envelope to the substratum; they also uncover a novel protein secretion mechanism, highlighting the ubiquitous connection between secretion and bacterial motility.

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