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Essential for Protein Regulation CYTOSKELETON NEWS NEWS FROM CYTOSKELETON INC. Rac GTP Rho GTPases Control Cell Migration P-Rex1 Related Publications Fli2 Rac Research Tools January GDP 2020 Tiam1 Rac GTP v Rho GTPases Control Cell Migration Meetings Directed cell migration depends upon integrin-containing deposition of the ECM protein fibronectin which supports Cold Spring Harbor focal adhesions connecting the cell’s actin cytoskeleton nascent lamellipodia formation. The fibronectin binds to Conference - Systems with the extracellular matrix (ECM) and transmitting integrin and serves as an ECM substrate for Rac1-dependent 18 Biology: Global Regulation of mechanical force. Focal adhesion formation and subsequent directional migration . N e Gene Expression migration require dynamic re-organization of actin-based w contractile fibers and protrusions at a cell’s trailing and Cell Directionality s March 11-14th leading edges, respectively, in response to extracellular Cold Spring Harbor, NY guidance cues. Migration is essential for healthy cell Rho-family-mediated remodeling of the actin cytoskeleton is Cytoskeleton Supported (and organism) development, growth, maturation, and necessary for the cell’s directional response to extracellular physiological responses to diseases, injuries, and/or immune guidance cues (e.g., chemokines, matrix-released molecules, system challenges. Various pathophysiological conditions growth factors, etc). The response is either a migration Cold Spring Harbor (e.g., cancer, fibrosis, infections, chronic inflammation) usurp toward or away from environmental cues and this directional Conference -Neuronal and/or compromise the dynamic physiological processes response requires dynamic reorganization of the actin Circuts underlying migration1-5. cytoskeleton. A central question is the identity of the March 18-21st signaling molecule (or molecules) that relays the extracellular 1-4 Cold Spring Harbor, NY Rho-family GTPases (e.g., RhoA, Rac1, Cdc42, and RhoJ) act information to the actin cytoskeleton . The dogma has as molecular switches, cycling between a GTP-bound “on” been PI3 kinase, however this hypothesis has been called Cytoskeleton Supported state and a GDP-bound “off” state. Activation is mediated into question19-24. A new family of candidates has emerged 1 by guanine nucleotide exchange factors (GEFs) and intrinsic – Rho-family GTPases . For example, Rac1 activity at the P Drosophila u Cold Spring Harbor GTPase activity is amplified/activated by GTP-activating leading edge of border cells migrating collectively b l Conference - from proteins (GAPs). Rho-family GTPases regulate the dynamic is necessary for stable, organized forward movement and ic a assembly and disassembly of actin filaments which are Rac1-mediated forward protrusions are increased as part of a t Neuroscience to Artificially necessary for the formation, extension, withdrawal, and E-cadherin-mediated positive feedback loop when E-cadherin ion Intelligent Systems disassembly of the cellular protrusions (i.e., filopodia and s March 24-28th lamellipodia; regulated by Cdc42 and Rac, respectively) at the Filopodia formation Filopodia formation Cancer cell invasion Cell directionality Cold Spring Harbor, NY front of the cell and of contractile actomyosin fibers (regulated 1-8 Fibronectin deposition Cytoskeleton Supported by RhoA) at the rear of the cell (Fig. 1). Interestingly, recent Stabilised presence of Lamellipodia research clearly demonstrates that RhoA is also active at the Filopodia Rho-family GTPases Branched 1,9-12 Cytoskeleton leading edge . Of particular interest is how these GTPases Bundled at plasma membrane F-actin network regulate cell migration and force generation through the F-actin Products dynamic re-organization of the actin cytoskeleton1-3,13,14 (Fig. FMNL2 Actin Proteins 1). This newsletter discusses the roles of Rho-family GTPases Cdc42 in establishing and regulating cell-ECM adhesions and cellular RhoA FAS Rac Activation Assays FHOD3 Arp2/3 GTP directionality during cell migration. GTP Golgi GTP Antibodies reorientation ECM Proteins Focal Adhesions Migration RhoA Fam65a P-Rex1 ELISA Kits Elimination of RhoA signaling prevents F-actin stress fiber GTP Fli2 R G-LISA® Kits formation; this finding introduced the importance of Rho- e s Rac e Pull-down Assays family GTPases in the regulation of interactions (i.e., focal a 1,7 GDP r adhesions) between cells and the ECM . Activated RhoJ (a Golgi ch Motor Proteins member of the Rho family and related to Cdc42) GTPase Non- T o Small G-Proteins localizes to integrin-containing focal adhesions where it migratory o Tiam1 l Tubulin & FtsZ Proteins regulates their disassembly. GTP-bound RhoJ recruits a multi- Nucleus s protein complex consisting of the Rac GEF β-Pix and Arf Contact Us GAPs GIT1/2 to focal adhesions, promoting Rac1 and Cdc42 Rac 15,16 GTP Direction of P: 1 (303) 322.2254 activation while prohibiting RhoA activation . The result Movement of these trafficking events is focal adhesion disassembly Stress bers F: 1 (303) 322.2257 and increased motility, concomitant with decreased RhoA Figure 1. Role of Rho-family GTPases in cell-ECM adhesion and cell migration. Cells can 7,15-17 migrate in a lamellipodium-based manner with Rho-family-mediated actin polymeriza- E: [email protected] activity and actomyosin contractility . An indirect means tion driving formation of lamellipodia (Rac) and filopodia (Cdc42) at the leading edge, of communication between focal adhesions (specifically the and Rac-mediated actomyosin contractility promoting retraction at the trailing edge. W: cytoskeleton.com Cdc42 mediates protrusion of actin-enriched invadopodia into the ECM via matrix metal- integrins within) and Rho-family GTPases is through the loprotease (MMP)-mediated matrix degradation. Inset(lower left) Lamellipodia ECM. For example, Cdc42, but not Rac1, activation triggers and tail retraction in cell, F-actin stained with Acti- Stain™ 488 (Cat. #PHDG1) www.cytoskeleton.com Rho Small G-Protein PRODUCTS Continued from Page 1 References mechanically transduces guidance cues25. Rac also regulates migration of 1. Warner H. et al. 2019. Control of adhesion and protrusion in cell migration by Rho fibroblasts26. During in vitro E-cadherin-mediated mechanotransduction in GTPases. Curr. Opin. Cell Biol. 56, 64-70. 2. Lawson C.D. and Ridley A.J. 2018. Rho GTPase signaling complexes in cell migration migrating mouse C2C12 myoblasts, the adhesion molecule activates Cdc42 in and invasion. J. Cell Biol. , 447-457. the leading edges of migrating cells. Cdc42 is required for E-cadherin-directed 217 27 3. Ridley A.J. 2011. Life at the leading edge. Cell. 145, 1012-1022. cell migration and mechanical force generation . Furthermore, Cdc42 also 4. Sit S.-T. and Manser E. 2011. Rho GTPases and their role in organizing the actin directs neutrophil migration as it is activated prior to the cell’s response to cytoskeleton. J. Cell Sci. 124, 679-683. environmental cues, while acting in concert with Rac activation, which likely 5. Hodges R.G. and Ridley A.J. 2016. Regulating Rho GTPases and their regulators. Nat. powers the cellular movement through widespread remodeling of the cell’s Rev. Mol. Cell Biol. 17, 496-510. actin cytoskeleton. Cdc42 activation also inhibits RhoA activity, suggesting that 6. Ridley A.J. et al. 1992. The small GTP-binding protein rac regulates growth factor- the two GTPases work in opposition during directed migration24. induced membrane ruffling. Cell. 70, 401-410. 7. Ridley A.J. and Hall A. 1992. The GTP-binding protein rho regulates the assembly of Summary focal adhesions and actin stress fibers in response to growth factors. Cell. 70, 389-399. 8. Nobes C.D. and Hall A. 1995. Rho, Rac, and Cdc42 GTPases regulate the assembly of multimolecular focal complexes associated with actin stress fibers, lamellipodia, and Despite the tremendous strides in understanding the role of Rho-family GTPases filopodia. Cell. 81, 53-62. in cell-ECM adhesions and cell migration, many questions remain unanswered. 9. Goulimari P. et al. 2005. Galpha12/13 is essential for directed cell migration and A majority of the cell culture data comes from 2D cultures which now must localized Rho-Dia1 function. J. Biol. Chem. 280, 42242-42251. be confirmed in 3D cell culture models. This is especially relevant when 10. Kurokawa K. and Matsuda M. 2005. Localized RhoA activation as a requirement for studying the role of Rho-family GTPases in cell-ECM (and cell-cell) interactions the induction of membrane ruffling. Mol. Biol. Cell. 16, 4294-4303. as these signaling cascades regulate not only basic physiological pathways, 11. Pertz O. et al. 2006. Spatiotemporal dynamics of RhoA activity in migrating cells. Nature. 440, 1069-1072. but are corrupted in human pathological conditions. Importantly, Rho-family 12. Machacek M. et al. 2009. Coordination of Rho GTPase activities during cell protrusion. GTPases are likely to have different roles (or at least proportionally different Nature 461, 99-103. contributions) to cell-ECM adhesions and migratory behavior depending on 13. Aspenstrom P. et al. 1996. Two GTPases, Cdc42 and Rac, bind directly to a protein cell type or context (or even cancer type in disease models). Of paramount implicated in the immunodeficiency disorder Wiskott-Aldrich syndrome. Curr. Biol. importance is also the identification of all Rho-family GTPase binding partners 6, 70-75. and an emphasis on studying the signaling cascades at a systems level that 14. Machesky L.M. et al. 1999. Scar, a WASp-related protein, activates
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