Rac (GTPase)

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Rac is a subfamily of the Rho family of GTPases, [1] small (~21 kDa) signaling G proteins (more specifically a GTPase). Just as other G proteins, Rac acts as a molecular switch, remaining inactive while bound to guanosine diphosphate (GDP) and activated once guanine nucleotide exchange factors (GEFs) remove GDP, permitting guanosine triphosphate (GTP) to bind. When bound to GTP, Rac is activated. In its activated state, Rac participates in the regulation of cell movement, through its involvement in structural changes to the actin cytoskeleton. [2] By changing the cytoskeletal dynamics within the cell, Rac-GTPases are able to facilitate the recruitment of neutrophils to the infected tissues, and to regulate degranulation of azurophil and integrin-dependent phagocytosis. [3]

Activated Rac also regulates the effector functions of the target proteins involved in downstream signaling. As an essential subunit of NOX2 (NADPH oxidase enzyme complex), Rac is required for ROS (reactive oxygen species) production involved in the formation of NETs (neutrophil extracellular traps, thus, facilitating the pathogen and debris clearance by neutrophils, and the reduction of inflammation. [3]

The abnormal activities of Rac including its hyperactivation, resistance to degradation, and abnormal localization of its signaling protein components were found to facilitate the development of cancerous cells and resist to anticancer treatment. [4]

Recent experiments on Drosophila suggest that Rac could be involved in mediating the process of forgetting. Hyperactivation of Rac increases memory decay whereas its inhibition prevents interference-induced forgetting and slows down passive memory decay. [5] [6]

Classification

The Rho family of GTPases includes Rac, Rho, and Cdc42 small G-protein groups. Rac comprises Rac1, Rac2, Rac3, and RhoG subgroups.

The extensive cross-talk within these groups of GTPase provides a significant impact on the biological responses of the cell, influencing the activity of the cell cycle machinery. Ras cooperates with Cdc42 to regulate Elk1 phosphorylation and transcriptional activity of SRF. Ras also cooperates with Rho and Ras to activate other downstream signaling pathways. [7]

Related Research Articles

GTPases are a large family of hydrolase enzymes that bind to the nucleotide guanosine triphosphate (GTP) and hydrolyze it to guanosine diphosphate (GDP). The GTP binding and hydrolysis takes place in the highly conserved P-loop "G domain", a protein domain common to many GTPases.

Small GTPases, also known as small G-proteins, are a family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate (GTP). They are a type of G-protein found in the cytosol that are homologous to the alpha subunit of heterotrimeric G-proteins, but unlike the alpha subunit of G proteins, a small GTPase can function independently as a hydrolase enzyme to bind to and hydrolyze a guanosine triphosphate (GTP) to form guanosine diphosphate (GDP). The best-known members are the Ras GTPases and hence they are sometimes called Ras subfamily GTPases.

GTPase-activating proteins or GTPase-accelerating proteins (GAPs) are a family of regulatory proteins whose members can bind to activated G proteins and stimulate their GTPase activity, with the result of terminating the signaling event. GAPs are also known as RGS protein, or RGS proteins, and these proteins are crucial in controlling the activity of G proteins. Regulation of G proteins is important because these proteins are involved in a variety of important cellular processes. The large G proteins, for example, are involved in transduction of signaling from the G protein-coupled receptor for a variety of signaling processes like hormonal signaling, and small G proteins are involved in processes like cellular trafficking and cell cycling. GAP's role in this function is to turn the G protein's activity off. In this sense, GAPs function is opposite to that of guanine nucleotide exchange factors (GEFs), which serve to enhance G protein signaling.

<span class="mw-page-title-main">Guanine nucleotide exchange factor</span> Proteins which remove GDP from GTPases

Guanine nucleotide exchange factors (GEFs) are proteins or protein domains that activate monomeric GTPases by stimulating the release of guanosine diphosphate (GDP) to allow binding of guanosine triphosphate (GTP). A variety of unrelated structural domains have been shown to exhibit guanine nucleotide exchange activity. Some GEFs can activate multiple GTPases while others are specific to a single GTPase.

The Rho family of GTPases is a family of small signaling G proteins, and is a subfamily of the Ras superfamily. The members of the Rho GTPase family have been shown to regulate many aspects of intracellular actin dynamics, and are found in all eukaryotic kingdoms, including yeasts and some plants. Three members of the family have been studied in detail: Cdc42, Rac1, and RhoA. All G proteins are "molecular switches", and Rho proteins play a role in organelle development, cytoskeletal dynamics, cell movement, and other common cellular functions.

<span class="mw-page-title-main">CDC42</span> Protein-coding gene in the species Homo sapiens

Cell division control protein 42 homolog is a protein that in humans is encoded by the CDC42 gene. Cdc42 is involved in regulation of the cell cycle. It was originally identified in S. cerevisiae (yeast) as a mediator of cell division, and is now known to influence a variety of signaling events and cellular processes in a variety of organisms from yeast to mammals.

<span class="mw-page-title-main">FGD1</span> Protein-coding gene in the species Homo sapiens

FYVE, RhoGEF and PH domain-containing protein 1 (FGD1) also known as faciogenital dysplasia 1 protein (FGDY), zinc finger FYVE domain-containing protein 3 (ZFYVE3), or Rho/Rac guanine nucleotide exchange factor FGD1 is a protein that in humans is encoded by the FGD1 gene that lies on the X chromosome. Orthologs of the FGD1 gene are found in dog, cow, mouse, rat, and zebrafish, and also budding yeast and C. elegans. It is a member of the FYVE, RhoGEF and PH domain containing family.

<span class="mw-page-title-main">Transforming protein RhoA</span> Protein and coding gene in humans

Transforming protein RhoA, also known as Ras homolog family member A (RhoA), is a small GTPase protein in the Rho family of GTPases that in humans is encoded by the RHOA gene. While the effects of RhoA activity are not all well known, it is primarily associated with cytoskeleton regulation, mostly actin stress fibers formation and actomyosin contractility. It acts upon several effectors. Among them, ROCK1 and DIAPH1 are the best described. RhoA, and the other Rho GTPases, are part of a larger family of related proteins known as the Ras superfamily, a family of proteins involved in the regulation and timing of cell division. RhoA is one of the oldest Rho GTPases, with homologues present in the genomes since 1.5 billion years. As a consequence, RhoA is somehow involved in many cellular processes which emerged throughout evolution. RhoA specifically is regarded as a prominent regulatory factor in other functions such as the regulation of cytoskeletal dynamics, transcription, cell cycle progression and cell transformation.

<span class="mw-page-title-main">RAC2</span> Protein-coding gene in the species Homo sapiens

Rac2 is a small signaling G protein, and is a member of the Rac subfamily of the family Rho family of GTPases. It is encoded by the gene RAC2.

<span class="mw-page-title-main">RhoG</span> Protein-coding gene in the species Homo sapiens

RhoG is a small monomeric GTP-binding protein, and is an important component of many intracellular signalling pathways. It is a member of the Rac subfamily of the Rho family of small G proteins and is encoded by the gene RHOG.

<span class="mw-page-title-main">Rnd1</span> Protein-coding gene in the species Homo sapiens

Rnd1 is a small signaling G protein, and is a member of the Rnd subgroup of the Rho family of GTPases. It is encoded by the gene RND1.

<span class="mw-page-title-main">Rnd3</span> Protein-coding gene in the species Homo sapiens

Rnd3 is a small signaling G protein, and is a member of the Rnd subgroup of the Rho family of GTPases. It is encoded by the gene RND3.

<span class="mw-page-title-main">Dedicator of cytokinesis protein 7</span> Protein found in humans

Dedicator of cytokinesis protein (Dock7) is a large protein encoded in the human by the DOCK7 gene, involved in intracellular signalling networks. It is a member of the DOCK-C subfamily of the DOCK family of guanine nucleotide exchange factors (GEFs) which function as activators of small G-proteins. Dock7 activates isoforms of the small G protein Rac.

TCL is a small signaling G protein, and is a member of the Rho family of GTPases.

Rif is a small signaling G protein, and is a member of the Rho family of GTPases. It is primarily active in the brain and plays a physiological role in the formation of neuronal dendritic spine. This process is regulated by FARP1, a type of activator for RhoA GTPases. Alternatively, Rif can induce the formation of actin stress fibers in epithelial cells, which is dependent on the activity levels of ROCK proteins since the absence of ROCK activity would mean Rif would be unable to stimulate the growth of stress fibers.

<span class="mw-page-title-main">Dedicator of cytokinesis protein 4</span> Protein found in humans

Dedicator of cytokinesis protein 4 (Dock4), is a large protein encoded in the human by the DOCK4 gene, involved in intracellular signalling networks. It is a member of the DOCK-B subfamily of the DOCK family of guanine nucleotide exchange factors (GEFs) which function as activators of small G-proteins. Dock4 activates the small G proteins Rac and Rap1.

<span class="mw-page-title-main">Dedicator of cytokinesis protein 11</span> Protein-coding gene in humans

Dedicator of cytokinesis protein 11 (Dock11), also known as Zizimin2, is a large protein encoded in the human by the DOCK11 gene, involved in intracellular signalling networks. It is a member of the DOCK-D subfamily of the DOCK family of guanine nucleotide exchange factors (GEFs) which function as activators of small G-proteins. Dock11 activates the small G protein Cdc42.

<i>Clostridioides difficile</i> toxin A Cytotoxin produced by Clostridioides difficile

Clostridioides difficile toxin A (TcdA) is a toxin produced by the bacteria Clostridioides difficile, formerly known as Clostridium difficile. It is similar to Clostridium difficile Toxin B. The toxins are the main virulence factors produced by the gram positive, anaerobic, Clostridioides difficile bacteria. The toxins function by damaging the intestinal mucosa and cause the symptoms of C. difficile infection, including pseudomembranous colitis.

<span class="mw-page-title-main">Alan Hall</span> British cell biologist and professor

Alan Hall FRS was a British cell biologist and a biology professor at the Sloan-Kettering Institute, where he was chair of the Cell Biology program. Hall was elected a Fellow of the Royal Society in 1999.

<span class="mw-page-title-main">PLEKHG2</span> Protein-coding gene in the species Homo sapiens

Pleckstrin homology domain containing, family G member 2 (PLEKHG2) is a protein that in humans is encoded by the PLEKHG2 gene. It is sometimes written as ARHGEF42, FLJ00018.

References

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  2. "Rac", Encyclopedia of Cancer, Springer Berlin Heidelberg, 2011, p. 3133, doi:10.1007/978-3-642-16483-5_4891, ISBN   9783642164828
  3. 1 2 Pantarelli C, Welch HC (November 2018). "Rac-GTPases and Rac-GEFs in neutrophil adhesion, migration and recruitment". European Journal of Clinical Investigation. 48 Suppl 2 (Suppl Suppl 2): e12939. doi:10.1111/eci.12939. PMC   6321979 . PMID   29682742.
  4. Sun D, Xu D, Zhang B (December 2006). "Rac signaling in tumorigenesis and as target for anticancer drug development". Drug Resistance Updates. 9 (6): 274–287. doi:10.1016/j.drup.2006.12.001. PMID   17234445.
  5. Shuai Y, Lu B, Hu Y, Wang L, Sun K, Zhong Y (February 2010). "Forgetting is regulated through Rac activity in Drosophila". Cell. 140 (4): 579–589. doi: 10.1016/j.cell.2009.12.044 . PMID   20178749.
  6. "Brain memory is actively cleared". scitechstory.com. Archived from the original on 2012-12-19.
  7. Bar-Sagi, Dafna; Hall, Alan (2010). "Ras and Rho GTPases". Cell. 103 (2): 227–238. doi: 10.1016/S0092-8674(00)00115-X . PMID   11057896. S2CID   14521188.