RAC2 (ras-related C3 botulinum toxin substrate 2 (rho family, small GTP binding protein Rac2))

2008-08-01   Teresa Gómez del Pulgar , Juan Carlos Lacal 

Centro Nacional de Biotecnología (CNB), Darwin 3, 28049 Madrid, Spain





The Rac2 gene sequence contains 7 exons (Courjal et al., 1997) and is expressed specifically in hematopoietic cells. Human Rac2 gene locus is silenced in non-hematopoietic cells by a mechanism that involves DNA methylation (Ladd et al., 2004). Cells that lack Rac2 expression exhibit increased cytosine methylation in the sequences flanking the gene, whereas cells that express Rac2 exhibit increased cytosine methylation within the body of the Rac2 gene.


The human Rac2 gene promoter lacks TATA and CCAAT boxes, utilizes multiple transcription initiation sites, and contains several putative Sp1 binding sites, which is common in promoters that lack TATA boxes (Ladd et al., 2004).
The transcript length is of 1471 nt translated to a 192 residues protein.



Rac2 protein belongs to the GTP-binding proteins of the Rho family and cycles between an active GTP-bound form and an inactive GDP-bound form. This regulatory cycle is exerted by three distinct families of proteins: guanine exchange factors (GEFs), GTPase-activating proteins (GAPs), and guanine nucleotide dissociation inhibitors (GDIs). Several GEFs have been shown to activate Rac2 selectively, Vav1 (Ming et al., 2007), Tiam1 (Haeusler et al., 2003), P-Rex1 (Welch et al., 2002), Swap70 (Sivalenka and Jessberger, 2004) and Dock2 (Nishihara et al., 2002). Two GAPs that act on Rac2 are Abr and Bcr (Chuang et al., 1995), as well as others found in leukocytes.
Rac2 function depends on association of the GTPase with membranes and subcellular localization, properties influenced by C-terminal lipid modifications, specifically is modified by the C20 GG isoprenoid.
Upon GTP loading, a conformational change takes place that allows Rac2 protein to interact with several downstream effectors that ultimately process the information and propagate the signal within the cell, causing changes in the actin cytoskeleton, release of inflammatory modulators and innate immunity. The signaling of active Rac2 is mediated by its interaction with effector proteins such as p67phox and cytochrome b-558 (Diebold and Bokoch, 2001), PLCbeta2 (Piechulek et al., 2005), nitric oxide synthase 2 (NOS2) (Kuncewicz et al., 2001) and Pak1 (Carstanjen et al., 2005).


Expression is restricted to hematopoietic cells and exhibits the highest expression in myeloid cells. Rac2 expression is regulated during the differentiation of hematopoietic and myeloid cells. There is some data suggesting that Rac2 might be expressed in tumors.


Once activated Rac2 is mainly localized in endomembranes.


As suggested by its restricted expression, Rac2 has a specialized role in many hematopoietic and immunological processes. Rac2 deficient mice show defects in stem cells, mast cells as well as B and T cells.
Role in hematopoietic stem-cell progenitor engraftment
The contribution of the GTPase Rac2 to the normal functioning of hematopoietic stem-cell progenitors (HSC/Ps) was addressed based on the phenotype of Rac2-/- mice (Gu et al., 2003). HSC/Ps from these mice showed normal short-term engraftment, but decreased adhesion, suggesting a key role for Rac2 in integrin-mediated stem-cell adhesion. In addition, Rac2-/- HSC/Ps formed colonies with both impaired growth and migration, and showed an increased rate of apoptosis.
In response to stromal derived factor 1, Rac2-/- cells failed in cortical F-actin assembly, and presented reduced cell spreading and actin-based membrane protrusion.
Role in neutrophils function
Several reports point out Rac2 is the predominant Rac GTPase functioning in neutrophils. These observations came from studies in neutrophils from Rac2-/- mice and a patient with a dominant-negative Rac2 mutation in which these cells showed decreased motility, adhesion, major defects in cortical F-actin assembly, and accordingly, chemotaxis and reduced phagocytosis and superoxide production by NAPH oxidase (Williams et al., 2000; Roberts et al., 1999; Li et al., 2002; Gu et al., 2003). Rac2 is required for oxidase activity through its direct interaction with p67-phox and cytochrome b 558.
Role in B-cell development
Rac2-/- mice exhibit multiple defects in B-cell development, with reduced numbers of peripheral blood B-cells and IgM-secreting plasma cells, a severe reduction in the number of marginal zone and peritoneal B1 cells (Croker et al., 2002). Rac2 participates in the positive selection through the B-cell receptor (BCR), since is activated by BCR cross-linking (Grill and Schrader, 2002).
Role in T-cell differentiation
Rac2 activity is required for interferon-gamma (IFNgamma) production both in vitro and in vivo during normal T-cell activation and Th1-cell differentiation, through simultaneous activation of both the NFkappaB and p38 pathways (Li et al., 2000).
Role in Mast cell survival
The absence of Rac2 results in defects growth, survival, chemotaxis, adhesion, and degranulation in mast cell (Yang et al., 2000). Rac2 is critical in regulating the growth factor-induced survival through activation of Akt and a change in expression levels of the Bcl-2 family members BAD and Bcl-XL (Yang et al., 2000).


Rac2 share significant sequence identity (~88%) with the other two members of the subfamily Rac: Rac1 and Rac3. The three proteins diverge primarily in the C-terminal 15 residues. Regarding to the biochemical properties, Rac2 shows a slower nucleotide association and is more efficiently activated by the Rac-GEF Tiam1 than Rac1 and Rac3.



Two single nucleotide polymorphisms (SNP) have been observed in gliomas (Idbaih et al., 2008). The SNPs rs2239774 in exon 2 (codon 27, GCC to GCG, Ala to Ala) and rs3179967 in exon 6 (codon 159, GCT to GCC, Ala to Ala) were observed in 15/78 and 7/78 cases, respectively. No association between these two SNPs with phenotype, tumor grade, patient age, and patient gender was seen.


A point mutation has been identified in one allele of the Rac2 gene resulting in the substitution of Asp57 by an Asn (Rac2D57N) in a patient with a primary immunodeficiency syndrome (Ambruso et al., 2000; Williams et al., 2000). Rac2D57N binds GDP but not GTP and inhibits oxidase activation and superoxide production in vitro.


So far only two studies have searched for the presence of somatic mutations, both of them analyzed human brain tumors. Hwang et al. found 26% of cases had Rac2 gene mutation, two cases with decreased Rac2 expression and four cases with normal Rac2 expression. One case showed the mutation site nearby the GTP-binding site, which may affect Rac2 GTPase activity, but the site of Rac2 mutation seems not to concentrate in the effector region. However, Idbaih et al. did not find missense mutations in a series of 78 gliomas.

Implicated in

Entity name
Lack of Rac2 activity causes immunodeficiency (Ambruso et al., 2000; Williams et al., 2000). A single patient was identified with a primary immunodeficiency syndrome resulting from a heterozygous mutation in the Rac2 gene. In the first 5 months after birth, the patient presented several bacterial infections, poor wound healing, and absence of pus in the wounds, indicative of a phagocyte defect. The neutrophils had decreased chemotactic motility, polarization, and secretion of azurophilic granules. Rac2 levels were reduced, suggesting a defect in this GTPase. Western blot analysis of lysates from patient neutrophils demonstrated decreased levels of Rac2 protein. Molecular analysis identified a point mutation in one allele of the Rac2 gene resulting in the substitution of Asp57 by an Asn (Rac2D57N). Rac2D57N inhibits oxidase activation and superoxide production in vitro. These data represent the description of an inhibitory mutation in a member of the Rho family of GTPases associated with a human immunodeficiency syndrome.
Entity name
Brain tumors
Expression of Rac2 was examined by RT-PCR and Northern blotting in human brain tumors: 10 astrocytomas, 8 meningiomas, and 8 pituitary adenomas (Hwang et al., 2005). The overexpression of Rac2 was evident in 1/10 astrocytomas and 1/8 meningiomas. No overexpression was found in pituitary adenomas. The decreased expression of Rac2 was found in 15 of 26 brain tumors (8/10 astrocytomas, 2/8 meningiomas and 5/8 pituitary adenomas).
Entity name
Head and neck squamous cell cancer
Western blot analysis showed increased expression of Rac2 in a malignant squamous cell cancer cell line and a premalignant dysplastic cell line compared to the normal human epidermal keratinocytes (Abraham et al., 2001). This observation was confirmed with an immunohistochemical study of 15 moderately to poorly differentiated head and neck squamous cell cancer specimens, where a specific increased expression of Rac2 in areas of squamous cell cancer compared to the normal tissue was observed. Rac2 shows nuclear staining in normal human epidermal keratinocytes increasing sequentially in premalignant and malignant cell lines. In addition, there is specific cytoplasmic staining of the malignant cancer cell line which is absent in the normal and premalignant cell lines. This differential cytoplasmic staining may be able to distinguish invasive squamous cell carcinoma from dysplastic lesions and benign normal mucosa. Consequently it has been proposed that this GTPase could have an important role in the diagnosis and staging of this tumor type.
Entity name
Activating mutations of KIT, which encodes the receptor for the cytokine stem cell factor, have been described in acute myeloid leukemia. Genetic disruption of Rac2 or pharmacologic evidence through treatment with Rac inhibitor NC23766, implicate Rac2 in regulating KIT-induced transformation in acute myeloid leukaemia (Munugalavadla et al., 2007). These results suggest Rac2 as a potential novel therapeutic target for the treatment of KIT-bearing acute myeloid leukemia.
Gene targeting of Rac1 and Rac2 significantly delays or abrogates development of chronic myelogenous leukemia (CML), a clonal myeloproliferative disease (MPD) initiated by expression of the p210-BCR- ABL fusion protein (Thomas et al., 2007). These genetic data were further substantiated experimentally by use of NSC23766, small molecule antagonist of Rac activation, to validate biochemically and functionally Rac as a molecular target in both a relevant animal model and in primary human CML cells in vitro and in a xenograft model in vivo. These findings indicate that Rac GTPases are critical for p210-BCR-ABL-mediated transformation and, therefore, suggest that the Rac GTPases may prove to be useful therapeutically by targeting alternative signaling pathways, which may be responsible for resistance and relapse in CML.


Pubmed IDLast YearTitleAuthors
115685562001Motility-related proteins as markers for head and neck squamous cell cancer.Abraham MT et al
107581622000Human neutrophil immunodeficiency syndrome is associated with an inhibitory Rac2 mutation.Ambruso DR et al
158146842005Rac2 regulates neutrophil chemotaxis, superoxide production, and myeloid colony formation through multiple distinct effector pathways.Carstanjen D et al
74797681995Abr and Bcr are multifunctional regulators of the Rho GTP-binding protein family.Chuang TH et al
92992431997Structure and chromosomal assignment to 22q12 and 17qter of the ras-related Rac2 and Rac3 human genes.Courjal F et al
119070952002The Rac2 guanosine triphosphatase regulates B lymphocyte antigen receptor responses and chemotaxis and is required for establishment of B-1a and marginal zone B lymphocytes.Croker BA et al
112245192001Molecular basis for Rac2 regulation of phagocyte NADPH oxidase.Diebold BA et al
158921192005Rho GTPase expression in tumourigenesis: evidence for a significant link.Gómez del Pulgar T et al
123844162002Activation of Rac-1, Rac-2, and Cdc42 by hemopoietic growth factors or cross-linking of the B-lymphocyte receptor for antigen.Grill B et al
145640092003Hematopoietic cell regulation by Rac1 and Rac2 guanosine triphosphatases.Gu Y et al
146757732003Comparative functional analysis of the Rac GTPases.Haeusler LC et al
158125942005Rac2 expression and mutation in human brain tumors.Hwang SL et al
182172102008Mutational analysis of Rac2 in gliomas.Idbaih A et al
114577252001Specific association of nitric oxide synthase-2 with Rac isoforms in activated murine macrophages.Kuncewicz T et al
154743142004Identification of a genomic fragment that directs hematopoietic-specific expression of Rac2 and analysis of the DNA methylation profile of the gene locus.Ladd PD et al
108648722000Role of the guanosine triphosphatase Rac2 in T helper 1 cell differentiation.Li B et al
170604552007The Rac effector p67phox regulates phagocyte NADPH oxidase by stimulating Vav1 guanine nucleotide exchange activity.Ming W et al
174832982007Genetic and pharmacologic evidence implicating the p85 alpha, but not p85 beta, regulatory subunit of PI3K and Rac2 GTPase in regulating oncogenic KIT-induced transformation in acute myeloid leukemia and systemic mastocytosis.Munugalavadla V et al
121760412002DOCK2 mediates T cell receptor-induced activation of Rac2 and IL-2 transcription.Nishihara H et al
161721252005Isozyme-specific stimulation of phospholipase C-gamma2 by Rac GTPases.Piechulek T et al
100720711999Deficiency of the hematopoietic cell-specific Rho family GTPase Rac2 is characterized by abnormalities in neutrophil function and host defense.Roberts AW et al
155428372004SWAP-70 regulates c-kit-induced mast cell activation, cell-cell adhesion, and migration.Sivalenka RR et al
179966502007Rac guanosine triphosphatases represent integrating molecular therapeutic targets for BCR-ABL-induced myeloproliferative disease.Thomas EK et al
119554342002P-Rex1, a PtdIns(3,4,5)P3- and Gbetagamma-regulated guanine-nucleotide exchange factor for Rac.Welch HC et al
109618592000Dominant negative mutation of the hematopoietic-specific Rho GTPase, Rac2, is associated with a human phagocyte immunodeficiency.Williams DA et al
108433882000Rac2 stimulates Akt activation affecting BAD/Bcl-XL expression while mediating survival and actin function in primary mast cells.Yang FC et al

Other Information

Locus ID:

NCBI: 5880
MIM: 602049
HGNC: 9802
Ensembl: ENSG00000128340


dbSNP: 5880
ClinVar: 5880
TCGA: ENSG00000128340


Gene IDTranscript IDUniprot

Expression (GTEx)



PathwaySourceExternal ID
MAPK signaling pathwayKEGGko04010
Wnt signaling pathwayKEGGko04310
Axon guidanceKEGGko04360
VEGF signaling pathwayKEGGko04370
Focal adhesionKEGGko04510
Adherens junctionKEGGko04520
Natural killer cell mediated cytotoxicityKEGGko04650
B cell receptor signaling pathwayKEGGko04662
Fc epsilon RI signaling pathwayKEGGko04664
Leukocyte transendothelial migrationKEGGko04670
Regulation of actin cytoskeletonKEGGko04810
Colorectal cancerKEGGko05210
Pancreatic cancerKEGGko05212
MAPK signaling pathwayKEGGhsa04010
Wnt signaling pathwayKEGGhsa04310
Axon guidanceKEGGhsa04360
VEGF signaling pathwayKEGGhsa04370
Focal adhesionKEGGhsa04510
Adherens junctionKEGGhsa04520
Natural killer cell mediated cytotoxicityKEGGhsa04650
B cell receptor signaling pathwayKEGGhsa04662
Fc epsilon RI signaling pathwayKEGGhsa04664
Leukocyte transendothelial migrationKEGGhsa04670
Regulation of actin cytoskeletonKEGGhsa04810
Pathways in cancerKEGGhsa05200
Colorectal cancerKEGGhsa05210
Pancreatic cancerKEGGhsa05212
Chemokine signaling pathwayKEGGko04062
Chemokine signaling pathwayKEGGhsa04062
Fc gamma R-mediated phagocytosisKEGGko04666
Fc gamma R-mediated phagocytosisKEGGhsa04666
Viral myocarditisKEGGhsa05416
Ras signaling pathwayKEGGhsa04014
Rap1 signaling pathwayKEGGhsa04015
Rap1 signaling pathwayKEGGko04015
cAMP signaling pathwayKEGGhsa04024
cAMP signaling pathwayKEGGko04024
Choline metabolism in cancerKEGGhsa05231
Choline metabolism in cancerKEGGko05231
Sphingolipid signaling pathwayKEGGhsa04071
Sphingolipid signaling pathwayKEGGko04071
Platelet activation, signaling and aggregationREACTOMER-HSA-76002
GPVI-mediated activation cascadeREACTOMER-HSA-114604
Signal TransductionREACTOMER-HSA-162582
Signaling by Rho GTPasesREACTOMER-HSA-194315
Rho GTPase cycleREACTOMER-HSA-194840
RHO GTPase EffectorsREACTOMER-HSA-195258
RHO GTPases Activate NADPH OxidasesREACTOMER-HSA-5668599
Signaling by GPCRREACTOMER-HSA-372790
GPCR downstream signalingREACTOMER-HSA-388396
G alpha (12/13) signalling eventsREACTOMER-HSA-416482
Signaling by WntREACTOMER-HSA-195721
Beta-catenin independent WNT signalingREACTOMER-HSA-3858494
PCP/CE pathwayREACTOMER-HSA-4086400
Developmental BiologyREACTOMER-HSA-1266738
Axon guidanceREACTOMER-HSA-422475
Semaphorin interactionsREACTOMER-HSA-373755
Sema4D in semaphorin signalingREACTOMER-HSA-400685
Sema4D induced cell migration and growth-cone collapseREACTOMER-HSA-416572
Fluid shear stress and atherosclerosisKEGGko05418
Fluid shear stress and atherosclerosisKEGGhsa05418

Protein levels (Protein atlas)

Not detected


Entity IDNameTypeEvidenceAssociationPKPDPMIDs
PA444760Leukemia, Myeloid, AcuteDiseaseClinicalAnnotationassociatedPD28485375


Pubmed IDYearTitleCitations
219005462012NADPH oxidase complex and IBD candidate gene studies: identification of a rare variant in NCF2 that results in reduced binding to RAC2.69
167723322006Rac1 and Rac2 regulate macrophage morphology but are not essential for migration.61
268924682016Long noncoding RNA AFAP1-AS1 indicates a poor prognosis of hepatocellular carcinoma and promotes cell proliferation and invasion via upregulation of the RhoA/Rac2 signaling.53
224118712012Rac2-MRC-cIII-generated ROS cause genomic instability in chronic myeloid leukemia stem cells and primitive progenitors.49
233822362013Transforming mutations of RAC guanosine triphosphatases in human cancers.47
235918732013Association between Gαi2 and ELMO1/Dock180 connects chemokine signalling with Rac activation and metastasis.45
187996532008Primary granule exocytosis in human neutrophils is regulated by Rac-dependent actin remodeling.40
220184702011Pathogen-derived effectors trigger protective immunity via activation of the Rac2 enzyme and the IMD or Rip kinase signaling pathway.40
172278222007Signaling requirements for translocation of P-Rex1, a key Rac2 exchange factor involved in chemoattractant-stimulated human neutrophil function.31
200650812010Rac1 and Rac2 GTPases are necessary for early erythropoietic expansion in the bone marrow but not in the spleen.31


Teresa Gómez del Pulgar ; Juan Carlos Lacal

RAC2 (ras-related C3 botulinum toxin substrate 2 (rho family, small GTP binding protein Rac2))

Atlas Genet Cytogenet Oncol Haematol. 2008-08-01

Online version: http://atlasgeneticsoncology.org/gene/42021/rac2