RAC3 (ras-related C3 botulinum toxin substrate 3 (rho family, small GTP binding protein Rac3))

2012-04-01   Nora C Heisterkamp 

Division of Hematology-Oncology, Childrens Hospital of Los Angeles, CA, USA

Identity

HGNC
LOCATION
17q25.3
LOCUSID
ALIAS
-
FUSION GENES

DNA/RNA

Note

6 exons, spread out over approximately 2,4 kb.

Description

The Rac3 gene encompasses 6 exons on chromosome 17. Exon 1 encodes residues 1-12, exon 2 residues 13-36, exon 3 residues 37-75, exon 4 residues 76-96, exon 5 residues 97-149 and exon 6 residues 150-192.

Transcription

Human Rac3 mRNA is a single species of around 1 kb. No splice variants have been reported. Factors that would regulate gene expression on a transcriptional level have not yet been reported.

Pseudogene

No pseudogenes of Rac3 are reported in human.

Proteins

Note

The Rac3 gene encodes a single protein of 192 amino acid residues.
Atlas Image
Schematic representation of the Rac3 protein (not to scale). Mutations that generate mutants that are locked in a certain conformation - constitutively active or dominant negative - are shown. The C-terminal end contains the CTVM motif that is post-translationally modified the three last amino acid residues are removed and the C residue is geranyl-geranylated.

Description

Rac3 is a small 21 kDa GTPase that acts as a molecular switch. In its active form, it is bound to GTP, whereas it is inactive in its GDP-bound form. Racs are controlled by guanidine activating proteins (GEFs) that exchange bound GDP for GTP and by GTPase activating proteins (GAPs) that promote GTP hydrolysis. Because of the hydrophobic isoprenyl moiety at the C-terminal end, it is associated with membranes. In the cytoplasm it associates with the chaperone RhoGDI.

Expression

Rac3 mRNA was reported in human cell lines including GM04155 (lymphoblastic leukemia), K562 (CML), 5838 (Ewing sarcoma), HL60 (promyelocytic leukemia) and DU4475 (breast cancer). Rac3 expression was reported using semi-quantitative RT/PCR in gastric tumor and adjacent normal tissue as well as gastric cancer cell lines. Expression of Rac3 using RT/PCR (38 cycles) was reported in human brain, liver, kidney and pancreas poly A RNA and also 19% of brain tumors expressed Rac3 mRNA. Rac3-specific polyclonal antibodies were used to show Rac3 protein in the brain (deep cerebellar nuclei and the pons) in 7 day old mice. Low level expression of mouse rac3 has been reported in bone-marrow-derived monocytes and in B-lineage lymphoblasts using standard and Real-Time RT/PCR. Expression of Rac3 is inferred because of the effect of siRNA knockdown in cell lines including HCT116 colon cancer, MDA-MB231 breast cancer, HeLa, and PC3 prostate cancer (Zhu et al., 2011). Real-time RT/PCR showed Rac3 mRNA in prostate cancer biopsy samples (Engers et al., 2007). Analysis of gene expression profiling datasets (Chang et al., 2005) in breast cancer samples showed Rac3 expression (Walker et al., 2011).

Localisation

The Rac3 protein is located on endomembranes and cell membranes. Nuclear localization was also reported (Walker et al., 2011).

Function

Rac proteins regulate a variety of functions including cytoskeletal organization, cell cycle, reactive oxygen species production, and vesicle trafficking. In its activity on reactive oxygen species production, Rac3 is able to activate Nox1, Nox2 and Nox3 (Miyano et al., 2009; Miyano and Sumimoto, 2012). Studies of null mutant Rac3 mice showed that Rac3 regulates cerebellar functions and in a mouse model plays a role in leukemia development caused by the Bcr/Abl oncogene. Point mutations (N26D, F37L, Y40C, N43D) were introduced into different critical residues of the effector domain of Rac3 and the effects of these were investigated on the ability of Rac3 to regulate membrane ruffles, c-jun activation and transformation. Transformation was assayed as the ability to cooperate with activated Raf in focus formation of NIH3T3 cells and the ability to promote growth of these cells in soft agar. Rac3 was found to negatively regulate autophagy in colon, breast and prostate cancer cell lines, since its knockdown stimulated LC3-II expression (Zhu et al., 2011). Different effects on migration are reported. Rac3 negatively regulates diapedesis of PC3 cells, since knockdown using siRNA increases migration of PC3 prostate cancer cells through a BMEC layer (Chatterjee et al., 2011). In contrast, overexpression of Rac3 in MCF7 breast cancer cells stimulates E2-induced migration (Walker et al., 2011).

Homology

Rac3 is most closely related to Rac1 and Rac2. On a nucleotide level human Rac3 has 77% identity with Rac1, 83% identity with Rac2 and 69% identity with RhoG. On an amino acid level, Rac3 and Rac1 differ in 14/192 residues (92% identical), whereas Rac3 and Rac2 differ in 22/192 residues (89% identical). Rac belongs to the extended Rho family of small G-proteins. Biochemically, Rac1 and Rac3 are closely related and have overlapping (Corbetta et al., 2009; Pennucci et al., 2011; Basso et al., 2011) as well as distinct functions. Rac3 differs from Rac1 in the presence of a residue in its C-terminal end, S151, which is A151 in Rac1 and mediates binding of Rac3 to ERα (Walker et al., 2011). Rac3 and Rac1 also differ in their effect on NIE-115 neuroblastoma cells, in which Rac3 induces cell rounding and Rac1 induces spreading (Hajdo-Milasinovic et al., 2007; Hajdo-Milasinovic et al., 2009).

Implicated in

Entity name
Breast cancer
Note
Using in situ hybridization, Rac3 was reported to lies outside of the BROV region commonly deleted in breast and ovarian cancer.
Activated Rac3 protein was reported in MDA-435, T47D and MCF7 breast cancer cell lines and 1 of 3 patient samples using a GST-Pak pull-down assay to detect activated Rac.
Transgenic mice with tissue specific expression of constitutively active (V12)Rac3 in the mammary gland were generated. Post-lactational female mice had delayed involution.
It was showed that introduction of a constitutively active Rac3 into the MDA-MB-435 breast cancer cell line caused increased invasion and motility in vitro.
In the MCF7 breast cancer cell line, E2-stimulated migration was decreased by siRNA-mediated knockdown of Rac3, and Rac3 interacted with the ERα in a ligand-dependent manner (Chatterjee et al., 2011). Meta-analysis of gene expression profiling datasets of breast cancer samples (Chang et al., 2005) for Rac3 showed that expression levels correlated with increased probability of metastatic events (Walker et al., 2011).
Entity name
Gastric cancer
Note
Semi-quantitative RT/PCR was used to examine Rac3 mRNA expression in gastric cancer tissues and 7 gastric cell lines. Rac3 expression was detected in the tumor samples but there was no statistically significant difference between the expression levels in gastric cancer and adjacent non-tumorous tissues. The cell lines had a varying but detectable Rac3 expression.
Entity name
Brain tumors
Note
RT-PCR was used to evaluate Rac3 mRNA expression in human brain tumor tissues. Expression of rac3 was reported in 3/9 meningiomas, 1/11 astrocytomas, 1/6 pituitary adenomas. The PCR fragments were subcloned and sequenced, and mutations were reported in Rac3 in 12/19 brain tumors including E10V, V14E, D35N, P35S, N43D, V46A, D57V, R57P, L67V, S83F, V85A, E100G, H104L, P109H, R120H, T125P, S158P, P180T, V182E, V182A, H184L and G186E.
Entity name
Prostate cancer
Note
Using real-time RT/PCR, increased Rac3 mRNA was detected in involved prostate cancer biopsy samples compared to adjacent normal tissue (Engers et al., 2007).

Bibliography

Pubmed IDLast YearTitleAuthors
214690922011Absence of Rac1 and Rac3 GTPases in the nervous system hinders thymic, splenic and immune-competence development.Basso V et al
162800462005Rac1 and Rac3 isoform activation is involved in the invasive and metastatic phenotype of human breast cancer cells.Baugher PJ et al
146221422003Differential distribution of Rac1 and Rac3 GTPases in the developing mouse brain: implications for a role of Rac3 in Purkinje cell differentiation.Bolis A et al
160277282005Roles of the Rac1 and Rac3 GTPases in human tumor cell invasion.Chan AY et al
157017002005Robustness, scalability, and integration of a wound-response gene expression signature in predicting breast cancer survival.Chang HY et al
217763862011Individual rac GTPases mediate aspects of prostate cancer cell and bone marrow endothelial cell interactions.Chatterjee M et al
159648302005Generation of rac3 null mutant mice: role of Rac3 in Bcr/Abl-caused lymphoblastic leukemia.Cho YJ et al
191265962009Essential role of Rac1 and Rac3 GTPases in neuronal development.Corbetta S et al
92992431997Structure and chromosomal assignment to 22q12 and 17qter of the ras-related Rac2 and Rac3 human genes.Courjal F et al
176390412007Prognostic relevance of increased Rac GTPase expression in prostate carcinomas.Engers R et al
92523441997Characterization of RAC3, a novel member of the Rho family.Haataja L et al
146757732003Comparative functional analysis of the Rac GTPases.Haeusler LC et al
194941302009Rac3 inhibits adhesion and differentiation of neuronal cells by modifying GIT1 downstream signaling.Hajdo-Milasinovic A et al
159930752005Expression of Rac3 in human brain tumors.Hwang SL et al
162670122005Rac3-mediated transformation requires multiple effector pathways.Keller PJ et al
146054862003Targeted expression of activated Rac3 in mammary epithelium leads to defective postlactational involution and benign mammary gland lesions.Leung K et al
195347242009The insert region of the Rac GTPases is dispensable for activation of superoxide-producing NADPH oxidases.Miyano K et al
221442772012Assessment of the role for Rho family GTPases in NADPH oxidase activation.Miyano K et al
108949302000The small GTPase RAC3 gene is located within chromosome band 17q25.3 outside and telomeric of a region commonly deleted in breast and ovarian tumours.Morris CM et al
149757552004Expression of seven main Rho family members in gastric carcinoma.Pan Y et al
219497602011Rac1 and Rac3 GTPases regulate the development of hilar mossy cells by affecting the migration of their precursors to the hilus.Pennucci R et al
212177742011RAC3 is a pro-migratory co-activator of ERα.Walker MP et al
218522302011A role for Rac3 GTPase in the regulation of autophagy.Zhu WL et al

Other Information

Locus ID:

NCBI: 5881
MIM: 602050
HGNC: 9803
Ensembl: ENSG00000169750

Variants:

dbSNP: 5881
ClinVar: 5881
TCGA: ENSG00000169750
COSMIC: RAC3

RNA/Proteins

Gene IDTranscript IDUniprot
ENSG00000169750ENST00000306897P60763
ENSG00000169750ENST00000580965J3QLK0
ENSG00000169750ENST00000584341J3KSC4

Expression (GTEx)

0
10
20
30
40
50
60
70
80
90

Pathways

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
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
Regulation of actin cytoskeletonKEGGhsa04810
Pathways in cancerKEGGhsa05200
Colorectal cancerKEGGhsa05210
Pancreatic cancerKEGGhsa05212
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
Signal TransductionREACTOMER-HSA-162582
Signaling by Rho GTPasesREACTOMER-HSA-194315
Rho GTPase cycleREACTOMER-HSA-194840
Signaling by WntREACTOMER-HSA-195721
Beta-catenin independent WNT signalingREACTOMER-HSA-3858494
PCP/CE pathwayREACTOMER-HSA-4086400
Fluid shear stress and atherosclerosisKEGGko05418
Fluid shear stress and atherosclerosisKEGGhsa05418

Protein levels (Protein atlas)

Not detected
Low
Medium
High

References

Pubmed IDYearTitleCitations
160277282005Roles of the Rac1 and Rac3 GTPases in human tumor cell invasion.79
162800462005Rac1 and Rac3 isoform activation is involved in the invasive and metastatic phenotype of human breast cancer cells.46
227866802012Matrix metalloproteinase induction of Rac1b, a key effector of lung cancer progression.45
229189552012Matrix compliance regulates Rac1b localization, NADPH oxidase assembly, and epithelial-mesenchymal transition.42
183193032008PAK is required for the disruption of E-cadherin adhesion by the small GTPase Rac.29
172446482007Rac1 and Rac3 have opposing functions in cell adhesion and differentiation of neuronal cells.23
233881332013Rac3 induces a molecular pathway triggering breast cancer cell aggressiveness: differences in MDA-MB-231 and MCF-7 breast cancer cell lines.21
246848022014F-box protein complex FBXL19 regulates TGFβ1-induced E-cadherin down-regulation by mediating Rac3 ubiquitination and degradation.17
218522302011A role for Rac3 GTPase in the regulation of autophagy.15
290616502017Rac3 regulates breast cancer invasion and metastasis by controlling adhesion and matrix degradation.13

Citation

Nora C Heisterkamp

RAC3 (ras-related C3 botulinum toxin substrate 3 (rho family, small GTP binding protein Rac3))

Atlas Genet Cytogenet Oncol Haematol. 2012-04-01

Online version: http://atlasgeneticsoncology.org/gene/42022/rac3-(ras-related-c3-botulinum-toxin-substrate-3-(rho-family-small-gtp-binding-protein-rac3))

Historical Card

2007-02-01 RAC3 (ras-related C3 botulinum toxin substrate 3 (rho family, small GTP binding protein Rac3)) by  Nora C Heisterkamp 

Division of Hematology-Oncology, Childrens Hospital of Los Angeles, CA, USA