ARAF

For other uses, see Araf (disambiguation).

ARAF
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 1WXM, 2MSE
Identifiers
Aliases	ARAF , A-Raf proto-oncogene, serine/threonine kinase, A-RAF, ARAF1, PKS2, RAFA1, Serine/threonine-protein kinase A-Raf
External IDs	OMIM: 311010; MGI: 88065; HomoloGene: 1249; GeneCards: ARAF; OMA:ARAF - orthologs
Gene location (Human) Chr. X chromosome (human) [1] Band Xp11.3 Start 47,561,205 bp [1] End 47,571,908 bp [1]
Gene location (Mouse) Chr. X chromosome (mouse) [2] Band X A1.3|X 16.3 cM Start 20,664,053 bp [2] End 20,726,758 bp [2]
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in muscle of thigh granulocyte gastrocnemius muscle body of stomach apex of heart body of pancreas right lobe of liver gastric mucosa transverse colon left uterine tube Top expressed in dorsomedial hypothalamic nucleus lateral hypothalamus mammillary body neural layer of retina ventral tegmental area paraventricular nucleus of hypothalamus ventromedial nucleus lateral septal nucleus arcuate nucleus dentate gyrus of hippocampal formation granule cell More reference expression data BioGPS More reference expression data
Gene ontology Molecular function transferase activity protein kinase activity nucleotide binding metal ion binding kinase activity protein serine/threonine kinase activity protein binding ATP binding MAP kinase kinase kinase activity mitogen-activated protein kinase kinase binding Cellular component mitochondrion cytosol cellular component Biological process intracellular signal transduction regulation of TOR signaling phosphorylation negative regulation of apoptotic process positive regulation of peptidyl-serine phosphorylation MAPK cascade protein phosphorylation regulation of proteasomal ubiquitin-dependent protein catabolic process signal transduction multicellular organism development negative regulation of signal transduction cell differentiation positive regulation of ERK1 and ERK2 cascade Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 369 11836 Ensembl ENSG00000078061 ENSMUSG00000001127 UniProt P10398 Q96II5 P04627 RefSeq (mRNA) NM_001256196 NM_001256197 NM_001654 NM_001159645 NM_009703 RefSeq (protein) NP_001243125 NP_001243126 NP_001645 NP_001243125.1 NP_001153117 NP_033833 Location (UCSC) Chr X: 47.56 – 47.57 Mb Chr X: 20.66 – 20.73 Mb PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

Serine/threonine-protein kinase A-Raf, or simply A-Raf, is an enzyme that in humans is encoded by the ARAF gene. ^[5] It belongs to the Raf kinase family of serine/threonine-specific protein kinases, which also includes Raf-1 and B-Raf. ^[6] A-Raf is involved in the MAPK/ERK pathway, where it contributes to cell signaling processes that regulate proliferation, survival, and differentiation. Compared to Raf-1 and B-Raf, A-Raf is less well studied and exhibits distinct structural and regulatory features, including low kinase activity and alternative splicing in cancer. In addition to its role in MAPK signaling, A-Raf has functions in apoptosis suppression, cancer metabolism, and endocytic trafficking.

Structure

A-Raf, a member of the Raf kinase family, shares a conserved domain architecture with B-Raf and C-Raf, comprising three conserved regions: CR1, CR2, and CR3.

• CR1 (Conserved Region 1): This N-terminal region contains the Ras-binding domain (RBD) and the cysteine-rich domain (CRD). The RBD facilitates interaction with activated Ras-GTP, anchoring A-Raf to the plasma membrane. ^[7] The CRD, characterized by its zinc-binding motif, contributes to membrane association and protein-protein interactions ^[8] Structural studies confirm the RBD and CRD function as a single entity during Ras binding. ^[9]
• CR2 (Conserved Region 2): Positioned between CR1 and CR3, CR2 is a serine/threonine-rich regulatory segment containing phosphorylation sites (e.g., Ser259 in Raf-1) that modulate A-Raf's activity and interactions with 14-3-3 proteins. ^[10] This region is critical for autoinhibition and activation dynamics. ^[11]
• CR3 (Conserved Region 3): The C-terminal kinase domain exhibits the bilobal architecture characteristic of protein kinases, with an ATP-binding site between the N-terminal and C-terminal lobes. ^[12] Structural analyses reveal similarities to tyrosine kinase-like (TKL) group members ^[13]

The RBD adopts a ubiquitin-like fold critical for Ras-GTP interaction. ^[14] , while the CRD's zinc-binding motif stabilizes membrane association. ^[15] A-Raf's activity is regulated by phosphorylation-dependent 14-3-3 binding. ^[16] and isoform dimerization, which is essential for MAPK pathway activation. ^{[17] [18]}

Function

A-Raf shares the canonical role of Raf kinases in the MAPK signaling cascade. Upon activation by Ras, A-Raf translocates from the cytosol to the plasma membrane, where it phosphorylates and activates MEK proteins. This activation leads to downstream ERK signaling and promotes cell cycle progression and proliferation. ^[19]

Among the Raf isoforms, A-Raf exhibits the lowest kinase activity toward MEK proteins. ^[20] This may be due to amino acid substitutions in a negatively charged region upstream of the kinase domain (the N-region), which result in low basal activity. ^[21]

A-Raf is also the only Raf kinase known to be regulated by steroid hormones. ^[22] In its inactive form, A-Raf is bound to 14-3-3 proteins in the cytosol; activation by Ras causes its translocation to the plasma membrane.

Beyond the MAPK pathway, A-Raf has additional functions. It inhibits MST2, a proapoptotic kinase, thereby suppressing apoptosis. This inhibitory activity is dependent on the expression of full-length A-Raf protein, which is maintained by the splicing factor hnRNP H. ^[23]

A-Raf also regulates energy metabolism by interacting with pyruvate kinase M2 (PKM2), a key enzyme in cancer cell glycolysis. By promoting a conformational shift from the dimeric to the tetrameric form of PKM2, A-Raf enhances its enzymatic activity and shifts glucose utilization from biosynthesis toward energy production. ^[24]

In addition, A-Raf has been implicated in endocytic membrane trafficking. Upon activation by receptor tyrosine kinases and Ras, A-Raf localizes to phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P₂)-rich membranes and signals to endosomes, leading to activation of ARF6, a key regulator of endocytosis. ^[25]

Clinical significance

A-Raf may contribute to tumorigenesis through multiple mechanisms. In cancer cells, overexpression of hnRNP H enhances the production of full-length A-Raf, which inhibits MST2 and prevents apoptosis. The downregulation of hnRNP H, in contrast, leads to alternative splicing of the ARAF gene and loss of this anti-apoptotic activity. ^[26]

A-Raf’s regulation of PKM2 activity further links it to cancer metabolism. By promoting glycolytic flux toward pyruvate and lactate production, A-Raf may help sustain the high energy demands of rapidly proliferating tumor cells. ^[27]

Because A-Raf modulates both apoptosis and metabolism—two critical hallmarks of cancer—it may represent a potential target for future cancer therapies.

Interactions

ARAF has been shown to interact with:

• EFEMP1, ^[28]
• MAP2K2, ^[29]
• PRPF6, ^{[28] [30]}
• RRAS, ^{[28] [30]}
• TIMM44, ^{[28] [30]} and
• TH1L. ^{[28] [31]}

References

1. GRCh38: Ensembl release 89: ENSG00000078061 – Ensembl, May 2017
2. GRCm38: Ensembl release 89: ENSMUSG00000001127 – Ensembl, May 2017
3. "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
4. "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
5. "Entrez Gene: ARAF V-raf murine sarcoma 3611 viral oncogene homolog".
6. Mark GE, Seeley TW, Shows TB, Mountz JD (September 1986). "Pks, a raf-related sequence in humans". Proceedings of the National Academy of Sciences of the United States of America. 83 (17): 6312–6316. Bibcode:1986PNAS...83.6312M. doi: 10.1073/pnas.83.17.6312 . PMC   386493 . PMID   3529082.
7. Tran TH, Chan AH, Young LC, Bindu L, Neale C, Messing S, et al. (February 2021). "KRAS interaction with RAF1 RAS-binding domain and cysteine-rich domain provides insights into RAS-mediated RAF activation". Nature Communications. 12 (1): 1176. Bibcode:2021NatCo..12.1176T. doi:10.1038/s41467-021-21422-x. PMC   7895934 . PMID   33608534.
8. Mott HR, Carpenter JW, Zhong S, Ghosh S, Bell RM, Campbell SL (August 1996). "The solution structure of the Raf-1 cysteine-rich domain: a novel ras and phospholipid binding site". Proceedings of the National Academy of Sciences of the United States of America. 93 (16): 8312–8317. Bibcode:1996PNAS...93.8312M. doi: 10.1073/pnas.93.16.8312 . PMC   38667 . PMID   8710867.
9. Tran TH, Chan AH, Young LC, Bindu L, Neale C, Messing S, et al. (February 2021). "KRAS interaction with RAF1 RAS-binding domain and cysteine-rich domain provides insights into RAS-mediated RAF activation". Nature Communications. 12 (1): 1176. Bibcode:2021NatCo..12.1176T. doi:10.1038/s41467-021-21422-x. PMC   7895934 . PMID   33608534.
10. Light Y, Paterson H, Marais R (July 2002). "14-3-3 antagonizes Ras-mediated Raf-1 recruitment to the plasma membrane to maintain signaling fidelity". Molecular and Cellular Biology. 22 (14): 4984–4996. doi:10.1128/MCB.22.14.4984-4996.2002. PMC   139778 . PMID   12077328.
11. Defrise M, Kinahan PE, Townsend DW, Michel C, Sibomana M, Newport DF (April 1997). "Exact and approximate rebinning algorithms for 3-D PET data". IEEE Transactions on Medical Imaging. 16 (2): 145–158. doi:10.1109/42.563660. PMID   9101324.
12. Defrise M, Kinahan PE, Townsend DW, Michel C, Sibomana M, Newport DF (April 1997). "Exact and approximate rebinning algorithms for 3-D PET data". IEEE Transactions on Medical Imaging. 16 (2): 145–158. doi:10.1109/42.563660. PMID   9101324.
13. Motegi A, Fujimoto J, Kotani M, Sakuraba H, Yamamoto T (July 2004). "ALK receptor tyrosine kinase promotes cell growth and neurite outgrowth". Journal of Cell Science. 117 (Pt 15): 3319–3329. doi:10.1242/jcs.01183. PMID   15226403.
14. Tran TH, Chan AH, Young LC, Bindu L, Neale C, Messing S, et al. (February 2021). "KRAS interaction with RAF1 RAS-binding domain and cysteine-rich domain provides insights into RAS-mediated RAF activation". Nature Communications. 12 (1): 1176. Bibcode:2021NatCo..12.1176T. doi:10.1038/s41467-021-21422-x. PMC   7895934 . PMID   33608534.
15. Mott HR, Carpenter JW, Zhong S, Ghosh S, Bell RM, Campbell SL (August 1996). "The solution structure of the Raf-1 cysteine-rich domain: a novel ras and phospholipid binding site". Proceedings of the National Academy of Sciences of the United States of America. 93 (16): 8312–8317. Bibcode:1996PNAS...93.8312M. doi: 10.1073/pnas.93.16.8312 . PMC   38667 . PMID   8710867.
16. Light Y, Paterson H, Marais R (July 2002). "14-3-3 antagonizes Ras-mediated Raf-1 recruitment to the plasma membrane to maintain signaling fidelity". Molecular and Cellular Biology. 22 (14): 4984–4996. doi:10.1128/MCB.22.14.4984-4996.2002. PMC   139778 . PMID   12077328.
17. Rimmer A (June 2018). "Overseas doctors must not be used just to fill rota gaps, says leading consultant". BMJ. 361: k2654. doi:10.1136/bmj.k2654. PMID   29907696.
18. Rushworth LK, Hindley AD, O'Neill E, Kolch W (March 2006). "Regulation and role of Raf-1/B-Raf heterodimerization". Molecular and Cellular Biology. 26 (6): 2262–2272. doi:10.1128/MCB.26.6.2262-2272.2006. PMC   1430271 . PMID   16508002.
19. Mercer K, Giblett S, Oakden A, Brown J, Marais R, Pritchard C (2005-04-25). "A-Raf and Raf-1 work together to influence transient ERK phosphorylation and Gl/S cell cycle progression". Oncogene. 24 (33): 5207–5217. doi: 10.1038/sj.onc.1208707 . ISSN   0950-9232. PMID   15856007.
20. Matallanas D, Birtwistle M, Romano D, Zebisch A, Rauch J, von Kriegsheim A, et al. (2011-03-01). "Raf Family Kinases Old Dogs Have Learned New Tricks". Genes & Cancer. 2 (3): 232–260. doi:10.1177/1947601911407323. ISSN   1947-6019. PMC   3128629 . PMID   21779496.
21. Baljuls A, Mueller T, Drexler HC, Hekman M, Rapp UR (2007-09-07). "Unique N-region determines low basal activity and limited inducibility of A-RAF kinase: the role of N-region in the evolutionary divergence of RAF kinase function in vertebrates". The Journal of Biological Chemistry. 282 (36): 26575–26590. doi: 10.1074/jbc.M702429200 . ISSN   0021-9258. PMID   17613527.
22. Lee JE, Beck TW, Wojnowski L, Rapp UR (1996-04-18). "Regulation of A-raf expression". Oncogene. 12 (8): 1669–1677. ISSN   0950-9232. PMID   8622887.
23. Rauch J, O'Neill E, Mack B, Matthias C, Munz M, Kolch W, et al. (2010-02-15). "Heterogeneous Nuclear Ribonucleoprotein H Blocks MST2-Mediated Apoptosis in Cancer Cells by Regulating a-raf Transcription". Cancer Research. 70 (4): 1679–1688. doi:10.1158/0008-5472.CAN-09-2740. ISSN   0008-5472. PMC   2880479 . PMID   20145135.
24. Mazurek S, Drexler HC, Troppmair J, Eigenbrodt E, Rapp UR (2007-11-01). "Regulation of Pyruvate Kinase Type M2 by A-Raf: A Possible Glycolytic Stop or Go Mechanism". Anticancer Research. 27 (6B): 3963–3971. ISSN   0250-7005. PMID   18225557.
25. Nekhoroshkova E, Albert S, Becker M, Rapp UR (2009-02-27). "A-RAF Kinase Functions in ARF6 Regulated Endocytic Membrane Traffic". PLOS ONE. 4 (2): e4647. Bibcode:2009PLoSO...4.4647N. doi: 10.1371/journal.pone.0004647 . ISSN   1932-6203. PMC   2645234 . PMID   19247477.
26. Rauch J, O'Neill E, Mack B, Matthias C, Munz M, Kolch W, et al. (2010-02-15). "Heterogeneous Nuclear Ribonucleoprotein H Blocks MST2-Mediated Apoptosis in Cancer Cells by Regulating a-raf Transcription". Cancer Research. 70 (4): 1679–1688. doi:10.1158/0008-5472.CAN-09-2740. ISSN   0008-5472. PMC   2880479 . PMID   20145135.
27. Christofk HR, Vander Heiden MG, Harris MH, Ramanathan A, Gerszten RE, Wei R, et al. (2008-03-13). "The M2 splice isoform of pyruvate kinase is important for cancer metabolism and tumour growth". Nature. 452 (7184): 230–233. Bibcode:2008Natur.452..230C. doi:10.1038/nature06734. ISSN   0028-0836. PMID   18337823. S2CID   16111842.
28. Yuryev A, Wennogle LP (February 2003). "Novel raf kinase protein-protein interactions found by an exhaustive yeast two-hybrid analysis". Genomics. 81 (2): 112–125. doi:10.1016/S0888-7543(02)00008-3. PMID   12620389.
29. Yin XL, Chen S, Yan J, Hu Y, Gu JX (February 2002). "Identification of interaction between MEK2 and A-Raf-1". Biochimica et Biophysica Acta (BBA) - Molecular Cell Research. 1589 (1): 71–76. doi: 10.1016/S0167-4889(01)00188-4 . PMID   11909642.
30. Yuryev A, Ono M, Goff SA, Macaluso F, Wennogle LP (July 2000). "Isoform-Specific Localization of A-RAF in Mitochondria". Molecular and Cellular Biology. 20 (13): 4870–4878. doi:10.1128/MCB.20.13.4870-4878.2000. PMC   85938 . PMID   10848612.
31. Yin XL, Chen S, Gu JX (February 2002). "Identification of TH1 as an interaction partner of A-Raf kinase". Molecular and Cellular Biochemistry. 231 (1–2): 69–74. doi:10.1023/A:1014437024129. PMID   11952167. S2CID   19362635.

Further reading

• Belanger BF, Williams WJ, Yin TC (1976). "A flexible renewal process simulator for neural spike trains". IEEE Transactions on Bio-medical Engineering. 23 (3): 262–266. doi:10.1109/TBME.1976.324641. PMID   1262038. S2CID   2411492.
• Popescu NC, Mark GE (1989). "Localization of the pKs gene, a raf related sequence on human chromosomes X and 7". Oncogene. 4 (4): 517–519. PMID   2717185.
• Beck TW, Huleihel M, Gunnell M, Bonner TI, Rapp UR (1987). "The complete coding sequence of the human A-raf-1 oncogene and transforming activity of a human A-raf carrying retrovirus". Nucleic Acids Research. 15 (2): 595–609. doi:10.1093/nar/15.2.595. PMC   340454 . PMID   3029685.
• Papin C, Eychène A, Brunet A, Pagès G, Pouysségur J, Calothy G, et al. (1995). "B-Raf protein isoforms interact with and phosphorylate Mek-1 on serine residues 218 and 222". Oncogene. 10 (8): 1647–1651. PMID   7731720.
• Lee JE, Beck TW, Brennscheidt U, DeGennaro LJ, Rapp UR (1994). "The complete sequence and promoter activity of the human A-raf-1 gene (ARAF1)". Genomics. 20 (1): 43–55. doi:10.1006/geno.1994.1125. PMID   8020955.
• Alessi DR, Saito Y, Campbell DG, Cohen P, Sithanandam G, Rapp U, et al. (1994). "Identification of the sites in MAP kinase kinase-1 phosphorylated by p74raf-1". The EMBO Journal. 13 (7): 1610–1619. doi:10.1002/j.1460-2075.1994.tb06424.x. PMC   394991 . PMID   8157000.
• Gardner AM, Vaillancourt RR, Johnson GL (1993). "Activation of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase by G protein and tyrosine kinase oncoproteins". Journal of Biological Chemistry. 268 (24): 17896–17901. doi: 10.1016/S0021-9258(17)46789-5 . PMID   8394352.
• Andersson B, Wentland MA, Ricafrente JY, Liu W, Gibbs RA (1996). "A "double adaptor" method for improved shotgun library construction". Analytical Biochemistry. 236 (1): 107–113. doi:10.1006/abio.1996.0138. PMID   8619474.
• Wu X, Noh SJ, Zhou G, Dixon JE, Guan KL (1996). "Selective activation of MEK1 but not MEK2 by A-Raf from epidermal growth factor-stimulated Hela cells". Journal of Biological Chemistry. 271 (6): 3265–3271. doi: 10.1074/jbc.271.6.3265 . PMID   8621729.
• Boldyreff B, Issinger OG (1997). "A-Raf kinase is a new interacting partner of protein kinase CK2 beta subunit". FEBS Letters. 403 (2): 197–199. Bibcode:1997FEBSL.403..197B. doi: 10.1016/S0014-5793(97)00010-0 . PMID   9042965.
• Yu W, Andersson B, Worley KC, Muzny DM, Ding Y, Liu W, et al. (1997). "Large-scale concatenation cDNA sequencing". Genome Research. 7 (4): 353–358. doi:10.1101/gr.7.4.353. PMC   139146 . PMID   9110174.
• Yuryev A, Ono M, Goff SA, Macaluso F, Wennogle LP (2000). "Isoform-specific localization of A-RAF in mitochondria". Molecular and Cellular Biology. 20 (13): 4870–4878. doi:10.1128/MCB.20.13.4870-4878.2000. PMC   85938 . PMID   10848612.
• King TR, Fang Y, Mahon ES, Anderson DH (2000). "Using a phage display library to identify basic residues in A-Raf required to mediate binding to the Src homology 2 domains of the p85 subunit of phosphatidylinositol 3'-kinase". Journal of Biological Chemistry. 275 (46): 36450–36456. doi: 10.1074/jbc.M004720200 . PMID   10967104.
• Fang Y, Johnson LM, Mahon ES, Anderson DH (2002). "Two phosphorylation-independent sites on the p85 SH2 domains bind A-Raf kinase". Biochemical and Biophysical Research Communications. 290 (4): 1267–1274. doi:10.1006/bbrc.2002.6347. PMID   11812000.
• Yin XL, Chen S, Yan J, Hu Y, Gu JX (2002). "Identification of interaction between MEK2 and A-Raf-1". Biochimica et Biophysica Acta (BBA) - Molecular Cell Research. 1589 (1): 71–76. doi: 10.1016/S0167-4889(01)00188-4 . PMID   11909642.
• Yin XL, Chen S, Gu JX (2002). "Identification of TH1 as an interaction partner of A-Raf kinase". Molecular and Cellular Biochemistry. 231 (1–2): 69–74. doi:10.1023/A:1014437024129. PMID   11952167. S2CID   19362635.
• Yuryev A, Wennogle LP (2003). "Novel raf kinase protein-protein interactions found by an exhaustive yeast two-hybrid analysis". Genomics. 81 (2): 112–125. doi:10.1016/S0888-7543(02)00008-3. PMID   12620389.
• Liu W, Shen X, Yang Y, Yin X, Xie J, Yan J, et al. (2004). "Trihydrophobin 1 is a new negative regulator of A-Raf kinase". Journal of Biological Chemistry. 279 (11): 10167–10175. doi: 10.1074/jbc.M307994200 . PMID   14684750.

External links

• Human ARAF genome location and ARAF gene details page in the UCSC Genome Browser .
• PDBe-KB provides an overview of all the structure information available in the PDB for Human Serine/threonine-protein kinase A-Raf