TRIB1

Tribbles homolog 1 is a protein kinase that in humans is encoded by the TRIB1 gene.[5][6][7] Orthologs of this protein pseudokinase (pseudoenzyme) can be found almost ubiquitously throughout the animal kingdom.[8] It exerts its biological functions through binding to signalling proteins of the MAPKK level of the MAPK pathway, therefore eliciting a regulatory role in the function of this pathway which mediates proliferation, apoptosis and differentiation in cells. Tribbles-1 is encoded by the trib1 gene, which in humans can be found on chromosome 8 at position 24.13 on the longest arm (q). Recent crystal structures show that Tribbles 1 has an unusual 3D structure, containing a 'broken' C-helix region, a binding site for ubiquitinated substrates such as C/EBPalpha and a key regulatory C-tail region.[9] Like TRIB2 and TRIB3, TRIB1 has recently been considered as a potential allosteric drug target.[10]

TRIB1
Available structures
PDBOrtholog search: PDBe RCSB
Identifiers
AliasesTRIB1, C8FW, GIG-2, GIG2, SKIP1, TRB-1, TRB1, tribbles pseudokinase 1
External IDsOMIM: 609461 MGI: 2443397 HomoloGene: 75216 GeneCards: TRIB1
Gene location (Human)
Chr.Chromosome 8 (human)[1]
Band8q24.13Start125,430,358 bp[1]
End125,438,403 bp[1]
RNA expression pattern
More reference expression data
Orthologs
SpeciesHumanMouse
Entrez

10221

211770

Ensembl

ENSG00000173334

ENSMUSG00000032501

UniProt

Q96RU8

Q8K4K4

RefSeq (mRNA)

NM_001282985
NM_025195

NM_144549

RefSeq (protein)

NP_001269914
NP_079471

NP_653132

Location (UCSC)Chr 8: 125.43 – 125.44 MbChr 15: 59.65 – 59.66 Mb
PubMed search[3][4]
Wikidata
View/Edit HumanView/Edit Mouse

Function

Tribbles-1 is one of three members of the Tribbles subfamily, which is a part of the CAMK Ser/Thr protein kinase family, of the protein kinase superfamily. The Tribbles subfamily is one of the pseudokinases, meaning that while expressing putative kinase regions in its structure, it is non-catalytic. The Tribbles subfamily lacks a functional ATP binding pocket, and therefore cannot phosphorylate its substrates; instead, Tribbles proteins function as scaffold proteins, which bind their substrates to localize them to or from their function [8]

Expression of Tribbles-1 is highly variable, constantly changing with respect to time and cell-type,[11] which suggests a large amount of regulation that exists in the cell. The protein's primary structure contains a PEST region, indicative of proteins that are highly susceptible to degradation in the cell; Tribbles-1 plays a role in regulating its own expression by binding to its substrate, which not only produces its function on the MAPK pathway, but also works to protect it from degradation whilst binding. This, in part, creates a positive feedback loop in the function of Tribbles-1, as the function of Tribbles-1 directly aids in the increase of the amount of it. As positive feedback loops are often seen throughout biology in circumstances that require the alleviation of an external stimulus, the positive feedback loop exhibited by Tribbles-1 suggests that it plays a functional role in cell response.

References
  1. GRCh38: Ensembl release 89: ENSG00000173334 - Ensembl, May 2017
  2. GRCm38: Ensembl release 89: ENSMUSG00000032501 - 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. Wilkin F, Suarez-Huerta N, Robaye B, Peetermans J, Libert F, Dumont JE, Maenhaut C (September 1997). "Characterization of a phosphoprotein whose mRNA is regulated by the mitogenic pathways in dog thyroid cells". European Journal of Biochemistry. 248 (3): 660–8. doi:10.1111/j.1432-1033.1997.t01-1-00660.x. PMID 9342215.
  6. Hegedus Z, Czibula A, Kiss-Toth E (July 2006). "Tribbles: novel regulators of cell function; evolutionary aspects". Cellular and Molecular Life Sciences. 63 (14): 1632–41. doi:10.1007/s00018-006-6007-9. PMID 16715410. S2CID 24556931.
  7. "Entrez Gene: TRIB1 tribbles homolog 1 (Drosophila)".
  8. Eyers PA, Keeshan K, Kannan N (April 2017). "Tribbles in the 21st Century: The Evolving Roles of Tribbles Pseudokinases in Biology and Disease". Trends in Cell Biology. 27 (4): 284–298. doi:10.1016/j.tcb.2016.11.002. PMC 5382568. PMID 27908682.
  9. Murphy JM, Nakatani Y, Jamieson SA, Dai W, Lucet IS, Mace PD (November 2015). "Molecular Mechanism of CCAAT-Enhancer Binding Protein Recruitment by the TRIB1 Pseudokinase". Structure. 23 (11): 2111–21. doi:10.1016/j.str.2015.08.017. PMID 26455797.
  10. Foulkes DM, Byrne DP, Bailey FP, Eyers PA (October 2015). "Tribbles pseudokinases: novel targets for chemical biology and drug discovery?". Biochemical Society Transactions. 43 (5): 1095–103. doi:10.1042/BST20150109. PMID 26517930.
  11. Sung HY, Francis SE, Crossman DC, Kiss-Toth E (April 2006). "Regulation of expression and signalling modulator function of mammalian tribbles is cell-type specific". Immunology Letters. 104 (1–2): 171–7. doi:10.1016/j.imlet.2005.11.010. PMID 16364454.

Further reading
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