Wikipedia

Obscurin

Obscurin is a protein that in humans is encoded by the OBSCN gene.[5][6][7] Obscurin belongs to the family of giant sarcomeric signaling proteins that includes titin and nebulin. Obscurin is expressed in cardiac and skeletal muscle, and plays a role in the organization of myofibrils during sarcomere assembly. A mutation in the OBSCN gene has been associated with hypertrophic cardiomyopathy and altered obscurin protein properties have been associated with other muscle diseases.

OBSCN
Available structures
PDBOrtholog search: PDBe RCSB
Identifiers
AliasesOBSCN, ARHGEF30, UNC89, obscurin, cytoskeletal calmodulin and titin-interacting RhoGEF
External IDsOMIM: 608616; MGI: 2681862; HomoloGene: 70869; GeneCards: OBSCN; OMA:OBSCN - orthologs
Orthologs
SpeciesHumanMouse
Entrez

84033

380698

Ensembl

ENSG00000154358

ENSMUSG00000061462

UniProt

Q5VST9

A2AAJ9

RefSeq (mRNA)

NM_001098623
NM_001271223
NM_052843
NM_001386125

NM_001171512
NM_199152

RefSeq (protein)

NP_001092093
NP_001258152
NP_443075

NP_001164983
NP_954603

Location (UCSC)Chr 1: 228.21 – 228.38 MbChr 11: 58.89 – 59.03 Mb
PubMed search[3][4]
Wikidata
View/Edit HumanView/Edit Mouse

Structure

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Human obscurin may exist as multiple splice variants of approximately 720 kDa,[8][9][10][11][12] however the full-length nature of only one has been described to date.[13] Obscurin is expressed in cardiac and skeletal muscle. The obscurin gene spans more than 150 kb, contains over 80 exons.[14] The encoded protein contains 68 Ig domains, 2 fibronectin domains, 1 IQ calmodulin-binding motif, 1 RhoGEF domain with an associated PH domain, and 2 serine-threonine kinase domains.[13] The dominant location of obscurin in mature myofibrils is at the sarcomeric M-band.[13][15] Titin, obscurin, obscurin-like-1 and myomesin form a ternary complex at sarcomeric M-bands that is critical for sarcomere mechanics.[16]

Function

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Obscurin belongs to the family of giant sarcomeric signaling proteins that includes titin and nebulin, and may have a role in the organization of myofibrils during assembly and may mediate interactions between the sarcoplasmic reticulum and myofibrils. Obscurin is the major cytoplasmic ligand for small ankyrin 1 (sANK1), a sarcoplasmic reticular protein, and the scaffolding function of obscurin appears to prevent degradation of sANK1.[17] These data indicate that obscurin serves as a signaling link between the sarcomeric and sarcoplasmic reticular domains,[18][19] Obscurin plays a role in the formation of new sarcomeres during myofibril assembly.[20] specifically, at the sarcomeric periphery where sites of initiation and progression of myofibrilogenesis lie.[21][22] Obscurin appears to be necessary for the proper incorporation of myosin filaments into sarcomeres and in the assembly of A-bands.[15][23] Moreover, the kinase domains of obscurin are enzymatically active and appear to be involved in the regulation of cell adhesion.[24]

Clinical significance

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Obscurin has been shown to exhibit a disease-related isoform switch in patients with dilated cardiomyopathy.[25] An obscurin mutation Arg4344Gln was identified in patients with hypertrophic cardiomyopathy, which disrupted binding of obscurin to the Z9-Z10 domains of titin.[26] A later study, however, was not able to reproduce this effect.[27] Due to lack of mechanistic evidence and the high prevalence among African Americans, the Arg4344Gln variant is currently not considered to be pathogenic.[28][29] Mutations found the gene encoding titin in patients with limb-girdle muscular dystrophy 2J or Salih myopathy decrease the ability of titin to bind obscurin, suggesting that this may be causative in disease manifestation.[30]

Interactions

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Obscurin has been shown to interact with Titin,[5][31] specifically, with the Novex-3 of Titin, a 6.5 kb exon located upstream of the cardiac-specific N2B exon.[32] The C-terminal region of Obscurin interacts with the cytoplasmic domain of small ankyrin 1[33][34] and with the exon 43' region of ankyrin B.[35] The Ig3 of obscurin binds myomesin at the linker between My4 and My5.[30]

References

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  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000154358 – Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000061462 – 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. ^ a b Young P, Ehler E, Gautel M (Jul 2001). "Obscurin, a giant sarcomeric Rho guanine nucleotide exchange factor protein involved in sarcomere assembly". The Journal of Cell Biology. 154 (1): 123–36. doi:10.1083/jcb.200102110. PMC 2196875. PMID 11448995.
  6. ^ Russell MW, Raeker MO, Korytkowski KA, Sonneman KJ (Jan 2002). "Identification, tissue expression and chromosomal localization of human Obscurin-MLCK, a member of the titin and Dbl families of myosin light chain kinases". Gene. 282 (1–2): 237–46. doi:10.1016/S0378-1119(01)00795-8. PMID 11814696.
  7. ^ "Entrez Gene: OBSCN obscurin, cytoskeletal calmodulin and titin-interacting RhoGEF".
  8. ^ "Q5VST9".
  9. ^ "Q5VST9-6".
  10. ^ "Q5VST9-2".
  11. ^ "Q5VST9-3".
  12. ^ "Q5VST9-5".
  13. ^ a b c Young P, Ehler E, Gautel M (Jul 2001). "Obscurin, a giant sarcomeric Rho guanine nucleotide exchange factor protein involved in sarcomere assembly". The Journal of Cell Biology. 154 (1): 123–36. doi:10.1083/jcb.200102110. PMC 2196875. PMID 11448995.
  14. ^ Fukuzawa A, Idowu S, Gautel M (2005). "Complete human gene structure of obscurin: implications for isoform generation by differential splicing". Journal of Muscle Research and Cell Motility. 26 (6–8): 427–34. doi:10.1007/s10974-005-9025-6. PMID 16625316. S2CID 20522555.
  15. ^ a b Carlsson L, Yu JG, Thornell LE (Jul 2008). "New aspects of obscurin in human striated muscles". Histochemistry and Cell Biology. 130 (1): 91–103. doi:10.1007/s00418-008-0413-z. PMID 18350308. S2CID 35469988.
  16. ^ Pernigo S, Fukuzawa A, Bertz M, Holt M, Rief M, Steiner RA, Gautel M (Feb 2010). "Structural insight into M-band assembly and mechanics from the titin-obscurin-like-1 complex". Proceedings of the National Academy of Sciences of the United States of America. 107 (7): 2908–13. Bibcode:2010PNAS..107.2908P. doi:10.1073/pnas.0913736107. PMC 2814874. PMID 20133654.
  17. ^ Lange S, Perera S, Teh P, Chen J (Jul 2012). "Obscurin and KCTD6 regulate cullin-dependent small ankyrin-1 (sAnk1.5) protein turnover". Molecular Biology of the Cell. 23 (13): 2490–504. doi:10.1091/mbc.E12-01-0052. PMC 3386213. PMID 22573887.
  18. ^ Bagnato P, Barone V, Giacomello E, Rossi D, Sorrentino V (Jan 2003). "Binding of an ankyrin-1 isoform to obscurin suggests a molecular link between the sarcoplasmic reticulum and myofibrils in striated muscles". The Journal of Cell Biology. 160 (2): 245–53. doi:10.1083/jcb.200208109. PMC 2172649. PMID 12527750.
  19. ^ Kontrogianni-Konstantopoulos A, Jones EM, Van Rossum DB, Bloch RJ (Mar 2003). "Obscurin is a ligand for small ankyrin 1 in skeletal muscle". Molecular Biology of the Cell. 14 (3): 1138–48. doi:10.1091/mbc.E02-07-0411. PMC 151585. PMID 12631729.
  20. ^ Borisov AB, Kontrogianni-Konstantopoulos A, Bloch RJ, Westfall MV, Russell MW (Sep 2004). "Dynamics of obscurin localization during differentiation and remodeling of cardiac myocytes: obscurin as an integrator of myofibrillar structure". The Journal of Histochemistry and Cytochemistry. 52 (9): 1117–27. doi:10.1369/jhc.3A6183.2004. PMID 15314079.
  21. ^ Borisov AB, Raeker MO, Kontrogianni-Konstantopoulos A, Yang K, Kurnit DM, Bloch RJ, Russell MW (Oct 2003). "Rapid response of cardiac obscurin gene cluster to aortic stenosis: differential activation of Rho-GEF and MLCK and involvement in hypertrophic growth". Biochemical and Biophysical Research Communications. 310 (3): 910–8. doi:10.1016/j.bbrc.2003.09.035. PMID 14550291.
  22. ^ Borisov AB, Martynova MG, Russell MW (Apr 2008). "Early incorporation of obscurin into nascent sarcomeres: implication for myofibril assembly during cardiac myogenesis". Histochemistry and Cell Biology. 129 (4): 463–78. doi:10.1007/s00418-008-0378-y. PMC 2761667. PMID 18219491.
  23. ^ Borisov AB, Sutter SB, Kontrogianni-Konstantopoulos A, Bloch RJ, Westfall MV, Russell MW (Mar 2006). "Essential role of obscurin in cardiac myofibrillogenesis and hypertrophic response: evidence from small interfering RNA-mediated gene silencing" (PDF). Histochemistry and Cell Biology. 125 (3): 227–38. doi:10.1007/s00418-005-0069-x. hdl:2027.42/47398. PMID 16205939. S2CID 13623244.
  24. ^ Hu LY, Kontrogianni-Konstantopoulos A (May 2013). "The kinase domains of obscurin interact with intercellular adhesion proteins". FASEB Journal. 27 (5): 2001–12. doi:10.1096/fj.12-221317. PMC 3633816. PMID 23392350.
  25. ^ Makarenko I, Opitz CA, Leake MC, Neagoe C, Kulke M, Gwathmey JK, et al. (October 2004). "Passive stiffness changes caused by upregulation of compliant titin isoforms in human dilated cardiomyopathy hearts". Circulation Research. 95 (7): 708–16. doi:10.1161/01.RES.0000143901.37063.2f. PMID 15345656.
  26. ^ Arimura T, Matsumoto Y, Okazaki O, Hayashi T, Takahashi M, Inagaki N, et al. (October 2007). "Structural analysis of obscurin gene in hypertrophic cardiomyopathy". Biochemical and Biophysical Research Communications. 362 (2): 281–7. doi:10.1016/j.bbrc.2007.07.183. PMID 17716621.
  27. ^ Fukuzawa A, Koch D, Grover S, Rees M, Gautel M (June 2021). "When is an obscurin variant pathogenic? The impact of Arg4344Gln and Arg4444Trp variants on protein-protein interactions and protein stability". Human Molecular Genetics. 30 (12): 1131–1141. doi:10.1093/hmg/ddab010. PMC 8188405. PMID 33438037.
  28. ^ Fukuzawa A, Koch D, Grover S, Rees M, Gautel M (June 2021). "When is an obscurin variant pathogenic? The impact of Arg4344Gln and Arg4444Trp variants on protein-protein interactions and protein stability". Human Molecular Genetics. 30 (12): 1131–1141. doi:10.1093/hmg/ddab010. PMC 8188405. PMID 33438037.
  29. ^ Manrai AK, Funke BH, Rehm HL, Olesen MS, Maron BA, Szolovits P, et al. (August 2016). "Genetic Misdiagnoses and the Potential for Health Disparities". The New England Journal of Medicine. 375 (7): 655–65. doi:10.1056/NEJMsa1507092. PMC 5292722. PMID 27532831.
  30. ^ a b Fukuzawa A, Lange S, Holt M, Vihola A, Carmignac V, Ferreiro A, et al. (June 2008). "Interactions with titin and myomesin target obscurin and obscurin-like 1 to the M-band: implications for hereditary myopathies". Journal of Cell Science. 121 (11): 1841–51. doi:10.1242/jcs.028019. PMID 18477606.
  31. ^ Pernigo S, Fukuzawa A, Pandini A, Holt M, Kleinjung J, Gautel M, Steiner RA (Feb 2015). "The crystal structure of the human titin:obscurin complex reveals a conserved yet specific muscle M-band zipper module". Journal of Molecular Biology. 427 (4): 718–36. doi:10.1016/j.jmb.2014.11.019. PMID 25490259.
  32. ^ Bang ML, Centner T, Fornoff F, Geach AJ, Gotthardt M, McNabb M, Witt CC, Labeit D, Gregorio CC, Granzier H, Labeit S (Nov 2001). "The complete gene sequence of titin, expression of an unusual approximately 700-kDa titin isoform, and its interaction with obscurin identify a novel Z-line to I-band linking system". Circulation Research. 89 (11): 1065–72. doi:10.1161/hh2301.100981. PMID 11717165.
  33. ^ Kontrogianni-Konstantopoulos A, Jones EM, Van Rossum DB, Bloch RJ (Mar 2003). "Obscurin is a ligand for small ankyrin 1 in skeletal muscle". Molecular Biology of the Cell. 14 (3): 1138–48. doi:10.1091/mbc.E02-07-0411. PMC 151585. PMID 12631729.
  34. ^ Busby B, Oashi T, Willis CD, Ackermann MA, Kontrogianni-Konstantopoulos A, Mackerell AD, Bloch RJ (Apr 2011). "Electrostatic interactions mediate binding of obscurin to small ankyrin 1: biochemical and molecular modeling studies". Journal of Molecular Biology. 408 (2): 321–34. doi:10.1016/j.jmb.2011.01.053. PMC 3367564. PMID 21333652.
  35. ^ Cunha SR, Mohler PJ (Nov 2008). "Obscurin targets ankyrin-B and protein phosphatase 2A to the cardiac M-line". The Journal of Biological Chemistry. 283 (46): 31968–80. doi:10.1074/jbc.M806050200. PMC 2581558. PMID 18782775.

Further reading

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