Myotilin is a
protein that in humans is encoded by the MYOTgene.[5][6][7] Myotilin (myofibrillar titin-like protein) also known as TTID (TiTin Immunoglobulin Domain) is a muscle protein that is found within the
Z-disc of
sarcomeres.
Structure
Myotilin is a 55.3 kDa protein composed of 496 amino acids.[8] Myotilin was originally identified as a novel
alpha-actinin binding partner with two
Ig-like domains, that localized to the
Z-disc.[9] The I-type
Ig-like domains reside at the C-terminal half, and are most homologous to
Ig domains 2-3 of
palladin and
Ig domains 4-5 of
myopalladin and more distantly related to
Z-discIg domains 7 and 8 of
titin. The C-terminal region hosts the binding sites for Z-band proteins, and 2
Ig domains are the site of homodimerization for myotilin.[10] By contrast, the N-terminal part of myotilin is unique, consisting of a
serine-rich region with no homology to known proteins. Several disease-associated mutations involve
serine residues within the
serine-rich domain.[11] Myotilin expression in human tissues is mainly restricted to striated muscles and nerves. In muscles, myotilin is predominantly found within the
Z-discs. Myotilin forms homodimers and binds
alpha-actinin,
actin,[12]Filamin C,[13]FATZ-1,[14]FATZ-2[14] and
ZASP.[15]
Function
Myotilin is a structural protein that, along with
titin and
alpha-actinin give structural integrity to
sarcomeres at
Z-discs in striated muscle. Myotilin induces the formation of actin bundles in vitro and in non-muscle cells. A ternary complex myotilin/
actin/
alpha-actinin can be observed in vitro and
actin bundles formed under these conditions appear more tightly packed than those induced by
alpha-actinin alone. It was demonstrated that myotilin stabilizes
F-actin by slowing down the disassembly rate. Ectopic overexpression of truncated myotilin causes the disruption of nascent myofibrils and the co-accumulation of myotilin and
titin in amorphous cytoplasmic precipitates. In mature
sarcomeres, wild-type myotilin colocalizes with
alpha-actinin and
Z-disctitin, showing the striated pattern typical of
sarcomeric proteins. Targeted disruption of the myotilin gene in mice does not cause significant alterations in muscle function.[16] On the other hand, transgenic mice with mutated myotilin develop muscle dystrophy.[17]
Clinical significance
Myotilin is mutated in various forms of muscular dystrophy: Limb-Girdle Muscular Dystrophy type 1A (LGMD1A), Myofibrillar Myopathy (MFM), Spheroid Body Myopathy and Distal Myopath.[11] The mechanism underlying the pathology is still under investigation. It has been shown that actin binding properties of myotilin housing pathogenic mutations (
Ser55
Phe,
Thr57
Ile,
Ser60
Cys, and
Ser95
Ile) are normal,[18] albeit with a slower rate of degradation.[19] Surprisingly, YFP-fusion constructs of myotilin mutants (
Ser55
Phe,
Ser55
Ile,
Thr57
Ile,
Ser60
Cys,
Ser60
Phe,
Ser95
Ile,
Arg405
Lys) localized normally to
Z-discs and exhibited normal dynamics in muscle cells.[20]
^"Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^"Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^Godley LA, Lai F, Liu J, Zhao N, Le Beau MM (Nov 1999). "TTID: A novel gene at 5q31 encoding a protein with titin-like features". Genomics. 60 (2): 226–33.
doi:
10.1006/geno.1999.5912.
PMID10486214.
^von Nandelstadh P, Grönholm M, Moza M, Lamberg A, Savilahti H, Carpén O (Oct 2005). "Actin-organising properties of the muscular dystrophy protein myotilin". Experimental Cell Research. 310 (1): 131–9.
doi:
10.1016/j.yexcr.2005.06.027.
PMID16122733.
^von Nandelstadh P, Soliymani R, Baumann M, Carpen O (May 2011). "Analysis of myotilin turnover provides mechanistic insight into the role of myotilinopathy-causing mutations". The Biochemical Journal. 436 (1): 113–21.
doi:
10.1042/BJ20101672.
PMID21361873.
Bartoloni L, Horrigan SK, Viles KD, Gilchrist JM, Stajich JM, Vance JM, Yamaoka LH, Pericak-Vance MA, Westbrook CA, Speer MC (Dec 1998). "Use of a CEPH meiotic breakpoint panel to refine the locus of limb-girdle muscular dystrophy type 1A (LGMD1A) to a 2-Mb interval on 5q31". Genomics. 54 (2): 250–5.
doi:
10.1006/geno.1998.5579.
PMID9828127.
Battle MA, Maher VM, McCormick JJ (Jun 2003). "ST7 is a novel low-density lipoprotein receptor-related protein (LRP) with a cytoplasmic tail that interacts with proteins related to signal transduction pathways". Biochemistry. 42 (24): 7270–82.
doi:
10.1021/bi034081y.
PMID12809483.
von Nandelstadh P, Grönholm M, Moza M, Lamberg A, Savilahti H, Carpén O (Oct 2005). "Actin-organising properties of the muscular dystrophy protein myotilin". Experimental Cell Research. 310 (1): 131–9.
doi:
10.1016/j.yexcr.2005.06.027.
PMID16122733.
Rual JF, Venkatesan K, Hao T, Hirozane-Kishikawa T, Dricot A, Li N, Berriz GF, Gibbons FD, Dreze M, Ayivi-Guedehoussou N, Klitgord N, Simon C, Boxem M, Milstein S, Rosenberg J, Goldberg DS, Zhang LV, Wong SL, Franklin G, Li S, Albala JS, Lim J, Fraughton C, Llamosas E, Cevik S, Bex C, Lamesch P, Sikorski RS, Vandenhaute J, Zoghbi HY, Smolyar A, Bosak S, Sequerra R, Doucette-Stamm L, Cusick ME, Hill DE, Roth FP, Vidal M (Oct 2005). "Towards a proteome-scale map of the human protein-protein interaction network". Nature. 437 (7062): 1173–8.
Bibcode:
2005Natur.437.1173R.
doi:
10.1038/nature04209.
PMID16189514.
S2CID4427026.
Foroud T, Pankratz N, Batchman AP, Pauciulo MW, Vidal R, Miravalle L, Goebel HH, Cushman LJ, Azzarelli B, Horak H, Farlow M, Nichols WC (Dec 2005). "A mutation in myotilin causes spheroid body myopathy". Neurology. 65 (12): 1936–40.
doi:
10.1212/01.wnl.0000188872.28149.9a.
PMID16380616.
S2CID9593230.
Garvey SM, Senderek J, Beckmann JS, Seboun E, Jackson CE, Hauser MA (May 2006). "Myotilin is not the causative gene for vocal cord and pharyngeal weakness with distal myopathy (VCPDM)". Annals of Human Genetics. 70 (Pt 3): 414–6.
doi:
10.1111/j.1529-8817.2005.00252.x.
PMID16674563.
S2CID26853063.
Pénisson-Besnier I, Talvinen K, Dumez C, Vihola A, Dubas F, Fardeau M, Hackman P, Carpen O, Udd B (Jul 2006). "Myotilinopathy in a family with late onset myopathy". Neuromuscular Disorders. 16 (7): 427–31.
doi:
10.1016/j.nmd.2006.04.009.
PMID16793270.
S2CID21589529.
Myotilin is a
protein that in humans is encoded by the MYOTgene.[5][6][7] Myotilin (myofibrillar titin-like protein) also known as TTID (TiTin Immunoglobulin Domain) is a muscle protein that is found within the
Z-disc of
sarcomeres.
Structure
Myotilin is a 55.3 kDa protein composed of 496 amino acids.[8] Myotilin was originally identified as a novel
alpha-actinin binding partner with two
Ig-like domains, that localized to the
Z-disc.[9] The I-type
Ig-like domains reside at the C-terminal half, and are most homologous to
Ig domains 2-3 of
palladin and
Ig domains 4-5 of
myopalladin and more distantly related to
Z-discIg domains 7 and 8 of
titin. The C-terminal region hosts the binding sites for Z-band proteins, and 2
Ig domains are the site of homodimerization for myotilin.[10] By contrast, the N-terminal part of myotilin is unique, consisting of a
serine-rich region with no homology to known proteins. Several disease-associated mutations involve
serine residues within the
serine-rich domain.[11] Myotilin expression in human tissues is mainly restricted to striated muscles and nerves. In muscles, myotilin is predominantly found within the
Z-discs. Myotilin forms homodimers and binds
alpha-actinin,
actin,[12]Filamin C,[13]FATZ-1,[14]FATZ-2[14] and
ZASP.[15]
Function
Myotilin is a structural protein that, along with
titin and
alpha-actinin give structural integrity to
sarcomeres at
Z-discs in striated muscle. Myotilin induces the formation of actin bundles in vitro and in non-muscle cells. A ternary complex myotilin/
actin/
alpha-actinin can be observed in vitro and
actin bundles formed under these conditions appear more tightly packed than those induced by
alpha-actinin alone. It was demonstrated that myotilin stabilizes
F-actin by slowing down the disassembly rate. Ectopic overexpression of truncated myotilin causes the disruption of nascent myofibrils and the co-accumulation of myotilin and
titin in amorphous cytoplasmic precipitates. In mature
sarcomeres, wild-type myotilin colocalizes with
alpha-actinin and
Z-disctitin, showing the striated pattern typical of
sarcomeric proteins. Targeted disruption of the myotilin gene in mice does not cause significant alterations in muscle function.[16] On the other hand, transgenic mice with mutated myotilin develop muscle dystrophy.[17]
Clinical significance
Myotilin is mutated in various forms of muscular dystrophy: Limb-Girdle Muscular Dystrophy type 1A (LGMD1A), Myofibrillar Myopathy (MFM), Spheroid Body Myopathy and Distal Myopath.[11] The mechanism underlying the pathology is still under investigation. It has been shown that actin binding properties of myotilin housing pathogenic mutations (
Ser55
Phe,
Thr57
Ile,
Ser60
Cys, and
Ser95
Ile) are normal,[18] albeit with a slower rate of degradation.[19] Surprisingly, YFP-fusion constructs of myotilin mutants (
Ser55
Phe,
Ser55
Ile,
Thr57
Ile,
Ser60
Cys,
Ser60
Phe,
Ser95
Ile,
Arg405
Lys) localized normally to
Z-discs and exhibited normal dynamics in muscle cells.[20]
^"Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^"Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
^Godley LA, Lai F, Liu J, Zhao N, Le Beau MM (Nov 1999). "TTID: A novel gene at 5q31 encoding a protein with titin-like features". Genomics. 60 (2): 226–33.
doi:
10.1006/geno.1999.5912.
PMID10486214.
^von Nandelstadh P, Grönholm M, Moza M, Lamberg A, Savilahti H, Carpén O (Oct 2005). "Actin-organising properties of the muscular dystrophy protein myotilin". Experimental Cell Research. 310 (1): 131–9.
doi:
10.1016/j.yexcr.2005.06.027.
PMID16122733.
^von Nandelstadh P, Soliymani R, Baumann M, Carpen O (May 2011). "Analysis of myotilin turnover provides mechanistic insight into the role of myotilinopathy-causing mutations". The Biochemical Journal. 436 (1): 113–21.
doi:
10.1042/BJ20101672.
PMID21361873.
Bartoloni L, Horrigan SK, Viles KD, Gilchrist JM, Stajich JM, Vance JM, Yamaoka LH, Pericak-Vance MA, Westbrook CA, Speer MC (Dec 1998). "Use of a CEPH meiotic breakpoint panel to refine the locus of limb-girdle muscular dystrophy type 1A (LGMD1A) to a 2-Mb interval on 5q31". Genomics. 54 (2): 250–5.
doi:
10.1006/geno.1998.5579.
PMID9828127.
Battle MA, Maher VM, McCormick JJ (Jun 2003). "ST7 is a novel low-density lipoprotein receptor-related protein (LRP) with a cytoplasmic tail that interacts with proteins related to signal transduction pathways". Biochemistry. 42 (24): 7270–82.
doi:
10.1021/bi034081y.
PMID12809483.
von Nandelstadh P, Grönholm M, Moza M, Lamberg A, Savilahti H, Carpén O (Oct 2005). "Actin-organising properties of the muscular dystrophy protein myotilin". Experimental Cell Research. 310 (1): 131–9.
doi:
10.1016/j.yexcr.2005.06.027.
PMID16122733.
Rual JF, Venkatesan K, Hao T, Hirozane-Kishikawa T, Dricot A, Li N, Berriz GF, Gibbons FD, Dreze M, Ayivi-Guedehoussou N, Klitgord N, Simon C, Boxem M, Milstein S, Rosenberg J, Goldberg DS, Zhang LV, Wong SL, Franklin G, Li S, Albala JS, Lim J, Fraughton C, Llamosas E, Cevik S, Bex C, Lamesch P, Sikorski RS, Vandenhaute J, Zoghbi HY, Smolyar A, Bosak S, Sequerra R, Doucette-Stamm L, Cusick ME, Hill DE, Roth FP, Vidal M (Oct 2005). "Towards a proteome-scale map of the human protein-protein interaction network". Nature. 437 (7062): 1173–8.
Bibcode:
2005Natur.437.1173R.
doi:
10.1038/nature04209.
PMID16189514.
S2CID4427026.
Foroud T, Pankratz N, Batchman AP, Pauciulo MW, Vidal R, Miravalle L, Goebel HH, Cushman LJ, Azzarelli B, Horak H, Farlow M, Nichols WC (Dec 2005). "A mutation in myotilin causes spheroid body myopathy". Neurology. 65 (12): 1936–40.
doi:
10.1212/01.wnl.0000188872.28149.9a.
PMID16380616.
S2CID9593230.
Garvey SM, Senderek J, Beckmann JS, Seboun E, Jackson CE, Hauser MA (May 2006). "Myotilin is not the causative gene for vocal cord and pharyngeal weakness with distal myopathy (VCPDM)". Annals of Human Genetics. 70 (Pt 3): 414–6.
doi:
10.1111/j.1529-8817.2005.00252.x.
PMID16674563.
S2CID26853063.
Pénisson-Besnier I, Talvinen K, Dumez C, Vihola A, Dubas F, Fardeau M, Hackman P, Carpen O, Udd B (Jul 2006). "Myotilinopathy in a family with late onset myopathy". Neuromuscular Disorders. 16 (7): 427–31.
doi:
10.1016/j.nmd.2006.04.009.
PMID16793270.
S2CID21589529.