Disease mutations in the “head” domain of the extra-sarcomeric protein desmin distinctly alter its assembly and network-forming properties
The intermediate filament protein desmin generates an extra-sarcomeric network in myocytes. Mutations in the desmin gene cause myofibrillar myopathy characterized by desmin-positive aggregates and myofibrillar dissolution. Past analysis revealed that the non-α-helical amino-terminal “head” domain of desmin is a vital coordinator of protein assembly. We have now characterized assembly and network-forming properties of five recently discovered myopathy-causing mutations residing in this domain. In vitro analyses with recombinant proteins show that two mutant variants residing in a conserved nonapeptide motif “SSYRRTFGG”—Ser13Phe and Arg16Cys—interfere with assembly by forming filamentous aggregates. Consistent with in vitro data, both mutant proteins are unable to generate a bona fide filament system in cells lacking an intermediate filament cytoskeleton. In cells expressing vimentin or desmin, both mutants firstly fail to integrate into the endogenous filament network and secondly severely affect its cellular localization. The other three mutations—Ser2Iso, Ser46Phe, and Ser46Tyr—influence in vitro filament properties less severely, but in vivo, Ser46Phe and Ser46Tyr impair de novo filament formation. These effects of the “head” mutant proteins on endogenous intermediate filament system and their competition for binding to cellular anchoring structures might explain part of the molecular mechanism that causes disease.
KeywordsDesmin Intermediate filament protein Myofibrillar myopathy Assembly Transfection
Harald Bär and Harald Herrmann acknowledge grants from the German Research Foundation (DFG; BA 2186/3-1 to H.B. and H.H.). Full-length cDNA of human LMNB1 cloned into the eukaryotic expression vector pEYFP-C1 was generously provided by Stephanie Geiger, DKFZ, Germany. The HL-1 cells were kindly provided by William C. Claycomb, Louisiana State University Medical Center, New Orleans, USA. We wish to thank Gloria Conover from Texas A&M University for critical reading of the manuscript.
Conflict of interest statement
The authors declare that they have no conflict of interests.
- 7.Pruszczyk P, Kostera-Pruszczyk A, Shatunov A, Goudeau B, Draminska A, Takeda K, Sambuughin N, Vicart P, Strelkov SV, Goldfarb LG, Kaminska A (2007) Restrictive cardiomyopathy with atrioventricular conduction block resulting from a desmin mutation. Int J Cardiol 117:244–253CrossRefPubMedGoogle Scholar
- 8.Arbustini E, Pasotti M, Pilotto A, Pellegrini C, Grasso M, Previtali S, Repetto A, Bellini O, Azan G, Scaffino M, Campana C, Piccolo G, Vigano M, Tavazzi L (2006) Desmin accumulation restrictive cardiomyopathy and atrioventricular block associated with desmin gene defects. Eur J Heart Fail 8:477–483CrossRefPubMedGoogle Scholar
- 9.Bär H, Goudeau B, Wälde S, Casteras-Simon M, Mücke N, Shatunov A, Goldberg YP, Clarke C, Holton JL, Eymard B, Katus HA, Fardeau M, Goldfarb L, Vicart P, Herrmann H (2007) Conspicuous involvement of desmin tail mutations in diverse cardiac and skeletal myopathies. Hum Mutat 28:374–386CrossRefPubMedGoogle Scholar
- 11.Bergman JE, Veenstra-Knol HE, van Essen AJ, van Ravenswaaij CM, den Dunnen WF, van den Wijngaard A, van Tintelen JP (2007) Two related Dutch families with a clinically variable presentation of cardioskeletal myopathy caused by a novel S13F mutation in the desmin gene. Eur J Med Genet 50:355–366CrossRefPubMedGoogle Scholar
- 26.Parry DA, Steinert PM (1995) Intermediate filament structure. Springer, New YorkGoogle Scholar