Interactions with titin and myomesin target obscurin and obscurin-like 1 to the M-band: implications for hereditary myopathies.
Obscurin, a giant modular muscle protein implicated in G-protein and protein-kinase signalling, can localize to both sarcomeric Z-disks and M-bands. Interaction of obscurin with the Z-disk is mediated by Z-disk titin. Here, we unravel the molecular basis for the unusual localization of obscurin, a Z-disk-associated protein, to the M-band, where its invertebrate analogue UNC-89 is also localized. The first three domains of the N-terminus of obscurin bind to the most C-terminal domain of M-band titin, as well as to the M-band protein myomesin. Both proteins also interact with the N-terminal domains of obscurin-like 1 (Obsl1), a small homologue of obscurin. Downregulation of myomesin by siRNA interference disrupts obscurin-M-band integration in neonatal cardiomyocytes, as does overexpression of the binding sites on either myomesin, obscurin or Obsl1. Furthermore, all titin mutations that have been linked to limb-girdle muscular dystrophy 2J (LGMD2J) or Salih myopathy weaken or abrogate titin-obscurin and titin-Obsl1 binding, and lead to obscurin mislocalization, suggesting that interference with the interaction of these proteins might be of pathogenic relevance for human disease.
Fukuzawa
Atsushi
A
King's College London, The Randall Division for Cell and Molecular Biophysics, and Cardiovascular Division, New Hunt's House, London, UK.
Lange
Stephan
S
Holt
Mark
M
Vihola
Anna
A
Carmignac
Virginie
V
Ferreiro
Ana
A
Udd
Bjarne
B
Gautel
Mathias
M
D000818:Animals; D000831:Animals, Newborn; D001665:Binding Sites / Q000235:genetics; D002478:Cells, Cultured; D064211:Connectin; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000378:metabolism*; D015536:Down-Regulation / Q000502:physiology; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry / Q000378:metabolism*; D009124:Muscle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000648:ultrastructure; D009135:Muscular Diseases / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D009154:Mutation / Q000235:genetics; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000648:ultrastructure; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000502:physiology; D034741:RNA, Small Interfering; D051381:Rats; D012518:Sarcomeres / Q000378:metabolism* / Q000648:ultrastructure
D064211:Connectin; D003598:Cytoskeletal Proteins; D020662:Guanine Nucleotide Exchange Factors; D009124:Muscle Proteins; C522001:OBSL1 protein, rat; C503780:Obscn protein, rat; D034741:RNA, Small Interfering; C577292:TCAP protein, human; C577295:Ttn protein, rat