Functional analysis of titin/connectin N2-B mutations found in cardiomyopathy.
Hypertrophic cardiomyopathy and dilated cardiomyopathy are two major clinical phenotypes of "idiopathic" cardiomyopathy. Recent molecular genetic analyses have now revealed that "idiopathic" cardiomyopathy is caused by mutations in genes for sarcomere components. We have recently reported several mutations in titin/connectin gene found in patients with hypertrophic cardiomyopathy or dilated cardiomyopathy. A hypertrophic cardiomyopathy-associated titin/connectin mutation (Arg740Leu) was found to increase the binding to actinin, while other dilated cardiomyopathy-associated titin/connectin mutations (Ala743Val and Val54Met) decreased the binding to actinin and Tcap/telethonin, respectively. We also reported several other mutations in the N2-B region of titin/connectin found in hypertrophic cardiomyopathy and dilated cardiomyopathy. Since the N2-B region expresses only in the heart, it was speculated that functional alterations due to the mutations cause cardiomyopathies. In this study, we investigated the functional changes caused by the N2-B region mutations by using yeast-two-hybrid assays. It was revealed that a hypertrophic cardiomyopathy-associated mutation (Ser3799Tyr) increased the binding to FHL2 protein, whereas a dilated cardiomyopathy-associated mutation (Gln4053ter) decreased the binding. In addition, another TTN mutation (Arg25618Gln) at the is2 region was found in familial DCM. Because FHL2 protein is known to tether metabolic enzymes to N2-B and is2 regions of titin/connectin, these observations suggest that altered recruitment of metabolic enzymes to the sarcomere may play a role in the pathogenesis of cardiomyopathies.
Matsumoto
Yuji
Y
Department of Molecular Pathogenesis, Medical Research Institute, Tokyo Medical and Dental University, 2-3-10 Kandasurugadai, Chiyoda-Ku, 101-0062, Tokyo , Japan.
Hayashi
Takeharu
T
Inagaki
Natsuko
N
Takahashi
Megumi
M
Hiroi
Shitoshi
S
Nakamura
Takeyuki
T
Arimura
Takuro
T
Nakamura
Kazufumi
K
Ashizawa
Naoto
N
Yasunami
Michio
M
Ohe
Toru
T
Yano
Katsusuke
K
Kimura
Akinori
A
D000368:Aged; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D044466:Asian People; D009202:Cardiomyopathies / Q000209:etiology / Q000235:genetics*; D002311:Cardiomyopathy, Dilated / Q000235:genetics; D002312:Cardiomyopathy, Hypertrophic / Q000235:genetics; D064211:Connectin; D004252:DNA Mutational Analysis; D005260:Female; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D060850:LIM-Homeodomain Proteins; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D009154:Mutation / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
D064211:Connectin; C105987:FHL2 protein, human; D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; D009124:Muscle Proteins; D050505:Mutant Proteins; C577285:TTN protein, human; D014157:Transcription Factors; D011494:Protein Kinases