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Myotonic Dystrophy Protein Kinase Is a Sarcoplasmic Reticulum Protein Specifically Localized in Type I Muscle Fibers without

By Colocalization Of Sercaii Atpase, Takayoshi Kobayashi, Masatake Shimokawa, Shoichi Ishiura Masahiko, Noriyoshi Kameda, Hiroaki Tanaka, Hidehiro Mizusawa, Hideho Ueda and Shinichi Ohno


Myotonic dystrophy (DM) is the most prevalent muscular dystrophy involving multisystem disorder. Previously we showed that the gene product of DM: myotonic dystrophy protein kinase (DMPK or myotonin protein kinase) was mainly localized in the terminal cisternae of the sarcoplasmic reticulum (SR) by immunoelectron microscopy. We describe here that DMPK is specifically localized in muscle fibers with slow myosin heavy chain (MHC), but not with fast MHC by using double immunofluorescent labeling of anti-DMPK and slow or fast MHCs antibodies. Staining pattern of DMPK is observed in three different intensities (strong, moderate and weak) in type I muscle fibers with even intensity of slow MHC staining. In the high magnification of a type I muscle fiber, the cross-striated bands of DMPK are not co-localized with those of slow MHC nor SERCA II ATPase, which is well known to be localized in longitudinal SRs. This is consistent with our previous study that DMPK is localized in the terminal cisternae of SRs. Our present finding is quite important to investigate the function of DMPK and to know the pathophysiological basis of DM because it is well known that specific type I atrophy is commonly observed in DM muscles

Year: 2014
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