Novel isoform of myotonin protein kinase: gene product of myotonic dystrophy is localized in the sarcoplasmic reticulum of skeletal muscle.

Abstract

It is quite important to know the exact localization and function of myotonin protein kinase (MtPK), identified as the gene product of myotonic dystrophy, the most prevalent disease with multisystem disorders among muscular dystrophies. To investigate the localization of MtPK, we raised a polyclonal antibody against a synthetic peptide chosen within the deduced sequence of MtPK. This antibody detected both a membrane-bound 70-kd protein and a soluble 55-kd protein on Western blots of human muscles. By using this antibody for immunohistochemical studies of both biopsied human skeletal muscle fibers and mature innervated cultured muscle fibers, we can now demonstrate by confocal laser scanning microscopy that MtPK is localized mainly in the I-band. By immunoelectron microscopy, it was determined that MtPK is a membrane-bound protein localized mainly in the terminal cisternae of the sarcoplasmic reticulum. To our knowledge, this is the first documentation of the ultrastructural localization of MtPK. This finding is quite important for clarifying the pathophysiological basis of myotonic dystrophy, which might be due to a dysregulation of calcium metabolism.

• Authors: M Shimokawa, S Ishiura, N Kameda, M Yamamoto, N Sasagawa, N Saitoh, H Sorimachi, H Ueda, S Ohno, K Suzuki, T Kobayashi
• Journal: The American journal of pathology (Am J Pathol) Vol. 150 Issue 4 Pg. 1285-95 (Apr 1997) ISSN: 0002-9440 [Print] United States
• PMID: 9094985 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Actins
• DMPK protein, human
• Isoenzymes
• Protein Kinases
• Myotonin-Protein Kinase
• Protein Serine-Threonine Kinases
• Myosins

Topics

• Actins (analysis)
• Adult
• Amino Acid Sequence
• Blotting, Western
• Cells, Cultured
• Gene Expression Regulation, Developmental
• Humans
• Isoenzymes (genetics, metabolism)
• Microscopy, Immunoelectron
• Molecular Sequence Data
• Muscle Development
• Muscle, Skeletal (enzymology, growth & development, ultrastructure)
• Myosins (analysis)
• Myotonic Dystrophy (enzymology, genetics, pathology)
• Myotonin-Protein Kinase
• Protein Kinases (genetics, metabolism)
• Protein Serine-Threonine Kinases
• Sarcoplasmic Reticulum (enzymology, ultrastructure)