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Role of protein kinase system in the signal transduction of stretch-mediated protooncogene expression and hypertrophy of cardiac myocytes (1993)

Yazaki, Yoshio ; Komuro, Issei ; Yamazaki, Tsutomu ; [et al.]

Springer

Molecular and cellular biochemistry 119 (1993), S. 11-16

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ISSN: 1573-4919

Keywords: protooncogenes ; cardiac hypertrophy ; mechanical stimulus ; protein kinase C ; MAP kinase

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Abstract To examine the molecular mechanisms by which mechanical stimuli induce protooncogene expression and hypertrophy of cardiac myocytes directly, we cultured rat neonatal cardiac myocytes in deformable dishes and imposed mechanical load on adherent cultured cardiac myocytes by stretching the dishes. Myocyte stretching increased total cell RNA content and mRNA levels of c-fos and skeletal α-actin followed by the aminoacid incorporation into cardiac proteins. CAT assay analysis indicated that the sequences containing serum response element were required for the efficient transcription of c-fos gene by stretching. This accumulation of c-fos mRNA by myocyte stretching was inhibited markedly by down-regulation of protein kinase C. Moreover, myocyte stretching increased inositol phosphate levels. These findings suggests that mechanical stimuli might directly induce protooncogene expression possibly via protein kinase C activation. Furthermore, we observed the activation of MAP kinase by myocytes stretching. This result suggests that MAP kinase activation induced by mechanical stimuli might increase the efficiency of protein synthesis on ribosomes induced by mechanical stimuli.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00926847

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Intracellular assembly of newly synthesized canine cardiac myosins (1990)

Seko, Yoshinori ; Naito, Shigeto ; Imataka, Kouji ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Cell Biochemistry and Function 8 (1990), S. 117-130

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ISSN: 0263-6484

Keywords: myosin heavy chain isozyme ; cultured cardiac myocyte ; thyroxine ; immunoelectron microscopy ; enzyme-labelled antibody ; monoclonal antibody ; myofilament ; polyribosome ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Medicine

Notes: To investigate how newly synthesized cardiac myosins are assembled into myofilaments, we analysed the distribution of newly produced α-myosin heavy chain isozyme in sarcomeres by immunoelectron microscopy using a monoclonal antibody (CMA19), which is specific for α-myosin heavy chain. Isozymic changes in myosin heavy chains from β to α type were induced in canine ventricular muscles and cultured ventricular myocytes by administration of 1-thyroxine. We incubated the glycerinated ventricular muscles or cultured ventricular myocytes with the enzyme (horseradish peroxidase) labelled Fab fragment of CMA19. After the reaction with 3, 3′-diaminobenzidine and osmification, we prepared ultrathin sections of the ventricular muscles or cultured ventricular myocytes and analysed their staining patterns by electron microscopy.There was apparent heterogeneity in the staining intensity of the myofilaments among different cells, among different myofibrils and even intramyofibrillarly. Higher magnification revealed that there were scattered foci of strong reaction which appeared to be foci of assembly of the newly synthesized α-myosin heavy chain. Immunocytochemical study also showed heterogeneous reactions within myofilaments and that there were scattered foci of myofilament assembly, which were closely associated with polyribosomes producing newly induced α-myosin heavy chain. These data suggest that newly synthesized cardiac myosins are assembled into myofilaments from the sites of synthesis, that is polyribosomes. This may explain the heterogeneity of the assembly pattern of newly synthesized cardiac myosins at the subcellular level.

Additional Material: 9 Ill.