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Paradoxical absence of M lines and downregulation of creatine kinase in mouse extraocular muscle.
- Source :
-
Journal of applied physiology (Bethesda, Md. : 1985) [J Appl Physiol (1985)] 2003 Aug; Vol. 95 (2), pp. 692-9. Date of Electronic Publication: 2003 Apr 25. - Publication Year :
- 2003
-
Abstract
- The M lines are structural landmarks in striated muscles, necessary for sarcomeric stability and as anchoring sites for the M isoform of creatine kinase (CK-M). These structures, especially prominent in fast skeletal muscles, are missing in rodent extraocular muscle, a particularly fast and active muscle group. In this study, we tested the hypotheses that 1). myomesin and M protein (cytoskeletal components of the M lines) and CK-M are downregulated in mouse extraocular muscle compared with the leg muscles, gastrocnemius and soleus; and 2). the expression of other cytosolic and mitochondrial CK isoforms is correspondingly increased. As expected, mouse extraocular muscles expressed lower levels of myomesin, M protein, and CK-M mRNA than the leg muscles. Immunocytochemically, myomesin and M protein were not detected in the banding pattern typically seen in other skeletal muscles. Surprisingly, message abundance for the other known CK isoforms was also lower in the extraocular muscles. Moreover, total CK activity was significantly decreased compared with that in the leg muscles. Based on these data, we reject our second hypothesis and propose that other energy-buffering systems may be more important in the extraocular muscles. The downregulation of major structural and metabolic elements and relative overexpression of two adenylate kinase isoforms suggest that the extraocular muscle group copes with its functional requirements by using strategies not seen in typical skeletal muscles.
- Subjects :
- Adenylate Kinase genetics
Adenylate Kinase metabolism
Animals
Connectin
Creatine Kinase, MM Form
Down-Regulation
Glycoproteins genetics
Immunohistochemistry
Isoenzymes genetics
Mice
Mice, Inbred C57BL
Muscle Proteins genetics
Oculomotor Muscles enzymology
RNA, Messenger metabolism
Reverse Transcriptase Polymerase Chain Reaction
Up-Regulation
Creatine Kinase metabolism
Glycoproteins metabolism
Isoenzymes metabolism
Muscle Proteins metabolism
Oculomotor Muscles anatomy & histology
Oculomotor Muscles metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 8750-7587
- Volume :
- 95
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- Journal of applied physiology (Bethesda, Md. : 1985)
- Publication Type :
- Academic Journal
- Accession number :
- 12716871
- Full Text :
- https://doi.org/10.1152/japplphysiol.00358.2003