title: Roles of the calcineurin and CaMK signaling pathways in fast-to-slow fiber type transformation of cultured adult mouse skeletal muscle fibers.
abstract: Two Ca2+-dependent signaling pathways, mediated by the Ca2+-activated phosphatase calcineurin and by the Ca2+-activated kinase Ca2+/calmodulin-dependent kinase (CaMK), are both believed to function in fast-to-slow skeletal muscle fiber type transformation, but questions about the relative importance of the two pathways still remain. Here, the differential gene expression during fast-to-slow fiber type transformation was studied using cultured adult flexor digitorum brevis (FDB) fibers and a custom minimicroarray system containing 21 fiber type-specific marker genes. After 3 days of culture, unstimulated fibers showed a generally slower gene expression profile; 3 days of electric field stimulation of cultured FDB fibers with a slow fiber-type pattern transformed the fibers to an even slower gene expression profile. Unstimulated FDB fibers overexpressing constitutively active calcineurin featured a slower gene expression profile, except four genes, indicating that transformation occurred, but was incomplete with activation of the calcineurin pathway alone. In both unstimulated FDB fibers and slow-type electrically stimulated FDB fibers, blocking of CaMK pathway with KN93 generated a faster gene expression profile compared with the negative control KN92, indicating that CaMK pathway functions during the transformation induced by both unstimulated culturing and slow fiber-type electrical stimulation. Moreover, neither the calcineurin nor the CaMK pathway alone could maximally activate the transformation, and coordination of the two pathways is required to accomplish a complete fast-to-slow fiber type transformation.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine Baltimore, Maryland 21201, USA.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Mu
authors.forename: Lisa D
authors.initials: LD
authors.lastname: Brown
authors.forename: Yewei
authors.initials: Y
authors.lastname: Liu
authors.forename: Martin F
authors.initials: MF
authors.lastname: Schneider
mesh_terms: D000818:Animals; D019703:Calcineurin / Q000502:physiology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology*; D002454:Cell Differentiation; D002478:Cells, Cultured; D004558:Electric Stimulation; D020869:Gene Expression Profiling; D051379:Mice; D008815:Mice, Inbred Strains; D018656:Muscle Fibers, Fast-Twitch / Q000166:cytology* / Q000378:metabolism; D018657:Muscle Fibers, Slow-Twitch / Q000166:cytology* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology* / Q000378:metabolism; D021141:Nucleic Acid Amplification Techniques; D020411:Oligonucleotide Array Sequence Analysis; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019703:Calcineurin