MEF2 responds to multiple calcium-regulated signals in the control of skeletal muscle fiber type.
Different patterns of motor nerve activity drive distinctive programs of gene transcription in skeletal muscles, thereby establishing a high degree of metabolic and physiological specialization among myofiber subtypes. Recently, we proposed that the influence of motor nerve activity on skeletal muscle fiber type is transduced to the relevant genes by calcineurin, which controls the functional activity of NFAT (nuclear family of activated T cell) proteins. Here we demonstrate that calcineurin-dependent gene regulation in skeletal myocytes is mediated also by MEF2 transcription factors, and is integrated with additional calcium-regulated signaling inputs, specifically calmodulin-dependent protein kinase activity. In skeletal muscles of transgenic mice, both NFAT and MEF2 binding sites are necessary for properly regulated function of a slow fiber-specific enhancer, and either forced expression of activated calcineurin or motor nerve stimulation up-regulates a MEF2-dependent reporter gene. These results provide new insights into the molecular mechanisms by which specialized characteristics of skeletal myofiber subtypes are established and maintained.
Wu
H
H
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Naya
F J
FJ
McKinsey
T A
TA
Mercer
B
B
Shelton
J M
JM
Chin
E R
ER
Simard
A R
AR
Michel
R N
RN
Bassel-Duby
R
R
Olson
E N
EN
Williams
R S
RS
D000818:Animals; D001483:Base Sequence; D019703:Calcineurin / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000502:physiology*; D020013:Calcium Signaling; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D004558:Electric Stimulation; D004742:Enhancer Elements, Genetic / Q000235:genetics; D064326:MEF2 Transcription Factors; D051379:Mice; D008822:Mice, Transgenic; D009046:Motor Neurons / Q000502:physiology; D018656:Muscle Fibers, Fast-Twitch / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D018657:Muscle Fibers, Slow-Twitch / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000201:enzymology / Q000294:innervation / Q000378:metabolism*; D018006:Myogenic Regulatory Factors; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D009928:Organ Specificity; D010766:Phosphorylation; D011485:Protein Binding; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D014157:Transcription Factors; D004247:DNA; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C517685:Camk4 protein, mouse; D019703:Calcineurin; D002118:Calcium