J Biol Chem, Vol. 274, Issue 45, 31961-31966, November 5, 1999
Contractile Activity Modifies Fru-2,6-P2 Metabolism
in Rabbit Fast Twitch Skeletal Muscle
Joan A.
Cadefau,
Joan
Parra,
Albert
Tauler§, and
Roser
Cussó
From the Department of Physiological Sciences I and
§ Department of Biochemistry and Molecular Biology, Division
IV, Institut d'Investigacions Biomèdiques August Pi i Sunyer,
University of Barcelona, Barcelona E-08036, Spain
Modification of muscular contractile patterns by
denervation and chronic low frequency stimulation induces structural,
physiological, and biochemical alterations in fast twitch skeletal muscles.
Fructose 2,6-bisphosphate is a potent activator of
6-phosphofructo-1-kinase, a key regulatory enzyme of glycolysis
in animal tissues. The concentration of
Fru-2,6-P2 depends on the activity of the
bifunctional enzyme,
6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2),
which catalyzes the synthesis and degradation of this metabolite. This
enzyme has several isoforms, the relative abundance of which depends on
the tissue metabolic properties. Skeletal muscle expresses two of these
isoforms; it mainly contains the muscle isozyme (M-type) and a small
amount of the liver isozyme (L-type), whose expression is under
hormonal control. Moreover, contractile activity regulates expression
of muscular proteins related with glucose metabolism. Fast twitch
rabbit skeletal muscle denervation or chronic low frequency stimulation
can provide information about the regulation of this enzyme. Our
results show an increase in Fru-2,6-P2 concentration after
2 days of denervation or stimulation. In denervated muscle, this
increase is mediated by a rise in liver PFK-2/FBPase-2 isozyme, while
in stimulated muscle it is mediated by a rise in muscle PFK-2/FBPase-2
isozyme. In conclusion, our results show that contractile activity
could alter the expression of PFK-2/FBPase-2.
Copyright © 1999 by The American Society for Biochemistry and Molecular Biology, Inc.