J. Biol. Chem., Vol. 263, Issue 20, 9733-9737, 07, 1988
The abundance of calmodulin mRNAs is regulated in phosphorylase kinase- deficient skeletal muscle
PK Bender, JR Dedman and CP Emerson Jr
Department of Biology, University of Virginia, Charlottesville 22901.
In the I/Lyn mouse strain a mutation on the X chromosome results in a
deficiency of the major calmodulin-regulated enzyme in skeletal muscle,
phosphorylase kinase. Calmodulin has been identified as the delta- subunit
of phosphorylase kinase, and it is estimated that approximately 40% of the
total calmodulin in rabbit skeletal muscle is associated with the
phosphorylase kinase hexadecamer (alpha, beta, gamma, delta)4. The absence
of phosphorylase kinase in I/Lyn skeletal muscle results in a reduction in
the total amount of calmodulin. The mechanisms affecting this reduction
were investigated by comparing the abundance and heterogeneities in
calmodulin mRNAs between normal and phosphorylase kinase-deficient skeletal
muscles. The results demonstrate that in normal tissue there are four
species of calmodulin mRNA distinguished by their molecular weight. All
four of these species are present in the deficient tissue, and none of them
are preferentially reduced. However, there is a 54% reduction in all four
mRNAs as well as in calmodulin in the deficient skeletal muscle relative to
normal skeletal muscle. These results indicate that the expression of
calmodulin mRNAs is coordinated with the expression of its major enzyme
target in skeletal muscle.
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