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Molecular and Cellular Biology, May 2000, p. 3442-3448, Vol. 20, No. 10
Department of Medicine, Division of
Metabolism, Endocrinology and Nutrition,1 and
Department of Pharmacology,3 University
of Washington, Seattle, Washington 98195; Mental Health
Research Institute, University of Michigan, Ann Arbor, Michigan
481094; and V.A. Puget Sound Health Care
System, Seattle, Washington 981082
Received 7 January 2000/Returned for modification 13 January
2000/Accepted 14 February 2000
Protein kinase inhibitor (PKI) is a potent endogenous inhibitor of
the cyclic AMP (cAMP)-dependent protein kinase (PKA). It functions by
binding the free catalytic (C) subunit with a high affinity and is also
known to export nuclear C subunit to the cytoplasm. The significance of
these actions with respect to PKI's physiological role is not well
understood. To address this, we have generated by homologous
recombination mutant mice that are deficient in PKI
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Deficient Gene Expression in Protein Kinase Inhibitor
Null Mutant Mice
, one of the
three isoforms of PKI. The mice completely lack PKI activity in
skeletal muscle and, surprisingly, show decreased basal and
isoproterenol-induced gene expression in muscle. Further examination
revealed reduced levels of the phosphorylated (active) form of the
transcription factor CREB (cAMP response element binding protein) in
the knockouts. This phenomenon stems, at least in part, from lower
basal PKA activity levels in the mutants, arising from a compensatory
increase in the level of the RI
subunit of PKA. The deficit in gene
induction, however, is not easily explained by current models of PKI
function and suggests that PKI may play an as yet undescribed role in
PKA signaling.
*
Corresponding author. Mailing address: V.A. Puget Sound
Health Care System, 1660 S. Columbian Way, Seattle, WA 98108. Phone: (206) 768-5490. Fax: (206) 764-2598. E-mail:
idzerda{at}u.washington.edu.
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