Volume 272, Number 2,
Issue of January 10, 1997
pp. 1368-1376
©1997 by The American Society for Biochemistry and Molecular Biology, Inc.
The Dual Specificity Mitogen-activated Protein Kinase
Phosphatase-1 and -2 Are Induced by the p42/p44MAPK
Cascade
(Received for publication, September 4, 1996, and in revised form, October 28, 1996)
Jean-Marc
Brondello
,
Anne
Brunet
,
Jacques
Pouysségur
and
Fergus R.
McKenzie
From the Université de Nice, Centre de Biochimie, CNRS UMR
134, Parc Valrose, 06108 Nice Cedex 02, France
Mitogen-activated protein (MAP) kinase
phosphatase-1 (MKP-1) and MKP-2 are two members of a recently described
family of dual specificity phosphatases that are capable of
dephosphorylating p42/p44MAPK. Overexpression of MKP-1 or
MKP-2 inhibits MAP kinase-dependent intracellular signaling
events and fibroblast proliferation. By using specific antibodies that
recognize endogenous MKP-1 and MKP-2 in CCL39 cells, we show that MKP-1
and MKP-2 are not expressed in quiescent cells, but are rapidly induced
following serum addition, with protein detectable as early as 30 min
(MKP-1) or 60 min (MKP-2). Serum induction of MKP-1 and MKP-2 is
sustained, with protein detectable up to 14 h after serum
addition. Induction of MKP-1 and, to a lesser extent, MKP-2 temporally
correlates with p42/p44MAPK inactivation.
To analyze the contribution of the MAP kinase cascade to MKP-1 and
MKP-2 induction, we examined CCL39 cells transformed with either
v-ras or a constitutively active direct upstream activator of MAP kinase, mitogen-activated protein kinase kinase-1 (MKK-1; MKK-1(SD/SD) mutant). In both cell models, MKP-1 and MKP-2 are constitutively expressed, with MKP-2 being prevalent. In addition, in
CCL39 cells expressing an estradiol-inducible
Raf-1::ER
chimera, activation of Raf alone is sufficient to induce MKP-1 and
MKP-2. The role of the MAP kinase cascade in MKP induction was
highlighted by the MKK-1 inhibitor PD 098059, which blunted both the
activation of p42/p44MAPK and the induction of MKP-1 and
MKP-2. However, the MAP kinase cascade is not absolutely required for
the induction of MKP-1, as this phosphatase, but not MKP-2, was induced
to detectable levels by agents that stimulate protein kinases A and C. Thus, activation of the p42/p44MAPK cascade promotes the
induction of MKP-1 and MKP-2, which may then attenuate
p42/p44MAPK-dependent events in an inhibitory
feedback loop.