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Molecular and Cellular Biology, September 2004, p. 8167-8183, Vol. 24, No. 18
0270-7306/04/$08.00+0 DOI: 10.1128/MCB.24.18.8167-8183.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
Regulates Keratinocyte Death and Survival by Regulating Activity and Subcellular Localization of a p38
-Extracellular Signal-Regulated Kinase 1/2 Complex
Departments of Physiology and Biophysics,1 Dermatology,2 Oncology,3 Biochemistry,4 Reproductive Biology, Case Western Reserve University School of Medicine, Cleveland, Ohio5
Received 16 April 2004/ Returned for modification 13 May 2004/ Accepted 9 June 2004
Protein kinase C
(PKC
) is an important regulator of apoptosis in epidermal keratinocytes. However, little information is available regarding the downstream kinases that mediate PKC
-dependent keratinocyte death. This study implicates p38
mitogen-activated protein kinase (MAPK) as a downstream carrier of the PKC
-dependent death signal. We show that coexpression of PKC
with p38
produces profound apoptosis-like morphological changes. These morphological changes are associated with increased sub-G1 cell population, cytochrome c release, loss of mitochondrial membrane potential, caspase activation, and PARP cleavage. This death response is specific for the combination of PKC
and p38
and is not produced by replacing PKC
with PKC
or p38
with p38
. A constitutively active form of MEK6, an upstream activator of p38
, can also produce cell death when coupled with p38
. In addition, concurrent p38
activation and extracellular signal-regulated kinase 1/2 (ERK1/2) inactivation are required for apoptosis. Regarding this inverse regulation, we describe a p38
-ERK1/2 complex that may coordinate these changes in activity. We further show that this p38
-ERK1/2 complex relocates into the nucleus in response to PKC
expression. This regulation appears to be physiological, since H2O2, a known inducer of keratinocyte apoptosis, promotes identical PKC
and p38
-ERK1/2 activity changes, leading to similar morphological changes.
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