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Molecular and Cellular Biology, October 2001, p. 6851-6858, Vol. 21, No. 20
Departments of
Medicine3 and Medical
Biophysics,1 University of Toronto, Princess
Margaret Hospital and Ontario Cancer Institute, Toronto, Ontario M5G
2M9, Canada, and Nagoya School of Medicine, Showa-ku,
Nagoya 464, Japan2
Received 13 February 2001/Returned for modification 13 March
2001/Accepted 19 July 2001
The mitogen-activated protein kinases (MAPKs) are signaling
molecules that become enzymatically activated through phosphorylation by diverse stimuli. Hematopoietic cytokines, growth factors, and stimulated lymphocyte antigen receptors may activate specific MAPKs by
altering the balance of MAPK-activating protein kinases and the protein
phosphatases that target their activation sites. Hematopoietic protein
tyrosine phosphatase (HePTP) is a hematopoiesis-specific cytoplasmic
protein tyrosine phosphatase whose expression is induced by mitogenic
stimuli. To investigate the role of HePTP in hematopoietic development,
we constructed mice deficient in this phosphatase using the technique
of homologous recombination. Primary lymphocytes from
HePTP
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.20.6851-6858.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Hematopoietic Protein Tyrosine Phosphatase
Suppresses Extracellular Stimulus-Regulated Kinase
Activation
/
mice show enhanced activation of extracellular
stimulus-regulated kinase (ERK) after both phorbol myristate acetate
(PMA) and anti-CD3-mediated T-cell receptor (TCR) stimulation,
suggesting a true physiological relationship between these two
molecules. Activation of MEK, the physiological activator of ERK, by
anti-CD3 or PMA is not affected by HePTP deletion. The distribution of
hematopoietic lineages in bone marrow and peripheral blood samples and
the in vitro proliferative capacity of bone marrow progenitors from
HePTP deletion mice do not deviate from those of matched littermate
controls. Similarly, lymphocyte activation and development are
indistinguishable in HePTP
/
mice and controls. We
conclude that HePTP is a physiological regulator of ERK on the basis of
these studies and hypothesize that its deletion is well compensated for
in the developing mouse through reduction of ERK targets or enhancement
of physiologically opposed signaling pathways.
*
Corresponding author. Present address: The Cross Cancer
Institute, 51160 University Avenue, Edmonton, Alberta T6G 1Z2, Canada. Phone: (780) 432-8771. Fax: (780) 432-8411. E-mail:
zanke{at}cancerboard.ab.ca.
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