Molecular and Cellular Biology, October 2001, p. 6999-7009, Vol. 21, No. 20
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.20.6999-7009.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Laboratory of Host Defense and Germfree Life, Research Institute for Disease Mechanism and Control, Nagoya University School of Medicine, Nagoya 466-8550, Japan,1 and Department of Medical Oncology, University of Colorado Health Science Center, Denver, Colorado 802622
Received 27 February 2001/Returned for modification 30 March 2001/Accepted 26 June 2001
We have isolated a cDNA homologous to known dual-specificity
phosphatases from a mouse macrophage cDNA library and termed it MKP-M
(for mitogen-activated protein kinase phosphatase isolated from
macrophages). Three other presumed splice variant isoforms have also
been identified for MKP-M. The longest and most abundant mRNA contains
an open reading frame corresponding to 677 amino acids and produces an
80-kDa protein. The deduced amino acid sequence of MKP-M is most
similar to those of hVH-5 (or mouse M3/6) and VHP1, a
Caenorhabditis elegans tyrosine
phosphatase. It includes an N-terminal rhodanase homology domain,
the extended active-site sequence motif
(V/L)X(V/I)HCXAG(I/V)SRSXT(I/V)XXAY(L/I)M (where X is any
amino acid), and a C-terminal PEST sequence. Northern blot analysis
revealed a dominant MKP-M mRNA species of approximately 5.5 kb detected
ubiquitously among all tissues examined. MKP-M was constitutively
expressed in mouse macrophage cell lines, and its expression levels
were rapidly increased by lipopolysaccharide (LPS) stimulation but not
by tumor necrosis factor alpha (TNF-
), gamma interferon,
interleukin-2 (IL-2), or IL-15 stimulation. Immunocytochemical analysis
showed MKP-M to be present within cytosol. When expressed in COS7
cells, MKP-M blocks activation of mitogen-activated protein kinases
with the selectivity c-Jun N-terminal kinase (JNK)
p38 = extracellular signal-regulated kinase. Furthermore, expression of
a catalytically inactive form of MKP-M in a mouse macrophage cell line
increased the intensity and duration of JNK activation and TNF-
secretion after LPS stimulation, suggesting that MKP-M is at least
partially responsible for the desensitization of LPS-mediated JNK
activation and cytokine secretion in macrophages.
This article has been cited by other articles:
| J. Bacteriol. | J. Virol. | Eukaryot. Cell |
|---|
| Microbiol. Mol. Biol. Rev. | Clin. Vaccine Immunol. | All ASM Journals |
|---|