Leukotriene D4 Activates Mitogen-activated Protein Kinase through a Protein Kinase Cα-Raf-1-dependent Pathway in Human Monocytic Leukemia THP-1 Cells*
- From the Department of Biochemistry and Molecular Biology, Faculty of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113, Japan
Abstract
Leukotriene D4(LTD4) is a major lipid mediator involved in inflammatory and allergic disorders including bronchial asthma. Despite its potent biological activity, little is known about the receptor and intracellular signaling pathways. Here we analyzed the signal transduction mechanisms through LTD4 receptors using human monocytic leukemia THP-1 cells. When these cells were stimulated with LTD4, intracellular calcium concentration was increased and mitogen-activated protein kinase (MAP kinase) was activated severalfold. This activation was inhibited by staurosporine or GF109203X treatment or abolished by protein kinase C depletion. Cytosolic protein kinase Cα was translocated to the membrane, and Raf-1 was activated by LTD4 treatment in a similar time course. LTD4-induced Raf-1 activation was diminished by protein kinase C depletion in the cells. A chemotactic response of THP-1 cells toward LTD4 was observed which was inhibited by pertussis toxin (PTX) pretreatment. Thus, LTD4 has at least two distinct signaling pathways in THP-1 cells, a PTX-insensitive mitogen-activated protein kinase activation through protein kinase Cα and Raf-1 and a PTX-sensitive chemotactic response. This cellular signaling can explain in part the versatile activities of LTD4 in macrophages under inflammatory and allergic conditions.
Footnotes
-
↵* This work was supported in part by grants-in-aid from the Ministry of Education, Science, Sports, and Culture of Japan and by grants from the Yamanouchi Foundation for Metabolic Disorders, Human Science Foundation, and Senri Life Science Foundation.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵‡ To whom correspondence should be addressed. Tel.: 81-3-5802-2925; Fax: 81-3-3813-8732; E-mail; tshimizu{at}m.u-tokyo.ac.jp.
-
↵1 The abbreviations used are: LTD4, leukotriene D4, (5S,6R,7E,9E,11Z,14Z)-5-hydroxy-6-(S-cysteinylglycinyl)-icosatetraen-1-oic acid; BAPTA/AM, 1,2-bis(O-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid acetoxymethyl ester; BSA, bovine serum albumin; DTT, dithiothreitol; G protein, GTP-binding protein; LT, leukotriene; MAP kinase, mitogen-activated protein kinase; PAGE, polyacrylamide gel electrophoresis; PKC, protein kinase C; PMSF, phenylmethylsulfonyl fluoride; PTX, pertussis toxin; TPA, 12-O-tetradecanoylphorbol-13-acetate.
-
- Received September 23, 1997.
- Revision received December 12, 1997.
- The American Society for Biochemistry and Molecular Biology, Inc.
