Genetic Evidence for a Tyrosine Kinase Cascade Preceding the Mitogen-activated Protein Kinase Cascade in Vertebrate G Protein Signaling*
- From the ‡Department of Physiology, Cornell University Medical College, New York, New York 10021, the §Cell Biology Program and Howard Hughes Medical Institute, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, the¶Department of Molecular Genetics, Kansai Medical University, 1 Fumizono-cho, Moriguchi 570, Japan, and the ‖McGill Cancer Center, McGill University, Montreal, Quebec, Canada H3G 1Y6
Abstract
The signal transduction pathway from heterotrimeric G proteins to the mitogen-activated protein kinase (MAPK) cascade is best understood in the yeast mating pheromone response, in which a serine/threonine protein kinase (STE20) serves as the critical linking component. Little is known in metazoans on how G proteins and the MAPK cascade are coupled. Here we provide genetic and biochemical evidence that a tyrosine kinase cascade bridges G proteins and the MAPK pathway in vertebrate cells. Targeted deletion of tyrosine kinase Csk in avian B lymphoma cells blocks the stimulation of MAPK by Gq-, but not Gi-, coupled receptors. In cells deficient in Bruton’s tyrosine kinase (Btk), Gi-coupled receptors failed to activate MAPK, while Gq-coupled receptor-mediated stimulation is unaffected. Taken together with our previous data on tyrosine kinases Lyn and Syk, the Gq-coupled pathway requires tyrosine kinases Csk, Lyn, and Syk, while the Gi-coupled pathway requires tyrosine kinases Btk and Syk to feed into the MAPK cascade in these cells. The central role of Syk is further strengthened by data showing that Syk can bind to purified Lyn, Csk, or Btk.
Footnotes
-
↵* This work was supported by grants from the National Institutes of Health, the National Science Foundation, and the American Heart Association.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.
-
↵** Cornell Scholar and a Beatrice F. Parvin Investigator of the American Heart Association New York City affiliate. To whom correspondence should be addressed. Tel.: 212-746-6362; Fax: 212-746-8690; E-mail: xyhuang{at}med.cornell.edu.
-
↵1 The abbreviations used are: MAPK, mitogen-activated protein kinase; PAGE, polyacrylamide gel electrophoresis; MBP, myelin basic protein; mAChR, muscarinic acetylcholine receptor; PH, pleckstrin-homology; BCR, B-cell receptor.
-
↵2 K. Bence and X.-Y. Huang, submitted for publication.
-
↵3 Y. Wan and X.-Y. Huang, unpublished data.
-
- Received February 7, 1997.
- Revision received April 17, 1997.
