Activation of the c-Jun N-terminal kinase pathway by a novel protein kinase related to human germinal center kinase

Activation of the c-Jun N-terminal kinase pathway by a novel protein kinase related to human germinal center kinase

^*Amgen Inc., Boulder, CO 80301; and ^‡Department of Microbiology and Immunology, Baylor College of Medicine, Houston, TX 77030

Edited by Philip W. Majerus, Washington University School of Medicine, St. Louis, MO, and approved June 26, 1997 (received for review April 14, 1997)

Abstract

The c-Jun N-terminal kinase (JNK), or stress-activated protein kinase plays a crucial role in cellular responses stimulated by environmental stress and proinflammatory cytokines. However, the mechanisms that lead to the activation of the JNK pathway have not been elucidated. We have isolated a cDNA encoding a novel protein kinase that has significant sequence similarities to human germinal center kinase (GCK) and human hematopoietic progenitor kinase 1. The novel GCK-like kinase (GLK) has a nucleotide sequence that encodes an ORF of 885 amino acids with 11 kinase subdomains. Endogenous GLK could be activated by UV radiation and proinflammatory cytokine tumor necrosis factor α. When transiently expressed in 293 cells, GLK specifically activated the JNK, but not the p42/44^MAPK/extracellular signal-regulated kinase or p38 kinase signaling pathways. Interestingly, deletion of amino acids 353–835 in the putative C-terminal regulatory region, or mutation of Lys-35 in the putative ATP-binding domain, markedly reduced the ability of GLK to activate JNK. This result indicates that both kinase activity and the C-terminal region of GLK are required for maximal activation of JNK. Furthermore, GLK-induced JNK activation could be inhibited by a dominant-negative mutant of mitogen-activated protein kinase kinase kinase 1 (MEKK1) or mitogen-activated protein kinase kinase 4/SAPK/ERK kinase 1 (SEK1), suggesting that GLK may function upstream of MEKK1 in the JNK signaling pathway.

Footnotes

↵ † K.D. and X.S.W. contributed equally to the work.
↵ § To whom reprint requests should be addressed at: Department of Microbiology and Immunology, Baylor College of Medicine, One Baylor Plaza M929, Houston, TX 77030.
↵ ¶ To whom reprint requests should be addressed at: Department of Biology, Amgen Inc., 3200 Walnut Street, AC-4B, Boulder, CO 80301. e-mail: bing.yao{at}amgen.com.
This paper was submitted directly (Track II) to the Proceedings Office.
Abbreviations: MAPK, mitogen-activated protein kinase; ERK, extracellular signal-regulated kinase; JNK, c-Jun N-terminal kinase; MKK or MEK, MAPK kinase; GCK, germinal center kinase; GLK, GCK-like kinase; HPK1, hematopoietic progenitor kinase 1; PAK, p21-activated protein kinase 1; HA, hemagglutinin; MBP, myelin basic protein; SAPK, stress-activated protein kinase; SEK1, SAPK/ERK kinase 1; GST, glutathione S-transferase; TNF-α, tumor necrosis factor α.
Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession no. AF00145).