SEK1 deficiency reveals mitogen-activated protein kinase cascade crossregulation and leads to abnormal hepatogenesis

Soula Ganiatsas, Lia Kwee, Yuko Fujiwara, Andrew Perkins, Tohru Ikeda, Mark A. Labow, Leonard I. Zon

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SEK1 (MKK4/JNKK) is a mitogen-activated protein kinase activator that has been shown to participate in vitro in two stress-activated cascades terminating with the SAPK and p38 kinases. To define the role of SEK1 in vivo, we studied stress-induced signaling in SEK1(-/-) embryonic stem and fibroblast cells and evaluated the phenotype of SEK1(-/-) mouse embryos during development. Studies of SEK1(-/-) embryonic stem cells demonstrated defects in stimulated SAPK phosphorylation but not in the phosphorylation of p38 kinase. In contrast, SEK1(-/-) fibroblasts exhibited defects in both SAPK and p38 phosphorylation, demonstrating that crosstalk exists between the stress-activated cascades. Tumor necrosis factor a and interleukin 1 stimulation of both stress-activated cascades are severely affected in the SEK1(-/-) fibroblast cells. SEK1 deficiency leads to embryonic lethality after embryonic day 12.5 and is associated with abnormal liver development. This phenotype is similar to c-jun null mouse embryos and suggests that SEK1 is required for phosphorylation and activation of c-jun during the organo- genesis of the liver.

Original languageEnglish
Pages (from-to)6881-6886
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number12
Publication statusPublished - 9 Jun 1998
Externally publishedYes

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