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  • Identification of a novel human kinase supporter of Ras (hKSR-2) that functions as a negative regulator of Cot (Tpl2) signaling.

Identification of a novel human kinase supporter of Ras (hKSR-2) that functions as a negative regulator of Cot (Tpl2) signaling.

The Journal of biological chemistry (2003-09-17)
Padma L Channavajhala, Leeying Wu, John W Cuozzo, J Perry Hall, Wei Liu, Lih-Ling Lin, Yuhua Zhang
ABSTRACT

Kinase suppressor of Ras (KSR) is an integral and conserved component of the Ras signaling pathway. Although KSR is a positive regulator of the Ras/mitogen-activated protein (MAP) kinase pathway, the role of KSR in Cot-mediated MAPK activation has not been identified. The serine/threonine kinase Cot (also known as Tpl2) is a member of the MAP kinase kinase kinase (MAP3K) family that is known to regulate oncogenic and inflammatory pathways; however, the mechanism(s) of its regulation are not precisely known. In this report, we identify an 830-amino acid novel human KSR, designated hKSR-2, using predictions from genomic data base mining based on the structural profile of the KSR kinase domain. We show that, similar to the known human KSR, hKSR-2 co-immunoprecipitates with many signaling components of the Ras/MAPK pathway, including Ras, Raf, MEK-1, and ERK-1/2. In addition, we demonstrate that hKSR-2 co-immunoprecipitates with Cot and that co-expression of hKSR-2 with Cot significantly reduces Cot-mediated MAPK and NF-kappaB activation. This inhibition is specific to Cot, because Ras-induced ERK and IkappaB kinase-induced NF-kappaB activation are not significantly affected by hKSR-2 co-expression. Moreover, Cot-induced interleukin-8 production in HeLa cells is almost completely inhibited by the concurrent expression of hKSR-2, whereas transforming growth factor beta-activated kinase 1 (TAK1)/TAK1-binding protein 1 (TAB1)-induced interleukin-8 production is not affected by hKSR-2 co-expression. Taken together, these results indicate that hKSR-2, a new member of the KSR family, negatively regulates Cot-mediated MAP kinase and NF-kappaB pathway signaling.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
COT (30-397), active, GST tagged human, PRECISIO® Kinase, recombinant, expressed in baculovirus infected Sf9 cells, ≥70% (SDS-PAGE), buffered aqueous glycerol solution
Sigma-Aldrich
Anti-c-Myc antibody, Mouse monoclonal, clone 9E10, purified from hybridoma cell culture