KSR (Phospho-Ser392) ELISA Kit

Nemoto S, Taguchi K, Matsumoto T, Kamata K, Kobayashi T. Pravastatin normalizes ET-1-induced contraction in the aorta of type 2 diabetic OLETF rats by suppressing the KSR1/ERK complex. Am J Physiol Heart Circ Physiol 303: H893-H902, 2012. First published August 10, 2012; doi:10.1152/ajpheart.01128.2011.-Endothelin (ET)-1 is a likely candidate for a key role in diabetic vascular complications. In the present study, we hypothesized that treatment with pravastatin (an inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase) would normalize the ET-1-induced contraction in aortas isolated from type 2 diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats. Contractile responses were examined by measuring isometric force in endothelium-denuded aortic helical strips from four groups: Long-Evans Tokushima Otsuka (LETO; genetic control), OLETF (type 2 diabetic), pravastatin-treated LETO, and pravastatin-treated OLETF rats. Both immunoblot analysis and immunoprecipitation assays were used to examine Src, protein phosphatase (PP) 2A, kinase suppressor of Ras (KSR)1, and ERK signaling pathway protein levels and activities. In endothelium-denuded aortas isolated from OLETF rats at the chronic stage of diabetes (56-60 wk) (vs. those from age-matched LETO rats), we found the following: 1) ET-1-induced contraction was enhanced, 2) ERK1/2 phosphorylation was increased, 3) phosphorylations of KSR1 and PP2A were reduced (i.e., enhancement of the kinase active state), 4) ERK1/2-KSR1 complexes were increased, and 5) Src tyrosine kinase activity was diminished. Endothelium-denuded aortas isolated from OLETF rats treated with pravastatin (10 mg/kg po, daily for 4 wk) exhibited normalized ET-1-induced contractions and suppressed ET-1-stimulated ERK phosphorylation, with the associated phosphorylated KSR1 and phosphorylated PP2A levels being increased toward normal levels. These results suggest that in type 2 diabetic rats, pravastatin normalizes ET-1-induced contraction in aortic smooth muscle via a suppression of PP2A/KSR1/ERK activities after an enhancement of Src kinase activity.

Given the frequency with which MAP kinase signaling is dysregulated in cancer, much effort has been focused on inhibiting RAS signaling for therapeutic benefit. KSR1, a pseudokinase that interacts with RAF, is a potential target; it was originally cloned in screens for suppressors of constitutively active RAS, and its deletion prevents RAS-mediated transformation of mouse embryonic fibroblasts. In this work, we used a genetically engineered mouse model of pancreatic cancer to assess whether KSR1 deletion would influence tumor development in the setting of oncogenic RAS. We found that Ksr1(-/-) mice on this background had a modest but significant improvement in all-cause morbidity compared to Ksr1(+/+) and Ksr1(+/-) cohorts. Ksr1(-/-) mice, however, still developed tumors, and precursor pancreatic intraepithelial neoplastic (PanIN) lesions were detected within a similar timeframe compared to Ksr1(+/+) mice. No significant differences in pERK expression or in proliferation were noted. RNA sequencing also did not reveal any unique genetic signature in Ksr1(-/-) tumors. Further studies will be needed to determine whether and in what settings KSR inhibition may be clinically useful.