Serine/Threonine protein phosphatases regulate the activity of insulin signaling molecules involved in glucose homeostasis. Aberration in their functions have been reported in adipocytes, hepatocytes and skeletal muscle cells lead to abnormalities in signal transduction causing diabetes. Neuronal system is insulin responsive. Malfunctions have been reported to lead to development of metabolic disorders like diabetic neuropathy and Alzheimer disease. Our understanding of phosphatase mediated regulation in general is anyway very limited and role of PP2C in insulin signaling pathway in neuronal system is practically non-existent. Further exploration is required to understand the role of Ser/Thr phosphatases in neuronal system. Therefore, the aim of this work was to identify the role of PP2C in neuronal insulin signaling. To achieve this, PP2C in the differentiated Neuro-2a (N2A) cells was inhibited by treating with a potent and specific inhibitor of PP2C, Sanguinarine Chloride (SC), in presence (100nM) or absence of insulin and the effect was tested on the activity of AS160 and GSK3β. In insulin stimulated state inhibition of PP2C caused a significant 37% and 56% of decrease in the phosphorylation of AS160 at Ser588 and Thr642 residues, respectively. Similarly, a 37% decrease was observed in phosphorylation of GSK3β at Ser9. However, the expression of AS160 and GSK3β were found to be unaffected. Data shows for the first time that PP2C mediated dephosphorylation might be involved in regulating the activity of AS160 and GSK3β in neuronal system and hence suggest a possibility of its playing a major negative role in regulating neuronal insulin signal transduction pathway.
Y. Yadav: None. C.S. Dey: None.
Department of Science & Technology, Government of India, New Delhi; Department of Science & Technology, Government of India, New Delhi (SR/S2/JCB-24/2008(G))