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Mechanism of lipid induced insulin resistance: activated PKCe is a key regulator

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Title Mechanism of lipid induced insulin resistance: activated PKCe is a key regulator
 
Creator Dasgupta, Suman
Bhattacharya, Sushmita
Maitra, Sudipta
Pal, Durba
Majumdar, Subeer S.
Datta, Asis
Bhattacharya, Samir
 
Subject Fatty acid
HMGA1
Insulin resistance
IRβ
PKCε
 
Description Fatty acids (FAs) are known to impair insulin signaling in target cells. Accumulating evidences suggest that one of the major sites of FAs adverse effect is insulin receptor (IR). However, the underlying mechanism is yet unclear. An important clue was indicated in leptin receptor deficient (db/db) diabetic mice where increased circulatory FAs was coincided with phosphorylated PKCε and reduced IR expression. We report here that central to this mechanism is the phosphorylation of PKCε by FAs. Kinase dead mutant of PKCε did not augment FA induced IRβ downregulation indicating phosphorylation of PKCε is crucial for FA induced IRβ reduction. Investigation with insulin target cells showed that kinase independent phosphorylation of PKCε by FA occurred through palmitoylation. Mutation at cysteine 276 and 474 residues in PKCε suppressed this process indicating participation of these two residues in palmitoylation. Phosphorylation of PKCε endowed it the ability to migrate to the nuclear region of insulin target cells. It was intriguing to search about how translocation of phosphorylated PKCε occurred without having canonical nuclear localization signal (NLS). We found that F-actin recognized phospho-form of PKCε and chaperoned it to the nuclear region where it interact with HMGA1 and Sp1, the transcription regulator of IR and HMGA1 gene respectively and impaired HMGA1 function. This resulted in the attenuation of HMGA1 driven IR transcription that compromised insulin signaling and sensitivity.
This research work was financially sup-
ported by the grant from Department of Science and Technology
(Grant No. VI-D&P/137/06-07/TDT), Ministry of Science and Technology, Govt. of India and a grant from National Institute of Plant Genome
Research, New Delhi.
 
Date 2014-04-04T09:00:33Z
2014-04-04T09:00:33Z
2011
3 January 2011
 
Type Article
 
Identifier Biochem. Biophys. Acta, 1812(4): 495-506
http://hdl.handle.net/123456789/174
 
Language en
 
Publisher Elsevier