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Role of the p66Shc isoform in insulin-like growth factor I receptor signaling through MEK/Erk and regulation of actin cytoskeleton in rat myoblasts.

Authors: Natalicchio, A  Laviola, L  De Tullio, C  Renna, LA  Montrone, C  Perrini, S  Valenti, G  Procino, G  Svelto, M  Giorgino, F 
Citation: Natalicchio A, etal., J Biol Chem. 2004 Oct 15;279(42):43900-9. Epub 2004 Jul 19.
Pubmed: (View Article at PubMed) PMID:15262993
DOI: Full-text: DOI:10.1074/jbc.M403936200

To investigate the role of Shc in IGF action and signaling in skeletal muscle cells, Shc protein levels were reduced in rat L6 myoblasts by stably overexpressing a Shc cDNA fragment in antisense orientation (L6/Shcas). L6/Shcas myoblasts showed marked reduction of the p66Shc protein isoform and no change in p52Shc or p46Shc proteins compared with control myoblasts transfected with the empty vector (L6/Neo). When compared with control, L6/Shcas myoblasts demonstrated 3-fold increase in Erk-1/2 phosphorylation under basal conditions and blunted Erk-1/2 stimulation by insulin-like growth factor I (IGF-I), in the absence of changes in total Erk-1/2 protein levels. Increased basal Erk-1/2 activation was paralleled by a greater proportion of phosphorylated Erk-1/2 in the nucleus of L6/Shcas myoblasts in the absence of IGF-I stimulation. The reduction of p66Shc in L6/Shcas myoblasts resulted in marked phenotypic abnormalities, such as rounded cell shape and clustering in islets or finger-like structures, and was associated with impaired DNA synthesis in response to IGF-I and lack of terminal differentiation into myotubes. In addition, L6/Shcas myoblasts were characterized by complete disruption of actin filaments and cell cytoskeleton. Treatment of L6/Shcas myoblasts with the MEK inhibitor PD98059 reduced the abnormal increase in Erk-1/2 activation to control levels and restored the actin cytoskeleton, re-establishing the normal cell morphology. Thus, the p66Shc isoform exerts an inhibitory effect on the mitogen-activated protein kinase signaling pathway in rodent myoblasts, which is necessary for maintenance of IGF responsiveness of the MEK/Erk pathway and normal cell phenotype.


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CRRD Object Information
CRRD ID: 1580336
Created: 2006-07-24
Species: All species
Last Modified: 2006-07-24
Status: ACTIVE


RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.