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Originally published online as doi:10.2353/ajpath.2009.080460 on March 5, 2009

Published online before print March 5, 2009
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(American Journal of Pathology. 2009;174:1459-1470.)
© 2009 American Society for Investigative Pathology
DOI: 10.2353/ajpath.2009.080460

PTEN Contributes to Profound PI3K/Akt Signaling Pathway Deregulation in Dystrophin-Deficient Dog Muscle

Marie Feron*, Laetitia Guevel*{dagger}, Karl Rouger{ddagger}, Laurence Dubreil{ddagger}, Marie-Claire Arnaud*, Mireille Ledevin{ddagger}, Lynn A. Megeney{dagger}, Yan Cherel{ddagger} and Vehary Sakanyan*§

From the Centre National de la Recherche Scientifique,* UMR6204, Laboratoire de Biotechnologie, Université de Nantes, Nantes, France; the Ottawa Health Research Institute,{dagger} Sprott Stem Cell Center, Ottawa, Canada; the L'institut National de la Recherche Agronomique,{ddagger} UMR703, Developpment et Pathologie du Tissu Musculaire Ecole Nationale Vétérinaire, Nantes, France; and ProtNeteomix,§ Nantes, France

Duchenne muscular dystrophy is the most common and severe form of muscular dystrophy, and although the genetic basis of this disease is well defined, the overall mechanisms that define its pathogenesis remain obscure. Alterations in individual signaling pathways have been described, but little information is available regarding their putative implications in Duchenne muscular dystrophy pathogenesis. Here, we studied the status of various major signaling pathways in the Golden Retriever muscular dystrophy dog that specifically reproduces the full spectrum of human pathology. Using antibody arrays, we found that Akt1, glycogen synthase kinase-3β (GSK3β), 70-kDa ribosomal protein S6 kinase (p70S6K), extracellular signal-regulated kinases 1/2, and p38{delta} and p38{gamma} kinases all exhibited decreased phosphorylation in muscle from a 4-month-old animal with Golden Retriever muscular dystrophy, revealing a deep alteration of the phosphatidylinositol 3-kinase (PI3K)/Akt and mitogen-activated protein kinase pathways. Immunohistochemistry analysis revealed the presence of muscle fibers exhibiting a cytosolic accumulation of Akt1, GSK3β, and phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase (PTEN), an enzyme counteracting PI3K-mediated Akt activation. Enzymatic assays established that these alterations in phosphorylation and expression levels were associated with decreased Akt and increased GSK3β and PTEN activities. PTEN/GSK3β-positive fibers were also observed in muscle sections from 3- and 36-month-old animals, indicating long-term PI3K/Akt pathway alteration. Collectively, our data suggest that increased PTEN expression and activity play a central role in PI3K/Akt/GSK3β and p70S6K pathway modulation, which could exacerbate the consequences of dystrophin deficiency.






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