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Biochem Biophys Res Commun. 2016 Jan 8;469(2):326-31. doi: 10.1016/j.bbrc.2015.11.068. Epub 2015 Nov 23.

Insulin dependent apolipoprotein B degradation and phosphatidylinositide 3-kinase activation with microsomal translocation are restored in McArdle RH7777 cells following serum deprivation.

Author information

1
Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry, Box 626, 601 Elmwood Avenue, Rochester, NY 14642, USA. Electronic address: Janet_Sparks@urmc.rochester.edu.
2
Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry, Box 626, 601 Elmwood Avenue, Rochester, NY 14642, USA.

Abstract

Previous studies in rat hepatocytes demonstrated that insulin-dependent apolipoprotein (apo) B degradation (IDAD) is lost when cells are maintained for 3 d under enriched culture conditions. Loss of IDAD correlates with increased expression of protein tyrosine phosphatase 1B (PTP1B) known to be associated with resistance to insulin signaling in the liver. McArdle RH7777 hepatoma (McA) cells cultured in serum containing medium are resistant to IDAD; demonstrate a 30% increase in apo B secretion, and express increased levels of PTP1B protein and mRNA. In addition, insulin-stimulated Class I phosphatidylinositide 3-kinase (PI3K) activity of anti-pY immunoprecipitates is severely blunted. IDAD resistance in McA cells correlates with diminished translocation of insulin-stimulated pY-IRS1 to intracellular membranes. Incubation of McA cells with RK682, a protein tyrosine phosphatase inhibitor, is sufficient to restore IDAD in resistant McA cells. Overall, results further support the importance of Class I PI3K activity in IDAD, and suggest that loss of this activity is sufficient to cause resistance. Although other factors are involved in downstream events including sortilin binding to apo B, autophagy, and lysosomal degradation, loss of signal generation and reduced localization of Class I PI3K to intracellular membranes plays a significant role in IDAD resistance.

KEYWORDS:

Apo B; IRS1; IRS2; Liver; PI3K; PTP1B; VLDL

PMID:
26616056
PMCID:
PMC4698036
DOI:
10.1016/j.bbrc.2015.11.068
[Indexed for MEDLINE]
Free PMC Article

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