Phosphoinositide 3-kinase catalytic subunit deletion and regulatory subunit deletion have opposite effects on insulin sensitivity in mice Academic Article uri icon

Overview

MeSH Major

  • Glucose Intolerance
  • Hyperinsulinism
  • Insulin Resistance
  • Phosphatidylinositol 3-Kinases

abstract

  • Studies ex vivo have shown that phosphoinositide 3-kinase (PI3K) activity is necessary but not sufficient for insulin-stimulated glucose uptake. Unexpectedly, mice lacking either of the PI3K regulatory subunits p85alpha or p85beta exhibit increased insulin sensitivity. The insulin hypersensitivity is particularly unexpected in p85alpha-/- p55alpha-/- p50alpha-/- mice, where a decrease in p110alpha and p110beta catalytic subunits was observed in insulin-sensitive tissues. These results raised the possibility that decreasing total PI3K available for stimulation by insulin might circumvent negative feedback loops that ultimately shut off insulin-dependent glucose uptake in vivo. Here we present results arguing against this explanation. We show that p110alpha+/- p110beta+/- mice exhibit mild glucose intolerance and hyperinsulinemia in the fasted state. Unexpectedly, p110alpha+/- p110beta+/- mice showed a approximately 50% decrease in p85 expression in liver and muscle. Consistent with this in vivo observation, knockdown of p110 by RNA interference in mammalian cells resulted in loss of p85 proteins due to decreased protein stability. We propose that insulin sensitivity is regulated by a delicate balance between p85 and p110 subunits and that p85 subunits mediate a negative role in insulin signaling independent of their role as mediators of PI3K activation.

publication date

  • March 2005

Research

keywords

  • Academic Article

Identity

Language

  • eng

PubMed Central ID

  • PMC549361

Digital Object Identifier (DOI)

  • 10.1128/MCB.25.5.1596-1607.2005

PubMed ID

  • 15713620

Additional Document Info

start page

  • 1596

end page

  • 607

volume

  • 25

number

  • 5