Evidence for a Role for the p110-alpha Isoform of PI3K in Skeletal Function

Biochem Biophys Res Commun. 2010 Jan 1;391(1):564-9. doi: 10.1016/j.bbrc.2009.11.099. Epub 2009 Nov 24.

Abstract

Signaling through phosphatidylinositol-3 kinases (PI3K) regulates fundamental cellular processes such as survival and growth, and these lipid kinases are currently being investigated as therapeutic targets in several contexts. In skeletal tissue, experiments using pan-specific PI3K inhibitors have suggested that PI3K signaling influences both osteoclast and osteoblast function, but the contributions of specific PI3K isoforms to these effects have not been examined. In the current work, we assessed the effects of pharmacological inhibitors of the class Ia PI3Ks, alpha, beta, and delta, on bone cell growth, differentiation and function in vitro. Each of the class Ia PI3K isoforms is expressed and functionally active in bone cells. No consistent effects of inhibitors of p110-beta or p110-delta on bone cells were observed. Inhibitors of p110-alpha decreased osteoclastogenesis by 60-80% (p<0.001 vs control) by direct actions on osteoclast precursors, and decreased the resorptive activity of mature osteoclasts by 60% (p<0.01 vs control). The p110-alpha inhibitors also decreased the growth of osteoblastic and stromal cells (p<0.001 vs control), and decreased differentiated osteoblast function by 30% (p<0.05 vs control). These data suggest that signaling through the p110-alpha isoform of class Ia PI3Ks positively regulates the development and function of both osteoblasts and osteoclasts. Therapeutic agents that target this enzyme have the potential to significantly affect bone homeostasis, and evaluation of skeletal endpoints in clinical trials of such agents is warranted.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bone and Bones / cytology
  • Bone and Bones / enzymology*
  • Cell Differentiation / drug effects
  • Cell Line
  • Mice
  • Osteoblasts / cytology
  • Osteoblasts / enzymology*
  • Osteoclasts / cytology
  • Osteoclasts / enzymology*
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / physiology*
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Isoforms / antagonists & inhibitors
  • Protein Isoforms / physiology
  • Protein Kinase Inhibitors / pharmacology
  • Rats

Substances

  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Isoforms
  • Protein Kinase Inhibitors