Activation of adenylyl cyclases, regulation of insulin status, and cell survival by G(alpha)olf in pancreatic beta-cells

Am J Physiol Regul Integr Comp Physiol. 2002 Mar;282(3):R870-80. doi: 10.1152/ajpregu.00374.2001.

Abstract

Because we recently identified the G(alpha)olf subunit in rat pancreatic beta-cells, we investigated the downstream effectors and the biological functions of this G protein in HEK-293T cells and the insulin-secreting mouse betaTC-3 cell line. With the use of transient transfection of HEK-293T cells with constitutively activated G(alpha)olf (G(alpha)olfQ214L, i.e., AG(alpha)olf), together with expression vectors encoding the adenylyl cyclase (AC) isoforms (AC-I to -VIII and soluble AC), compared with cotransfections using AG(alphas) (G(alphas)R201C), we observed that AG(alpha)olf preferentially activates AC-I and -VIII, which are also expressed in beta-cells. Stable overexpression of wild-type or AG(alpha)olf in betaTC-3 cells resulted in partial attenuation of insulin secretion and biosynthesis, suggesting that chronic activation of the G(alpha)olf-signaling pathway is associated with beta-cell desensitization. In agreement, transfected betaTC-3 cells present a decreased insulin content with respect to parental cells, whereas the proinsulin convertases PC-1 and PC-2 were unaffected. Furthermore, betaTC-3-AG(alpha)olf cells are resistant to serum starvation-induced apoptosis. Our findings suggest that G(alpha)olf is involved in insulin status, cell survival, and regeneration of the insulin-secreting beta-cells during development and diabetes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenylyl Cyclases / metabolism*
  • Aspartic Acid Endopeptidases / metabolism
  • Cell Survival / drug effects
  • Cells, Cultured
  • Cyclic AMP / biosynthesis
  • Enzyme Activation
  • Epithelial Cells / metabolism
  • GTP-Binding Protein alpha Subunits
  • GTP-Binding Protein alpha Subunits, Gs / pharmacology
  • Heterotrimeric GTP-Binding Proteins / genetics
  • Heterotrimeric GTP-Binding Proteins / metabolism
  • Heterotrimeric GTP-Binding Proteins / pharmacology*
  • Humans
  • Insulin / metabolism*
  • Insulin Secretion
  • Insulinoma / metabolism
  • Islets of Langerhans / physiology*
  • Isoenzymes / metabolism
  • Kidney / metabolism
  • Male
  • Pancreas / metabolism
  • Proprotein Convertase 2
  • Proprotein Convertases
  • RNA / metabolism
  • Reference Values
  • Subtilisins / metabolism
  • Testis / metabolism
  • Tissue Distribution

Substances

  • GTP-Binding Protein alpha Subunits
  • Insulin
  • Isoenzymes
  • olfactory G protein subunit alpha olf
  • RNA
  • Cyclic AMP
  • Proprotein Convertases
  • Subtilisins
  • Proprotein Convertase 2
  • Aspartic Acid Endopeptidases
  • GTP-Binding Protein alpha Subunits, Gs
  • Heterotrimeric GTP-Binding Proteins
  • Adenylyl Cyclases