Niclosamide Blocks Glucagon Phosphorylation of Ser552 on β-catenin in Primary Rat Hepatocytes via PKA Signalling

Biochem J. 2016 May 1;473(9):1247-55. doi: 10.1042/BCJ20160121. Epub 2016 Mar 10.

Abstract

Recently, it has been found that glucagon is able to activate the β-catenin signalling pathway leading to increased cyclin D1 and c-Myc expression in liver. Therefore the main aim of the present study is to determine whether the effect of glucagon activating β-catenin signalling leading to increased target gene expression is mediated through cAMP activation of PKA (protein kinase A). Primary rat hepatocytes were incubated with insulin, glucagon or adrenaline (epinephrine) and a range of inhibitors of PI3K (phosphoinositide 3-kinase), Wnt, mitochondrial uncoupler (niclosamide) or PKA inhibitors to dissect out the pathway leading to increased Ser(552) phosphorylation on β-catenin following glucagon exposure. In primary rat hepatocytes, we found that short exposure to glucagon or adrenaline caused a rapid increase in Ser(552) phosphorylation on β-catenin that leads to increased cyclin D1 and c-Myc expression. A range of PI3K and Wnt inhibitors were unable to block the effect of glucagon phosphorylating β-catenin. Interestingly, both niclosamide and the PKA inhibitor H89 blocked the glucagon effect on β-catenin signalling, leading to a reduction in target gene expression. Likewise, niclosamide inhibited cAMP levels and the direct addition of db-cAMP (dibutyryl-cAMP sodium salt) also resulted in Ser(552) phosphorylation of β-catenin. We have identified a new pathway via glucagon signalling that leads to increased β-catenin activity that can be reversed with the antihelminthic drug niclosamide, which has recently shown promise as a potential treatment of T2D (Type 2 diabetes). This novel finding could be useful in liver cancer treatment, particularly in the context of T2D with increased β-catenin activity.

Keywords: H89; Type 2 diabetes; cancer; glucagon; niclosamide; protein kinase A (PKA); β-catenin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bucladesine / pharmacology
  • Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • Diabetes Mellitus, Type 2 / drug therapy
  • Diabetes Mellitus, Type 2 / metabolism
  • Glucagon / metabolism*
  • Hepatocytes / metabolism*
  • Male
  • Niclosamide / pharmacology*
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphorylation / drug effects
  • Proto-Oncogene Proteins c-myc / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Signal Transduction / drug effects*
  • beta Catenin / metabolism*

Substances

  • Proto-Oncogene Proteins c-myc
  • beta Catenin
  • Bucladesine
  • Niclosamide
  • Glucagon
  • Phosphatidylinositol 3-Kinases
  • Cyclic AMP-Dependent Protein Kinases