Protein Kinase Inhibitor β Enhances the Constitutive Activity of G-protein-coupled Zinc Receptor GPR39

Biochem J. 2014 Aug 15;462(1):125-32. doi: 10.1042/BJ20131198.

Abstract

GPR39 is a G-protein-coupled zinc receptor that protects against diverse effectors of cell death. Its protective activity is mediated via constitutive activation of Gα13 and the RhoA pathway, leading to increased SRE (serum-response element)-dependent transcription; the zinc-dependent immediate activation of GPR39 involves Gq-mediated increases in cytosolic Ca2+ and Gs coupling leading to increased cAMP levels. We used the cytosolic and soluble C-terminus of GPR39 in a Y2H (yeast-2-hybrid) screen for interacting proteins, thus identifying PKIB (protein kinase A inhibitor β). Co-expression of GPR39 with PKIB increased the protective activity of GPR39 via the constitutive, but not the ligand-mediated, pathway. PKIB inhibits protein kinase A by direct interaction with its pseudosubstrate domain; mutation of this domain abolished the inhibitory activity of PKIB on protein kinase A activity, but had no effect on the interaction with GPR39, cell protection and induction of SRE-dependent transcription. Zinc caused dissociation of PKIB from GPR39, thereby liberating it to associate with protein kinase A and inhibit its activity, which would result in a negative-feedback loop with the ability to limit activation of the Gs pathway by zinc.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CHO Cells
  • Cell Line
  • Cell Membrane / metabolism
  • Cricetulus
  • Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
  • HeLa Cells
  • Humans
  • Intracellular Signaling Peptides and Proteins / biosynthesis
  • Intracellular Signaling Peptides and Proteins / physiology*
  • Mice
  • Protein Kinase Inhibitors / pharmacology*
  • Receptors, G-Protein-Coupled / metabolism*
  • Two-Hybrid System Techniques
  • Zinc / metabolism
  • Zinc / pharmacology

Substances

  • GPR39 protein, human
  • Intracellular Signaling Peptides and Proteins
  • PKIB protein, human
  • Protein Kinase Inhibitors
  • Receptors, G-Protein-Coupled
  • Cyclic AMP-Dependent Protein Kinases
  • Zinc