Relaxin stimulates protein kinase C zeta translocation: requirement for cyclic adenosine 3',5'-monophosphate production

Mol Endocrinol. 2005 Apr;19(4):1012-23. doi: 10.1210/me.2004-0279. Epub 2004 Dec 16.


Relaxin is a polypeptide hormone that activates the leucine-rich repeat containing G protein-coupled receptors, LGR7 and LGR8. In an earlier study, we reported that relaxin produces a biphasic time course and the second wave of cAMP is highly sensitive to phosphoinositide-3 kinase inhibitors (LY294002 and wortmannin). LY294002 inhibits relaxin-mediated increases in cAMP production by 40-50% across a large range of relaxin concentrations. Here we show that protein kinase C zeta (PKCzeta) is a component of relaxin signaling in THP-1 cells. Sphingomyelinase increases cAMP production due to the release of ceramide, a direct activator of PKCzeta. Chelerythrine chloride (a general PKC inhibitor) inhibits relaxin induced cAMP production to the same degree (approximately 40%) as LY294002. Relaxin stimulates PKCzeta translocation to the plasma membrane in THP-1, MCF-7, pregnant human myometrial 1-31, and mouse mesangial cells, as shown by immunocytochemistry. PKCzeta translocation is phosphoinositide-3 kinase dependent and independent of cAMP production. Antisense PKCzeta oligodeoxynucleotides (PKCzeta-ODNs) deplete both PKCzeta transcript and protein levels in THP-1 cells. PKCzeta-ODNs abolish relaxin-mediated PKCzeta translocation and inhibit relaxin stimulation of cAMP by 40%, as compared with mock and random ODN controls. Treatment with LY294002 in the presence of PKCzeta-ODNs results in little further inhibition. In summary, we present a novel role for PKCzeta in relaxin-mediated stimulation of cAMP.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Membrane / metabolism
  • Cells, Cultured
  • Chromones / pharmacology
  • Cyclic AMP / metabolism*
  • Humans
  • Mice
  • Monocytes / chemistry
  • Monocytes / drug effects
  • Monocytes / metabolism
  • Morpholines / pharmacology
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / metabolism*
  • Protein Kinase Inhibitors / pharmacology
  • Protein Transport / drug effects
  • Protein Transport / physiology
  • Relaxin / pharmacology
  • Relaxin / physiology*


  • Chromones
  • Morpholines
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase Inhibitors
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • Relaxin
  • Cyclic AMP
  • protein kinase C zeta
  • Protein Kinase C