Bile acids stimulate PKCα autophosphorylation and activation: role in the attenuation of prostaglandin E1-induced cAMP production in human dermal fibroblasts

Man Le, Lada Krilov, Jianping Meng, Kelli Chapin-Kennedy, Susan Ceryak, Bernard Bouscarel

Abstract

The aim was to identify the specific PKC isoform(s) and their mechanism of activation responsible for the modulation of cAMP production by bile acids in human dermal fibroblasts. Stimulation of fibroblasts with 25–100 μM of chenodeoxycholic acid (CDCA) and ursodeoxycholic acid (UDCA) led to YFP-PKCα and YFP-PKCδ translocation in 30–60 min followed by a transient 24- to 48-h downregulation of the total PKCα, PKCδ, and PKCε protein expression by 30–50%, without affecting that of PKCζ. Increased plasma membrane translocation of PKCα was associated with an increased PKCα phosphorylation, whereas increased PKCδ translocation to the perinuclear domain was associated with an increased accumulation of phospho-PKCδ Thr505 and Tyr311 in the nucleus. The PKCα specificity on the attenuation of cAMP production by CDCA was demonstrated with PKC downregulation or inhibition, as well as PKC isoform dominant-negative mutants. Under these same conditions, neither phosphatidylinositol 3-kinase, p38 MAP kinase, p42/44 MAP kinase, nor PKA inhibitors had any significant effect on the CDCA-induced cAMP production attenuation. CDCA concentrations as low as 10 μM stimulated PKCα autophosphorylation in vitro. This bile acid effect required phosphatidylserine and was completely abolished by the presence of Gö6976. CDCA at concentrations less than 50 μM enhanced the PKCα activation induced by PMA, whereas greater CDCA concentrations reduced the PMA-induced PKCα activation. CDCA alone did not affect PKCα activity in vitro. In conclusion, although CDCA and UDCA activate different PKC isoforms, PKCα plays a major role in the bile acid-induced inhibition of cAMP synthesis in fibroblasts. This study emphasizes potential consequences of increased systemic bile acid concentrations and cellular bile acid accumulation in extrahepatic tissues during cholestatic liver diseases.

  • ursodeoxycholic acid
  • chenodeoxycholic acid
  • taurocholic acid
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