Submitted on July 25, 2005
Accepted on March 2, 2006
Bile acids stimulate PKC
autophosphorylation and activation; role in the attenuation of prostaglandin E1-induced cAMP production in human dermal fibroblasts
Man Le1, Lada Krilov1, Jianping Meng1, Kelli Chapin-Kennedy1, Susan Ceryak1, and Bernard Bouscarel1*
1 Medicine, George Washington University, Washington, District of Columbia, United States; Biochemistry and Molecular Biology, Washington University, Washington, District of Columbia, United States; Pharmacology and Physiology, Washington university, Washington, District of Columbia, United States
* To whom correspondence should be addressed. E-mail: bbouscarel{at}mfa.gwu.edu.
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-PKC
and YFP-PKC
translocation in 30-60 min followed by a transient 24-48h down-regulation of the total PKC, PKC and PKC
protein expression by 30-50%, without affecting that of PKC
. Phospho- PKC translocated to the plasma membrane, while phospho-PKC Thr505 and Tyr311translocated to the perinuclear domain and nucleus in particular. The attenuation of cAMP production by CDCA was PKC specific, demonstrated using both inhibitors and PKC isoform DN mutants. Under these same conditions, neither PI3 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 PKC autophosphorylation in vitro. This bile acid effect required phosphatidylserine and was completely abolished by the presence of Go6976. CDCA at concentrations less than 50 µM enhanced the PKC activation induced by PMA while greater CDCA concentrations reduced the PMA-induced PKC activation. CDCA alone did not affect PKC activity in vitro. In conclusion, while CDCA and UDCA activate different PKC isoforms, PKC 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.
