Protein kinase C and preconditioning: role of the sarcoplasmic reticulum.

Abstract

Activation of protein kinase C (PKC) is cardioprotective, but the mechanism(s) by which PKC mediates protection is not fully understood. Inasmuch as PKC has been well documented to modulate sarcoplasmic reticulum (SR) Ca2+ and because altered SR Ca2+ handling during ischemia is involved in cardioprotection, we examined the role of PKC-mediated alterations of SR Ca2+ in cardioprotection. Using isolated adult rat ventricular myocytes, we found that addition of 1,2-dioctanoyl-sn-glycerol (DOG), to activate PKC under conditions that reduced myocyte death associated with simulated ischemia and reperfusion, also reduced SR Ca2+. Cell death was 57.9 +/- 2.9% and 47.3 +/- 1.8% in untreated and DOG-treated myocytes, respectively (P < 0.05). Using fura 2 fluorescence to monitor Ca2+ transients and caffeine-releasable SR Ca2+, we examined the effect of DOG on SR Ca2+. Caffeine-releasable SR Ca2+ was significantly reduced (by approximately 65%) after 10 min of DOG treatment compared with untreated myocytes (P < 0.05). From our examination of the mechanism by which PKC alters SR Ca2+, we present the novel finding that DOG treatment reduced the phosphorylation of phospholamban (PLB) at Ser16. This effect is mediated by PKC-epsilon, because a PKC-epsilon-selective inhibitory peptide blocked the DOG-mediated decrease in phosphorylation of PLB and abolished the DOG-induced reduction in caffeine-releasable SR Ca2+. Using immunoprecipitation, we further demonstrated that DOG increased the association between protein phosphatase 1 and PLB. These data suggest that activated PKC-epsilon reduces SR Ca2+ content through PLB dephosphorylation and that reduced SR Ca2+ may be important in cardioprotection.

• Authors: Ken Yamamura, Charles Steenbergen, Elizabeth Murphy
• Journal: American journal of physiology. Heart and circulatory physiology (Am J Physiol Heart Circ Physiol) Vol. 289 Issue 6 Pg. H2484-90 (Dec 2005) ISSN: 0363-6135 [Print] United States
• PMID: 16055516 (Publication Type: Journal Article)

Chemical References

• Protein Kinase C
• Phosphoprotein Phosphatases
• Protein Phosphatase 1
• Calcium

Topics

• Animals
• Calcium (metabolism)
• Cell Hypoxia (physiology)
• Ischemia (metabolism)
• Ischemic Preconditioning, Myocardial (methods)
• Male
• Myocytes, Cardiac (metabolism)
• Phosphoprotein Phosphatases (metabolism)
• Protein Kinase C (metabolism)
• Protein Phosphatase 1
• Rats
• Rats, Sprague-Dawley
• Sarcoplasmic Reticulum (metabolism)