Adenosine A1 receptors induce translocation of PKC ε to the caveolar membrane of cardiac myocytes

Caveolae are specialized microdomains of the plasma membrane. They play an important role in the cardioprotective effect of ischemic preconditioning. Both adenosine receptors and PKC ε , which have been shown to reside in the caveolae of cardiac myocytes, are associated with ischemic preconditioning. However, the potential link between adenosine receptors and PKC ε has not been elucidated. The present study was designed to test the hypothesis that adenosine A1 receptors induce the translocation of PKC ε to the plasma membrane within caveolae. Immunoblot analysis from the homogenate of freshly isolated cardiac myocytes revealed that the intensity of 100 kD band corresponding to PKC ε increased significantly in the membrane fractions in cells pretreated with adenosine (100 μM) when compared with non‐stimulated cells. The effect of adenosine on PKC ε translocation was blocked by a specific A1 antagonist 8‐cyclopentyl‐1,3‐dipropylxanthine (DPCPX, 1 μM). Western blot in caveolin‐enriched fractions prepared from isolated cardiac myocytes showed that immunoreactivity for PKC ε increased significantly from cells treated with adenosine but not with adenosine plus DPCPX. Furthermore, PKC ε was detected in the anti‐caveolin‐3 immunoprecipitates from caveolar fractions. In conclusion, we demonstrate that activation of adenosine A1 receptors promotes the translocation of PKC ε to the caveolin‐enriched plasma membrane of cardiac myocytes.