Adenovirus-mediated overexpression of diacylglycerol kinase-ζ inhibits endothelin-1-induced cardiomyocyte hypertrophy

Background - Diacylglycerol (DAG) is a lipid second messenger that transiently accumulates in cells stimulated by endothelin-1 (ET-1) and other G alpha q protein-coupled receptor agonists. Diacylglycerol kinase (DGK) is thought to be an enzyme that controls the cellular levels of DAG by converting it to phosphatidic acid; however, the functional role of DGK has not been examined in cardiomyocytes. Because DGK inactivates DAG, a strong activator of protein kinase C (PKC), we hypothesized that DGK inhibited ET-1 - induced activation of a DAG- PKC signaling cascade and subsequent cardiomyocyte hypertrophy. Methods and Results - Real-time reverse transcription - polymerase chain reaction demonstrated a significant increase of DGK-zeta mRNA by ET-1 in cardiomyocytes. To determine the functional role of DGK-zeta, we overexpressed DGK-zeta in cardiomyocytes using a recombinant adenovirus encoding rat DGK-zeta( Ad-DGK zeta). ET-1 - induced translocation of PKC-epsilon was blocked by Ad-DGK zeta ( P < 0.01). Ad-DGK zeta also inhibited ET-1 - induced activation of extracellular signal - regulated kinase (P<0.01). Luciferase reporter assay revealed that ET-1 - mediated increase of activator protein-1 (AP1) DNA-binding activity was significantly inhibited by DGK-zeta ( P < 0.01). In cardiomyocytes transfected with DGK-zeta, ET-1 failed to cause gene induction of atrial natriuretic factor, increases in [H-3]- leucine uptake, and increases in cardiomyocyte surface area. Conclusions - We demonstrated for the first time that DGK-zeta blocked ET-1 - induced activation of the PKC-epsilon - ERK-AP1 signaling pathway, atrial natriuretic factor gene induction, and resultant cardiomyocyte hypertrophy. DGK-zeta might act as a negative regulator of hypertrophic program in response to ET-1, possibly by controlling cellular DAG levels.