Phosphorylation of carnitine palmitoyltransferase‐1 in heart mitochondria

Abstract

Aim: Carnitine palmitoyltransferase‐1 (CPT‐1) catalyzes the entry of long‐chain acyl CoA's to the cytoplasm, an important control step in fatty acid oxidation. Previous studies from our laboratory indicate that the maximum activity and malonyl CoA sensitivity of CPT‐1 are acutely regulated by metoprolol in the rat heart. The aim of the present study was to determine whether incubation of isolated mitochondria from left ventricular tissue with protein kinase A, Akt or calcium/ calmodulin‐dependent protein kinase alters the maximum activity or malonyl CoA sensitivity of CPT‐1. Methods: Isolated mitochondria from normal Wistar rats were incubated with purified preparations of PKA, CAMK II or Akt for 10 minutes. Phosphorylation of CPT‐1 isoforms was measured by co‐immunoprecipitation with phosphothreonine and phosphoserine antibodies, and the activity and malonyl CoA sensitivity of CPT‐1 was assayed. Results: PKA and CAMK‐II phosphorylated CPT‐1. PKA decreased CPT‐1 malonyl CoA sensitivity whereas CAMK‐II increased CPT‐1 malonyl CoA sensitivity. There was no effect on the maximum activity of CPT‐1. Conclusions: PKA and CAMK‐II regulate CPT‐1 sensitivity in isolated heart mitochondria in vitro. These kinases may be counter‐regulatory in the control of CPT‐1 malonyl CoA sensitivity.