G. Velasco et al., EVIDENCE THAT THE AMP-ACTIVATED PROTEIN-KINASE STIMULATES RAT-LIVER CARNITINE PALMITOYLTRANSFERASE-I BY PHOSPHORYLATING CYTOSKELETAL COMPONENTS, FEBS letters, 439(3), 1998, pp. 317-320
The activity of hepatic carnitine palmitoyltransferase I (CPT-I) may b
e modulated by interactions with cytoskeletal components [Velasco et a
l, (1998) J, Biol. Chem, 273, 21497-21504]. We have studied whether th
e AMP-activated protein kinase (AMPK) is involved in this process. AMP
K stimulated CPT-I in permeabilized hepatocytes but not in isolated li
ver mitochondria. In addition, AMPK: abrogated the inhibition of CPT-I
of isolated mitochondria induced by a cytoskeletal fraction. These tw
o effects of AMPK were not evident when the kinase was inactivated by
pretreatment with protein phosphatase 2C, Cytokeratins 8 and 18 were p
hosphorylated by AMPK in vitro and by incubation of intact hepatocytes
with 5-aminoimidazole-4-carboxamide ribonucleoside, a cell-permeable
activator of AMPK. These results provide the first evidence that AMPK
stimulates CPT-I by direct phosphorylation of cytoskeletal components.
(C) 1998 Federation of European Biochemical Societies.