The cAMP dependent kinase mediates glucose deprivation-induced apoptosis in hepatic cells

FERRETI, AC; LAROCCA, MC; OCHOA EJ; FAVRE, C

Varsovia, Polonia

Congreso; European Conference on Cancer and Ageing 2007; 2007

SENECA

Glycolysis and apoptosis are two highly conserved finely regulated multi-step processes for maintaining cellular homeostasis, which are linked by mechanisms not fully understood. Among mammal cells, hepatocytes have a crucial role in glucose metabolism. The cAMP dependent kinase (PKA) mediates the modulation of diverse hepatocytes functions. The specificity of PKA phosphorylation reactions is ensured by its compartmentalization by its anchoring proteins (AKAPs). Our aim was to analyze if glucose deprivation induces apoptosis in hepatic cells, and if PKA was involved in this pathway. Primary cultured hepatocytes or the hepatocarcinome derived cells HepG2 were incubated for 6 h in the presence (C) or abscence (Glc0) of glucose, with or without the PKA inhibitor H89. After the incubations the cell viability apoptosis was assesed. Cell viability as assesed by Tripan Blue exclusion and LDH release to the medium did not differ amont groups in any case. Glucose deprivation induced caspase 3 activation in primary cultured hepatocytes (C vs Glc0 (8,6 ± 1,8 vs 12,0 ± 2,2) pmol product/mg protein/min, p<0,05), but not in HepG2 cells. This effect was prevented by the incubation of the cells with H89 (C+H89 vs Glc0+H89 (7,6 ± 4,7 vs 7,0 ± 2,7) pmol product/mg protein/min). Apoptotic phenotype in glucose deprived hepatocytes was confirmed by the analysis of nuclear DAPI staining. Our results indicate that glucose deprivation induces apoptosis in primary cultured hepatocytes but not in HepG2 cells. It would be interesting to analyze how the transformed HepG2 cells have lost the apoptotic response to glucose deprivation. We also found that PKA mediates this pathway. There is a protein complex assembled by the AKAP WAVE-1 in mithocondrias of hepatocytes pulling together the glycolitic enzyme Hexokinase-4, PKA, the protein phosphatase PP1, and the proapoptotic protein BAD. Our results supports the hypothesis that this complex may be modulating cellular response to low the energy status of the cell.