Effects Of Overexpression Of Heat Shock Protein 70 On Energy Metabolism

Abstract

Heat shock protein 70 (hsp70) plays a pivotal role in maintaining cell homestasis. We have demonstrated that Hsp 70 is induced in skeletal muscle during training (J Appl Physiol 86, 101–104, 1999) and that the HSP70 response to training is related to exercise intensity rather than to exercise volume. (Int J Sports Med 21: 351–355, 2000). PURPOSE hsp70 has chaperoning function on cellular proteins and on mitochondria. Until now, it remains obscure whether increased Hsp70 has a direct effect on energy metabolism and therefore, a cell culture model was selected. METHODS A cell line (HeLa cells) was established expressing different levels of Hsp70 using a regulable Tet-On gene expression system. Changes in metabolites and intracellular ATP level were determined. In addition, activities of enzymes involved in glycolysis (phosphofructokinase, PFK; lactate dehydrogenase, LDH), citric acid cycle (citric synthase, CS) and oxidative phosphorylation (NADH dehydrogenase, complex I) were analyzed. RESULTS The results showed that glucose consumption and lactate excretion were significantly elevated in cells expressing increased Hsp70. Simultaneously, the activity of the PFK and LDH was markedly increased in cells with relatively high level of Hsp70 (>71.4 ηg), and a good correlation to hsp70 was observed. For complex I, the activity remained constant except a notable decrease in cells with low level of Hsp70 (LL, 134.2 ηg) compared with that in LL. CONCLUSIONS Upregulated Hsp70 in HeLa cells resulted in an increase in ATP level, which is related to an enhanced glycolytic capacity. This could be related to hsp70-protein interactions and mitochondrial biogenesis.