Regulation of energy metabolism of heart myoblasts

Cell energy metabolism is very complicated and its regulation is crucial for cell growth and protection from stress. The research presented here offers new insights into the regulation of the energy metabolism in rat myoblast cells. I have shown that high density lipoprotein (HDL) enforces coupling between glycolysis and mitochondrial respiration (the Pasteur effect). Cells with a robust Pasteur effect are protected against stress. Myoblast cells grown in HDL also seem to have more active mitochondria than the control cells (no additional HDL), as they tend to consume more oxygen. I hypothesized that the exposure to HDL causes changes in cellular protein expression levels. Therefore, I employed comparative proteomic techniques to identify these changes. Specifically, two-dimensional gel electrophoresis and reversed phase HPLC coupled to tandem mass spectrometry were used to determine protein expression levels. Both rat heart (H9c2) and thigh (L6) myoblasts were studied and differences between cells grown with additional 250 μg/ml HDL and control cells were observed. I identified proteins in approximately 15 spots on each gel that seem to differ between the control cells and those grown in additional HDL. All the proteins were from the 7–10 pI region and the 30–50 kDa mass range. The most striking differences were in the expression of Annexin II, GAPDH, and VDAC. I have also confirmed by Western blots that these three proteins are upregulated in cells grown with additional HDL. Annexin II and GAPDH are related to the regulation of metabolism, while VDAC is a part of mitochondrial transition pore, involved in transport of ATP and ADP between the matrix and cytosol. These results suggest that HDL enforces coupling of respiration and glycolysis by increasing the expression of glycolytic and mitochondrial proteins that mediate exchange of mitochondrial ATP and ADP with the cytoplasm.