The Mitochondrial Electron Transport Chain Complex Rearranges During Muscle Differentiation

Mitochondria are semi-autonomous organelles with bilayer membrane structure,which participate in many vital processes such as energy production,signal transduction and redox potential regulation.The oxidative phosphorylation system on mitochondrial inner membrane produces ATP.The whole system consists of electron transfer chain complex,electron carrier and H +-ATP synthase.Recent studies have shown that electron transfer chain complexes can organize into supercomplexes with the participation of some assembly factors to generate energy,i.e.the plastic model of the organization mechanism of the complexes,rather than the random collision model with high degree of freedom of movement.The distribution of mitochondria in organisms depends on different cell types.The higher the energy demand in cells,the more mitochondria are,such as muscle cells.Some studies have shown that the energy level of cells changes during muscle differentiation,and some energy-related transcription factors change significantly.Whenever the energy level changes,the electron transfer chain complex will also change accordingly.We used C2C12 cells as a model to study the muscle differentiation.BN-PAGE detected the changes of mitochondrial electron transport chain complexes during the differentiation of C2C12 cells.Compared with the pre-differentiation stage,complexes I,III and IV abundance increased gradually after 2,4 and 6 days of cell differentiation.These results indicated that the electron transfer chain complexes have changed during differentiation.Western blots detect the changes of the electron transport chain complexes some subunits during the differentiation of C2C12 cells.Compared with the pre-differentiation stage,complex IV subunits and complex V subunits increased,while complex I subunits and complex III subunits either increased,unchanged or decreased.BN-PAGE and In-gel activity assays found that supercomplexes also changed.These results indicated that the change of different subunits in each complex is inconsistent with the stage of differentiation,suggesting the rearrangement of the electron transfer chain.To mimic this rearrangement of electron transport chains,the expression of complex III subunits and IV subunits was reduced by transfection of si RNA during the differentiation of C2C12 cells.Western blot showed that decreasing the expression of COX1 enhanced significantly the differentiation of C2C12 cells;decreasing the expression of COX2 and COX3 might inhibit the differentiation of C2C12 cells;immunofluorescence staining also showed that the expression of MHC were enhanced significantly by decreasing the expression of COX1;decreasing the expression of COX8 A affected complex IV,which resulted in the total protein content of complex,the other two complexes remained unchanged.Decreasing the expression of complex III subunits UQCRQ and UQCR11 may have an effect on the differentiation of C2C12 cells.In addition to the active synthesis of mitochondrial electron transfer chain complexes in differentiated myocytes to meet their energy needs,cancer tissue also needs a lot of energy because of its infinite proliferation characteristics.Compared with normal tissues,the expression of mitochondrial respiratory chain complex I subunit NDUFS1,complex II subunits SDHA and SDHB changed or remained unchanged in the adjacent tissues and changed in the cancerous tissues.The expression of complex III subunit CYBB,complex IV subunit COX5 A and complex V subunit ATP5 B unchanged in the adjacent tissues and the cancerous tissues.At the same time,we also detected mitochondrial electron transfer chain complexes in mouse blood,presumably from immune cells in the blood.In summary,we found that in the process of muscle differentiation,the electron transport chain complexes rearranges,regulates energy generation,and then affects cell differentiation...