Plasma membrane coenzyme Q(10) and growth control

Coenzyme Q is distributed among cellular membranes and it has a significant concentration at the plasma membrane. The plasma membrane contains a trans -membrane electron transport system, which is centered on coenzyme Q. This molecule is maintained reduced by NAD(P)H-dependent enzymes and can reduce other antioxidants such as tocopheroxyl quinone and ascorbate free radical. Its antioxidant property and its ability to maintain in the reduced state the other antioxidants offers a system to protect membrane components again st oxidations and prevents oxidative-stress-dependent cellular damage. Grow th factor withdrawal induces cell growth arrest and apoptosis through an ox idative-stress-induced pathway. Coenzyme Q can stimulate growth of differen t cell lines under serum deficiency, mainly by preventing apoptosis. The pr otection caused by coenzyme Q is independent of the Bcl-2 protein. Plasma m embrane coenzyme Q appears to be essential in the regulation of the redox e quilibrium of the cell and redox-dependent pathways.