CALCIUM SIGNALING AND CELL-PROLIFERATION

The orderly sequence of events that constitutes the cell cycle is care fully regulated. A part of this regulation depends upon the ubiquitous calcium signalling system. Many growth factors utilize the messenger inositol trisphosphate (InsP(3)) to set up prolonged calcium signals, often organized in an oscillatory pattern. These repetitive calcium sp ikes require both the entry of external calcium and its release from i nternal stores. One function of this calcium signal is to activate the immediate early genes responsible for inducing resting cells (G(0)) t o re-enter the cell cycle. It may also promote the initiation of DNA s ynthesis at the G(1)/S transition. Finally, calcium contributes to the completion of the cell cycle by stimulating events at mitosis. The ro le of calcium in cell proliferation is highlighted by the increasing n umber of anti-cancer therapies and immunosuppressant drugs directed to wards this calcium signalling pathway.