NUCLEAR CALMODULIN RESPONDS RAPIDLY TO CALCIUM INFLUX AT THE PLASMALEMMA

We have studied the rate and extent of calcium binding to calmodulin i n neuronal cytosol and nucleus during brief calcium influx across the plasmalemma. Rat sensory neurones were whole-cell patch clamped using a pipette containing a fluorescent analogue of calmodulin that reports when it has bound calcium. Cytosolic and nuclear signals were separat ed using a confocal microscope, Plasmalemmal calcium influx during a o ne second depolarization that activated L type calcium channels caused large fractions of calmodulin in both the cytosol and nucleus to bind calcium, Thus, contrary to previous predictions, nuclear processes th at require the calcium:caimodulin complex will be activated readily by even brief cell stimulation.