LOCALIZED CALCIUM SPIKES AND PROPAGATING CALCIUM WAVES

Ca2+ signals control or modulate diverse cellular processes such as cell growth, muscle contraction, hormone secretion, and neuronal plasticity [1-3]. Elevations in intracellular Ca2+ concentrations can be highly localized to micron and submicron domains [4, 5] or propagated as intra- and intercellular waves over distances as large as 1 mm [6-8]. Localized, subcellular Ca2+ spikes are thought to selectively activate effector systems such as Ca2+ activated chloride currents in pancreatic acinar cells [9], neurotransmitter release in synaptic nerve terminals [4, 10, 11], and morphological changes in neural growth cones [5, 12, 13]. In contrast, long-ranged Ca2+ waves synchronize the activities of different cytoplasmic regions of a single cell, such as cortical granule exocytosis after egg fertilization [6, 7] or coordinate the activities of many cells, such as ciliary beating in pulmonary epithelium [8, 14, 15]. The purpose of this review is to delineate the role of Ca2+ in the generation of localized, subcellular Ca2+ spikes and long-ranged intracellular and intercellular Ca2+ waves.