Microdomain calcium signaling in secretory protozoan cell: Identification and functional localization of membrane proteins in calcium stores of Parameciums cells

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Signaling by Ca2+ involves Ca2+-influx as well as Ca2+ release channels in store membranes. Upon stimulation, Ca2+ signals have to be precisely localized, i.e., colocalized with target molecules to generate a quick response. So far, we have found in the Paramecium tetraurelia genome data base six different types of Ca2+-release channels (ryanodine and !P3 receptors, and mixed types without precedent-to be preferentially analyzed). Some are unexpectedly localized to the osmoregulatory system, others to the Endoplasmic Reticulum or to cortical Ca-stores. Understanding this complex situation requires detailed characterization and localization of Ca2+- channels and of target structures.