Dynamic cellular translocation of caldendrin is facilitated by the Ca2+-myristoyl switch of recoverin

P>Caldendrin and recoverin are Ca2+-sensor proteins operating in neuronal systems. In a search for novel binding partners of recoverin, we employed an affinity column and identified caldendrin as a possible interaction partner. Caldendrin and recoverin co-localized in the retina in a subset of bipolar cells and in the pineal gland as revealed by immunofluorescence studies. The binding process was controlled by Ca2+ as revealed by pull-down assays, and surface plasmon resonance studies. Importantly, caldendrin existed as a Ca2+-independent homodimer whereas a complex of recoverin and caldendrin formed with low to moderate affinity in the presence of Ca2+. Co-transfection of COS-7 cells with plasmids harboring the gene for fluorescently labeled recoverin and caldendrin was used to study the cellular distribution by time-lapse fluorescence microscopy. Apparently, the increase of intracellular Ca2+ facilitates the translocation of caldendrin to intracellular membranes, which is under control of complex formation with recoverin