Annexin VI modulates Ca2+ and K+ conductances of spinal cord and dorsal root ganglion neurons

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Abstract
Annexin VI is a member of a Ca(2+)-dependent phospholipid-binding protein family that participates in the transduction of the intracellular Ca2+ signal. We have identified annexin VI as one of the major annexins expressed differentially by sensory neurons of dorsal root ganglia (DRG) and by neurons of spinal cord (SC) of the rat and the mouse. This annexin shows a preferential localization at the plasma membrane of the soma and cellular processes, particularly in motoneurons of the SC. This finding suggests an active role of annexin VI in the Ca(2+)-dependent regulation of plasma membrane functions. To test this possibility, the neuronal function of annexin VI was evaluated by whole cell electrophysiology of mouse embryo SC and DRG neurons. An antibody was developed that has the property of neutralizing annexin VI-phospholipid interactions. The intracellular perfusion of individual neurons in culture, either from SC or DRG, with monospecific affinity-purified anti-annexin VI antibodies resulted in an increase in the magnitude of the K+ current and in an increase in the Ca2+ current in sensory neurons. Our results suggest that the endogenous annexin VI regulates the Ca2+ conductance, which indirectly modifies Ca(2+)-dependent ionic conductances in SC and DRG neurons.