ANNEXIN-VI MODULATES CA2-CORD AND DORSAL-ROOT GANGLION NEURONS( AND K+ CONDUCTANCES OF SPINAL)

Annexin VI is a member of a Ca2+ dependent phospholipid-binding protei n family that participates in the transduction of the intracellular Ca 2+ signal. We have identified annexin VI as one of the major annexins expressed differentially by sensory neurons of dorsal root ganglia (DR G) and by neurons of the spinal cord (SC) of the rat and the mouse. Th is annexin shows a preferential localization at the plasma membrane of the soma and cellular processes, particularly in motoneurons of the S C. This finding suggests an active role of annexin VI in the Ca2+-depe ndent regulation of plasma membrane functions. To test this possibilit y, the neuronal function of annexin VI was evaluated by whole cell ele ctrophysiology of mouse embryo SC and DRG neurons. An antibody was dev eloped that has the property of neutralizing annexin VI-phospholipid i nteractions. The intracellular perfusion of individual neurons in cult ure, either from SC or DRG, with monospecific affinity-purified anti-a nnexin VI antibodies resulted in an increase in the magnitude of the K + current and in an increase in the Ca2+ current in sensory neurons. O ur results suggest that the endogenous annexin VI regulates the Ca2+ c onductance, which indirectly modifies Ca2+-dependent ionic conductance s in SC and DRG neurons.