Interaction of dynamin I with NAP-22, a neuronal protein enriched in the presynaptic region

Neurons have well-developed membrane microdomains called "rafts" that are recovered as a detergent resistant low-density membrane microdomain fraction (DRM). NAP-22 is one of the major protein components of neu ronal DRM and localizes in the presynaptic region. In order to know the role of NAP -22 in the synaptic trans mission, NAP -22 binding proteins in the cytosol were searched with an affinity screening with NAP-22 as a bait and several protein bands were detected. Using mass-analysis and western blotting, one of the main band of similar to 90 kDa was identified as dynamin I. The GTPase activity of dynamin I was partly inhibited by NAP-22 expressed in bacteria and this inhibition was recovered by the addition of calmodulin, a NAP-22 binding protein The GTPase activity of dynamin was known to be activated with acidic membrane lipids such as phosphatidylserine and the addition of NAP-22, a phosphatidylserine binding protein, inhibited the activation of the GTPase by this lipid Since NAP 22 localizes on the presynaptic plasma membrane and on synaptic vesicles, these results suggest the participation of NAP-22 in the membrane cycling through binding to dynamin and acidic membrane lipids at the presynaptic region.