The effects of phospholipids and fatty acids on the oligomer formation of NAP-22.

Recovery of various signal transduction molecules in the detergent-resistant membrane microdomain (DRM) fraction suggests the importance of this region in cellular functions. NAP-22 (also called BASP1 or CAP-23) is a neuron-enriched calmodulin-binding protein and one of the major proteins in the DRM fraction of the neuronal cell membrane. Previous studies showed tight binding activity of NAP-22 to acidic membrane lipids and the self-interaction of NAP-22, i.

Inhibitory effect of NAP-22 on the phosphatase activity of synaptojanin-1.

Endocytosis of the synaptic vesicle is a complicated process, in which many proteins and lipids participate. Phosphatidylinositol 4,5-bisphosphate (PIP(2) ) plays important roles in the process, and the dynamic regulation of this lipid is one of the key events. Synaptojanin is a PIP(2) phosphatase, and dephosphorylation of PIP(2) of the clathrin coated-vesicle results in the uncoating of the vesicle.

Biochemical interaction of an actin-capping protein, CapZ, with NAP-22.

NAP-22 is a neuronal protein localized in the presynaptic membrane and synaptic vesicles and recovered in a Triton-insoluble low-density microdomain fraction after biochemical fractionation of the synaptic plasma membrane. NAP-22 organizes membrane microdomains through binding to membrane lipids such as cholesterol, phosphatidylethanolamine, and phosphatidylinositol 4,5-bisphosphate. In this study, NAP-22-binding proteins were screened through the pull-down assay using brain-derived NAP-22 bound to Sepharose 4B.