Immunochemical assessment of neural visinin-like calcium-binding protein 3 expression in rat brain

Expression of neural visinin-like calcium-binding protein 3 (NVP3) was assessed by immunoblot and immunohistochemical analyses in rat brain. NVP3 was markedly expressed in the cerebellum, at a concentration of 9.5microM. On SDS-PAGE, native NVP3 migrated at 23kDa, identical to the recombinant myristoyl-form, but somewhat faster than the non-myristoyl-form. Both forms bound 3 moles of calcium. The myristoyl-form exhibited a cooperativity in binding calcium and calcium-dependent membrane-binding, but the non-myristoyl-form did not. At 3 months, NVP3 was primarily localized in the Purkinje cells, with intense staining in the cell bodies, dendrites and axons. The cerebellar granule cells and basal nuclear neurons were faintly stained. During development of the cerebellum, NVP3-positive Purkinje cells first appeared on post-natal day 14 (P14). The staining intensity then increased and plateaued on P28. Labeling showed a tendency to accumulate in the dendrites and nerve terminals in a fine granular pattern. During aging process, NVP3 levels decreased by 43% at 12 months and 68% at 24 months, while the levels of NVP1, synaptophysin and drebrin were preferentially preserved. These results suggest that NVP3 is involved in dendritic arborization and postsynaptic function in cerebellar Purkinje cells and that presynaptic nerve terminals are another functional site of the protein.