Evidence for different functional properties of the neuronal calcium sensor proteins VILIP-1 and VILIP-3: from subcellular localization to cellular function.

The visinin-like-proteins VILIP-1 and -3 are EF-hand calcium-binding proteins and belong to the family of neuronal calcium sensor (NCS) proteins. Members of this family are involved in the calcium-dependent regulation of signal transduction cascades mainly in the nervous system. VILIP-1 and VILIP-3 are expressed in different populations of neuronal cells. To gain insights into the different functional characteristics of VILIP-1 and -3, we have compared the localization of the proteins in intact cells and the calcium-dependent membrane association in subcellular fractions. Furthermore, we have investigated the different functional properties of the two proteins in activating cGMP signal pathways and have defined different sets of protein interaction partners. Our data indicate that VILIP-3, which is mainly expressed in Purkinje cells, and VILIP-1, which is expressed in granule cells in the cerebellum, show a different calcium-dependent subcellular localization, may activate different cellular signaling pathways, and thus have signaling functions which seem to be cell-type specific.