CALBINDIN-D-28K IN NERVE-CELL NUCLEI

Calbindin-D-28k is a member of the large EF-hand family of calcium-bin ding proteins, that is believed to function, in part, as a cytosolic c alcium buffer. Recent studies have demonstrated that cells containing Calbindin-D-28k are protected from degeneration caused by conditions t hat elevate intracellular calcium concentrations. Since its initial di scovery in 1966, Calbindin-D-28k has been localized in the cytoplasm o f many neuronal populations, but its nuclear localization has been unc ertain. Using light and electron microscopic immunohistochemistry, and nuclear fractionation methods, we demonstrate localization of Calbind in-D-28k not only in the cytoplasm, but also in the nucleus of rodent midbrain dopaminergic neurons and cerebellar Purkinje cells. The Calbi ndin-D-28k immunoreactive staining intensity in the nucleus was routin ely equal or greater than that in the cytoplasm. Since calcium signals are propagated to the nucleus, where they can regulate gene expressio n, the existence of nuclear Calbindin-D-28k has important implications for cellular function. (C) 1997 IBRO. Published by Elsevier Science L td.