Calbindin28kDa and calmodulin are hyperabundant in rat dental enamel cells. Identification of the protein phosphatase calcineurin as a principal calmodulin target and of a secretion-related role for calbindin28kDa.

Abstract

Enamel cells are likely to experience heavy demands for intracellular calcium homeostasis during the secretion and hypermineralization of dental enamel. Here, the two major high-affinity calcium-binding proteins in rat enamel epithelium were identified as calbindin28kDa and calmodulin, using a microscale approach. Both proteins were hyperabundant, totalling up to 2% of the soluble protein and surpassing the amounts in cerebellum, the benchmark tissue. Calbindin28kDa and calmodulin accounted for 26% of the total calcium-binding capacity in enamel cell cytosol, under near physiological conditions. Numerous calmodulin-binding proteins were detected with an overlay assay, indicating that calmodu..