CALBINDIN-D(28K) EXPRESSION IN TRANSFECTED MOUSE NIH3T3 CELLS

Calbindin D28K (formerly known as vitamin D-dependent calcium binding protein and referred to here as calbindin) is found in a wide variety of tissues, but only in certain cells within those tissues. Apart from its ability to bind calcium, nothing is known about its function in t hese cells. To investigate its role we have transfected the chick calb indin cDNA into mouse NIH3T3 fibroblasts and established a new cell li ne where calbindin is permanently expressed. Immunofluorescence studie s show that calbindin is distributed throughout the cytoplasm, and tre atment of the cells with cycloheximide shows that it has a relatively long half-life within the cell. Measurements of intracellular calcium concentration using Fura-2 suggest that the presence of calbindin with in the cells does not affect the increase in intracellular calcium lev els which occurs in response to serum stimulation or the rate at which these return to the basal level, but that it may act as a buffer for the entry of extracellular calcium.