ALPHA-PARVALBUMIN REDUCES DEPOLARIZATION-INDUCED ELEVATIONS OF CYTOSOLIC-FREE CALCIUM IN HUMAN NEUROBLASTOMA CELLS

We investigated whether the expression of human alpha-parvalbumin affe cts depolarization-induced elevations of the cytosolic free calcium co ncentration ([Ca2+](i)) in human neuroblastoma SKNBE2 cells. A full le ngth human parvalbumin cDNA was cloned by PCR from human cerebellum an d transiently transfected into SKNBE2 cells. Immunofluorescence staini ng using an antibody raised against parvalbumin revealed a transfectio n efficacy of about 14%. In parvalbumin-expressing SKNBE2 cells, parva lbumin concentration determined by quantitative Western blotting amoun ted to 0.42 mM. Transfected SKNBE2 cells were depolarized for 2 min by 50 mM K+. During this period, [Ca2+](i) was monitored by video microf luorimetry using the Ca2+ indicator Fura-2. In a fraction of cells, de polarization induced a transient elevation in [Ca2+](i). The size of t his elevation was compared with the immunofluorimetrically determined expression of parvalbumin on a cell-to-cell basis. Cells with a signif icant parvalbumin immunofluorescence responded to depolarization with smaller elevations in [Ca2+](i) than non-parvalbumin-expressing cells. Resting [Ca2+](i) did not differ between parvalbumin-expressing and c ontrol cells. These observations indicate that large depolarization-in duced transient elevations of [Ca2+](i) in neuroblastoma cells can be suppressed by parvalbumin.