α-Parvalbumin reduces depolarizationminduced elevations of cytosolic free calcium in human neuroblastoma cells

Abstract We investigated whether the expression of human α-parvalbumin affects depolarization-induced elevations of the cytosolic free calcium concentration ([Ca 2+ ] i ) in human neuroblastoma SKNBE2 cells. A full length human parvalbumin cDNA was cloned by PCR from human cerebellum and transiently transfected into SKNBE2 cells. Immunofluorescence staining using an antibody raised against parvalbumin revealed a transfection efficacy of about 14%. In parvalbumin-expressing SKNBE2 cells, parvalbumin concentration determined by quantitative Western blotting amounted to 0.42 mM. Transfected SKNBE2 cells were depolarized for 2 min by 50 mM K + . During this period, [Ca 2+ ] i was monitored by video microfluorimetry using the Ca 2+ indicator Fura-2. In a fraction of cells, depolarization induced a transient elevation in [Ca 2+ ] i The size of this elevation was compared with the immunofluorimetrically determined expression of parvalbumin on a cell-to-cell basis. Cells with a significant parvalbumin immunofluorescence responded to depolarization with smaller elevations in [Ca 2+ ] i than non-parvalbumin-expressing cells. Resting [Ca 2+], did not differ between parvalbumin-expressing and control cells. These observations indicate that large depolarization-induced transient elevations of [Ca 2+ ] i in neuroblastoma cells can be suppressed by parvalbumin.