Localization of voltage-sensitive Ca2+ fluxes and neuropeptide Y immunoreactivity to varicosities in SH-SY5Y human neuroblastoma cells differentiated by treatment with the protein kinase inhibitor staurosporine

: Kukkonen JP, Shariatmadari R, Courtney MJ, Akerman KEO

Publisher: OXFORD UNIV PRESS

: 1997

: European Journal of Neuroscience

: EUROPEAN JOURNAL OF NEUROSCIENCE

: EUR J NEUROSCI

: 9

: 1

: 140

: 150

: 11

: 0953-816X

DOI: https://doi.org/10.1111/j.1460-9568.1997.tb01362.x

The distribution of voltage-sensitive elevations of the level of Ca2+ in untreated SH-SY5Y cells and cells that had been induced to differentiate with staurosporine was investigated by monitoring fura-2 fluorescence in cell suspensions, and by using microfluorometry and quantitative fluorescence imaging on cell bodies and on cellular processes. Cell bodies of both types of cells displayed small Ca2+ elevations, which were composed of transient and sustained components. Elevations were partially sensitive to the L- and N-channel blockers nifedipine (1 mu M) and omega-conotoxin GVIA (100 nM) respectively. Up to ten times higher Ca2+ elevations were observed in varicosities of treated cells than in cell bodies of treated and untreated cells. These elevations were insensitive to compounds known to release Ca2+ from intracellular stores. Elevations of Ca2+ were sustained, and they were insensitive to 5 mu M nifedipine, 100 nM omega-agatoxin IVA and 100 nM omega-conotoxin GVIA, and partially sensitive to 2 mu M omega-conotoxin GVIA, indicating predominance of non-L-type, non-ll-type, non-P-type channel activity. The intracellular localization of neuropeptide Y, a marker of differentiation in these cells, was also investigated by fluorescence immunocytochemistry. Varicosities of treated cells displayed marked fluorescence when viewed in a confocal microscope. These findings show that the varicosities of staurosporine-treated cells exhibit some of the functional properties of nerve terminals, The varicosities resemble boutons en passant nerve endings and they seem to express Ca2+ channels different from those in the cell body.