Mechanistic and functional changes in Ca 2+ entry after retinoic acid-induced differentiation of neuroblastoma cells

Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Framlington Place, Newcastle-upon-Tyne NE2 4HH, UK.
Biochemical Journal (Impact Factor: 4.4). 07/2005; 388(Pt 3):941-8. DOI: 10.1042/BJ20042127
Source: PubMed


We have investigated effects of neuronal differentiation on hormone-induced Ca2+ entry. Fura-2 fluorescence measurements of undifferentiated SH-SY5Y neuroblastoma cells, stimulated with methacholine, revealed the presence of voltage-operated Ca2+-permeable, Mn2+-impermeable entry pathways, and at least two voltage-independent Ca2+- and Mn2+-permeable entry pathways, all of which apparently contribute to both peak and plateau phases of the Ca2+ signal. Similar experiments using 9-cis retinoic acid-differentiated cells, however, revealed voltage-operated Ca2+-permeable, Mn2+-impermeable channels, and, more significantly, the absence or down-regulation of the most predominant of the voltage-independent entry pathways. This down-regulated pathway is probably due to CCE (capacitative Ca2+ entry), since thapsigargin also stimulated Ca2+ and Mn2+ entry in undifferentiated but not differentiated cells. The Ca2+ entry components remaining in methacholine-stimulated differentiated cells contributed to only the plateau phase of the Ca2+ signal. We conclude that differentiation of SH-SY5Y cells results in a mechanistic and functional change in hormone-stimulated Ca2+ entry. In undifferentiated cells, voltage-operated Ca2+ channels, CCE and NCCE (non-CCE) pathways are present. Of the voltage-independent pathways, the predominant one appears to be CCE. These pathways contribute to both peak and plateau phases of the Ca2+ signal. In differentiated cells, CCE is either absent or down-regulated, whereas voltage-operated entry and NCCE remain active and contribute to only the plateau phase of the Ca2+ signal.

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    • "Roughly half of the neurons initially generated die by apoptosis in a well-defined interval, coincident with the establishment of synaptic connections. This cell death is known as naturally occurring programmed cell death and it is believed to match the number of innervating neurons to the size of the target cell population, as well as to eliminate aberrant synaptic contacts (Encinas et al., 2000; C. Rasetti-Escargueil et al. Brown et al., 2005). The human neuroblastoma SH-SY5Y cell line was originally derived from a sympathetic ganglion and contains tyrosine hydroxylase and dopamine β-hydroxylase: the requisite enzymes for synthesis of norepinephrine (Ross and Biedler, 1985; Ciccarone et al., 1989). "
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