Mechanistic and functional changes in Ca2+ entry after retinoic acid-induced differentiation of neuroblastoma cells.
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.
Brown
Anna M
AM
Institute for Cell and Molecular Biosciences, The Medical School, University of Newcastle, Framlington Place, Newcastle-upon-Tyne NE2 4HH, UK.
Riddoch
Fiona C
FC
Robson
Andrew
A
Redfern
Christopher P F
CP
Cheek
Timothy R
TR
D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D002413:Cations, Divalent / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects*; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008345:Manganese / Q000378:metabolism; D016210:Methacholine Chloride / Q000494:pharmacology; D018721:Muscarinic Agonists / Q000494:pharmacology; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology*
D015220:Calcium Channels; D002413:Cations, Divalent; D004791:Enzyme Inhibitors; D018721:Muscarinic Agonists; D016210:Methacholine Chloride; D008345:Manganese; D014212:Tretinoin; D019284:Thapsigargin; D002118:Calcium