Ym. Usachev et al., Differentiation induces up-regulation of plasma membrane Ca2+-ATPase and concomitant increase in Ca2+ efflux in human neuroblastoma cell line IMR-32, J NEUROCHEM, 76(6), 2001, pp. 1756-1765
Precise regulation of intracellular Ca2+ concentration ([Ca2+](i)) is achie
ved by the coordinated function of Ca2+ channels and Ca2+ buffers. Neuronal
differentiation induces up-regulation of Ca2+ channels. However, little is
known about the effects of differentiation on the expression of the plasma
membrane Ca2+-ATPase (PMCA), the principal Ca2+ extrusion mechanism in neu
rons. In this study, we examined the regulation of PMCA expression during d
ifferentiation of the human neuroblastoma cell line IMR-32. [Ca2+](i) was m
onitored in single cells using indo-1 microfluorimetry. When the Ca2+-ATPas
e of the endoplasmic reticulum was blocked by cyclopiazonic acid, [Ca2+](i)
recovery after small depolarization-induced Ca2+ loads was governed primar
ily by PMCAs. [Ca2+](i) returned to baseline by a process described by a mo
noexponential function in undifferentiated cells (tau = 52 +/- 4 s; n = 25)
. After differentiation for 12-16 days, the [Ca2+](i) recovery rate increas
ed by more than threefold (tau = 17 +/- 1 s, n = 31). Western blots showed
a pronounced increase in expression of three major PMCA isoforms in IMR-32
cells during differentiation, including PMCA2, PMCA3 and PMCA4. These resul
ts demonstrate up-regulation of PMCAs on the functional and protein level d
uring neuronal differentiation in vitro. Parallel amplification of Ca2+ inf
lux and efflux pathways may enable differentiated neurons to precisely loca
lize Ca2+ signals in time and space.