Differentiation induces up-regulation of plasma membrane Ca(2+)-ATPase and concomitant increase in Ca(2+) efflux in human neuroblastoma cell line IMR-32

• Published in: Journal of neurochemistry Vol. 76; no. 6; pp. 1756 - 1765
• Main Authors: Usachev, Y M, Toutenhoofd, S L, Goellner, G M, Strehler, E E, Thayer, S A
• Format: Journal Article
• Language: English
• Published: England 01-03-2001
• Subjects: Calcium - metabolism; Calcium Channels - physiology; Calcium-Transporting ATPases - antagonists & inhibitors; Calcium-Transporting ATPases - metabolism; Cell Differentiation; Cell Membrane - physiology; Endoplasmic Reticulum - enzymology; Enzyme Inhibitors - pharmacology; Fluorescent Dyes; Humans; Indoles - pharmacology; Isoenzymes - metabolism; Membrane Potentials - drug effects; Membrane Potentials - physiology; Neuroblastoma; Potassium Chloride - pharmacology; Tumor Cells, Cultured
• ISSN: 0022-3042
• DOI: 10.1046/j.1471-4159.2001.00169.x

Precise regulation of intracellular Ca(2+) concentration ([Ca(2+)](i)) is achieved by the coordinated function of Ca(2+) channels and Ca(2+) buffers. Neuronal differentiation induces up-regulation of Ca(2+) channels. However, little is known about the effects of differentiation on the expression of the plasma membrane Ca(2+)-ATPase (PMCA), the principal Ca(2+) extrusion mechanism in neurons. In this study, we examined the regulation of PMCA expression during differentiation of the human neuroblastoma cell line IMR-32. [Ca(2+)](i) was monitored in single cells using indo-1 microfluorimetry. When the Ca(2+)-ATPase of the endoplasmic reticulum was blocked by cyclopiazonic acid, [Ca(2+)](i) recovery after small depolarization-induced Ca(2+) loads was governed primarily by PMCAs. [Ca(2+)](i) returned to baseline by a process described by a monoexponential function in undifferentiated cells (tau = 52 +/- 4 s; n = 25). After differentiation for 12-16 days, the [Ca(2+)](i) recovery rate increased 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 results demonstrate up-regulation of PMCAs on the functional and protein level during neuronal differentiation in vitro. Parallel amplification of Ca(2+) influx and efflux pathways may enable differentiated neurons to precisely localize Ca(2+) signals in time and space.