Journal
JOURNAL OF NEUROCHEMISTRY
Volume 76, Issue 6, Pages 1756-1765Publisher
BLACKWELL SCIENCE LTD
DOI: 10.1046/j.1471-4159.2001.00169.x
Keywords
Ca2+-ATPase; Ca2+ channels; calcium; IMR-32 cell line; neuronal differentiation; PMCA
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Funding
- NIDA NIH HHS [DA09293, DA07304, DA07097, DA11806] Funding Source: Medline
- NIGMS NIH HHS [GM58710] Funding Source: Medline
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Precise regulation of intracellular Ca2+ concentration ([Ca2+](i)) is achieved 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 neurons. In this study, we examined the regulation of PMCA expression during differentiation of the human neuroblastoma cell line IMR-32. [Ca2+](i) was monitored in single cells using indo-1 microfluorimetry. When the Ca2+-ATPase of the endoplasmic reticulum was blocked by cyclopiazonic acid, [Ca2+](i) recovery after small depolarization-induced Ca2+ loads was governed primarily by PMCAs. [Ca2+](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 [Ca2+](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 Ca2+ influx and efflux pathways may enable differentiated neurons to precisely localize Ca2+ signals in time and space.
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