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Differentiation induces up‐regulation of plasma membrane Ca 2+ ‐ATPase and concomitant increase in Ca 2+ efflux in human neuroblastoma cell line IMR‐32
Author(s) -
Usachev Yuriy M.,
Toutenhoofd Sonja L.,
Goellner Geoffrey M.,
Strehler Emanuel E.,
Thayer Stanley A.
Publication year - 2001
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2001.00169.x
Subject(s) - plasma membrane ca2+ atpase , depolarization , endoplasmic reticulum , cyclopiazonic acid , biology , microbiology and biotechnology , cellular differentiation , cell culture , intracellular , atpase , biochemistry , chemistry , endocrinology , enzyme , genetics , gene
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 (τ = 52 ± 4 s; n = 25). After differentiation for 12–16 days, the [Ca 2+ ] i recovery rate increased by more than threefold (τ = 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.