The Ca2+ pump and Ca2+ release functions of intracellular Ca2+ pools have been well characterized. However, the nature and identity of Ca2+ pools as well as the physiological implications of Ca2+ levels within them, have remained elusive. Ca2+ pools appear to be contained within the endoplasmic reticulum (ER); however, ER is a heterogeneous and widely distributed organelle, with numerous other functions than Ca2+ regulation. Studies described here center on trying to determine more about subcellular distribution of Ca2+ pools, the levels of Ca2+ within Ca2+ pools, and how these intraluminal Ca2+ levels may be physiologically related to ER function. Experiments utilizing in situ high resolution subcellular morphological analysis of ER loaded with ratiometric fluroescent Ca2+ dyes, indicate a wide distribution of inositol 1,4,5-trisphosphate (InsP3)-sensitive Ca2+ pools within cells, and large changes in the levels of Ca2+ within pools following InsP3-mediated Ca2+ release. Such changes in Ca2+ may be of great significance to the translation, translocation, and folding of proteins in ER, in particular with respect to the function of the now numerously described luminal Ca2+-sensitive chaperonin proteins. Studies have also focussed on the physiological role of pool Ca2+ changes with respect to cell growth. Emptying of pools using Ca2+ pump blockers can result in cells entering a stable quiescent G0-like growth state. After treatment with the irreversible pump blocker, thapsigargin, cells remain in this state until they are stimulated with essential fatty acids whereupon new pump protein is synthesized, functional Ca2+ pools return, and cells reenter the cell cycle. During the Ca2+ pool-depleted growth-arrested state, cells express a Ca2+ influx channel that is distinct from the store-operated Ca2+ influx channels activated after short-term depletion of Ca2+ pools. Overall, these studies indicate that significant changes in intraluminal ER Ca2+ do occur and that such changes appear linked to alteration of essential ER functions as well as to the cell cycle-state and the growth of cells.
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Review Article|
April 01 1996
Calcium pools, calcium entry, and cell growth
Donald L. Gill;
Donald L. Gill
1Department of Biological Chemistry, University of Maryland School of Medicine, Baltimore, Maryland 21201.
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Richard T. Waldron;
Richard T. Waldron
1Department of Biological Chemistry, University of Maryland School of Medicine, Baltimore, Maryland 21201.
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Krystyna E. Rys-Sikora;
Krystyna E. Rys-Sikora
1Department of Biological Chemistry, University of Maryland School of Medicine, Baltimore, Maryland 21201.
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Carmen A. Ufret-Vincenty;
Carmen A. Ufret-Vincenty
1Department of Biological Chemistry, University of Maryland School of Medicine, Baltimore, Maryland 21201.
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Matthew N. Graber;
Matthew N. Graber
1Department of Biological Chemistry, University of Maryland School of Medicine, Baltimore, Maryland 21201.
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Cécile J. Favre;
Cécile J. Favre
1Department of Biological Chemistry, University of Maryland School of Medicine, Baltimore, Maryland 21201.
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Amparo Alfonso
Amparo Alfonso
1Department of Biological Chemistry, University of Maryland School of Medicine, Baltimore, Maryland 21201.
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Publisher: Portland Press Ltd
Received:
December 07 1995
Online ISSN: 1573-4935
Print ISSN: 0144-8463
© 1996 Plenum Publishing Corporation
1996
Biosci Rep (1996) 16 (2): 139–157.
Article history
Received:
December 07 1995
Citation
Donald L. Gill, Richard T. Waldron, Krystyna E. Rys-Sikora, Carmen A. Ufret-Vincenty, Matthew N. Graber, Cécile J. Favre, Amparo Alfonso; Calcium pools, calcium entry, and cell growth. Biosci Rep 1 April 1996; 16 (2): 139–157. doi: https://doi.org/10.1007/BF01206203
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