A Role for Calcium Influx in the Regulation of Mitochondrial Calcium in Endothelial Cells (*)
- From the Department of Human Anatomy and Cell Biology, University of Liverpool, Ashton Street, Liverpool L69 3BX, United Kingdom and the
- Department of Biomedical Sciences, University of Padova, Via Trieste 75, 35121 Padova, Italy
- § To whom correspondence should be addressed. Tel.: (+44) 151 794 5510; Fax: (+44) 151 794 5517; awms{at}liv.ac.uk.
Abstract
By using an endothelial cell line (ECV304), derived from human umbilical vein and transfected with recombinant aequorin targeted
to the mitochondrial matrix, we find that stimulation with ATP evokes long lasting increases in mitochondrial Ca
([Ca
]
) that largely depend on Ca
influx. In these cells, the release of stored Ca
is inefficient at elevating [Ca
]
. Consequently it appears that in ECV304 cells, bulk cytosolic Ca
([Ca
]
) is the main determinant of [Ca
]
changes.
In ECV304 cells <4% of mitochondria are within 700 nm of the endoplasmic reticulum as opposed to 65% in HeLa cells, whereas
14% are within 700 nm of the inner surface of the plasma membrane, compared with <6% in HeLa cells. Following Ca
depletion, readdition of extracellular Ca
evokes an increase in [Ca
]
but not in [Ca
]
. Under these conditions, microdomains of high [Ca
]
may occur beneath the plasma membrane of ECV304 cells resulting in the preferential elevation of Ca
in mitochondria located in this region.
A model is discussed in which the localization of mitochondria with respect to Ca
sources is the main determinant of their in situ Ca
uptake kinetics. Thus, in any given cell type mitochondria may be localized to suit the energy and metabolic demands of their
physiological actions.
Footnotes
-
↵* This work was supported by grants from the Medical Research Council, The Royal Society, The Wellcome Trust, and the University of Liverpool Research Development Fund (to A. W. M. S.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵1 The abbreviations used are:
- [Ca
]
-
cytosolic free calcium concentration
- [Ca
]
-
mitochondrial matrix free calcium concentration
- Ca
-
extracellular calcium
- ECV304
-
human umbilical vein-derived endothelial cell line
- MH75
-
HeLa cell clone stably transfected with mitochondrially targeted aequorin
- InsP
-
inositol 1,4,5-trisphosphate
- FCCP
-
carbonyl cyanide p-trifluoromethoxyphenylhydrazone
- ER
-
endoplasmic reticulum
- cytAEQ
-
cytoplasmic aequorin
- mtAEQ
-
mitochondrial aequorin.
- [Ca
-
↵2R. Rizzuto and T. Pozzan, unpublished data.
-
- Received September 25, 1995.
- Revision received February 26, 1996.
- © 1996 by The American Society for Biochemistry and Molecular Biology, Inc.
