Recombinant expression of the plasma membrane Na(+)/Ca(2+) exchanger affects local and global Ca(2+) homeostasis in Chinese hamster ovary cells.
The cardiac type Na(+)/Ca(2+) exchanger (NCX1) has been transiently expressed in Chinese hamster ovary cells, which do not contain an endogenous exchanger, together with aequorin chimeras that are targeted to different intracellular compartments to investigate intracellular Ca(2+) homeostasis. The expression of NCX decreased the endoplasmic reticulum Ca(2+) concentration, [Ca(2+)](er), in resting cells, showing that the exchanger was operative under these conditions. It induced a greater reduction in the height of the mitochondrial and cytosolic Ca(2+) transients in agonist-stimulated cells than would have been expected from the [Ca(2+)](er) decrease. It also had a major effect on the sub-plasma membrane Ca(2+) concentration, [Ca(2+)](pm): after a transient [Ca(2+)](pm) rise induced by the activation of capacitative Ca(2+) influx, [Ca(2+)](pm) settled to a value about 3-fold higher than in controls. The sustained [Ca(2+)](pm) increase after the transient was due to the operation of the exchanger, either directly by operating in the Ca(2+) entry mode, or indirectly by removing the Ca(2+) inhibition on the capacitative Ca(2+) influx channels.
Brini
Marisa
M
Department of Biochemistry and Center for the Study of Biomembranes of the National Research Council, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy. brini@mail.bio.unipd.it
Manni
Sabrina
S
Carafoli
Ernesto
E
D000255:Adenosine Triphosphate / Q000378:metabolism; D000331:Aequorin / Q000235:genetics / Q000378:metabolism; D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D006224:Cricetinae; D003600:Cytosol / Q000378:metabolism; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000235:genetics / Q000378:metabolism*
D005456:Fluorescent Dyes; D011993:Recombinant Fusion Proteins; D019831:Sodium-Calcium Exchanger; C110374:sodium-calcium exchanger 1; D000331:Aequorin; D000255:Adenosine Triphosphate; D002118:Calcium