Recombinant expression of the voltage-dependent anion channel enhances the transfer of Ca2+ microdomains to mitochondria.
Although the physiological relevance of mitochondrial Ca2+ homeostasis is widely accepted, no information is yet available on the molecular identity of the proteins involved in this process. Here we analyzed the role of the voltage-dependent anion channel (VDAC) of the outer mitochondrial membrane in the transmission of Ca2+ signals between the ER and mitochondria by measuring cytosolic and organelle [Ca2+] with targeted aequorins and Ca2+-sensitive GFPs. In HeLa cells and skeletal myotubes, the transient expression of VDAC enhanced the amplitude of the agonist-dependent increases in mitochondrial matrix Ca2+ concentration by allowing the fast diffusion of Ca2+ from ER release sites to the inner mitochondrial membrane. Indeed, high speed imaging of mitochondrial and cytosolic [Ca2+] changes showed that the delay between the rises occurring in the two compartments is significantly shorter in VDAC-overexpressing cells. As to the functional consequences, VDAC-overexpressing cells are more susceptible to ceramide-induced cell death, thus confirming that mitochondrial Ca2+ uptake plays a key role in the process of apoptosis. These results reveal a novel function for the widely expressed VDAC channel, identifying it as a molecular component of the routes for Ca2+ transport across the mitochondrial membranes.
Rapizzi
Elena
E
Department of Experimental and Diagnostic Medicine, Section of General Pathology, Telethon Center for Cell Imaging and Interdisciplinary Center for the Study of Inflammation, University of Ferrara, Via Borsari 46, I-44100 Ferrara, Italy.
Pinton
Paolo
P
Szabadkai
Gyorgy
G
Wieckowski
Mariusz R
MR
Vandecasteele
Gregoire
G
Baird
Geoff
G
Tuft
Richard A
RA
Fogarty
Kevin E
KE
Rizzuto
Rosario
R
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D016257:Fura-2 / Q000031:analogs & derivatives* / Q000378:metabolism; D006367:HeLa Cells; D006706:Homeostasis; D006801:Humans; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism*; D017136:Ion Transport; D008928:Mitochondria / Q000378:metabolism*; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism; D018272:Porins / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism; D050994:Voltage-Dependent Anion Channels; D051028:bcl-2-Associated X Protein
D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D007473:Ion Channels; C064769:N-acetylsphingosine; D018272:Porins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011993:Recombinant Fusion Proteins; D050994:Voltage-Dependent Anion Channels; D051028:bcl-2-Associated X Protein; C049925:fura-2-am; D013110:Sphingosine; D002118:Calcium; D016257:Fura-2