Close Contacts with the Endoplasmic Reticulum as Determinants of Mitochondrial Ca~2+ Responses

摘要

The spatial relation between mitochondria and endoplasmic reticulum (ER) in living HeLa cells was analyzed at high resolution three dimensions with two differently colored, specifically targeted green fluorescent proteins. Numerous close contacts were ob- served between these organelles, and mitohondria in situ formed a largely intercon- nected, dynamic network. A Ca~2+ -sensitive photoprotein targeted to the outer face of the inner mitochondrial membrane showed that, upon opening of the inositol 1,4,50 triphosphate (IP_3)-gated channels of the ER, the mitochondrial surface was exposed to a higher concentration of Ca~2+ than was the bulk cytosol. These results emphasize the importance of cell architecture and the distribution of organelles in regulation of C~2+ signaling.