Monitoring mitochondrial calcium and metabolism in the beating MCU-KO heart
Anna Kosmach, Bárbara Román, Junhui Sun, Armel N. Femnou, Fan Zhang, Chengyu Liu, Christian A. Combs, Robert S. Balaban, Elizabeth Murphy
Abstract
Optical methods for measuring intracellular ions including Ca 2+ revolutionized our understanding of signal transduction. However, these methods are not extensively applied to intact organs due to issues including inner filter effects, motion, and available probes. Mitochondrial Ca 2+ is postulated to regulate cell energetics and death pathways that are best studied in an intact organ. Here, we develop a method to optically measure mitochondrial Ca 2+ and demonstrate its validity for mitochondrial Ca 2+ and metabolism using hearts from wild-type mice and mice with germline knockout of the mitochondria calcium uniporter (MCU-KO). We previously reported that germline MCU-KO hearts do not show an impaired response to adrenergic stimulation. We find that these MCU-KO hearts do not take up Ca 2+ , consistent with no alternative Ca 2+ uptake mechanisms in the absence of MCU. This approach can address the role of mitochondrial Ca 2+ to the myriad of functions attributed to alterations in mitochondrial Ca 2+ .