Diversity of mitochondrial Ca²⁺ signaling in rat neonatal cardiomyocytes: evidence from a genetically directed Ca²⁺ probe mitycam-E31Q

Haviland, S., Cleemann, L., Kettlewell, S., Smith, G. L. and Morad, M. (2014) Diversity of mitochondrial Ca²⁺ signaling in rat neonatal cardiomyocytes: evidence from a genetically directed Ca²⁺ probe mitycam-E31Q. Cell Calcium, 56(3), pp. 133-146. (doi: 10.1016/j.ceca.2014.06.001) (PMID:24994483)

Abstract

ICa-gated Ca2+ release (CICR) from the cardiac SR is the main mechanism mediating the rise of cytosolic Ca2+, but the extent to which mitochondria contribute to the overall Ca2+ signaling remains controversial. To examine the possible role of mitochondria in Ca2+ signaling, we developed a low affinity mitochondrial Ca2+ probe, mitycam-E31Q (300–500 MOI, 48–72 h) and used it in conjunction with Fura-2AM to obtain simultaneous TIRF images of mitochondrial and cytosolic Ca2+ in cultured neonatal rat cardiomyocytes. Mitycam-E31Q staining of adult feline cardiomyocytes showed the typical mitochondrial longitudinal fluorescent bandings similar to that of TMRE staining, while neonatal rat cardiomyocytes had a disorganized tubular or punctuate appearance. Caffeine puffs produced rapid increases in cytosolic Ca2+ while simultaneously measured global mitycam-E31Q signals decreased more slowly (increased mitochondrial Ca2+) before decaying to baseline levels. Similar, but oscillating mitycam-E31Q signals were seen in spontaneously pacing cells. Withdrawal of Na+ increased global cytosolic and mitochondrial Ca2+ signals in one population of mitochondria, but unexpectedly decreased it (release of Ca2+) in another mitochondrial population. Such mitochondrial Ca2+ release signals were seen not only during long lasting Na+ withdrawal, but also when Ca2+ loaded cells were exposed to caffeine-puffs, and during spontaneous rhythmic beating. Thus, mitochondrial Ca2+ transients appear to activate with a delay following the cytosolic rise of Ca2+ and show diversity in subpopulations of mitochondria that could contribute to the plasticity of mitochondrial Ca2+ signaling.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Smith, Professor Godfrey and Kettlewell, Dr Sarah
• Authors: Haviland, S., Cleemann, L., Kettlewell, S., Smith, G. L., and Morad, M.
• College/School: College of Medical Veterinary and Life Sciences > School of Cardiovascular & Metabolic Health
• Journal Name: Cell Calcium
• Publisher: Elsevier
• ISSN: 01434160
• ISSN (Online): 1532-1991