Mitochondria Shape Hormonally Induced Cytoplasmic Calcium Oscillations and Modulate Exocytosis

Abstract

EXPERIMENTAL PROCEDURESPituitary Cell Isolation-Anterior pituitary glands were removed from 4 -6-week-old male rats that had been castrated at week 2 by the supplier. Rats were euthanized by placing them in an empty chamber that was then filled with CO 2 . Tissue was enzymatically dispersed (24), and cells were cultured for up to 4 days.[Ca 2ϩ ] Measurements-The loading of membrane-permeant Ca 2ϩ indicators, and subsequent photometry was described previously (8). In experiments where mitochondrial membrane potential was monitored, cells were incubated in TMRE (600 nM) for 5 min following loading with Ca 2ϩ indicators, and TMRE (100 nM) was present in the bath throughout the experiment. Corrections were applied to fluorescence signals to * This work was supported in part by National Institutes of Health Grant AR17803, by Cooperative Agreement U54 HD12629 (as part of the Specialized Cooperative Centers Program in Reproductive Research), and by funds from the the W. M. Keck Foundation. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.§ Supported by a fellowship from the Lalor Foundation and by National Institutes of Health Training Grant 2T32HD07453. To whom correspondence should be addressed: G-424 Health Sciences Bldg., Dept. of Physiology and Biophysics, University of Washington, Seattle, 1 The abbreviations used are: [Ca 2ϩ ] cyt , free cytoplasmic calcium concentration; GnRH, gonadotropin-releasing hormone; [Ca 2ϩ ] mit , free mitochondrial calcium concentration; CCCP, carbonyl cyanide m-chlorophenyl-hydrazone; IP 3 , inositol 1,4,5-trisphosphate; TMRE, tetramethylrhodamine ethyl ester.

Mitochondrial Reactive Oxygen Species Regulate Spatial Profile of Proinflammatory Responses in Lung Venular Capillaries

“…MIT uptake that augments induced Ca 2ϩ CYT increases (5,35,36). By contrast, in our experiments, blockade of Ca 2ϩ…”

“…Mitochondria regulate Ca 2ϩ CYT by both importing and exporting Ca 2ϩ across the inner membrane by means of a uniporter and a Na ϩ /Ca 2ϩ exchanger, respectively (5,35). In several cell types (35,36), the net effect is to buffer increases in Ca 2ϩ…”

Stable Interactions between Mitochondria and Endoplasmic Reticulum Allow Rapid Accumulation of Calcium in a Subpopulation of Mitochondria

“…Although this probe has been extensively used by different groups, its subcellular localization is far from ideal; most likely because of this, its use has given rise to partially contradictory results in different cell types (7)(8)(9)(10). The search for alternative calcium indicators has prompted the development of a number of genetically encoded fluorescent probes.…”

Mitochondria Recycle Ca2+ to the Endoplasmic Reticulum and Prevent the Depletion of Neighboring Endoplasmic Reticulum Regions

“…By acting as a Ca 2ϩ buffering system at these strategic locations, mitochondria can modulate the rate of Ca 2ϩ release by IP 3 receptors (21,22) or the rate of capacitative Ca 2ϩ entry through CRAC channels (20). Through this intimate connection with the calcium sources, mitochondria strongly shape calcium signals and, depending on the cellular context, can either potentiate or inhibit Ca 2ϩ oscillations (23)(24)(25)(26). Our understanding of the calcium homeostasis of intracellular compartments is still incomplete, because the highly dynamic Ca 2ϩ signals occurring within organelles are difficult to measure.…”