Dataset Information

Calsequestrin accumulation in rough endoplasmic reticulum promotes perinuclear Ca2+ release.

ABSTRACT: Molecular mechanisms underlying Ca(2+) regulation by perinuclear endoplasmic/sarcoplasmic reticulum (ER/SR) cisternae in cardiomyocytes remain obscure. To investigate the mechanisms of changes in cardiac calsequestrin (CSQ2) trafficking on perinuclear Ca(2+) signaling, we manipulated the subcellular distribution of CSQ2 by overexpression of CSQ2-DsRed, which specifically accumulates in the perinuclear rough ER. Adult ventricular myocytes were infected with adenoviruses expressing CSQ2-DsRed, CSQ2-WT, or empty vector. We found that perinuclear enriched CSQ2-DsRed, but not normally distributed CSQ2-WT, enhanced nuclear Ca(2+) transients more potently than cytosolic Ca(2+) transients. Overexpression of CSQ2-DsRed produced more actively propagating Ca(2+) waves from perinuclear regions than did CSQ2-WT. Activities of the SR/ER Ca(2+)-ATPase and ryanodine receptor type 2, but not inositol 1,4,5-trisphosphate receptor type 2, were required for the generation of these perinuclear initiated Ca(2+) waves. In addition, CSQ2-DsRed was more potent than CSQ2-WT in inducing cellular hypertrophy in cultured neonatal cardiomyocytes. Our data demonstrate for the first time that CSQ2 retention in the rough ER/perinuclear region promotes perinuclear Ca(2+) signaling and predisposes to ryanodine receptor type 2-mediated Ca(2+) waves from CSQ2-enriched perinuclear compartments and myocyte hypotrophy. These findings provide new insights into the mechanism of CSQ2 in Ca(2+) homeostasis, suggesting that rough ER-localized Ca(2+) stores can operate independently in raising levels of cytosolic/nucleoplasmic Ca(2+) as a source of Ca(2+) for Ca(2+)-dependent signaling in health and disease.

SUBMITTER: Guo A

PROVIDER: S-EPMC3351355 | biostudies-literature | 2012 May

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Calsequestrin accumulation in rough endoplasmic reticulum promotes perinuclear Ca2+ release.

Guo Ang A Cala Steven E SE Song Long-Sheng LS

The Journal of biological chemistry 20120328 20

Molecular mechanisms underlying Ca(2+) regulation by perinuclear endoplasmic/sarcoplasmic reticulum (ER/SR) cisternae in cardiomyocytes remain obscure. To investigate the mechanisms of changes in cardiac calsequestrin (CSQ2) trafficking on perinuclear Ca(2+) signaling, we manipulated the subcellular distribution of CSQ2 by overexpression of CSQ2-DsRed, which specifically accumulates in the perinuclear rough ER. Adult ventricular myocytes were infected with adenoviruses expressing CSQ2-DsRed, CSQ ...[more]

PMID: 22457350

Similar Datasets

Project description:Phototransduction in Drosophila is mediated by phospholipase C (PLC) and Ca2+-permeable TRP channels, but the function of endoplasmic reticulum (ER) Ca2+ stores in this important model for Ca2+ signaling remains obscure. We therefore expressed a low affinity Ca2+ indicator (ER-GCaMP6-150) in the ER, and measured its fluorescence both in dissociated ommatidia and in vivo from intact flies of both sexes. Blue excitation light induced a rapid (tau ∼0.8 s), PLC-dependent decrease in fluorescence, representing depletion of ER Ca2+ stores, followed by a slower decay, typically reaching ∼50% of initial dark-adapted levels, with significant depletion occurring under natural levels of illumination. The ER stores refilled in the dark within 100-200 s. Both rapid and slow store depletion were largely unaffected in InsP3 receptor mutants, but were much reduced in trp mutants. Strikingly, rapid (but not slow) depletion of ER stores was blocked by removing external Na+ and in mutants of the Na+/Ca2+ exchanger, CalX, which we immuno-localized to ER membranes in addition to its established localization in the plasma membrane. Conversely, overexpression of calx greatly enhanced rapid depletion. These results indicate that rapid store depletion is mediated by Na+/Ca2+ exchange across the ER membrane induced by Na+ influx via the light-sensitive channels. Although too slow to be involved in channel activation, this Na+/Ca2+ exchange-dependent release explains the decades-old observation of a light-induced rise in cytosolic Ca2+ in photoreceptors exposed to Ca2+-free solutions.SIGNIFICANCE STATEMENT Phototransduction in Drosophila is mediated by phospholipase C, which activates TRP cation channels by an unknown mechanism. Despite much speculation, it is unknown whether endoplasmic reticulum (ER) Ca2+ stores play any role. We therefore engineered flies expressing a genetically encoded Ca2+ indicator in the photoreceptor ER. Although NCX Na+/Ca2+ exchangers are classically believed to operate only at the plasma membrane, we demonstrate a rapid light-induced depletion of ER Ca2+ stores mediated by Na+/Ca2+ exchange across the ER membrane. This NCX-dependent release was too slow to be involved in channel activation, but explains the decades-old observation of a light-induced rise in cytosolic Ca2+ in photoreceptors bathed in Ca2+-free solutions.

Project description:Guanine nucleotides have been reported to stimulate reticular Ca2+ release. By using the structure-linked latency of microsomal mannose-6-phosphate phosphatase as an index of microsomal permeability [Arion, Ballas, Lange & Wallin (1976) J. Biol. Chem. 251, 4901-4907], the effects of GTP on Ca2+ release and membrane permeability were compared in liver microsomes. In a stripped rough-microsome preparation, GTP caused a dose-dependent increase in mannose 6-phosphate permeability. Half-maximal and maximal effects were observed at 3 microM- and 10 microM-GTP respectively. The time course of the change in membrane permeability coincided with the time course of GTP-dependent Ca2+ release. This increase in microsomal permeability displayed positive to-operativity with respect to GTP (Hill coefficient = 1.8). By analogy to the GTP-dependent Ca2+ release process, guanosine 5'-[gamma-thio]triphosphate and guanosine 5'-[beta gamma-imido]-triphosphate inhibited the ability of GTP to alter microsomal permeability, but were without effect when added alone. In the presence of 50 microM-GTP, complete inhibition of the GTP-dependent increase in microsomal permeability was achieved with 10 microM-guanosine 5'-[gamma-thio]triphosphate, whereas a 25% inhibition was observed with 10 microM-guanosine 5'-[beta gamma-imido]triphosphate. In contrast with previous observations in crude microsomal preparations, GTP-dependent Ca2+ release in the stripped rough-microsome preparation did not require the addition of poly(ethylene glycol), although the latter did stimulate the rate of Ca2+ release. The ability of GTP to alter microsomal permeability was blocked by prior treatment with the thiol reagent p-hydroxymercuribenzoate; complete inhibition was observed after a 10 min exposure to 50 microM. Inhibition was reversed by subsequent treatment with dithiothreitol. The marked similarities between the two GTP-sensitive processes indicate that they may function via the same mechanism.

Dataset Information

Calsequestrin accumulation in rough endoplasmic reticulum promotes perinuclear Ca2+ release.

Publications

Calsequestrin accumulation in rough endoplasmic reticulum promotes perinuclear Ca2+ release.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets