Dataset Information

Direct in vivo monitoring of sarcoplasmic reticulum Ca2+ and cytosolic cAMP dynamics in mouse skeletal muscle.

ABSTRACT: Skeletal muscle contraction depends on the release of Ca(2+) from the sarcoplasmic reticulum (SR), but the dynamics of the SR free Ca(2+) concentration ([Ca(2+)](SR)), its modulation by physiological stimuli such as catecholamines, and the concomitant changes in cAMP handling have never been directly determined. We used two-photon microscopy imaging of GFP-based probes expressed in mouse skeletal muscles to monitor, for the first time in a live animal, the dynamics of [Ca(2+)](SR) and cAMP. Our data, which were obtained in highly physiological conditions, suggest that free [Ca(2+)](SR) decreases by approximately 50 microM during single twitches elicited through nerve stimulation. We also demonstrate that cAMP levels rise upon beta-adrenergic stimulation, leading to an increased efficacy of the Ca(2+) release/reuptake cycle during motor nerve stimulation.

SUBMITTER: Rudolf R

PROVIDER: S-EPMC2063810 | biostudies-other | 2006 Apr

REPOSITORIES: biostudies-other

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Direct in vivo monitoring of sarcoplasmic reticulum Ca2+ and cytosolic cAMP dynamics in mouse skeletal muscle.

Rudolf Rüdiger R Magalhães Paulo J PJ Pozzan Tullio T

The Journal of cell biology 20060417 2

Skeletal muscle contraction depends on the release of Ca(2+) from the sarcoplasmic reticulum (SR), but the dynamics of the SR free Ca(2+) concentration ([Ca(2+)](SR)), its modulation by physiological stimuli such as catecholamines, and the concomitant changes in cAMP handling have never been directly determined. We used two-photon microscopy imaging of GFP-based probes expressed in mouse skeletal muscles to monitor, for the first time in a live animal, the dynamics of [Ca(2+)](SR) and cAMP. Our ...[more]

PMID: 16618815

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Project description:Variations of free calcium concentration ([Ca2+]) are powerful intracellular signals, controlling contraction as well as metabolism in muscle cells. To fully understand the role of calcium redistribution upon excitation and contraction in skeletal muscle cells, the local [Ca2+] in different compartments needs to be taken into consideration. Fluorescent probes allow the determination of [Ca2+] in the cytosol where myofibrils are embedded, the lumen of the sarcoplasmic reticulum (SR) and the mitochondrial matrix. Previously, models have been developed describing intracellular calcium handling in skeletal and cardiac muscle cells. However, a comprehensive model describing the kinetics of the changes in free calcium concentration in these three compartments is lacking. We designed a new 3D compartmental model of the half sarcomere with radial symmetry, which accounts for diffusion of Ca2+ into the three compartments and simulates its dynamics at rest and at various rates of stimulation in mice skeletal muscle fibers. This model satisfactorily reproduces both the amplitude and time course of the variations of [Ca2+] in the three compartments in mouse fast fibers. As an illustration of the applicability of the model, we investigated the effects of Calsequestrin (CSQ) ablation. CSQ is the main Ca2+ buffer in the SR, localized in close proximity of its calcium release sites and near to the mitochondria. CSQ knock-out mice muscles still preserve a near-normal contractile behavior, but it is unclear whether this is caused by additional SR calcium buffering or a significant contribution of calcium entry from extracellular space, via stored-operated calcium entry (SOCE). The model enabled quantitative assessment of these two scenarios by comparison to measurements of local calcium in the cytosol, the SR and the mitochondria. In conclusion, the model represents a useful tool to investigate the impact of protein ablation and of pharmacological interventions on intracellular calcium dynamics in mice skeletal muscle.

Dataset Information

Direct in vivo monitoring of sarcoplasmic reticulum Ca2+ and cytosolic cAMP dynamics in mouse skeletal muscle.

Publications

Direct in vivo monitoring of sarcoplasmic reticulum Ca2+ and cytosolic cAMP dynamics in mouse skeletal muscle.

Similar Datasets

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