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Marcucci L, Nogara L, Canato M, Germinario E, Raffaello A, Carraro M, Bernardi P, Pietrangelo L, Boncompagni S, Protasi F, Paolocci N, Reggiani C. Mitochondria can substitute for parvalbumin to lower cytosolic calcium levels in the murine fast skeletal muscle. Acta Physiol (Oxf) 2024; 240:e14208. [PMID: 39077881 DOI: 10.1111/apha.14208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 07/09/2024] [Accepted: 07/15/2024] [Indexed: 07/31/2024]
Abstract
AIM Parvalbumin (PV) is a primary calcium buffer in mouse fast skeletal muscle fibers. Previous work showed that PV ablation has a limited impact on cytosolic Ca2+ ([Ca2+]cyto) transients and contractile response, while it enhances mitochondrial density and mitochondrial matrix-free calcium concentration ([Ca2+]mito). Here, we aimed to quantitatively test the hypothesis that mitochondria act to compensate for PV deficiency. METHODS We determined the free Ca2+ redistribution during a 2 s 60 Hz tetanic stimulation in the sarcoplasmic reticulum, cytosol, and mitochondria. Via a reaction-diffusion Ca2+ model, we quantitatively evaluated mitochondrial uptake and storage capacity requirements to compensate for PV lack and analyzed possible extracellular export. RESULTS [Ca2+]mito during tetanic stimulation is greater in knock-out (KO) (1362 ± 392 nM) than in wild-type (WT) (855 ± 392 nM), p < 0.05. Under the assumption of a non-linear intramitochondrial buffering, the model predicts an accumulation of 725 μmoles/L fiber (buffering ratio 1:11 000) in KO, much higher than in WT (137 μmoles/L fiber, ratio 1:4500). The required transport rate via mitochondrial calcium uniporter (MCU) reaches 3 mM/s, compatible with available literature. TEM images of calcium entry units and Mn2+ quenching showed a greater capacity of store-operated calcium entry in KO compared to WT. However, levels of [Ca2+]cyto during tetanic stimulation were not modulated to variations of extracellular calcium. CONCLUSIONS The model-based analysis of experimentally determined calcium distribution during tetanic stimulation showed that mitochondria can act as a buffer to compensate for the lack of PV. This result contributes to a better understanding of mitochondria's role in modulating [Ca2+]cyto in skeletal muscle fibers.
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Affiliation(s)
- Lorenzo Marcucci
- Department of Biomedical Sciences, University of Padova, Padova, Italy
- Center for Biosystems Dynamics Research, RIKEN, Suita, Japan
| | - Leonardo Nogara
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Marta Canato
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Elena Germinario
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Anna Raffaello
- Department of Biomedical Sciences, University of Padova, Padova, Italy
- Myology Center, University of Padova, Padova, Italy
| | - Michela Carraro
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Paolo Bernardi
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Laura Pietrangelo
- CAST, Center for Advanced Studies and Technology, University G. d'Annunzio of Chieti-Pescara, Chieti, Italy
- DMSI, Department of Medicine and Aging Sciences, University G. d'Annunzio of Chieti-Pescara, Chieti, Italy
| | - Simona Boncompagni
- CAST, Center for Advanced Studies and Technology, University G. d'Annunzio of Chieti-Pescara, Chieti, Italy
- DNICS, Department of Neuroscience and Clinical Sciences, University G. d'Annunzio of Chieti-Pescara, Chieti, Italy
| | - Feliciano Protasi
- CAST, Center for Advanced Studies and Technology, University G. d'Annunzio of Chieti-Pescara, Chieti, Italy
- DMSI, Department of Medicine and Aging Sciences, University G. d'Annunzio of Chieti-Pescara, Chieti, Italy
| | - Nazareno Paolocci
- Department of Biomedical Sciences, University of Padova, Padova, Italy
- Division of Cardiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Carlo Reggiani
- Department of Biomedical Sciences, University of Padova, Padova, Italy
- Science and Research Center Koper, Institute for Kinesiology Research, Koper, Slovenia
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Bolaños P, Calderón JC. Excitation-contraction coupling in mammalian skeletal muscle: Blending old and last-decade research. Front Physiol 2022; 13:989796. [PMID: 36117698 PMCID: PMC9478590 DOI: 10.3389/fphys.2022.989796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 08/08/2022] [Indexed: 11/13/2022] Open
Abstract
The excitation–contraction coupling (ECC) in skeletal muscle refers to the Ca2+-mediated link between the membrane excitation and the mechanical contraction. The initiation and propagation of an action potential through the membranous system of the sarcolemma and the tubular network lead to the activation of the Ca2+-release units (CRU): tightly coupled dihydropyridine and ryanodine (RyR) receptors. The RyR gating allows a rapid, massive, and highly regulated release of Ca2+ from the sarcoplasmic reticulum (SR). The release from triadic places generates a sarcomeric gradient of Ca2+ concentrations ([Ca2+]) depending on the distance of a subcellular region from the CRU. Upon release, the diffusing Ca2+ has multiple fates: binds to troponin C thus activating the contractile machinery, binds to classical sarcoplasmic Ca2+ buffers such as parvalbumin, adenosine triphosphate and, experimentally, fluorescent dyes, enters the mitochondria and the SR, or is recycled through the Na+/Ca2+ exchanger and store-operated Ca2+ entry (SOCE) mechanisms. To commemorate the 7th decade after being coined, we comprehensively and critically reviewed “old”, historical landmarks and well-established concepts, and blended them with recent advances to have a complete, quantitative-focused landscape of the ECC. We discuss the: 1) elucidation of the CRU structures at near-atomic resolution and its implications for functional coupling; 2) reliable quantification of peak sarcoplasmic [Ca2+] using fast, low affinity Ca2+ dyes and the relative contributions of the Ca2+-binding mechanisms to the whole concert of Ca2+ fluxes inside the fibre; 3) articulation of this novel quantitative information with the unveiled structural details of the molecular machinery involved in mitochondrial Ca2+ handing to understand how and how much Ca2+ enters the mitochondria; 4) presence of the SOCE machinery and its different modes of activation, which awaits understanding of its magnitude and relevance in situ; 5) pharmacology of the ECC, and 6) emerging topics such as the use and potential applications of super-resolution and induced pluripotent stem cells (iPSC) in ECC. Blending the old with the new works better!
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Affiliation(s)
- Pura Bolaños
- Laboratory of Cellular Physiology, Centre of Biophysics and Biochemistry, Venezuelan Institute for Scientific Research (IVIC), Caracas, Venezuela
| | - Juan C. Calderón
- Physiology and Biochemistry Research Group-PHYSIS, Faculty of Medicine, University of Antioquia, Medellín, Colombia
- *Correspondence: Juan C. Calderón,
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Reggiani C, Marcucci L. A controversial issue: Can mitochondria modulate cytosolic calcium and contraction of skeletal muscle fibers? J Gen Physiol 2022; 154:213356. [PMID: 35849108 PMCID: PMC9297197 DOI: 10.1085/jgp.202213167] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Mitochondria are characterized by a high capacity to accumulate calcium thanks to the electrochemical gradient created by the extrusion of protons in the respiratory chain. Thereby calcium can enter crossing the inner mitochondrial membrane via MCU complex, a high-capacity, low-affinity transport mechanism. Calcium uptake serves numerous purposes, among them the regulation of three dehydrogenases of the citric cycle, apoptosis via permeability transition, and, in some cell types, modulation of cytosolic calcium transients. This Review is focused on mitochondrial calcium uptake in skeletal muscle fibers and aims to reanalyze its functional impact. In particular, we ask whether mitochondrial calcium uptake is relevant for the control of cytosolic calcium transients and therefore of contractile performance. Recent data suggest that this may be the case, at least in particular conditions, as modified expression of MCU complex subunits or of proteins involved in mitochondrial dynamics and ablation of the main cytosolic calcium buffer, parvalbumin.
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Affiliation(s)
- Carlo Reggiani
- Department of Biomedical Sciences, University of Padova, Padova, Italy,Science and Research Center Koper, Institute for Kinesiology Research, Koper, Slovenia,Correspondence to Carlo Reggiani:
| | - Lorenzo Marcucci
- Department of Biomedical Sciences, University of Padova, Padova, Italy,Center for Biosystems Dynamics Research, RIKEN, Suita, Japan
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