Priority Strategy of Intracellular Ca2+ Homeostasis in Skeletal Muscle Fibers during the Multiple Stresses of Hibernation

Intracellular calcium (Ca2+) homeostasis plays a vital role in the preservation of skeletal muscle. In view of the well-maintained skeletal muscle found in Daurian ground squirrels (Spermophilus dauricus) during hibernation, we hypothesized that hibernators possess unique strategies of intracellular Ca2+ homeostasis. Here, cytoplasmic, sarcoplasmic reticulum (SR), and mitochondrial Ca2+ levels, as well as the potential Ca2+ regulatory mechanisms, were investigated in skeletal muscle fibers of Daurian ground squirrels at different stages of hibernation. The results showed that cytoplasmic Ca2+ levels increased in the skeletal muscle fibers during late torpor (LT) and inter-bout arousal (IBA), and partially recovered when the animals re-entered torpor (early torpor, ET). Furthermore, compared with levels in the summer active or pre-hibernation state, the activity and protein expression levels of six major Ca2+ channels/proteins were up-regulated during hibernation, including the store-operated Ca2+ entry (SOCE), ryanodine receptor 1 (RyR1), leucine zipper-EF-hand containing transmembrane protein 1 (LETM1), SR Ca2+ ATPase 1 (SERCA1), mitochondrial calcium uniporter complex (MCU complex), and calmodulin (CALM). Among these, the increased extracellular Ca2+ influx mediated by SOCE, SR Ca2+ release mediated by RyR1, and mitochondrial Ca2+ extrusion mediated by LETM1 may be triggers for the periodic elevation in cytoplasmic Ca2+ levels observed during hibernation. Furthermore, the increased SR Ca2+ uptake through SERCA1, mitochondrial Ca2+ uptake induced by MCU, and elevated free Ca2+ binding capacity mediated by CALM may be vital strategies in hibernating ground squirrels to attenuate cytoplasmic Ca2+ levels and restore Ca2+ homeostasis during hibernation. Compared with that in LT or IBA, the decreased extracellular Ca2+ influx mediated by SOCE and elevated mitochondrial Ca2+ uptake induced by MCU may be important mechanisms for the partial cytoplasmic Ca2+ recovery in ET. Overall, under extreme conditions, hibernating ground squirrels still possess the ability to maintain intracellular Ca2+ homeostasis.

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Effect of External Calcium and other Divalent Cations on K+ Contractures in Denervated Slow Skeletal Muscle Fibers of the Frog

Journal of Biomedical and Allied Research ◽

10.37191/mapsci-2582-4937-1(2)-009 ◽

2019 ◽

Author(s):

Leonardo Hernández

Keyword(s):

Skeletal Muscle ◽

Binding Capacity ◽

Divalent Cations ◽

Muscle Fibers ◽

Free Calcium ◽

Slow Skeletal Muscle ◽

Skeletal Muscle Fibers ◽

Free Calcium Concentration ◽

Chronic Denervation ◽

Denervated Muscles

The influence of Ca2+ and other divalent cations on contractile responses of slow skeletal muscle fibers of the frog (Rana pipiens) under conditions of chronic denervation was investigated.Isometric tension was recorded from slow bundles of normal and denervated cruralis muscle in normal solution and in solutions with free calcium concentration solution or in solutions where other divalent cations (Sr2+, Ni2+, Co2+ or Mn2+) substituted for calcium. In the second week after nerve section, in Ca2+-free solutions, we observed that contractures (evoked from 40 to 80 mM-K+) of non-denervated muscles showed significantly higher tensions (p<0.05), than those from denervated bundles. Likewise, in solutions where calcium was substituted by all divalent cations tested, with exception of Mn2+, the denervated bundles displayed lower tension than non-denervated, also in the second week of denervation. In this case, the Ca2+ substitution by Sr2+ caused the higher decrease in tension, followed by Co2+ and Ni2+, which were different to non-denervated bundles, as the lowest tension was developed by Mn2+, followed by Co2+, and then Ni2+ and Sr2+. After the third week, we observed a recovery in tension. These results suggest that denervation altering the binding capacity to divalent cations of the voltage sensor.

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Functional reconstitution of the mitochondrial Ca2+/H+ antiporter Letm1

The Journal of General Physiology ◽

10.1085/jgp.201311096 ◽

2013 ◽

Vol 143 (1) ◽

pp. 67-73 ◽

Cited By ~ 75

Author(s):

Ming-Feng Tsai ◽

Dawei Jiang ◽

Linlin Zhao ◽

David Clapham ◽

Christopher Miller

Keyword(s):

Transport Mechanism ◽

Turnover Rate ◽

Leucine Zipper ◽

Transmembrane Protein ◽

Ruthenium Red ◽

Mitochondrial Calcium Uniporter ◽

Mitochondrial Inner Membrane ◽

Calcium Uniporter ◽

Ef Hand ◽

Inner Membrane Protein

The leucine zipper, EF hand–containing transmembrane protein 1 (Letm1) gene encodes a mitochondrial inner membrane protein, whose depletion severely perturbs mitochondrial Ca2+ and K+ homeostasis. Here we expressed, purified, and reconstituted human Letm1 protein in liposomes. Using Ca2+ fluorophore and 45Ca2+-based assays, we demonstrate directly that Letm1 is a Ca2+ transporter, with apparent affinities of cations in the sequence of Ca2+ ≈ Mn2+ > Gd3+ ≈ La3+ > Sr2+ >> Ba2+, Mg2+, K+, Na+. Kinetic analysis yields a Letm1 turnover rate of 2 Ca2+/s and a Km of ∼25 µM. Further experiments show that Letm1 mediates electroneutral 1 Ca2+/2 H+ antiport. Letm1 is insensitive to ruthenium red, an inhibitor of the mitochondrial calcium uniporter, and CGP-37157, an inhibitor of the mitochondrial Na+/Ca2+ exchanger. Functional properties of Letm1 described here are remarkably similar to those of the H+-dependent Ca2+ transport mechanism identified in intact mitochondria.

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Novel findings on ultrastructural protection of skeletal muscle fibers during hibernation of Daurian ground squirrels: Mitochondria, nuclei, cytoskeleton, glycogen

Journal of Cellular Physiology ◽

10.1002/jcp.28008 ◽

2019 ◽

Vol 234 (8) ◽

pp. 13318-13331 ◽

Cited By ~ 6

Author(s):

Zhe Wang ◽

Shan‐Feng Jiang ◽

Jin Cao ◽

Kun Liu ◽

Shen‐Hui Xu ◽

...

Keyword(s):

Skeletal Muscle ◽

Muscle Fibers ◽

Ground Squirrels ◽

Skeletal Muscle Fibers

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Up-regulation of sarcoplasmic reticulum function protects skeletal muscle against cytoplasmic calcium overload during hibernation in ground squirrels

10.21203/rs.2.22469/v1 ◽

2020 ◽

Author(s):

Zhe Wang ◽

Jie Zhang ◽

XiuFeng Ma ◽

Hui Chang ◽

Xin Peng ◽

...

Keyword(s):

Skeletal Muscle ◽

Sarcoplasmic Reticulum ◽

Protein Expression ◽

Calcium Binding ◽

Muscle Fibers ◽

Ground Squirrels ◽

Calcium Overload ◽

Free Calcium ◽

Cytoplasmic Calcium ◽

Skeletal Muscle Fibers

Abstract We investigated the potential mechanism of the (sarcoplasmic reticulum) SR in maintenance of calcium (Ca2+) homeostasis of slow-twitch muscle (soleus, SOL), fast-twitch muscle (extensor digitorum longus, EDL) and mixed muscle (gastrocnemius, GAS) in hibernating ground squirrels (Spermophilus dauricus). Results showed that cytosolic and SR Ca2+ concentrations in distinct skeletal muscle fibers increased and decreased during late torpor, respectively, but both returned to summer-active levels during early torpor. Ryanodine receptor1 (RyR1) and sarco/endoplasmic reticulum Ca2+ ATPase isoform 1 (SERCA1) protein expression increased during hibernation. Up-regulation factors of SERCA activity: Phospholamban phosphorylation increased in the SOL and GAS, β-adrenergic receptor-2 protein expression increased in the GAS, and calmodulin kinase-2 phosphorylation increased in the SOL during hibernation. Down-regulation factors of SERCA activity: Sarcolipin and SERCA1 co-localization decreased in the EDL and GAS. These data suggest that SERCA activity in skeletal muscle fibers increases likely during hibernation. FKBP12/calsequestrin1 (negative regulatory factors of RyR1) and RyR1 co-localization decreased in the GAS, indicating that the RyR1 channel opening probability increased during hibernation. Dihydropyridine receptors protein expression and its co-localization with RYR1 decreased during hibernation prompts that the contractility of skeletal muscle was weakened. Protein expression of Ca2+-binding proteins calsequestrin1 and calmodulin increased indicating that the ability of intracellular free calcium binding increased during whole hibernation period. These findings confirm that the release, uptake, and binding of free Ca2+ in the SR were enhanced in different skeletal muscles during hibernation. Up-regulation of muscular sarcoplasmic reticulum function protects skeletal muscle fibers against cytoplasmic calcium overload during hibernation in ground squirrels.

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Gene expression changes of single skeletal muscle fibers in response to modulation of the mitochondrial calcium uniporter (MCU)

Genomics Data ◽

10.1016/j.gdata.2015.05.023 ◽

2015 ◽

Vol 5 ◽

pp. 64-67 ◽

Cited By ~ 10

Author(s):

Francesco Chemello ◽

Cristina Mammucari ◽

Gaia Gherardi ◽

Rosario Rizzuto ◽

Gerolamo Lanfranchi ◽

...

Keyword(s):

Gene Expression ◽

Skeletal Muscle ◽

Muscle Fibers ◽

Mitochondrial Calcium ◽

Mitochondrial Calcium Uniporter ◽

Calcium Uniporter ◽

Skeletal Muscle Fibers

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The “KIMWIPE” Effect in Ultra-Thin Cryosections

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100119119 ◽

1985 ◽

Vol 43 ◽

pp. 458-459

Author(s):

I. Taylor ◽

P. Ingram ◽

J.R. Sommer

Keyword(s):

Skeletal Muscle ◽

Electrical Stimulation ◽

Muscle Fibers ◽

Ice Crystals ◽

Crystal Formation ◽

Ice Crystal ◽

Thin Sections ◽

Skeletal Muscle Fibers ◽

Freeze Dried ◽

Ice Crystal Formation

In studying quick-frozen single intact skeletal muscle fibers for structural and microchemical alterations that occur milliseconds, and fractions thereof, after electrical stimulation, we have developed a method to compare, directly, ice crystal formation in freeze-substituted thin sections adjacent to all, and beneath the last, freeze-dried cryosections. We have observed images in the cryosections that to our knowledge have not been published heretofore (Figs.1-4). The main features are that isolated, sometimes large regions of the sections appear hazy and have much less contrast than adjacent regions. Sometimes within the hazy regions there are smaller areas that appear crinkled and have much more contrast. We have also observed that while the hazy areas remain still, the regions of higher contrast visibly contract in the beam, often causing tears in the sections that are clearly not caused by ice crystals (Fig.3, arrows).

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NOS I IN PIGEON SKELETAL MUSCLE FIBERS*

The Japanese Journal of Pharmacology ◽

10.1016/s0021-5198(19)41554-0 ◽

1997 ◽

Vol 75 ◽

pp. 36

Author(s):

R Gossrau ◽

Z Grozdanovic

Keyword(s):

Skeletal Muscle ◽

Muscle Fibers ◽

Skeletal Muscle Fibers

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Development of a human neuromuscular tissue-on-a-chip model on a 24-well-plate-format compartmentalized microfluidic device

Lab on a Chip ◽

10.1039/d1lc00048a ◽

2021 ◽

Author(s):

Kazuki Yamamoto ◽

Nao Yamaoka ◽

Yu Imaizumi ◽

Takunori Nagashima ◽

Taiki Furutani ◽

...

Keyword(s):

Skeletal Muscle ◽

Microfluidic Device ◽

Motor Neurons ◽

Muscle Fibers ◽

Three Dimensional ◽

Tissue Model ◽

Skeletal Muscle Fibers

A three-dimensional human neuromuscular tissue model that mimics the physically separated structures of motor neurons and skeletal muscle fibers is presented.

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