Temperature and pH effects on Ca2+ sensitivity of cardiac myofibrils: a comparison of trout with mammals

Churcott, C. S.; Moyes, Christopher D.; Bressler, Bernard; Baldwin, K. M.; Tibbits, Glen F.

doi:10.1152/ajpregu.1994.267.1.r62

Cited by 47 publications

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“…Specifically, an acute decrease in temperature reduces the Ca 2+ sensitivity of the contractile element and this translates into a reduction in force generation (Churcott et al, 1994;Harrison and Bers, 1990), and limits the capacity of the heart to pump blood around the body. The ability of many temperate fish species to maintain cardiac function at low temperatures following seasonal acclimation provides an excellent opportunity to study mechanisms of thermal acclimation .…”

Section: Introductionmentioning

confidence: 99%

Cold acclimation increases cardiac myofilament function and ventricular pressure generation in trout

Klaiman

Pyle

Gillis

2014

Journal of Experimental Biology

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Reducing temperature below the optimum of most vertebrate hearts impairs contractility and reduces organ function. However, a number of fish species, including the rainbow trout, can seasonally acclimate to low temperature. Such ability requires modification of physiological systems to compensate for the thermodynamic effects of temperature on biological processes. The current study tested the hypothesis that rainbow trout compensate for the direct effect of cold temperature by increasing cardiac contractility during cold acclimation. We examined cardiac contractility, following thermal acclimation (4, 11 and 17°C), by measuring the Ca 2+ sensitivity of force generation by chemically skinned cardiac trabeculae as well as ventricular pressure generation using a modified Langendorff preparation. We demonstrate, for the first time, that the Ca 2+ sensitivity of force generation was significantly higher in cardiac trabeculae from 4°C-acclimated trout compared with those acclimated to 11 or 17°C, and that this functional change occurred in parallel with a decrease in the level of cardiac troponin T phosphorylation. In addition, we show that the magnitude and rate of ventricular pressure generation was greater in hearts from trout acclimated to 4°C compared with those from animals acclimated to 11 or 17°C. Taken together, these results suggest that enhanced myofilament function, caused by modification of existing contractile proteins, is at least partially responsible for the observed increase in pressure generation after acclimation to 4°C. In addition, by examining the phenotypic plasticity of a comparative model we have identified a strategy, used in vivo, by which the force-generating capacity of cardiac muscle can be increased.

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Section: Introductionmentioning

confidence: 99%

Cold acclimation increases cardiac myofilament function and ventricular pressure generation in trout

Klaiman

Pyle

Gillis

2014

Journal of Experimental Biology

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“…Functional comparison of cardiac myofibrils from mammals and rainbow trout suggests that trout cardiac muscle has a higher inherent Ca 2ϩ affinity (6). It is thought that this higher affinity facilitates cardiac function at the low temperatures (0-20°C) normally experienced by this fish (6).…”

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confidence: 99%

Sequence mutations in teleost cardiac troponin C that are permissive of high Ca²⁺affinity of site II

Gillis

Tibbits

2003

American Journal of Physiology-Cell Physiology

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Cardiac myofibrils isolated from trout heart have been demonstrated to have a higher sensitivity for Ca2+ than mammalian cardiac myofibrils. Using cardiac troponin C (cTnC) cloned from trout and mammalian hearts, we have previously demonstrated that this comparatively high Ca2+ sensitivity is due, in part, to trout cTnC (ScTnC) having twice the Ca2+ affinity of mammalian cTnC (McTnC) over a broad range of temperatures. The amino acid sequence of ScTnC is 92% identical to McTnC. To determine the residues responsible for the high Ca2+ affinity, the function of a number of ScTnC and McTnC mutants was characterized by monitoring an intrinsic fluorescent reporter that monitors Ca2+ binding to site II (F27W). The removal of the COOH terminus (amino acids 90–161) from ScTnC and McTnC maintained the difference in Ca2+ affinity between the truncated cTnC isoforms (ScNTnC and McNTnC). The replacement of Gln29 and Asp30 in ScNTnC with the corresponding residues from McNTnC, Leu and Gly, respectively, reduced Ca2+ affinity to that of McNTnC. These results demonstrate that Gln29 and Asp30 in ScTnC are required for the high Ca2+ affinity of site II.

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“…To identify the mechanisms responsible for the high sensitivity of trout cardiac myofibrils, we have cloned and sequenced cardiac troponin C (cTnC) 1 from the trout heart (ScTnC) (2). The amino acid sequence of this protein is 93% identical to mammalian (human/bovine/porcine isoform) cTnC (McTnC) (2).…”

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Effect of Temperature and the F27W Mutation on the Ca²⁺ Activated Structural Transition of Trout Cardiac Troponin C

et al. 2003

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The Ca 2+ sensitivity of cardiac contractile element is reduced at lower temperatures, in contrast to that in fast skeletal muscle. Cardiac troponin C (cTnC) replacement in mammalian skinned fibers showed that TnC plays a critical role in this phenomenon (Harrison and Bers, (1990), Am. J. Physiol. 258, C282-8). Understanding the differences in affinity and structure between cTnCs from cold-adapted ectothermic species and mammals may bring new insights into how the different isoforms provide different resistances to cold. We followed the Ca 2+ titration to the regulatory domain of rainbow trout cTnC by NMR (wild type at 7 and 30°C and F27W mutant at 30°C) and fluorescence (F27W mutant, at 7 and 30°C) spectroscopies. Using NMR spectroscopy, we detected Ca 2+ binding to site I of trout cTnC at high concentrations. This places trout cTnC between mammalian cTnC, in which site I is completely inactive, and skeletal TnC, in which site I binds Ca 2+ during muscle activation, and which is not as much affected by lower temperatures. This binding was seen both at 7 and at 30°C. Despite the low Ca 2+ affinity, trout TnC site I may increase the likelihood of an opening of the regulatory domain, thus increasing the affinity for TnI. This way, it may be responsible for trout cTnC's capacity to function at lower temperatures.Functional comparison of mammalian cardiac myofibrils with those isolated from trout reveal that trout cardiac myofibrils were more sensitive to Ca 2+ as reflected in their ability to generate half-maximal tension at lower [Ca 2+ ] (1). To identify the mechanisms responsible for the high sensitivity of trout cardiac myofibrils, we have cloned and sequenced cardiac troponin C (cTnC) 1 from the trout heart (ScTnC) (2). The amino acid sequence of this protein is 93% identical to mammalian (human/bovine/porcine isoform) cTnC (McTnC) (2). Using F27W mutants in fluorescence studies, we have demonstrated that site II of ScTnC has twice the Ca 2+ affinity of McTnC (3). We believe, therefore, that the higher Ca 2+ sensitivity of the trout cardiac myofilaments is a consequence of the high Ca 2+ affinity of ScTnC as it is the binding of Ca 2+ to cTnC that initiates the contractile reaction and regulates myocyte contractility.When activated by Ca 2+

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Temperature and pH effects on Ca2+ sensitivity of cardiac myofibrils: a comparison of trout with mammals

Cited by 47 publications

References 0 publications

Cold acclimation increases cardiac myofilament function and ventricular pressure generation in trout

Cold acclimation increases cardiac myofilament function and ventricular pressure generation in trout

Sequence mutations in teleost cardiac troponin C that are permissive of high Ca²⁺affinity of site II

Effect of Temperature and the F27W Mutation on the Ca²⁺ Activated Structural Transition of Trout Cardiac Troponin C

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Temperature and pH effects on Ca2+ sensitivity of cardiac myofibrils: a comparison of trout with mammals

Cited by 47 publications

References 0 publications

Cold acclimation increases cardiac myofilament function and ventricular pressure generation in trout

Cold acclimation increases cardiac myofilament function and ventricular pressure generation in trout

Sequence mutations in teleost cardiac troponin C that are permissive of high Ca2+affinity of site II

Effect of Temperature and the F27W Mutation on the Ca2+ Activated Structural Transition of Trout Cardiac Troponin C

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Resources

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Sequence mutations in teleost cardiac troponin C that are permissive of high Ca²⁺affinity of site II

Effect of Temperature and the F27W Mutation on the Ca²⁺ Activated Structural Transition of Trout Cardiac Troponin C