Thermal Sensitivity of Mitochondrial Respiration Efficiency and Protein Phosphorylation in the Clam Mercenaria mercenaria |
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Authors: | P N Ulrich A G Marsh |
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Institution: | (1) College of Marine and Earth Studies, University Delaware, 700 Pilottown Road, Lewes, DE 19958, USA |
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Abstract: | The mitochondria of intertidal invertebrates continue to function when organisms are exposed to rapid substantial shifts in
temperature. To test if mitochondrial physiology of the clam Mercenaria mercenaria is compromised under elevated temperatures, we measured mitochondrial respiration efficiency at 15°C, 18°C, and 21°C using
a novel, high-throughput, microplate respirometry methodology developed for this study. Though phosphorylating (state 3) and
resting (state 4) respiration rates were unaffected over this temperature range, respiratory control ratios (RCRs: ratio of
state 3 to state 4 respiration rates) decreased significantly above 18°C (p < 0.05). The drop in RCR was not associated with reduction of phosphorylation efficiency, suggesting that, while aerobic
scope of mitochondrial respiration is limited at elevated temperatures, mitochondria continue to efficiently produce adenosine
triphosphate. We further investigated the response of clam mitochondria to elevated temperatures by monitoring phosphorylation
of mitochondrial protein. Three proteins clearly demonstrated significant time- and temperature-specific phosphorylation patterns.
The protein-specific patterns of phosphorylation may suggest that a suite of protein kinases and phosphatases regulate mitochondrial
physiology in response to temperature. Thus, while aerobic scope of clam mitochondrial respiration is reduced at moderate
temperatures, specific protein phosphorylation responses reflect large shifts in function that are initiated within the organelle
at higher temperatures. |
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Keywords: | Mitochondria Temperature Respiration Protein phosphorylation |
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