Ulrich P N, Marsh A G
College of Marine and Earth Studies, University Delaware, 700 Pilottown Road, Lewes, DE 19958, USA.
Mar Biotechnol (NY). 2009 Sep-Oct;11(5):608-18. doi: 10.1007/s10126-009-9177-2. Epub 2009 Feb 5.
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 degrees C, 18 degrees C, and 21 degrees 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 degrees 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.
当潮间带无脊椎动物暴露于温度迅速大幅变化时，其线粒体仍能继续发挥功能。为了测试硬壳蛤的线粒体生理机能在温度升高时是否会受到损害，我们使用了一种为本研究开发的新型高通量微孔板呼吸测定法，在15摄氏度、18摄氏度和21摄氏度下测量了线粒体呼吸效率。尽管在这个温度范围内磷酸化（状态3）和静息（状态4）呼吸速率未受影响，但呼吸控制率（RCR：状态3与状态4呼吸速率之比）在18摄氏度以上显著下降（p < 0.05）。RCR的下降与磷酸化效率的降低无关，这表明，虽然线粒体呼吸的有氧范围在温度升高时受到限制，但线粒体仍能继续高效地产生三磷酸腺苷。我们通过监测线粒体蛋白的磷酸化进一步研究了硬壳蛤线粒体对温度升高的反应。三种蛋白明显呈现出显著的时间和温度特异性磷酸化模式。蛋白特异性的磷酸化模式可能表明，一组蛋白激酶和磷酸酶会响应温度调节线粒体生理机能。因此，虽然硬壳蛤线粒体呼吸的有氧范围在中等温度下会降低，但特定的蛋白磷酸化反应反映了在较高温度下细胞器内启动的功能的巨大变化。
