Annexin V Binding Perturbs the Cardiolipin Fluidity Gradient in Isolated Mitochondria. Can It Affect Mitochondrial Function?

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• 作者：Francesco M. Megli ; Marina Mattiazzi ; Teresa Di Tullio ; and Ernesto Quagliariello
• 刊名：Biochemistry
• 出版年：2000
• 出版时间：May 9, 2000
• 年：2000
• 卷：39
• 期：18
• 页码：5534 - 5542
• 全文大小：85K
• 年卷期：v.39,no.18(May 9, 2000)
• ISSN：1520-4995

文摘

The phosholipid bilayer fluidity of isolated mitochondria and phospholipid vesicles after calcium-dependent binding of annexin V was studied using EPR spectroscopy. The membranes were probed atdifferent depths by alternatively using cardiolipin, phosphatidylcholine, or phosphatidylethanolamine spinlabeled at position C-5 or C-12 or C-16 of the mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> acyl chain. Computer-aided spectral titration facilitatedobserving and quantitating the EPR spectrum from phospholipid spin labels affected by annexin binding,and spectral mobility was calibrated by comparison with standard spectra scanned at various temperatures.In most cases it was found that binding of the protein to the membranes makes the inner bilayer morerigid up to acyl position C-12 than afterward, in agreement with the previously observed effect in SUVs[Megli, F. M., Selvaggi, M., Liemann, S., Quagliariello, E., and Huber, R. (1998) Biochemistry 37, 10540-10546]. Moreover, in isolated mitochondrial membranes, cardiolipin apparently is more readily affectedthan the other main phospholipids, while in vesicles made from mitochondrial phospholipids, the differentspecies are affected in essentially the same way. This behavior is consistent with the existence of distinctcardiolipin pools in mitochondria, and with the already advanced hypothesis that these domains are thebinding site for annexin V to the isolated organelles [Megli, F. M., Selvaggi, M., De Lisi, A., andQuagliariello, E. (1995) Biochim. Biophys. Acta 1236, 273-278]. Keeping in mind the funcional importanceof cardiolipin in the mitochondrial membrane, the question is raised as to whether the observed influenceof annexin V binding to this phospholipid and its consequent local fluidity alteration might affect themitochondrial functionality, at least in vitro.