Calzia Daniela, Garbarino Greta, Caicci Federico, Manni Lucia, Candiani Simona, Ravera Silvia, Morelli Alessandro, Traverso Carlo Enrico, Panfoli Isabella
Department of Pharmacy, DIFAR-Biochemistry Lab, University of Genova, Italy.
DISTAV, University of Genova, Italy.
Biochimie. 2014 Jul;102:78-82. doi: 10.1016/j.biochi.2014.02.007. Epub 2014 Feb 21.
Rod photoreceptors efficiently carry out phototransduction cascade, an energetically costly process. Our recent data in bovine rod outer segment (OS) demonstrated that ATP for phototransduction is produced by an extramitochondrial oxidative phosphorylation, thanks to the expression of the Electron Transport Chain (ETC) complexes and of F1Fo ATP synthase in disks. Here we have focused on mouse retinas, reporting the activity of ETC complexes I, II, IV assayed directly on unfixed mouse eye sections, as well as immunogold TEM analysis of fixed mouse eye sections to verify the presence of ND4L subunit of ETC complex I and subunit IV of ETC complex IV in rod OS. Data suggest the presence of functional ETC in mouse rod OS, like their bovine counterpart. The protocol here developed for in situ assay of the ETC complexes activity represents a reliable method for the detection of ETC dysfunction in mice models of retinal pathologies. In fact, the ETC is a major source of reactive oxygen intermediates, and oxidative stress, especially when ectopically expressed in the OS. In turn, oxidative stress contributes to many retinal pathologies, such as diabetic retinopathy, age related macular degeneration, photoreceptor death after retinal detachment and some forms of retinitis pigmentosa.
视杆光感受器能高效地进行光转导级联反应，这是一个耗能巨大的过程。我们最近在牛视杆外段（OS）获得的数据表明，光转导所需的ATP是通过线粒体外氧化磷酸化产生的，这得益于电子传递链（ETC）复合物和F1Fo ATP合酶在盘膜中的表达。在此，我们聚焦于小鼠视网膜，报告了直接在未固定的小鼠眼切片上检测到的ETC复合物I、II、IV的活性，以及对固定的小鼠眼切片进行免疫金透射电镜分析，以验证视杆OS中ETC复合物I的ND4L亚基和ETC复合物IV的亚基IV的存在。数据表明，小鼠视杆OS中存在功能性ETC，与牛的视杆OS类似。这里开发的用于原位检测ETC复合物活性的方法，是检测视网膜病变小鼠模型中ETC功能障碍的可靠方法。事实上，ETC是活性氧中间体的主要来源，而氧化应激，尤其是在OS中异位表达时。反过来，氧化应激会导致许多视网膜病变，如糖尿病性视网膜病变、年龄相关性黄斑变性、视网膜脱离后的光感受器死亡以及某些形式的视网膜色素变性。
