线粒体和微管骨架相互作用的分子机制

Mitochondria are double-membrane organelles essential for cell proliferation. Mitochondria are maintained as an elongated tubular shape in the cytoplasm where they undergo constant fusion and fission. Mitochondria morphology and dynamics are critical for their functions. More importantly, mitochondrial functions are also determined by its cytoplasmic distribution and anchorage. Although studies of kinesins and dynein mediated mitochondria movement in the neuron have leaded to a general understanding of motor-dependent mitochondria distribution and anchorage, it remains to be determined a complementary motor-independent but microtubule-dependent mechanism underlying mitochondria distribution and anchorage within the cytoplasm. In our previous publication, we have shown the novel microtubule associated protein mmb1p serves as a key protein regulating the interactions between mitochondria and microtubules. Our further investigation found that mmb1p also needs receptor proteins for localizing to the microtubule and mitochondria, and such receptor proteins have been identified. In this proposal, we aim to mechanistically and functionally dissect the interactions between the receptor proteins and mmb1p. Specially, we will determine the roles of the interactions between mmb1p and the microtubule associated protein alp14p, and between mmb1p and the mitochondria outer membrane proteins dnm1p, fis1p, tom7p and mmd1p. Our work will provide mechanistic insights into understanding mitochondria-microtubule interactions, and this will further our understanding of mitochondria distribution and anchorage within the cytoplasm.

线粒体是细胞增殖所不可或缺的细胞器。线粒体功能的完整性不仅取决于自身结构形态的完整性和自身的动态性，而且决定于自身在细胞质中的准确分布和锚定。人们对线粒体在细胞质中分布和锚定的理解仅仅停留在单一的基于驱动蛋白介导的线粒体在神经元细胞中的运动和分布模型。而这一模型还不足以解释为什么大部分在细胞质中的线粒体均呈现相对静止的锚定态。我们前期的研究鉴定了参与锚定线粒体于微管的核心蛋白mmb1p，并对mmb1p介导线粒体分布的功能进行了详细的阐述。我们近期深入的研究还发现mmb1p的定位和功能实际上可能受到多种接头蛋白的调控。因此，我们建议通过整合利用酵母遗传学、生物化学、细胞生物学以及生物光子学等多种技术手段从多角度研究mmb1p与它的接头蛋白的相互作用及其细胞生物学功能，从而详细阐明线粒体与微管作用的分子机理。

线粒体是细胞的能量工厂。因此，线粒体在细胞质中的准确定位和分布不仅决定其功能行使的准确性，而且将影响与其关联的细胞器行使功能，进而最终影响细胞增殖和分裂。本项目主要研究和理解裂殖酵母线粒体在细胞质中正确定位和分布的分子基础和调控机理。研究工作瞄准我们先期鉴定的线粒体调控关键蛋白mmb1p，评估mmb1p与微管结合蛋白alp14p和线粒体蛋白dnm1p、fis1p、tom70p 、mmd1p的相互作用关系和功能。我们通过利用人工嵌合蛋白结合高分辨活细胞显微镜观察分析，阐明了线粒体与微管细胞骨架的连接是线粒体在细胞质中准确定位和分布的关键，并且该连接过程可由具有线粒体和微管双重结合特异性的单个蛋白或蛋白质复合物来完成。同时，我们的研究工作表明alp14p和线粒体蛋白dnm1p、fis1p、tom70p 、mmd1p均不是关键的调控mmb1p与微管和线粒体结合的蛋白。通过高内涵显微镜分析筛选，我们鉴定到了较多mmb1p功能相关新基因（暂命名为mmb2-5）。这些基因的缺失均导致与mmb1p缺失类似的不同程度的线粒体聚集表型。我们正在深入发掘这些基因的线粒体调控功能。综上所述，该项目的实施不仅使人们深刻地理解了线粒体如何在细胞质中准确定位和分布，而且为推动更为精细的线粒体分布调控分子机制的研究奠定了基础。