Lundin Victor F, Srayko Martin, Hyman Anthony A, Leroux Michel R
Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, Canada.
Dev Biol. 2008 Jan 1;313(1):320-34. doi: 10.1016/j.ydbio.2007.10.022. Epub 2007 Oct 24.
The efficient folding of actin and tubulin in vitro and in Saccharomyces cerevisiae is known to require the molecular chaperones prefoldin and CCT, yet little is known about the functions of these chaperones in multicellular organisms. Whereas none of the six prefoldin genes are essential in yeast, where prefoldin-independent folding of actin and tubulin is sufficient for viability, we demonstrate that reducing prefoldin function by RNAi in Caenorhabditis elegans causes defects in cell division that result in embryonic lethality. Our analyses suggest that these defects result mainly from a decrease in alpha-tubulin levels and a subsequent reduction in the microtubule growth rate. Prefoldin subunit 1 (pfd-1) mutant animals with maternally contributed PFD-1 develop to the L4 larval stage with gonadogenesis defects that include aberrant distal tip cell migration. Importantly, RNAi knockdown of prefoldin, CCT or tubulin in developing animals phenocopy the pfd-1 cell migration phenotype. Furthermore, reducing CCT function causes more severe phenotypes (compared with prefoldin knockdown) in the embryo and developing gonad, consistent with a broader role for CCT in protein folding. Overall, our results suggest that efficient chaperone-mediated tubulin biogenesis is essential in C. elegans, owing to the critical role of the microtubule cytoskeleton in metazoan development.
已知肌动蛋白和微管蛋白在体外及酿酒酵母中的有效折叠需要分子伴侣预折叠蛋白和伴侣蛋白 CCT，但对于这些伴侣蛋白在多细胞生物中的功能却知之甚少。在酵母中，六个预折叠蛋白基因无一不可或缺，在酵母中，肌动蛋白和微管蛋白不依赖预折叠蛋白的折叠足以维持生存能力，而我们证明，通过 RNA 干扰降低秀丽隐杆线虫中预折叠蛋白的功能会导致细胞分裂缺陷，进而导致胚胎致死。我们的分析表明，这些缺陷主要是由于α-微管蛋白水平降低以及随后微管生长速率下降所致。具有母源提供的 PFD-1 的预折叠蛋白亚基 1（pfd-1）突变动物发育到 L4 幼虫阶段，出现性腺发育缺陷，包括异常的远端末梢细胞迁移。重要的是，在发育中的动物中通过 RNA 干扰敲低预折叠蛋白、CCT 或微管蛋白会模拟 pfd-1 细胞迁移表型。此外，降低 CCT 的功能（与敲低预折叠蛋白相比）在胚胎和发育中的性腺中会导致更严重的表型，这与 CCT 在蛋白质折叠中更广泛的作用一致。总体而言，我们的结果表明，由于微管细胞骨架在后生动物发育中的关键作用，高效的伴侣蛋白介导的微管蛋白生物合成在秀丽隐杆线虫中至关重要。
