Maier Peter, Rathfelder Nicole, Maeder Celine I, Colombelli Julien, Stelzer Ernst H K, Knop Michael
EMBL, Cell Biology and Biophysics Unit, Heidelberg, Germany.
EMBO J. 2008 Sep 17;27(18):2363-74. doi: 10.1038/emboj.2008.168. Epub 2008 Aug 28.
Precise control over organelle shapes is essential for cellular organization and morphogenesis. During yeast meiosis, prospore membranes (PSMs) constitute bell-shaped organelles that enwrap the postmeiotic nuclei leading to the cellularization of the mother cell's cytoplasm and to spore formation. Here, we analysed how the PSMs acquire their curved bell-shaped structure. We discovered that two antagonizing forces ensure PSM shaping and proper closure during cytokinesis. The Ssp1p-containing coat at the leading edge of the PSM generates a pushing force, which is counteracted by a novel pathway, the spore membrane-bending pathway (SpoMBe). Using genetics, we found that Sma2p and Spo1p, a phospholipase, as well as several GPI-anchored proteins belong to the SpoMBe pathway. They exert a force all along the membrane, responsible for membrane bending during PSM biogenesis and for PSM closure during cytokinesis. We showed that the SpoMBe pathway involves asymmetric distribution of Sma2p and does not involve a GPI-protein-containing matrix. Rather, repulsive forces generated by asymmetrically distributed and dynamically moving GPI-proteins are suggested as the membrane-bending principle.
精确控制细胞器形状对于细胞组织和形态发生至关重要。在酵母减数分裂过程中，前孢子膜（PSM）构成钟形细胞器，包裹减数分裂后的细胞核，导致母细胞细胞质细胞化并形成孢子。在这里，我们分析了PSM如何获得其弯曲的钟形结构。我们发现两种拮抗力量确保了胞质分裂期间PSM的塑形和正确闭合。PSM前沿含Ssp1p的包被产生一种推力，而一种新的途径——孢子膜弯曲途径（SpoMBe）可抵消这种推力。通过遗传学方法，我们发现Sma2p和磷脂酶Spo1p以及几种糖基磷脂酰肌醇（GPI）锚定蛋白属于SpoMBe途径。它们沿着膜施加一种力，负责PSM生物发生期间的膜弯曲以及胞质分裂期间的PSM闭合。我们表明，SpoMBe途径涉及Sma2p的不对称分布，且不涉及含GPI蛋白的基质。相反，由不对称分布且动态移动的GPI蛋白产生的排斥力被认为是膜弯曲的原理。
