Caballero-Lima David, Sudbery Peter E
Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom.
Mol Biol Cell. 2014 Apr;25(7):1097-110. doi: 10.1091/mbc.E13-11-0688. Epub 2014 Feb 5.
The exocyst, a conserved multiprotein complex, tethers secretory vesicles before fusion with the plasma membrane; thus it is essential for cell surface expansion. In both Saccharomyces cerevisiae and mammalian cells, cell surface expansion is halted during mitosis. In S. cerevisiae, phosphorylation of the exocyst component Exo84 by Cdk1-Clb2 during mitosis causes the exocyst to disassemble. Here we show that the hyphae of the human fungal pathogen Candida albicans continue to extend throughout the whole of mitosis. We show that CaExo84 is phosphorylated by Cdk1, which is necessary for efficient hyphal extension. This action of Cdk1 depends on the hyphal-specific cyclin Hgc1, the homologue of G1 cyclins in budding yeast. Phosphorylation of CaExo84 does not alter its localization but does alter its affinity for phosphatidylserine, allowing it to recycle at the plasma membrane. The different action of Cdk1 on CaExo84 and ScExo84 is consistent with the different locations of the Cdk1 target sites in the two proteins. Thus this conserved component of polarized growth has evolved so that its phosphoregulation mediates the dramatically different patterns of growth shown by these two organisms.
外泌体是一种保守的多蛋白复合物，在分泌囊泡与质膜融合之前将其 tether；因此它对细胞表面扩张至关重要。在酿酒酵母和哺乳动物细胞中，细胞表面扩张在有丝分裂期间会停止。在酿酒酵母中，有丝分裂期间 Cdk1-Clb2 对外泌体成分 Exo84 的磷酸化会导致外泌体解体。在这里我们表明，人类真菌病原体白色念珠菌的菌丝在整个有丝分裂过程中持续延伸。我们表明 CaExo84 被 Cdk1 磷酸化，这是高效菌丝延伸所必需的。Cdk1 的这种作用取决于菌丝特异性细胞周期蛋白 Hgc1，它是芽殖酵母中 G1 细胞周期蛋白的同源物。CaExo84 的磷酸化不会改变其定位，但会改变其对磷脂酰丝氨酸的亲和力，使其能够在质膜上循环利用。Cdk1 对 CaExo84 和 ScExo84 的不同作用与这两种蛋白质中 Cdk1 靶位点的不同位置一致。因此，这种极化生长的保守成分已经进化，以便其磷酸化调节介导这两种生物体所显示的截然不同的生长模式。
