Departament de Bioquímica i Biologia Molecular, Facultat de Ciències Biològiques, Universitat de València, Valencia, Spain.
FEMS Yeast Res. 2010 Feb;10(1):28-37. doi: 10.1111/j.1567-1364.2009.00591.x. Epub 2009 Oct 30.
The characterization of mutant strains in the gene encoding karyopherin Kap123 has revealed several morphogenetic defects. Inactivation of KAP123 caused alterations in the actin cytoskeleton, resulting in hyperpolarization and resistance to the actin polymerization inhibitor latrunculin B. In fact, the level of actin filaments is increased in kap123 mutant cells. In addition to the defect in actin cytoskeleton, the kap123 mutant cells showed a weakened cell wall, cell lysis and a growth defect in either the presence of sodium dodecyl sulfate or at high temperatures, which is alleviated by osmotic stabilizers. These defects in cell integrity and the actin cytoskeleton suggested a relationship with the protein kinase C (PKC) cell integrity pathway. Slt2, the mitogen-activated protein kinase of the PKC cell integrity pathway, is constitutively activated in the absence of Kap123, which is consistent with the existence of cell integrity defects. Analysis of the subcellular localization of nuclear proteins involved in cell wall gene expression indicated that the localization of the Slt2 kinase and the transcription factors Rlm1, Swi6 and Paf1 was not affected by Kap123. Finally, we identified karyopherin Kap95 as the transport factor responsible for the nuclear import of Slt2 and Rlm1.
对编码核转运蛋白 Kap123 的基因突变株的特征分析揭示了几种形态发生缺陷。KAP123 的失活导致肌动蛋白细胞骨架发生改变，从而导致超极化和对肌动蛋白聚合抑制剂拉曲库林 B 的抗性。事实上，kap123 突变细胞中的肌动蛋白丝水平增加。除了肌动蛋白细胞骨架缺陷外，kap123 突变细胞还表现出细胞壁减弱、细胞裂解和在十二烷基硫酸钠存在或高温下生长缺陷，这可以通过渗透稳定剂来缓解。这些细胞完整性和肌动蛋白细胞骨架的缺陷表明与蛋白激酶 C (PKC) 细胞完整性途径有关。Slt2 是 PKC 细胞完整性途径的丝裂原激活蛋白激酶，在缺乏 Kap123 的情况下被持续激活，这与细胞完整性缺陷的存在一致。参与细胞壁基因表达的核蛋白的亚细胞定位分析表明，Slt2 激酶和转录因子 Rlm1、Swi6 和 Paf1 的定位不受 Kap123 的影响。最后，我们确定了核转运蛋白 Kap95 是负责 Slt2 和 Rlm1 核输入的转运因子。
