Involvement of protein kinase C in the suppression of apoptosis and in polarity establishment in Aspergillus nidulans under conditions of heat stress.
Involvement of protein kinase C in the suppression of apoptosis and in polarity establishment in Aspergillus nidulans under conditions of heat stress.
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DOI：
10.1371/journal.pone.0050503
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
Horiuchi H
中科院分区：
文献类型：
--
作者：
Katayama T;Uchida H;Ohta A;Horiuchi H
pkcA基因在丝状真菌细粒曲霉中编码蛋白激酶C (PKC)，对其生存能力至关重要。然而，人们对它的功能知之甚少。为了解决这个问题，我们构建并表征了pkcA的温度敏感突变体。这些突变体的分生孢子在42°C时轻微膨胀并表现出凋亡表型。渗透稳定剂抑制了细胞凋亡表型。在这些条件下，分生孢子膨胀很大，不形成胚管。此外，未观察到F-actin的极化分布。然后，我们利用bckA的缺失突变体，bckA是酿酒酵母bck1的同源物，编码有丝分裂原激活蛋白（MAP）激酶激酶激酶，并在细胞壁完整性途径中发挥PKC下游的功能。这些突变体在42°C时表现出凋亡表型，但在渗透稳定条件下，它们在极性建立方面没有表现出缺陷。这些结果表明PkcA在热胁迫条件下的萌发过程中发挥了多种作用。其中第一个作用是抑制细胞凋亡诱导，而另一个则涉及极性的建立。前者依赖于MAP激酶级联，而后者则不依赖。此外，在热胁迫条件下，野生型菌株和bckA缺失突变体在去极化后观察到的再极化，在pkcA-ts突变体中没有观察到。这表明在这些条件下，PkcA在菌丝生长过程中也起着独立于MAP激酶级联的极性建立作用。
The pkcA gene, which encodes a protein kinase C (PKC) in the filamentous fungus Aspergillus nidulans, is essential for its viability. However, little is known about its functions. To address this issue, we constructed and characterized temperature-sensitive mutants of pkcA. The conidia of these mutants swelled slightly and exhibited apoptotic phenotypes at 42°C. The apoptotic phenotypes were suppressed by an osmotic stabilizer. Under these conditions, the conidia swelled extensively and did not form germ tubes. Moreover, polarized distribution of F-actin was not observed. We then utilized deletion mutants of bckA, an ortholog of Saccharomyces cerevisiae bck1 that encodes a mitogen-activated protein (MAP) kinase kinase kinase and functions downstream of PKC in the cell wall integrity pathway. These mutants exhibited apoptotic phenotypes at 42°C, but they did not show defects in polarity establishment under osmotically stabilized conditions. These results suggest that PkcA plays multiple roles during germination under conditions of heat stress. The first of these roles is the suppression of apoptosis induction, while the other involves polarity establishment. The former depends on the MAP kinase cascade, whereas the latter does not. In addition, repolarization, which was observed after depolarization in the wild-type strain and the bckA deletion mutant under conditions of heat stress, was not observed in the pkcA-ts mutant. This suggests that PkcA also plays role in polarity establishment during hyphal growth independent of the MAP kinase cascade under these conditions.
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