The utilization of different carbon sources in filamentous fungi underlies a complex regulatory network governed by signaling events of different protein kinase pathways, including the high osmolarity glycerol (HOG) and protein kinase A (PKA) pathways. This work unraveled cross-talk events between these pathways in governing the utilization of preferred (glucose) and non-preferred (xylan, xylose) carbon sources in the reference fungus Aspergillus nidulans. An initial screening of a library of 103 non-essential protein kinase (NPK) deletion strains identified several mitogen-activated protein kinases (MAPKs) to be important for carbon catabolite repression (CCR). We selected the MAPKs Ste7, MpkB, and PbsA for further characterization and show that they are pivotal for HOG pathway activation, PKA activity, CCR via regulation of CreA cellular localization and protein accumulation, as well as for hydrolytic enzyme secretion. Protein-protein interaction studies show that Ste7, MpkB, and PbsA are part of the same protein complex that regulates CreA cellular localization in the presence of xylan and that this complex dissociates upon the addition of glucose, thus allowing CCR to proceed. Glycogen synthase kinase (GSK) A was also identified as part of this protein complex and shown to potentially phosphorylate two serine residues of the HOG MAPKK PbsA. This work shows that carbon source utilization is subject to cross-talk regulation by protein kinases of different signaling pathways. Furthermore, this study provides a model where the correct integration of PKA, HOG, and GSK signaling events are required for the utilization of different carbon sources.

丝状真菌中不同碳源的利用为复杂的调节网络奠定了基础，该调节网络受不同蛋白激酶途径（包括高渗透压甘油（HOG）和蛋白激酶A（PKA）途径）的信号事件支配。这项工作揭示了控制参考真菌构巢曲霉中首选（葡萄糖）和非首选（木聚糖，木糖）碳源的利用过程中这些途径之间的串扰事件。。最初筛选了103个非必需蛋白激酶（NPK）缺失菌株的文库，确定了几种促分裂原活化蛋白激酶（MAPK）对于碳分解代谢物阻遏（CCR）具有重要意义。我们选择了MAPK Ste7，MpkB和PbsA进行进一步表征，并表明它们对于HOG途径激活，PKA活性，通过调节CreA细胞定位和蛋白质积聚以及水解酶分泌至关重要。蛋白质-蛋白质相互作用研究表明，Ste7，MpkB和PbsA是同一蛋白质复合物的一部分，该蛋白质复合物在木聚糖存在下调节CreA细胞的定位，并且该复合物在添加葡萄糖后会解离，从而使CCR得以进行。糖原合酶激酶（GSK）A也被鉴定为该蛋白复合物的一部分，并显示可能将HOG MAPKK PbsA的两个丝氨酸残基磷酸化。这项工作表明碳源的利用受到不同信号途径的蛋白激酶的串扰调节。此外，本研究提供了一个模型，其中需要利用不同碳源正确整合PKA，HOG和GSK信号事件。