Schöppner Philipp, Lutz Anne Pia, Lutterbach Bernard Johannes, Brückner Stefan, Essen Lars-Oliver, Mösch Hans-Ulrich
Department of Genetics, Philipps-Universität, Karl-von-Frisch-Strasse 8, 35043 Marburg, Germany.
Department of Biochemistry, Philipps-Universität, Hans-Meerwein-Strasse 4, 35043 Marburg, Germany.
J Fungi (Basel). 2022 Apr 8;8(4):379. doi: 10.3390/jof8040379.
In the yeast and other ascomycetes, the maintenance of cell wall integrity is governed by a family of plasma-membrane spanning sensors that include the Wsc-type proteins. These cell wall proteins apparently sense stress-induced mechanical forces at the cell surface and target the cell wall integrity (CWI) signaling pathway, but the structural base for their sensor function is yet unknown. Here, we solved a high-resolution crystal structure of the extracellular cysteine-rich domain (CRD) of yeast Wsc1, which shows the characteristic PAN/Apple domain fold with two of the four Wsc1 disulfide bridges being conserved in other PAN domain cores. Given the general function of PAN domains in mediating protein-protein and protein-carbohydrate interactions, this finding underpins the importance of Wsc domains in conferring sensing and localization functions. Our Wsc1 CRD structure reveals an unusually high number of surface-exposed aromatic residues that are conserved in other fungal CRDs, and can be arranged into three solvent-exposed clusters. Mutational analysis demonstrates that two of the aromatic clusters are required for conferring Wsc1-dependent resistance to the glucan synthase inhibitor caspofungin, and the chitin-binding agents Congo red and Calcofluor white. These findings suggest an essential role of surface-exposed aromatic clusters in fungal Wsc-type sensors that might include an involvement in stress-induced sensor-clustering required to elicit appropriate cellular responses via the downstream CWI pathway.
在酵母和其他子囊菌中，细胞壁完整性的维持由一类跨质膜传感器家族调控，其中包括Wsc型蛋白。这些细胞壁蛋白显然能感知细胞表面应激诱导的机械力，并靶向细胞壁完整性（CWI）信号通路，但其传感器功能的结构基础尚不清楚。在此，我们解析了酵母Wsc1细胞外富含半胱氨酸结构域（CRD）的高分辨率晶体结构，该结构显示出典型的PAN/Apple结构域折叠，四个Wsc1二硫键中的两个在其他PAN结构域核心中保守。鉴于PAN结构域在介导蛋白质-蛋白质和蛋白质-碳水化合物相互作用中的一般功能，这一发现突显了Wsc结构域在赋予传感和定位功能方面的重要性。我们的Wsc1 CRD结构揭示了在其他真菌CRD中保守的异常大量的表面暴露芳香族残基，这些残基可排列成三个溶剂暴露簇。突变分析表明，其中两个芳香族簇是赋予Wsc1对葡聚糖合酶抑制剂卡泊芬净、几丁质结合剂刚果红和荧光增白剂抗性所必需的。这些发现表明，表面暴露的芳香族簇在真菌Wsc型传感器中起着至关重要的作用，这可能包括参与应激诱导的传感器聚集，以通过下游CWI途径引发适当的细胞反应。
