Department of Life Science, Chung-Ang University, Seoul, 06974, Republic of Korea.
J Microbiol. 2020 Sep;58(9):805-811. doi: 10.1007/s12275-020-0288-9. Epub 2020 Sep 1.
Cryptococcus neoformans is an opportunistic fungal pathogen causing cryptococcal meningoencephalitis. Interestingly, the cell wall of C. neoformans contains chitosan, which is critical for its virulence and persistence in the mammalian host. C. neoformans (H99) has three chitin deacetylases (CDAs), which convert chitin to chitosan. Herein, the classification of the chitin-related protein (CRP) family focused on cryptococcal CDAs was analyzed by phylogenetics, evolutionary pressure (d/d), and 3D modeling. A phylogenetic tree of 110 CRPs revealed that they can be divided into two clades, CRP I and II with bootstrap values (> 99%). CRP I clade comprises five groups (Groups 1-5) with a total of 20 genes, while CRP II clade comprises sixteen groups (Groups 6-21) with a total of 90 genes. CRP I comprises only fungal CDAs, including all three C. neoformans CDAs, whereas CRP II comprises diverse CDAs from fungi, bacteria, and amoeba, along with other carbohydrate esterase 4 family proteins. All CDAs have the signal peptide, except those from group 11. Notably, CDAs with the putative O-gycosylation site possess either the glycosylphosphatidylinositol (GPI)-anchor motif for CRP I or the chitin-binding domain (CBD) for CRP II, respectively. This evolutionary conservation strongly indicates that the O-glycosylation modification and the presence of either the GPI-anchor motif or the chitin-binding domain is important for fungal CDAs to function efficiently at the cell surface. This study reveals that C. neoformans CDAs carrying GPI anchors have evolved divergently from fungal and bacterial CDAs, providing new insights into evolution and classification of CRP family.
新型隐球菌是一种机会性真菌病原体，可引起隐球菌性脑膜脑炎。有趣的是，新型隐球菌的细胞壁含有壳聚糖，这对于其在哺乳动物宿主中的毒力和持久性至关重要。新型隐球菌（H99）有三种几丁质脱乙酰酶（CDAs），它们将几丁质转化为壳聚糖。本文通过系统发育、进化压力（d/d）和 3D 建模分析了与几丁质相关的蛋白（CRP）家族中新型隐球菌 CDAs 的分类。110 个 CRP 的系统发育树表明，它们可以分为两个分支，CRP I 和 II，bootstrap 值（>99%）。CRP I 分支包含五个组（第 1-5 组），共有 20 个基因，而 CRP II 分支包含十六个组（第 6-21 组），共有 90 个基因。CRP I 仅包含真菌 CDAs，包括新型隐球菌的所有三种 CDA，而 CRP II 包含真菌、细菌和变形虫的各种 CDAs，以及其他碳水化合物酯酶 4 家族蛋白。所有 CDA 都具有信号肽，除了第 11 组的 CDA 之外。值得注意的是，具有假定的 O-糖基化位点的 CDA 分别具有 CRP I 的糖基磷脂酰肌醇（GPI）锚定基序或 CRP II 的几丁质结合结构域（CBD）。这种进化保守性强烈表明，O-糖基化修饰以及 GPI 锚定基序或几丁质结合结构域的存在对于真菌 CDA 在细胞表面有效发挥功能非常重要。本研究表明，携带 GPI 锚的新型隐球菌 CDA 与真菌和细菌的 CDA 已经从进化上分化开来，为 CRP 家族的进化和分类提供了新的见解。
