PDF(Pubmed)
Abstract：
The cellular surface of the pathogenic filamentous fungus Aspergillus fumigatus is enveloped in a mannose layer, featuring well-established fungal-type galactomannan and O-mannose-type galactomannan. This study reports the discovery of cell wall component in A. fumigatus mycelium, which resembles N-glycan outer chains found in yeast. The glycosyltransferases involved in its biosynthesis in A. fumigatus were identified, with a focus on two key α-(1→2)-mannosyltransferases, Mnn2 and Mnn5, and two α-(1→6)-mannosyltransferases, Mnn9 and Van1. In vitro examination revealed the roles of recombinant Mnn2 and Mnn5 in transferring α-(1→2)-mannosyl residues. Proton nuclear magnetic resonance (1H-NMR) analysis of cell wall extracts from the ∆mnn2∆mnn5 strain indicated the existence of an α-(1→6)-linked mannan backbone in the A. fumigatus mycelium, with Mnn2 and Mnn5 adding α-(1→2)-mannosyl residues to this backbone. The α-(1→6)-linked mannan backbone was absent in strains where mnn9 or van1 was disrupted in the parental ∆mnn2∆mnn5 strain in A. fumigatus. Mnn9 and Van1 functioned as α-(1→6)-linked mannan polymerases in heterodimers when co-expressed in Escherichia coli, indicating their crucial role in biosynthesizing the α-(1→6)-linked mannan backbone. Disruptions of these mannosyltransferases did not affect fungal-type galactomannan biosynthesis. This study provides insights into the complexity of fungal cell wall architecture and a better understanding of mannan biosynthesis in A. fumigatus.
OBJECTIVE: This study unravels the complexities of mannan biosynthesis in A. fumigatus, a key area for antifungal drug discovery. It reveals the presence of α-(1→6)-linked mannan structures resembling yeast N-glycan outer chains in A. fumigatus mycelium, offering fresh insights into the fungal cell wall\'s design. Key enzymes, Mnn2, Mnn5, Mnn9, and Van1, are instrumental in this process, with Mnn2 and Mnn5 adding specific mannose residues and Mnn9 and Van1 assembling the α-(1→6)-linked mannan structures. Although fungal-type galactomannan\'s presence in the cell wall is known, the existence of an α-(1→6)-linked mannan adds a new dimension to our understanding. This intricate web of mannan biosynthesis opens avenues for further exploration and enhances our understanding of fungal cell wall dynamics, paving the way for targeted drug development.
OBJECTIVE: This study unravels the complexities of mannan biosynthesis in A. fumigatus, a key area for antifungal drug discovery. It reveals the presence of α-(1→6)-linked mannan structures resembling yeast N-glycan outer chains in A. fumigatus mycelium, offering fresh insights into the fungal cell wall\'s design. Key enzymes, Mnn2, Mnn5, Mnn9, and Van1, are instrumental in this process, with Mnn2 and Mnn5 adding specific mannose residues and Mnn9 and Van1 assembling the α-(1→6)-linked mannan structures. Although fungal-type galactomannan\'s presence in the cell wall is known, the existence of an α-(1→6)-linked mannan adds a new dimension to our understanding. This intricate web of mannan biosynthesis opens avenues for further exploration and enhances our understanding of fungal cell wall dynamics, paving the way for targeted drug development.
摘要：
致病丝状真菌烟曲霉的细胞表面包裹在甘露糖层中，具有公认的真菌型半乳甘露聚糖和O-甘露糖型半乳甘露聚糖。本研究报道了烟曲霉菌丝体中细胞壁成分的发现，类似于在酵母中发现的N-聚糖外链。鉴定了烟曲霉中参与其生物合成的糖基转移酶，重点是两个关键的α-（1→2）-甘露糖基转移酶，Mnn2和Mnn5，以及两种α-(1→6)-甘露糖基转移酶，Mnn9和Van1。体外检查揭示了重组Mnn2和Mnn5在转移α-（1→2）-甘露糖基残基中的作用。来自Δmnn2Δmnn5菌株的细胞壁提取物的质子核磁共振（1H-NMR）分析表明，烟曲霉菌丝体中存在α-（1→6）连接的甘露聚糖主链，Mnn2和Mnn5向该主链添加α-（1→2）-甘露糖基残基。在烟曲霉的亲本Δmnn2Δmnnn5菌株中mnn9或van1被破坏的菌株中，不存在α-（1→6）连接的甘露聚糖主链。Mnn9和Van1在大肠杆菌中共表达时，在异源二聚体中充当α-（1→6）连接的甘露聚糖聚合酶，表明它们在生物合成α-（1→6）连接的甘露聚糖主链中的关键作用。这些甘露糖基转移酶的破坏不会影响真菌型半乳甘露聚糖的生物合成。这项研究提供了对真菌细胞壁结构复杂性的见解，并更好地了解了烟曲霉中甘露聚糖的生物合成。
目的：本研究揭示了烟曲霉中甘露聚糖生物合成的复杂性，抗真菌药物发现的关键领域。它揭示了在烟曲霉菌丝体中存在类似酵母N-聚糖外链的α-（1→6）连接的甘露聚糖结构，提供对真菌细胞壁设计的新见解。关键酶，Mnn2、Mnn5、Mnn9和Van1在这个过程中发挥了作用，Mnn2和Mnn5添加了特定的甘露糖残基，Mnn9和Van1组装了α-（1→6）连接的甘露聚糖结构。尽管已知细胞壁中存在真菌型半乳甘露聚糖，α-（1→6）连接的甘露聚糖的存在为我们的理解增加了一个新的维度。这种复杂的甘露聚糖生物合成网络为进一步探索开辟了途径，并增强了我们对真菌细胞壁动力学的理解，为靶向药物开发铺平道路。
目的：本研究揭示了烟曲霉中甘露聚糖生物合成的复杂性，抗真菌药物发现的关键领域。它揭示了在烟曲霉菌丝体中存在类似酵母N-聚糖外链的α-（1→6）连接的甘露聚糖结构，提供对真菌细胞壁设计的新见解。关键酶，Mnn2、Mnn5、Mnn9和Van1在这个过程中发挥了作用，Mnn2和Mnn5添加了特定的甘露糖残基，Mnn9和Van1组装了α-（1→6）连接的甘露聚糖结构。尽管已知细胞壁中存在真菌型半乳甘露聚糖，α-（1→6）连接的甘露聚糖的存在为我们的理解增加了一个新的维度。这种复杂的甘露聚糖生物合成网络为进一步探索开辟了途径，并增强了我们对真菌细胞壁动力学的理解，为靶向药物开发铺平道路。
