Bertran-Mas Joan, De Giorgio Ettore, Martín Nicolás, Llimargas Marta
Institut de Biologia Molecular de Barcelona, IBMB-CSIC, Department of Cells and Tissues, Parc Científic de Barcelona, Barcelona, Spain.
Institut Curie, PSL Research University, CNRS UMR3215, INSERM U934, UPMC Paris-Sorbonne, Paris, France.
PLoS Genet. 2025 Sep 8;21(9):e1011847. doi: 10.1371/journal.pgen.1011847. eCollection 2025 Sep.
Chitin is a major component of arthropod extracellular matrices, including the exoskeleton and the midgut peritrophic matrix. It plays a key role in the development, growth and viability of insects. Beyond the biological importance of this aminopolysaccharide, chitin also receives considerable attention for its practical applications in medicine and biotechnology, as it is a superior biopolymer with excellent physicochemical and mechanical properties. Chitin is synthesised and deposited extracellularly by chitin synthases. Most insects encode two types of chitin synthases: type A, which are presumed to be required for exoskeleton formation, and type B, which are thought to produce the peritrophic matrix. However, the factors that contribute to the specificity of each type of chitin synthase remain unclear. Here, we leverage the advantages of Drosophila melanogaster for functional manipulations to evaluate the mechanisms of activity and the functional requirements of Kkv (Chitin synthase A) and Chs2 (Chitin synthase B). We first demonstrate that Chs2 is expressed and required in a specific region of the larval proventriculus responsible for producing chitin in the peritrophic matrix. We then assess whether the two chitin synthases can functionally substitute for each other. Additionally, we examine their subcellular localisation in different tissues and their ability to deposit chitin in combination with known auxiliary proteins. Our results indicate that these two different chitin synthases are not functionally interchangeable and that they use distinct cellular and molecular mechanisms to deposit chitin. We suggest that the specificity of insect chitin synthases may underlie the production of chitin polymers with different properties, conferring different physiological activities to the extracellular matrices.
几丁质是节肢动物细胞外基质的主要成分，包括外骨骼和中肠围食膜。它在昆虫的发育、生长和生存能力中起着关键作用。除了这种氨基多糖的生物学重要性外，几丁质因其在医学和生物技术中的实际应用也受到了广泛关注，因为它是一种具有优异物理化学和机械性能的优质生物聚合物。几丁质由几丁质合酶在细胞外合成并沉积。大多数昆虫编码两种类型的几丁质合酶：A型，推测其参与外骨骼的形成；B型，被认为负责产生围食膜。然而，导致每种类型几丁质合酶特异性的因素仍不清楚。在这里，我们利用黑腹果蝇进行功能操作的优势，来评估Kkv（几丁质合酶A）和Chs2（几丁质合酶B）的活性机制和功能需求。我们首先证明Chs2在幼虫前胃负责在围食膜中产生几丁质的特定区域表达并发挥作用。然后，我们评估这两种几丁质合酶是否能在功能上相互替代。此外，我们研究了它们在不同组织中的亚细胞定位以及它们与已知辅助蛋白结合沉积几丁质的能力。我们的结果表明，这两种不同的几丁质合酶在功能上不可互换，它们利用不同的细胞和分子机制来沉积几丁质。我们认为昆虫几丁质合酶的特异性可能是产生具有不同性质的几丁质聚合物的基础，赋予细胞外基质不同的生理活性。
