纤维化IV型胶原蛋白沉积在果蝇脂肪体中的正常和病理学作用

Basement membranes (BMs) are planar complexes of extracellular matrix (ECM) proteins underlying epithelial and endothelial tissues and surrounding muscles, nerves and adipocytes. BMs and their main component Collagen IV are important regulators of morphogenesis, cell signaling, wound healing, immune responses and tumor progression. Multiple interactions among BM components have been described in vitro. However, it is not known how these interactions determine the assembly of BMs into homogeneously thin sheets rather than amorphous aggregates or whether alternative modes of organization for these ECM components are possible. Besides their roles in normal developmental and physiology, a wide array of human disorders result from defects in ECM assembly or composition. Such is the case of fibrotic diseases, characterized by excessive and aberrant accumulation of BM and other ECM material triggered by damage reaction mechanisms poorly understood. The techniques available in Drosophila, coupled to conservation of BM components and little genetic redundancy, offer many advantages and opportunities to understand fibrotic aggregates and gain insights into the roles of BM components in normal and altered physiology. Taking advantage of our expertise, preliminary data and Drosophila genetic tools, I propose to study the normal and pathological roles of Collagen IV non-BM deposits. I hypothesize that non-BM Collagen IV deposits have important biological effects in both normal tissue development and pathological conditions. To test this main hypothesis, the research I propose here intends to (1) characterize the normal role of Collagen IV non-BM deposits in adipose tissue, which represent a novel form of ECM organization, (2) elucidate mechanisms by which the innate immune system reacts or suppresses reactions to ECM aggregates and (3) use both normal and pathological fibrotic aggregates as a model to test the antifibrotic potential in vivo of several Collagen-binding proteins. By demonstrating the functional importance of non-BM Collagen IV, the research I propose will uncover novel ways of ECM organization. It will also fill a long-standing gap in the understanding of the organization into tissues of adipose cells, which form true tissues despite being non-epithelial. Research proposed here will also uncover clinically-relevant ECM-immune system interactions. Finally, results from this project may have broad implications for the understanding and treatment of fibrotic diseases and other diseases involving abnormal ECM accumulation.

基膜是胞外间质（ECM）蛋白的平面复合物。它和它的主要组分IV型胶原蛋白是形态发生、细胞信号传导、创面愈合、免疫应答、和肿瘤进展的重要调控因子。基膜组分的相互作用如何决定基膜组装成均匀的薄片，而不是无规则的聚集体，或这些组分是否有其他组装模式目前未知。ECM的组装或组成缺陷导致多种疾病，如基膜和其他ECM成分过多及异常累积引起的纤维化疾病。但是，人们对引发累积的损伤反应机制知之甚少。我拟研究IV型胶原蛋白基膜外沉积物在正常和病理条件下对组织发育的作用。我计划（1）研究IV型胶原蛋白基膜外沉积物在脂肪体中的作用，而这种沉积代表了一种新的ECM整合方式，（2）阐明天然免疫系统对ECM聚集物的反应或抑制反应机制（3）用正常以及病理纤维化聚集体作为模型测试多种胶原蛋白结合蛋白的体内抗纤维化潜能。本课题将揭示ECM整合新方式，推进理解脂肪体细胞整合成脂肪体方式及医疗相关的ECM免疫系统相互作用.

基底膜是片状的细胞外基质。它们的组分参与调节形态发生、细胞信号传导、伤口愈合、免疫反应和肿瘤进展等过程。基底膜是一种紧凑的聚合物，含有层粘连蛋白、巢蛋白、胶原蛋白IV和串珠素蛋白，它们被包装在均匀的薄平面层中。虽然基底膜的形态和成分的定义十分清晰，但有许多基底膜的例子偏离了这个平面结构。事实上，基底膜组分存在于难以归类为基底膜的非平面矩阵中。在该项目中，我提议研究含有胶原蛋白IV和其他主要基底膜成分的非典型（非基底膜）基质沉积物。我假设非基底膜基质沉积物在组织发育中具有重要的生物学作用。为了验证这一假设，我提出的研究描述了几个非典型非基底膜沉积物的例子，并揭示了为基底膜提供形态、成分和功能多样性的机制。我们研究了巢蛋白敲除果蝇并发现了巢蛋白的组织特异性功能，揭示了基底膜组装的组织特异性机制(Dai et al., 2018, PLoS Genet)。通过先前的筛选性研究，我们发现spectraplakin Shot蛋白的缺失导致胶原蛋白和基质释放缺陷，进一步发现Shot参与维持基质分泌细胞中的微管组织，对于防止纤维化聚集体的形成至关重要(Sun et al., 2019, Dev Cell)。我们在果蝇翅膀中发现了另一个非典型基底膜样结构，其中非典型层粘连蛋白斑点介导背腹方向上双层翅膀基底侧的粘附(Sun et al., 2021, Cell Rep)。最后，我们发现JAK/STAT激活细胞因子可以穿过前胸腺的基底膜，在组织损伤的全身反应中介导器官间通讯(Cao et al., 2022, Dis Mod Mech)。该项目的结果显著促进了我们对非典型基底膜和其他非基底膜形式的基质沉积物的理解。我们的研究证明了非基底膜细胞外基质的功能重要性，并揭示了细胞外基质组装的新途径。重要的是，它填补了在理解翅膀粘连和保守的基底膜蛋白即巢蛋白的作用方面长期存在的空白。从我们的研究结果来看，越来越清楚的是，非典型基底膜相当普遍，即使是典型的平面基底膜也有很多我们还不理解的多样性。除了在正常发育和生理学中的作用外，大量人类疾病是由细胞外基质组装或组成的缺陷引起的。该项目的结果可能对理解和治疗纤维化疾病和其他涉及异常细胞外基质积累的疾病具有广泛的意义。