胎球蛋白A在间质性膀胱炎发病机制中的作用研究

Interstitial cystitis (IC), or bladder pain syndrome, is a chronic inflammatory condition of the submucosal and muscular layers of the bladder. Despite a plethora of studies gone into the etiology of this disease, the cause of IC is still unknown, and to date no study has been conducted to establish the relationship between proteins and IC. Clinical research reveals some unexpected but significant similarities between IC and prion-associated diseases in terms of pathological symptom, therapeutic drugs and the chemical nature of pathogens, which prompts that the cause of IC may have something to do with infectious proteinous particles. A so-called nanobacteria was proven to be a pathogenic microorganism proven closely linked with IC, as reported in previous references. This microbe, however, does not contain nucleic acids, while its major component is demonstrated to be Fetuin-A, a protein being more abundant in fetal than adult blood. In sharp contrast to its normal counterpart, Fetuin-A identified from nanobacteria displays strong cellular toxicity. In this project, we aim to reveal structural differences between normal and nanobacterial Fetuin-A using interdisciplinary techniques, in particular those from molecular and structural biology, and test if IC is cause by protein conformational changes. The results obtained from this study would provide mechanistic insights into IC's pathology, and propose feasible protective measures against IC. Our final goal is to primarily screen out drug candidates for IC's therapy by means of structural-based drug design. In short, we believe that the outcome from our study would bring about novel pathological theories and therapeutic strategies for this poorly-understood disease.

间质性膀胱炎（IC）病因学研究众多，但其发病机制仍不清楚，对其进行致病性蛋白质的相关研究尚无报道。临床发现，朊病毒相关疾病与IC在病理学表现、临床治疗药物、病原"微生物"的化学本质等方面具有出人意料的相似之处，启示IC发病可能与某种具有感染性的蛋白质颗粒有关。既往称之为纳米细菌的微生物被证实与IC发病密切相关，该"微生物"前期被证实不含核酸，而只含一种称之为胎球蛋白A（Fetuin-A）的蛋白质，但其却具有正常Fetuin-A所不具备的细胞毒性。本研究拟借助分子生物学与结构生物学手段，揭示正常Fetuin-A与纳米细菌Fetuin-A的结构差异，证实纳米细菌本质即为变构Fetuin-A，阐明IC为一种Fetuin-A结构改变引起的蛋白分子构象病。基于Fetuin-A蛋白二者结构差异，深入探索导致蛋白变构的可能诱发因素，筛选可用于治疗IC的药物候选分子，为临床防治IC提供新理论与新策略。

本研究严格按照课题计划进行，实验证实纳米细菌是导致间质性膀胱炎（IC）发病的重要病原微生物之一，且与胎球蛋白A（Fetuin-A）密切相关，并通过体外培养纳米细菌成功检测到Fetuin-A。随后通过致病性研究发现：纳米细菌Fetuin-A感染膀胱上皮细胞后，膀胱粘膜组织出现炎症反应，可见大量成纤维细胞和肥大细胞增生。感染睾丸后，组织出现慢性炎症及钙化。表明纳米细菌 Fetuin-A 具有致炎、致纤维化及至钙化作用。而正常Fetuin-A不具有细胞毒性，为证实纳米细菌本质即为变构的Fetuin-A，阐明IC为一种Fetuin-A结构改变引起的蛋白分子构象病，我们借助分子生物学与结构生物学手段，尝试结晶两种Fetuin-A并分析其结构。目前已成功完成了重组小鼠Fetuin-A蛋白的诱导表达和纯化，但结晶条件仍需进一步优化。