Lysosomal Diseases

黏脂质沉积症IV型（MLIV）是一种常染色体隐性遗传病，其特征为急性精神运动迟缓、失速和视觉异常，包括视网膜变性、角膜混浊、视神经萎缩和斜视。在大多数MLIV患者的组织中发现溶酶体包涵体。储存材料的组成是不均匀的，包括脂质和粘多糖形成特征的多同心片层，以及可溶性的颗粒状蛋白质。MLIV是由粘磷脂-1 （MCOLN1，也称为TRPML1）突变引起的，粘磷脂-1是一种内溶酶体阳离子通道，属于瞬时受体电位（TRP）离子通道超家族。全细胞膜片钳以及天然内溶酶体膜的记录表明，MCOLN1作为一个内部（从管腔到细胞质）的整流通道，可渗透到Ca2+， Na+， K+和Fe2+/ Mn2+，其活性因低ph而增强。为了更好地了解这种疾病的病理，我们使用基因组编辑来敲除Dario rerio（斑马鱼）中存在的两个MCOLN1基因。我们的模型成功地再现了MLIV患者观察到的视网膜和神经肌肉缺陷，表明该模型适合于研究疾病的发病机制。重要的是，我们的模型揭示了MLIV病理的起源和进展的新见解，包括自噬体积累对肌肉营养不良的贡献以及mcoln1在胚胎发育，毛细胞活力和细胞维持中的作用。鉴于这种生物适合大规模体内药物筛选，因此在斑马鱼中产生MLIV模型特别重要，从而为治疗发现提供了新的机会。

Mucolipidosis type IV (MLIV) is an autosomal recessive disorder characterized by acute psychomotor delays, achlorydria, and visual abnormalities including retinal degeneration, corneal clouding, optic atrophy, and strabismus. Lysosomal inclusions are found in most tissues in MLIV patients. The composition of the storage material is heterogeneous and includes lipids and mucopolysaccharides forming characteristic multiconcentric lamellae, as well as soluble, granulated proteins. MLIV is caused by mutations in mucolipin-1 (MCOLN1, also known as TRPML1), an endo-lysosomal cation channel belonging to the transient receptor potential (TRP) superfamily of ion channels. Whole cell patch clamp, as well as recording of native endolysosomal membranes, suggest that MCOLN1 functions as an inwardly (from lumen to cytoplasm) rectifying channel permeable to Ca2+, Na+, K+ and Fe2+/ Mn2+ whose activity is potentiated by low pH. To better understand the pathology of this disease, we used genome editing to knockout the two mcoln1 genes present in Dario rerio (zebrafish). Our model successfully reproduced the retinal and neuromuscular defects observed in MLIV patients, indicating that this model is suitable for studying the disease pathogenesis. Importantly, our model revealed novel insights into the origins and progression of the MLIV pathology, including the contribution of autophagosome accumulation to muscle dystrophy and the role of mcoln1 in embryonic development, hair cell viability and cellular maintenance. The generation of a MLIV model in zebrafish is particularly relevant given the suitability of this organism for large-scale in vivo drug screening, thus providing novel opportunities for therapeutic discovery. Pompe disease, a severe muscle wasting disorder characterized by altered lysosomal function. Profound muscle atrophy is a hallmark of Pompe disease, a rare genetic disorder caused by a deficiency of acid alphaglucosidase (GAA), the enzyme that breaks down glycogen to glucose within lysosomes. Absence of the enzyme leads to a rapidly fatal cardiomyopathy and skeletal muscle myopathy in infants; low levels of residual enzyme activity are associated with childhood and adult onset progressive skeletal muscle myopathy usually without cardiac involvement. Recently, we found dysregulation of mTOR signaling in the diseased muscle cells and focused on the identification of potential sites for therapeutic intervention. Importantly, reactivation of mTOR in the whole muscle of Pompe mice by TSC knockdown or arginine supplementation resulted in the reversal of atrophy and a striking removal of autophagic buildup. The only available therapy for Pompe disease is enzyme replacement therapy (ERT) with human recombinant GAA. This therapy restores cardiac function, but its effect in skeletal muscle is much less robust. The massive autophagic buildup in Pompe skeletal muscle negatively affects the trafficking and lysosomal delivery of the recombinant enzyme. Since we showed that restoration of mTORC1 activity in Pompe skeletal muscle dramatically reduces autophagosome accumulation, we evaluated whether ERT may work more efficiently when autophagic buildup is removed or diminished. For this, we used a dual approach in which restoration of mTORC1 activity by TSC depletion was combined with ERT. Notable, this approach resulted in increased muscle mass and reduced glycogen accumulation, suggesting reversal of the lysosomal pathology. Therefore, we proposed that a combination of TSC-mediated activation of mTOR with ERT may have the potential to address multiple aspects of the disease pathology. An alternative approach to improve treatment of Pompe patients is designing a more efficient recombinant GAA. In collaboration with Amicus Therapeutics, we have tested a novel rhGAA (ATB200) that has substantially higher M6P content, thus improving interaction with the CIM6PR and delivery to target tissues. Injection of ATB200 in a murine Pompe model, together with a small-molecule pharmacological chaperone that prevents loss of activity and denaturalization, significantly reversed intralysosomal glycogen accumulation and autophagic build-up, leading to improved muscle function.