Alterations in synaptic growth and lipid-raft organization in a fly MLIV model

描述（由申请方提供）：许多溶酶体贮积病（LSD）引起儿童期发作的神经变性，导致严重的精神发育迟滞和眼科异常。一般来说，LSD是众所周知的难以治疗，因为尽管这些疾病是单基因起源的，但它们通常会影响许多细胞信号传导 级联和细胞生物学过程。与LSD相关的多效性阻碍了同时靶向多种疾病结局的合适治疗策略的发展。此外，越来越清楚的是，LSD还具有神经发育异常的特征，例如皮质和胼胝体中轴突发育减少。不幸的是，与LSD相关的这些神经元缺陷的机制基础仍然知之甚少。该提案的总体目标是使用称为粘脂沉积症IV型（MLIV）的LSD的果蝇模型来解决这些概念上的差距，该模型由称为TRPML 1的溶酶体Ca 2+通道中的功能突变丧失引起。我们以前建立的飞TRPML 1同源物，TRPML，是一个晚内体/两性体钙通道，驱动这些囊泡与溶酶体的融合。在这里，我们将利用果蝇的遗传可塑性来解决LSD神经病理学的关键机制问题。在目标1中，我们将测试的假设，TRPML的损失导致胆固醇富集有序膜微区称为脂筏的组织的改变。由于脂筏对于过多的细胞信号传导过程的功能是至关重要的，因此这些结构域的稳定性的改变可以为与溶酶体功能障碍相关的多效性提供机制解释。在目标2中，我们将测试TRPML通过激活神经元中的发育c-Jun激酶（JNK）信号促进突触生长的假设。有趣的是，JNK激活减少导致皮质和胼胝体轴突束发育不全和发育不全。因此，溶酶体功能障碍信号传导后JNK活化降低可能是LSD以轴突生长缺陷为特征的分子解释。如果成功的话，这些研究应该为我们提供一些与溶酶体功能障碍相关的常见神经学结局的机制性见解，并有助于建立治疗LSD神经学后遗症的概念。

DESCRIPTION (provided by applicant): Many lysosomal storage diseases (LSDs) cause childhood-onset neurodegeneration leading to profound psychomotor retardation and ophthalmological abnormalities. In general, LSDs are notoriously difficult to treat because although these diseases are monogenic in origin, they typically affect a host of cellular signaling cascades and cell biological processes. The pleiotropy associated with LSDs prevents the development of suitable therapeutic strategies that simultaneously target the multiple disease outcomes. Moreover, it is becoming increasingly clear that LSDs are also characterized by neurodevelopmental abnormalities such as diminished axonal development in the cortex and corpus callosum. Unfortunately, the mechanistic basis for these neuronal defects associated with LSDs remain poorly understood. The overarching goal of this proposal is to address these conceptual gaps using a Drosophila model of an LSD called mucolipidosis type IV (MLIV) that arises from loss of function mutations in a lysosomal Ca2+ channel called TRPML1. We previously established that the fly TRPML1 homolog, TRPML, is a late-endosomal/amphisomal Ca2+ channel that drives the fusion of these vesicles with lysosomes. Here, we will leverage the genetic tractability of the Drosophila to address the critical mechanistic questions regarding the neuropathology of LSDs. In Aim 1, we will test the hypothesis that loss of TRPML results in alterations in the organization of cholesterol-enriched ordered membrane microdomains called lipid rafts. Because lipid rafts are critical for the functioning of a plethora of cellular signalig processes, alterations in the stability of these domains could provide a mechanistic explanation for the pleiotropy associated with lysosomal dysfunction. In Aim 2, we will test the hypothesis that TRPML promotes synaptic growth by activating developmental c-Jun Kinase (JNK) signaling in neurons. Interestingly, diminished JNK activation results in hypoplasia and agenesis of axonal tracts of the cortex and corpus callosum. Therefore, decreased JNK activation following lysosomal dysfunction signaling may be the molecular explanation for why LSDs are characterized by axonal growth defects. If successful, these studies should provide us with mechanistic insight into some of the common neurological outcomes associated with lysosomal dysfunction and also aid in the establishment of concepts for therapeutically targeting the neurological sequelae of LSDs.