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

描述(申请人提供)：许多溶酶体储存性疾病(LSD)会导致儿童期起病的神经变性，导致严重的精神运动迟缓和眼科异常。一般来说，众所周知，LSD很难治疗，因为尽管这些疾病起源于单基因，但它们通常会影响一系列细胞信号。 级联和细胞生物学过程。与LSD相关的多效性阻止了同时针对多种疾病结果的适当治疗策略的发展。此外，越来越清楚的是，LSD也以神经发育异常为特征，如皮质和胼胝体中的轴突发育减退。不幸的是，这些与LSD相关的神经元缺陷的机制基础仍然知之甚少。这项建议的首要目标是使用一种名为黏脂沉积症IV(MLIV)的LSD的果蝇模型来解决这些概念上的差距，这种LSD是由一种名为TRPML1的溶酶体钙通道功能突变的丧失引起的。我们先前已经证实，Fly TRPML1同源基因TRPML是一种晚期内体/两体钙通道，驱动这些小泡与溶酶体的融合。在这里，我们将利用果蝇的遗传可控性来解决有关LSD神经病理学的关键机制问题。在目标1中，我们将检验这一假设，即TRPML的丢失会导致被称为脂筏的富含胆固醇的有序膜微域的组织发生变化。由于脂筏对于大量细胞信号传递过程的功能至关重要，这些结构域稳定性的改变可能为溶酶体功能障碍相关的多效性提供一个机制解释。在目标2中，我们将验证TRPML通过激活神经元中发育的c-Jun激酶(JNK)信号来促进突触生长的假设。有趣的是，JNK活性降低会导致皮质和胼胝体轴索发育不良和发育不全。因此，溶酶体功能障碍信号传递后JNK活性降低可能是LSD以轴突生长缺陷为特征的分子解释。如果成功，这些研究将为我们提供一些与溶酶体功能障碍相关的常见神经学后果的机械性见解，并有助于建立针对LSD神经后遗症的治疗概念。

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.