ROLE OF APOD IN NEURODEGENERATION

载脂蛋白D （apoD）是脂钙蛋白转运体超家族的一员，与神经退行性疾病、神经损伤和神经再生有关。例如，在阿尔茨海默病中，内嗅皮层和脊髓液中apoD增加，apoD增加与apoE4基因型的遗传相关。在溶酶体胆固醇储存障碍，尼曼-皮克C型病（NP-C）中，apoD基因被诱导，apoD蛋白水平在脑和血浆中增加数倍。在大鼠的再生坐骨神经中，在挤压损伤后，apoD水平几乎增加了500倍。ApoD mRNA和蛋白水平也被证明在中枢神经系统损伤后上调。最后，apoD基因表达已被证明在非典型抗精神病药的反应中增加，这表明它可能是神经元信号转导的调节剂。在细胞水平上，我们发现apoD和NPC1（大多数NP-C病例中基因缺陷的产物）是囊泡运输途径的组成部分，该途径指导胆固醇和糖脂的后内吞运动。NPC1在神经元突触周围的星形细胞足突中富集。另一方面，ApoD存在于少突胶质前体细胞、周细胞和血管周围成纤维细胞中。在培养的外周细胞和胶质细胞中，apoD和NPC1以依赖胆固醇和糖脂的方式定位于内吞囊泡。本研究旨在进一步探讨apoD在神经变性中的作用。为了实现这些研究，我们将使用apoD敲除、apoD转基因（表达人类apoD基因）和apoD/NPC1双敲除小鼠来研究以下具体目的：(1) apoD敲除、apoD转基因和apoD/NPC1双敲除小鼠的发育、行为和神经表型，以及它们对神经毒性和神经退行性病变的反应；(2)apoD敲除和apoD/NPC1双敲除小鼠的胆固醇运输；(3)利用荧光共振能量转移（FRET）实现apoD和NPC1蛋白的功能相互作用；(4)apoD和NPC1介导的胶质和神经元胆固醇稳态调节。

Apolipoprotein D (apoD), a member of the lipocalin superfamily of transporters has been implicated in neurodegenerative disorders, neural injury and in neural regeneration. For instance, in Alzheimer's disease, there is increased apoD in the entorhinal cortex and in spinal fluid and the increased apoD correlates with inheritance of the apoE4 genotype. In the lysosomal cholesterol storage disorder, Niemann-Pick type C disease (NP-C), there is an induction of the apoD gene and apoD protein levels are increased several-fold in the brain and in plasma. In the regenerating sciatic nerve in the rat, following a crush injury, there is an almost 500-fold increase in apoD levels. ApoD mRNA and protein levels have also been shown to be upregulated following injury to the central nervous system. Finally, apoD gene expression has been shown to be increased in response to atypical neuroleptics suggesting that it may be a modulator of neuronal signal transduction. At a cellular level, we have found that apoD and NPC1, the product of the gene defective in most cases of NP-C, are components of a vesicular trafficking pathway that directs the retroendocytic movement of cholesterol and glycolipids. NPC1 is enriched in astrocytic foot processes around neuronal synapses. ApoD, on the other hand, is present in oligodendrocyte precursor cells, in pericytes, and in perivascular fibroblasts. In cultured peripheral cells and in glia, apoD and NPC1 localize to endocytic vesicles in a cholesterol- and glycolipid-dependent manner. The proposed studies aim to investigate further the role of apoD in neurodegeneration. To enable these studies we will use apoD knockout, apoD transgenic (expressing the human apoD gene) and apoD/NPC1 double knockout mice to investigate the following specific aims: (1) the developmental, behavioral and neurological phenotypes of apoD knockout, apoD transgenic and apod/NPC1 double knockout mice, and their response to neurotoxic and neurodegenerative lesions (2) cholesterol trafficking in apoD knockout and apoD/NPC1 double knockout mice (3) functional interaction(s) of apoD and NPC1 proteins using fluorescence resonance energy transfer (FRET), and (4) apoD and NPC1-mediated regulation of glial and neuronal cholesterol homeostasis.