Model for SorCS1-mediated Diabetes with Dementia

描述（由申请人提供）：2型糖尿病（T2D或T2DM）增加阿尔茨海默病（AD）的风险，SORCS1基因与T2D和AD相关。我们已经对SorCS1在阿尔茨海默病淀粉样蛋白代谢中的可能作用进行了研究。(一)?前体蛋白（APP），以确定这两种疾病的协调遗传联系的分子机制。SorCS1cb-myc在培养细胞中的过表达导致a ？代（Lane et al., 2010）。内源性小鼠A？40和A？42个水平升高(A？40岁,p = 0.044;一个吗?42, p=0.007)，这可能与Sorcs1与AD和DM遗传关联的性别二态性特征相似。由于SorL1（另一种AD连接的vps10结构域蛋白）直接与Vps35相互作用以调节APP代谢，我们研究了sorcs1bc -myc可能与APP、SorL1和/或Vps35相互作用的可能性。我们很容易从非转基因小鼠脑中恢复SorCS1:APP， SorCS1:SorL1和SorCS1:Vps35复合物。值得注意的是，雌性Sorcs1-/-小鼠大脑中Vps35总蛋白水平下降了49% (p=0.009)， SorL1总蛋白水平下降了29% （p=0.003）。我们假设SorCS1功能障碍可能导致APP/A?？为了进一步验证这一假设，我们提出以下具体目标：通过以下方法评估SorCS1蛋白相互作用基序和SorCS1/SorL1/APP复合物形成对APP代谢的重要性：(a)在过表达SorCS1的培养细胞中表征APP代谢；(b)检测SorCS1胞质和胞外结构域蛋白-蛋白相互作用基序突变对SorCS1/SorL1/APP三元复合物形成和APP代谢的影响；(c)测试一种假定的致病性SorCS1多态性对SorCS1/SorL1/APP三方复合物形成和APP代谢的影响；(d)通过将病毒基因转移到原代培养物中，证实了在Aim 1aii和1aiii中发现的功能域的重要性。具体目标2。利用Sorcs1亚形态和斑块形成的人类瑞典APP/PS双基因小鼠与Sorcs1亚形态小鼠杂交，表征：(i)内源性APP代谢；（ii）海马形态测定、树突树突和脊柱结构；(c)学习行为。衰老（3个月，6个月，12个月）的影响也将被研究。具体目标3。对Sorcs1-/-小鼠和与Sorcs1-/-小鼠杂交形成斑块的人类瑞典APP/PS共转基因小鼠进行标准葡萄糖和胰岛素耐量试验和代谢谱表型分析。

DESCRIPTION (provided by applicant): Type 2 diabetes mellitus (T2D or T2DM) increases the risk for Alzheimer's disease (AD), and SORCS1 is genetically linked to both T2D and AD. We have undertaken a study of the possible role(s) for SorCS1 in metabolism of the Alzheimer's amyloid-? (A?)?precursor protein (APP), in order to define the molecular mechanisms underlying this coordinate genetic linkage to both diseases. Overexpression of SorCS1cb-myc in cultured cells caused a reduction (p=0.002) in?A? generation (Lane et al., 2010). Endogenous murine A?40 and A?42 levels were increased (A?40, p=0.044; A?42, p=0.007) in the brains of female Sorcs1 hypomorphic mice, possibly paralleling the sexual dimorphism that is characteristic of the genetic associations of SORCS1 with AD and DM. Since SorL1, another AD-linked Vps10-domain protein, directly interacts with Vps35 to modulate APP metabolism, we investigated the possibility that SorCS1cb-myc might interact with APP, SorL1, and/or Vps35. We readily recovered SorCS1:APP, SorCS1:SorL1, and SorCS1:Vps35 complexes from nontransgenic mouse brain. Notably, total Vps35 protein levels were decreased by 49% (p=0.009) and total SorL1 protein levels were decreased by 29% (p=0.003) in the brains of female Sorcs1-/- mice. We hypothesize that dysfunction of SorCS1 may contribute to both the APP/A??disturbance underlying AD and the insulin/glucose metabolism disturbance underlying DM. In order to test this hypothesis further, we propose the following specific aims: Specific Aim 1. To evaluate the importance of SorCS1 protein interaction motifs and SorCS1/SorL1/APP complex formation on APP metabolism by: (a) Characterizing APP metabolism in cultured cells overexpressing SorCS1; (b) Testing the effects of mutations of protein-protein interacting motifs in the cytoplasmic and ectodomains of SorCS1 on both the formation of tripartite SorCS1/SorL1/APP complexes and APP metabolism; (c) Testing the effect of a putative pathogenic SorCS1 polymorphism on both the formation of tripartite SorCS1/SorL1/APP complexes and APP metabolism; (d) Confirming the importance of functional domains identified in Aim 1aii and 1aiii by viral gene transfer into primary cultures. Specific Aim 2. To employ Sorcs1 hypomorphic and plaque forming human Swedish APP/PS bigenic mice crossed with Sorcs1 hypomorphic mice for characterization of: (i) endogenous APP metabolism; (ii) hippocampal morphometry, dendritic arborization, and spine structure; (c) learning behavior. Aging (3 mo, 6 mo, 12 mo) effects will also be studied. Specific Aim 3. To perform standard glucose and insulin tolerance tests and metabolic profile phenotyping of Sorcs1-/- mice and plaque-forming" human Swedish APP/PS co-transgenic mice crossed with Sorcs1 -/- mice. PUBLIC HEALTH RELEVANCE: Type 2 diabetes mellitus (T2DM) increases the risk for Alzheimer's disease (AD). Both diseases are highly complex, and several mechanisms have been proposed for this association, including hypercholesterolemia, vasculopathic factors, and insulin resistance, among others. We sought and identified a genetic factor, SORCS1, that is an excellent candidate for modulation of a coordinated risk for both diseases, and we now propose to work out mechanistic details for how SorCS1 controls risk for AD and T2DM.