The role of APOL1 polymorphisms in promoting HIV-related kidney injury

 描述(申请人提供)：尽管抗逆转录病毒治疗在提高死亡率方面取得了成功，但艾滋病毒感染者的死亡风险仍然增加，并增加了包括慢性肾脏疾病在内的非传染性疾病的负担。艾滋病毒相关性肾病(HIVAN)几乎只发生在非洲血统的人中，载脂蛋白L1(APOL1)的多态是这种额外风险的主要原因。G1或G2肾脏风险等位基因纯合子(或G1/G2复合杂合子)的人患非糖尿病终末期肾病的风险显著增加，患HIVAN的风险增加30倍。关于这些变异导致进展性CKD风险增加的机制，我们知之甚少。由于拥有两个肾脏风险等位基因的绝大多数人不会患上肾脏疾病，因此需要进行“二次打击”，如艾滋病毒感染，以揭示APOL1介导的肾脏损伤的易感性。我们的长期目标是阐明APOL1肾脏风险等位基因使个人易患肾衰竭的机制，以设计新的策略来预防和治疗这一脆弱人群的肾脏疾病。这项建议的目的是确定APOL1肾脏风险等位基因促进HIV诱导的人类肾脏细胞损伤的新机制。我们的中心假设是，APOL1肾脏风险等位基因改变了细胞蛋白与APOL1结合的能力，从而通过最终促进细胞死亡的细胞通路失调来促进HIV诱导的损伤。我们的假设得到了来自我们实验室和其他实验室的数据的支持，这些数据表明：1)移植肾脏(而不是受者)的APOL1基因型增加了移植后肾功能衰竭的风险，表明肾脏细胞中局部APOL1的表达促进了肾脏损伤；2)在体外，APOL1风险等位基因在肾脏细胞中的过度表达比野生型等位基因的毒性更大；3)我们实验室的初步数据表明，在HIV感染的背景下，与APOL1结合的细胞蛋白(包括那些在细胞周期和天然免疫中起作用的蛋白)存在差异。我们将测试我们的假设，并在两个具体目标上解决至关重要的问题。在我们的第一个具体目标中，我们将使用新的等基因人类足细胞、肾小管和血管内皮细胞系来描述在HIV感染的背景下APOL1风险等位基因失控的细胞过程。在我们的第二个特定目标中，我们使用先前从HIV阳性的局灶节段性肾小球硬化(FSGS)患者的活检组织和来自肾病综合征研究网络(NEPEUNT)的数据来确定HIV阳性FSGS患者和HIV阴性FSGS患者的肾脏活检标本中差异表达的基因，我们将使用创新的蛋白质组和RNA表达分析来识别在以下背景下受APOL1风险等位基因差异调控的RNA和蛋白质 并确定在艾滋病毒感染后与APOL1风险变异体结合发生变化的蛋白质。这些结果将产生积极影响，因为它们将提供新的见解，提高我们预防和治疗艾滋病毒/艾滋病感染者和非洲裔艾滋病毒阴性者肾脏疾病的能力。

 DESCRIPTION (provided by applicant): Despite the success of antiretroviral therapy in improving mortality, HIV-infected persons remain at increased risk of death and have increased burden of non-infectious diseases including chronic kidney disease (CKD). HIV-associated nephropathy (HIVAN) occurs almost exclusively in persons of African ancestry and polymorphisms in Apolipoprotein L1 (APOL1) account for the majority of this excess risk. Persons who are homozygous for the G1 or G2 renal risk alleles (or G1/G2 compound heterozygotes) have markedly increased risk of non-diabetic ESRD and a 30-fold increased risk of HIVAN. Little is known regarding the mechanisms by which these variants confer increased risk of progressive CKD. As the great majority of persons harboring two renal risk alleles do not develop kidney disease, a "second hit", such as HIV infection, is required to unmask the predisposition to APOL1-mediated kidney injury. Our long-term goal is to delineate the mechanisms by which APOL1 renal risk alleles predispose individuals to kidney failure to devise new strategies to prevent and kidney disease this vulnerable population. The objective of this proposal is to identify novel mechanisms by which APOL1 renal risk alleles promote HIV-induced injury in human kidney cells. Our central hypothesis is that APOL1 renal risk alleles alter the ability of cellular proteins to bind to APOL1, thereby promoting HIV- induced injury via dysregulation of cellular pathways that ultimately promote cell death. Our hypothesis is supported by data from our lab and others demonstrating that: 1) APOL1 genotype of a transplanted kidney (and not the recipient) confers increased risk of kidney failure after transplantation, suggesting that local APOL1 expression in kidney cells promotes kidney injury; 2) overexpression of APOL1 risk alleles in kidney cells is more toxic than wild type alleles in vitro; 3) preliminary data from our laboratory demonstrating differences in cellular proteins (including those with roles in cell cycle and innate immunity) that bind APOL1 in the context of HIV infection. We will test our hypothesis and address critically important questions in two specific aims. In our first specific aim, we will use novel isogenic human podocyte, tubular, and endothelial cell lines to delineate the cellular processes that are dysregulated by APOL1 risk alleles in the context of HIV infection. In our second specific aim, we use biopsies previously collected from HIV-positive patients with focal segmental glomerulosclerosis (FSGS) and data from the Nephrotic Syndrome Study Network (NEPTUNE) to determine genes that are differentially expressed in kidney biopsy specimens from HIV-positive versus HIV- negative patients with FSGS and we will use innovative proteomic and RNA expression analyses to identify RNA and proteins that are differentially regulated by APOL1 risk alleles in the context of HIV infection and to identify proteins that display altered binding to APOL1 risk variants after HIV infection. These results will have a positive impact because they will provide new insights that will improve our ability to prevent and treat kidney disease in persons living with HIV/AIDS and in HIV-negative persons of African ancestry.