A functional SRC1 SNP in bone biology

描述(申请人提供)：雌激素受体ER1和ER2的活性是通过与辅因子的相互作用来调节的，其中包括类固醇受体辅活化子1(SRC1)。SRC1已被证明是雌激素反应的关键调节因子。特别是在骨骼方面，SRC1-/-小鼠表现出骨量减少，雌激素无法恢复卵巢切除所致的骨丢失。也有证据表明，SRC1可能在选择性雌激素受体调节剂(SERM)的反应中发挥作用，如抗雌激素他莫昔芬。抗雌激素具有组织特异性的混合激动剂/拮抗剂活性，SRC1过表达可导致某些组织中激动剂的增加和拮抗剂活性的降低。低雌激素水平与骨密度(BMD)降低有关，有可能导致骨质疏松。众所周知，骨质疏松症有一个主要的遗传成分，并且已经确定了潜在的致病基因。在我们旨在研究基因变异在抗雌激素反应中的作用的研究中，我们最近发现并随后开始描述SRC1(P1272S)的非同义单核苷酸多态(SNP)。我们的初步数据显示，SRC1P1272S变异体表现出ER共激活减少，即半衰期较短。在接受他莫昔芬治疗12个月的乳腺癌患者中，与携带野生型等位基因的患者相比，SNP携带者的骨密度显著降低，这可能反映了他莫昔芬在骨骼中的激动剂活性的丧失。我们假设SRC1P1272S SNP导致骨细胞中ER活性降低，这是蛋白质翻转增加的结果。我们还假设携带SNP的小鼠将表现出骨量减少和对激素的骨骼反应降低。为了解决我们的假设，我们将i)表征SRC1SNP对骨细胞ER活性的影响，ii)破译P1272S变异体共激活活性降低的机制(S)，以及iii)建立SRC1P1278S/P1278S敲入小鼠模型，并鉴定骨表型。AIMS的成功完成将提供支持临床观察的功能数据，并将为后续的R01提交提供强有力的数据。最终，我们希望我们的研究将导致进一步描述一种可用于“个性化药物”的SNPs，并在这个特定的案例中，识别将从骨骼强化药物或其他干预措施中受益的人。1 与公共卫生相关：我们已经在核受体辅因子SRC1中发现了一个功能性非同义变体，它显示出共激活潜力降低，导致雌激素受体活性降低。总而言之，我们的初步数据表明，这种SNP可能导致骨丢失增加。在这里，我们建议通过对该变体在骨细胞中的分析，通过对其潜在机制的研究，并最终通过产生和表征小鼠敲入模型，来提供进一步的功能支持。

DESCRIPTION (provided by applicant): The activity of the estrogen receptors ER1 and ER2 are regulated via interaction with cofactors, among them the steroid receptor coactivator 1 (SRC1). SRC1 has been shown to be a critical regulator of estrogen response. With particular regard to bone, SRC1-/- mice showed osteopenia, and estrogen failed to restore ovariectomy-induced bone loss. There is also evidence that SRC1 may play a role in the response to selective estrogen receptor modulators (SERMs) such as the antiestrogen tamoxifen. Antiestrogens have tissue-specific mixed agonist/antagonist activity, and SRC1 overexpression can result in increased agonist, and decreased antagonist activity in some tissues. Low estrogen levels are associated with decreased bone mineral density (BMD) potentially resulting in osteoporosis. It is known that osteoporosis has a major genetic component, and potential causal genes have been identified. In our studies aimed at examining the role of genetic variants in response to antiestrogens, we recently identified, and subsequently started to characterize, a non-synonymous single nucleotide polymorphism (SNP) in SRC1 (P1272S). Our preliminary data show that the SRC1 P1272S variant displays decreased co-activation of ER, and that is has a shorter half life. In breast cancer patients treated with tamoxifen for 12 months, SNP carriers showed significantly decreased BMD compared to those with wildtype alleles, possibly reflecting a loss of tamoxifen's agonist activity in bone. We hypothesize that the SRC1 P1272S SNP results in decreased ER activity in bone cells, and that this is a result of increased protein turn-over. We also hypothesize that mice harboring the SNP will display osteopenia, and decreased skeletal response to hormone. To address our hypotheses we will i) characterize the effect of the SRC1 SNP on ER activity in bone cells, ii) decipher the mechanism(s) underlying the decreased co-activation activity of the P1272S variant, and iii) generate an SRC1P1278S/P1278S knock-in mouse model, and characterize bone phenotypes. Successful completion of the aims will provide functional data supporting the clinical observation, and would allow strong data for a subsequent R01 submission. Ultimately, we hope that our studies will lead to the further characterization of a SNPs which could be used to "personalize medicine", and in this specific case, to identify people who would benefit from bone-strengthening medications, or other interventions. 1 PUBLIC HEALTH RELEVANCE: We have identified a functional non-synonymous variant in the nuclear receptor cofactor SRC1 which displays decreased coactivation potential, resulting in decreased activity of the estrogen receptor. Collectively, our preliminary data suggest that this SNP could result in increased bone loss. Here we propose to provide further functional support through the analysis of this variant in bone cells, through the study of the underlying mechanism, and finally through the generation and characterization of a mouse knock-in model.