Photoreceptor Rescue By Inhibition of Dopamine Signaling

通过抑制多巴胺信号传导来拯救感光器

• 批准号: 6703557
• 负责人: JUDITH Mosinger OGILVIE
• 金额: $ 3.92万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-02-01 至 2004-08-15
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6703557
• 关键词: antibody; biological signal transduction; cell surface receptors; clinical research; cyclic GMP; dopamine; dopamine antagonists; dopamine receptor; electrophysiology; genetically modified animals; histology; immunocytochemistry; immunoprecipitation; laboratory mouse; phosphodiesterases; retina; retinitis pigmentosa; rod cell; visual photoreceptor; western blottings

DESCRIPTION (provided by applicant): The rod photoreceptors of the rd1 mouse degenerate in vivo or in organ culture by one month of age as a result of a defect in the beta-subunit of the cGMP-phosphodiesterase gene. As with most models of retinitis pigmentosa, the underlying mechanism of degeneration remains poorly understood. Dopamine is a neuromodulator affecting most, if not all, cell types in the vertebrate retina. We have discovered that dopamine antagonists from either the D1- or D2-receptor families completely block the degeneration of photoreceptors in the rd1 retinal organ culture model. Current theoretical models and observations of dopaminergic function fail to explain this surprising result. For example, only the D4 receptor subtype has been clearly identified in mouse photoreceptors; yet a D1-family antagonist is equally protective. Also, D1- and D2-family receptors generally act through opposing pathways to modulate the effects of the other; here they give the same result. Finally, dopamine generally has subtle, modulatory effects in the retina; here the effect on cell survival is dramatic and complete - no morphological difference can be detected between wild type and treated rdl organ cultures after 4 weeks, when nearly all of the rods have degenerated in the untreated rd1 culture. We propose experiments to address these differences and to test the significance of our findings in vivo. First, we will determine whether the absence of dopamine receptors can increase photoreceptor survival and function in the rd1 mouse retina in vivo. Secondly, we will address two aspects of the underlying mechanism, first testing a novel hypothesis concerning dopamine receptors, a subtype of the larger G-protein-coupled receptor family. In a recent paradigm shift, G-protein-coupled receptors, previously thought to function only as monomers, are now recognized to sometimes form heterodimers with atypical pharmacology and function. Such novel characteristics have recently been demonstrated with opioid, GABA, and other GPCRs. The formation of heterodimers comprised of different dopamine receptor subtypes could explain many of the perceived incongruities. We will also determine if D1-family dopamine receptors are present in rd1 photoreceptors. The proposed experiments will generate two important results. First, we will determine the importance of dopamine signaling in photoreceptor degeneration in vivo, which could lead to entirely new therapeutic approaches for retinal degeneration. Secondly, we will investigate the underlying mechanism including testing a dopamine receptor heterodimer-induced model of degeneration which could lead to a new area of investigation in retinal cell biology.

描述（由申请人提供）：由于cGMP-磷酸二酯酶基因的β亚基缺陷，rd 1小鼠的视杆细胞在体内或器官培养物中退化至1月龄。与大多数视网膜色素变性模型一样，对变性的潜在机制仍然知之甚少。多巴胺是一种神经调质，影响大多数，如果不是全部，在脊椎动物视网膜细胞类型。我们已经发现来自D1或D2受体家族的多巴胺拮抗剂完全阻断rd 1视网膜器官培养模型中的光感受器的变性。 目前的理论模型和多巴胺能功能的观察无法解释这一令人惊讶的结果。例如，在小鼠光感受器中仅清楚地鉴定出D4受体亚型;然而，D1-受体家族中的D4受体亚型在小鼠光感受器中仅被鉴定出。 对抗者同样具有保护性。此外，D1和D2家族受体通常通过相反的途径发挥作用，以调节另一个的作用;在这里，它们给出了相同的结果。最后，多巴胺通常在视网膜中具有微妙的调节作用;这里对细胞存活的作用是显著和完全的-在4周后，当几乎所有的杆在未处理的rd 1培养物中退化时，在野生型和处理的rd 1器官培养物之间没有检测到形态学差异。我们提出实验来解决这些差异，并在体内测试我们的研究结果的意义。首先，我们将确定是否多巴胺受体的缺乏可以增加光感受器的生存和功能在rd 1小鼠视网膜在体内。其次，我们将解决两个方面的潜在机制，首先测试一个新的假设，多巴胺受体，一个亚型的更大的G蛋白偶联受体家族。在最近的范式转变中，G蛋白偶联受体，以前被认为只作为单体发挥作用，现在被认为有时会形成异二聚体， 药理作用这些新的特征最近已被证明与阿片类药物，GABA，和其他GPCR。由不同多巴胺受体亚型组成的异二聚体的形成可以解释许多感知到的不一致性。我们还将确定是否D1家族多巴胺受体存在于rd 1光感受器中。这些实验将产生两个重要的结果。首先，我们将确定多巴胺信号在体内感光细胞变性中的重要性，这可能导致视网膜变性的全新治疗方法。其次，我们将研究潜在的机制，包括测试多巴胺受体异二聚体诱导的变性模型，这可能导致一个新的领域 视网膜细胞生物学的研究。