CARMA3-mediated NF-kappaB activation in GPCR signaling pathways

描述（由申请人提供）：G蛋白偶联受体（GPCR）构成细胞表面受体的大家族，并在调节细胞存活和增殖中发挥重要作用。它们通过异源三聚体G蛋白刺激鸟嘌呤核苷酸交换的能力跨越细胞质膜传递环境信号，异源三聚体G蛋白诱导由支架/接头分子和效应酶组成的多个信号级联，导致包括NF-κ B在内的许多转录因子的激活。NF-κ B是一个转录因子家族，在调节促炎细胞因子和促生存因子的表达中起关键作用。溶血磷脂酸（LPA）是一种有效的生物活性脂质，其具有多种生物学作用，特别是作为细胞增殖、迁移和存活的诱导剂，从而调节伤口愈合、血管重塑以及肿瘤进展和转移。LPA与其受体（GPCR家族成员）结合，启动多种信号传导途径，导致诱导促炎和促血管生成细胞因子。也已经显示NF-kB是介导LPA诱导的细胞因子产生的关键转录因子。然而，GPCR，如LPA受体，如何诱导NF-κ B激活仍然是未知的。在本申请中，我们建议研究GPCR诱导NF-κ B活化的分子机制。我们的初步研究表明，由几种GPCR配体（包括LPA、内皮素-1和5-羟色胺）诱导的NF-kB活化依赖于两种适配器/支架分子CARMA 3和BcMO。基于我们的初步研究，我们假设CARMA 3和BcMO介导一种新的GPCR信号转导途径，导致NF-κ B的激活。在本申请中，我们提出了三个具体的目标来阐明这种新的信号转导途径。它们是：1）确定GPCR如何导致CARMA 3的激活; 2）确定CARMA 3激活下游信号级联的分子机制; 3）确定CARMA 3是否是KSHV GPCR诱导的NF-κ B激活和恶性肿瘤所必需的。阐明这种新的信号转导途径不仅将揭示GPCR诱导NF-κ B活化的一般机制，而且还提供用于调节炎症、伤口愈合、血管生成和癌症的治疗靶点。

DESCRIPTION (provided by applicant): G protein-coupled receptors (GPCRs) constitute a large family of cell surface receptors, and play an important role in regulating cell survival and proliferation. They transduce environmental signals across the cytoplasm membrane through their ability to stimulate guanine nucleotide exchange by heterotrimeric G proteins, which induce multiple signaling cascades composed of scaffold/adaptor molecules and effector enzymes, leading to activation of many transcription factors including NF-kB. NF-kB is a family of transcription factors that play pivotal roles in regulating the expression of pro-inflammatory cytokines and pro-survival factors. Lysophosphatidic acid (LPA) is a potent bioactive lipid that elicits a wide variety of biological actions, particularly as an inducer of cell proliferation, migration, and survival, thereby, regulating wound healing, vascular remodeling, and tumor progression and metastasis. Binding LPA to its receptor, a GPCR family member, initiates multiple signaling pathways, leading to induction of pro-inflammatory and pro-angiogenic cytokines. It has also been shown that NF-kB is the key transcription factor mediating LPA- induced cytokine production. However, how GPCRs, such as LPA receptors, induce NF-kB activation remains largely unknown. In this application, we propose to investigate the molecular mechanism by which GPCRs induce NF-kB activation. Our preliminary studies indicate that NF-kB activation induced by several GPCR ligands, including LPA, endothelin-1, and serotonin, is dependent on two adaptor/scaffold molecules, CARMA3 and BcMO. Based on our preliminary studies, we hypothesize that CARMA3 and BcMO mediate a novel GPCR signal transduction pathway, leading to activation of NF-kB. In this application, we propose three specific aims to elucidate this novel signal transduction pathway. They are 1) to determine how the GPCR leads to activation of CARMA3; 2) to determine the molecular mechanism by which CARMA3 activates downstream signaling cascades; 3) to determine whether the CARMA3 is required for KSHV GPCR-induced NF-kB activation and malignancy. Elucidating this novel signal transduction pathway not only will reveal a general mechanism by which GPCRs induce NF-kB activation, but also provide therapeutic targets for modulating inflammation, wound healing, angiogenesis, and cancer.