PROTRH GENE TRANSCRIPTION AND BIOSYNTHESES BY LEPTIN

描述（由申请人提供）：瘦素主要在脂肪组织中产生，在向调节食欲、能量消耗和神经内分泌功能的脑中心提供关于能量储存和能量平衡的信息方面具有中心生理作用。瘦素的作用之一是通过促甲状腺素释放激素（TRH）肽激活下丘脑-垂体-甲状腺（HPT）轴，从而增加能量消耗。在过去三年的资金，我们能够提供有力的证据，存在一个直接（室旁核，PVN）和间接（弓状核，ARC）途径的瘦素作用的调节TRH激素原的生物合成。我们证明，瘦素可以直接调节促甲状腺激素释放激素原的生物合成和分泌在培养的下丘脑神经元的黑素皮质素（α-黑素细胞刺激激素，α-MSH）的输入无关。我们还观察到的共同定位的瘦素受体（ObRb）与促甲状腺激素释放激素前体的神经元的PVN，强烈建议直接影响瘦素促甲状腺激素释放激素神经元。这一假设得到了进一步的支持，在PVN内的ObRb mRNA表达的演示，并显示TRH神经元表达SOCS-3 mRNA（这是直接瘦素作用的敏感标志物）瘦素给药后，大鼠。最近，我们首次证明了STATS在TRH神经元中的激活瘦素在体内，提供了进一步的证据的潜在的关键作用的STAT 3转录因子，以调节瘦素的proTRH启动子的活性。我们最近还证明，由于瘦素作用，TRH生物合成的增加与参与TRH和其他proTRH肽成熟的加工酶PCI和PC 2的上调有关。 目的#1我们将检验以下假设：存在两组不同或重叠的携带ObRb（直接途径）和MC 4 R（间接途径）的PVN-TRH神经元，它们被瘦素和α-MSH靶向以通过增加通过HPT轴的能量消耗来调节能量平衡，并通过向LH和DMH发送突触来潜在地抑制食物摄入。 目的#2我们将检验瘦素主要通过直接途径调节HPT轴的假设。 因为我们发现瘦素调节促甲状腺激素释放激素原并通过上调PC 1和PC 2生物合成来协调其加工，我们假设瘦素也可能调节其他酶、辅伴侣和完全激素原加工和成熟所必需的抑制剂。B）由于黑皮质素系统代表作用于TRH神经元的间接途径，我们还将确定α- MSH是否影响PCI、PC 2、proSAAS、7 B2和CPE的生物合成、成熟和活性.

DESCRIPTION (provided by applicant): Leptin, principally produced in adipose tissue, has a central physiologic role in providing information on energy stores and energy balance to brain centers that regulate appetite, energy expenditure and neuroendocrine function. One of the actions of leptin is to activate the Hypothalamic-Pituitary-Thyroid (HPT) axis through the thyrotropin-releasing hormone (TRH) peptide thereby increasing energy expenditure. During the last three years of funding, we were able to provide strong evidence for the existence of a direct (paraventricular nucleus, PVN) and an indirect (arcuate nucleus, ARC) pathway of leptin action on the regulation of the TRH prohormone biosynthesis. We demonstrated that leptin could directly regulate proTRH biosynthesis and TRH secretion in cultured hypothalamic neurons independently of the melanocortin (alpha-melanocyte-stimulating-hormone, alpha-MSH) input. We also observed the colocalization of the leptin receptor (ObRb) with proTRH in neurons of the PVN, strongly suggesting direct effects of leptin on TRH neurons. This hypothesis was further supported by the demonstration of ObRb mRNA expression within the PVN, and by showing that TRH neurons express SOCS-3 mRNA (which is the sensitive marker of direct leptin action) after leptin administration to rats. Recently, we demonstrated for the first time activation of STATS in TRH neurons by leptin in vivo, providing further evidence of a potential key role of the STAT3 transcription factor to regulate the activity of the proTRH promoter by leptin. We also recently demonstrated that the increase in TRH biosynthesis due to leptin action was associated with an up-regulation of the processing enzymes PCI and PC2, involved in the maturation of TRH and other proTRH peptides. Aim #1 We will test the hypothesis that there are two different or overlapping groups of PVN-TRH neurons carrying the ObRb (direct pathway) and the MC4R (indirect pathway) that are targeted by leptin and alpha-MSH to regulate the energy balance by increasing energy expenditure through the HPT axis, and potentially inhibiting food intake by sending synapses to the LH and DMH. Aim #2 We will test the hypothesis that leptin regulates the HPT axis primarily through the direct pathway. AIM #3 A) Because we found that leptin regulates proTRH and coordinates its processing by also up-regulating PCI and PC2 biosynthesis, we hypothesize that leptin might also regulate the other enzymes, co-chaperones, and inhibitors necessary for full prohormone processing and maturation. B) Since the melanocortin system represents the indirect pathway of action on TRH neurons, we will also determine whether alpha- MSH affects the biosynthesis, maturation and activity of PCI, PC2, proSAAS, 7B2 and CPE.