Role of palmitoylation of the serotonin 5-HT1A receptor in regulation of physiological and pathological receptor functions.

5-羟色胺（5-羟色胺或5-HT）是一种重要的神经递质，通过激活异质性表达的5-HT受体在中枢神经系统中介导广泛的功能作用。5-羟色胺能系统，特别是5-HT1A受体（5-HT1AR）不仅参与大脑生理功能的调节，而且与重度抑郁和焦虑有关。除了5-HT1AR在抑郁症发病机制及其临床用药中的重要作用外，其潜在机制尚不完全清楚。5-HT1AR经历翻译后棕榈酰化，这对于受体介导的抑制性Gi/o蛋白激活和下游效应信号传导至关重要。受体棕榈酰化还负责脂筏中5-HT1AR的定位，在受体功能的调节中起重要作用。在我们的初步实验中，我们已经确定DHHC5、DHHC9和DHHC21蛋白属于DHHC （Asp-His-His-Cys）蛋白家族，是负责5-HT1AR棕榈酰化的酶。特异性短发夹（sh） rna敲低这些dhhc可导致5-HT1AR棕榈酰化显著降低，并强烈影响受体介导的信号传导。此外，我们在啮齿动物和人类大脑中证实了5-HT1AR的体内棕榈酰化，并在恐惧条件小鼠海马中发现5-HT1AR棕榈酰化减少，DHHC21表达减少，提示棕榈酰化参与焦虑发生。本研究的主要目标是从分子上确定酶促5-HT1AR棕榈酰化的调节机制，并分析生理和病理条件下受体棕榈酰化在神经元特性调节中的作用。第二个主要目标是阐明5-HT1AR棕榈酰化在抑郁症的发生、维持和发病机制中的功能作用。这也暗示了5-HT1AR棕榈酰化作为治疗抑郁症的潜在治疗靶点的重要性。为了实现这些目标，我们将应用参与者实验室提供的尖端技术的协同组合（例如，培养神经元以及小鼠和人类大脑样本中的棕榈酰化分析，定量分子显微镜，FRET，单细胞水平和神经网络的电生理记录，啮齿动物中不同抑郁模型的应用以及行为分析）。这些研究的综合结果将极大地推进我们对棕榈酰化在生理和病理条件下对神经元功能调节的影响的基础知识，为5-HT1AR棕榈酰化治疗抑郁症和焦虑症的可能治疗作用提供信息。

Serotonin (5-hydroxytryptamine or 5-HT) is an important neurotransmitter mediating a wide range of functional effects in the central nervous system via activation of heterogeneously expressed 5-HT receptors. The serotonergic system and in particular 5-HT1A receptor (5-HT1AR) are implicated not only into regulation of physiological functions in the brain, but also in major depression and anxiety. Besides the important role of 5-HT1AR in the pathogenesis of depressive disorders and in their clinical medications, underlying mechanisms are not completely understood. The 5-HT1AR undergoes post-translational palmitoylation which is essential for receptor-mediated activation of inhibitory Gi/o-proteins and down-stream effector signaling. Receptor palmitoylation is also responsible for the localization of the 5-HT1AR in lipid rafts, which plays an important role in regulation of receptor functions. In our preliminary experiments we have identified DHHC5, DHHC9 and DHHC21 proteins belonging to the DHHC (Asp-His-His-Cys) protein family as enzymes responsible for the 5-HT1AR palmitoylation. Knocking-down of these DHHCs by specific short hairpin (sh)RNAs leads to substantially reduced 5-HT1AR palmitoylation and strongly affects receptor-mediated signaling. In addition, we have demonstrated in vivo palmitoylation of 5-HT1AR in rodent and human brains, and also found reduced 5-HT1AR palmitoylation as well as decreased DHHC21 expression in the hippocampus of fear conditioned mice, suggesting involvement of palmitoylation in anxiogenesis.The major goal of this proposal is to molecularly define mechanisms regulating enzymatic 5-HT1AR palmitoylation and analyze involvement of receptor palmitoylation in modulation of neuronal properties under physiological and pathological conditions. The second major goal is to elucidate the functional role of 5-HT1AR palmitoylation for the developing, maintaining and pathogenesis depressive disorders. This also implies importance of the 5-HT1AR palmitoylation as a potential therapeutic target for the treatment of depression. To achieve these goals we will apply the synergistic combination of cutting edge techniques presented in the participant labs (e.g. analysis of palmitoylation in cultured neurons as well as in brain samples from mice and humans, quantitative molecular microscopy, FRET, electrophysiological recordings at the single cell level and neuronal network, application of different depression models in rodents, and behavioral analysis). The combined outcomes of these investigations will greatly advance our fundamental knowledge about the impact of palmitoylation for regulation of neuronal functions under physiological and pathological conditions, providing information about the possible therapeutic role of 5-HT1AR palmitoylation for treating depression and anxiety disorders.