Instituto de Investigación en Biomedicina de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Partner Institute of the Max Planck Society, Buenos Aires C1425FQD, Argentina.
Fundación Instituto Leloir, Instituto de Investigaciones Bioquímicas de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires C1405BWE, Argentina.
J Neurosci. 2021 Jan 27;41(4):689-710. doi: 10.1523/JNEUROSCI.2322-20.2020. Epub 2020 Dec 1.
Circadian rhythms have been extensively studied in ; however, still little is known about how the electrical properties of clock neurons are specified. We have performed a behavioral genetic screen through the downregulation of candidate ion channels in the lateral ventral neurons (LNvs) and show that the hyperpolarization-activated cation current I is important for the behaviors that the LNvs influence: temporal organization of locomotor activity, analyzed in males, and sleep, analyzed in females. Using whole-cell patch clamp electrophysiology we demonstrate that small LNvs (sLNvs) are bursting neurons, and that I is necessary to achieve the high-frequency bursting firing pattern characteristic of both types of LNvs in females. Since firing in bursts has been associated to neuropeptide release, we hypothesized that I would be important for LNvs communication. Indeed, herein we demonstrate that I is fundamental for the recruitment of pigment dispersing factor (PDF) filled dense core vesicles (DCVs) to the terminals at the dorsal protocerebrum and for their timed release, and hence for the temporal coordination of circadian behaviors. Ion channels are transmembrane proteins with selective permeability to specific charged particles. The rich repertoire of parameters that may gate their opening state, such as voltage-sensitivity, modulation by second messengers and specific kinetics, make this protein family a determinant of neuronal identity. Ion channel structure is evolutionary conserved between vertebrates and invertebrates, making any discovery easily translatable. Through a screen to uncover ion channels with roles in circadian rhythms, we have identified the I channel as an important player in a subset of clock neurons of the fruit fly. We show that lateral ventral neurons (LNvs) need I to fire action potentials in a high-frequency bursting mode and that this is important for peptide transport and the control of behavior.
昼夜节律在 中已经被广泛研究；然而，对于时钟神经元的电特性如何被指定，仍然知之甚少。我们通过下调侧腹神经节（LNvs）中的候选离子通道进行了行为遗传筛选，并表明超极化激活阳离子电流 I 对 LNvs 影响的行为很重要：在雄性中分析的运动活动的时间组织，以及在雌性中分析的睡眠。使用全细胞膜片钳电生理学，我们证明了小 LNvs（sLNvs）是爆发神经元，并且 I 对于实现雌性中两种类型 LNvs 的高频爆发式放电模式是必要的。由于爆发式放电与神经肽释放有关，我们假设 I 对于 LNvs 的通讯很重要。事实上，我们在此证明 I 对于将色素分散因子（PDF）填充的致密核心囊泡（DCV）募集到背侧原脑的末端以及它们的定时释放是至关重要的，从而对于昼夜节律行为的时间协调是至关重要的。离子通道是对特定带电粒子具有选择性通透性的跨膜蛋白。其开放状态的丰富参数可能包括电压敏感性、第二信使的调制和特定的动力学，这使得这个蛋白质家族成为神经元身份的决定因素。离子通道的结构在脊椎动物和无脊椎动物之间是保守的，因此任何发现都很容易转化。通过筛选揭示在昼夜节律中起作用的离子通道，我们已经确定 I 通道是果蝇时钟神经元的一个重要组成部分。我们表明，侧腹神经节（LNvs）需要 I 以高频爆发模式发射动作电位，这对于肽运输和行为控制很重要。
