Deletion of LRRTM1 and LRRTM2 in adult mice impairs basal AMPA receptor transmission and LTP in hippocampal CA1 pyramidal neurons
Deletion of LRRTM1 and LRRTM2 in adult mice impairs basal AMPA receptor transmission and LTP in hippocampal CA1 pyramidal neurons
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DOI：
10.1073/pnas.1803280115
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发表时间：
2018-06-05
影响因子：
11.1
通讯作者：
Malenka, Robert
中科院分区：
文献类型：
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作者：
Bhouri, Mehdi;Morishita, Wade;Malenka, Robert
富含亮氨酸重复跨膜（LRRTM）蛋白是影响突触形成和功能的突触细胞粘附分子。它们在遗传上与神经精神疾病相关，并且通过它们的突触作用可能调节哺乳动物大脑中神经回路的建立和功能。在这里，我们利用LRRTM1和LRRTM2双条件性基因敲除小鼠（LRRTM1，2 cKO）的产生来研究LRRTM1，2在海马CA1锥体神经元中成熟兴奋性突触的作用。使用表达Cre重组酶的慢病毒在CA1神经元中体内遗传缺失LRRTM1，2显著损害了长时程增强（LTP），这种损害通过同时表达LRRTM2而不是LRRTM4来挽救。LRRTM2的细胞内尾的突变或缺失不影响其拯救LTP的能力，而旨在削弱其与突触前神经毒素结合的点突变阻止了LTP的拯救。与以前使用shRNA介导的LRRTM1，2敲除的工作相反，在成熟突触处敲除这些蛋白质也引起AMPA受体介导的突触传递的减少，但不引起NMDA受体介导的突触传递的减少，并且对突触前功能没有可检测的影响。培养神经元树突棘中重组光活化AMPA受体亚基GluA 1的成像显示，在不存在LRRTM1，2的情况下，它的稳定性较差。这些结果说明了条件性遗传缺失实验的优势，阐明内源性突触蛋白的功能，并建议LRRTM1，2蛋白质有助于稳定突触AMPA受体在成熟的棘在基础突触传递和LTP。
Leucine-rich repeat transmembrane (LRRTM) proteins are synaptic cell adhesion molecules that influence synapse formation and function. They are genetically associated with neuropsychiatric disorders, and via their synaptic actions likely regulate the establishment and function of neural circuits in the mammalian brain. Here, we take advantage of the generation of a LRRTM1 and LRRTM2 double conditional knockout mouse (LRRTM1,2 cKO) to examine the role of LRRTM1,2 at mature excitatory synapses in hippocampal CA1 pyramidal neurons. Genetic deletion of LRRTM1,2 in vivo in CA1 neurons using Cre recombinase-expressing lentiviruses dramatically impaired long-term potentiation (LTP), an impairment that was rescued by simultaneous expression of LRRTM2, but not LRRTM4. Mutation or deletion of the intracellular tail of LRRTM2 did not affect its ability to rescue LTP, while point mutations designed to impair its binding to presynaptic neurexins prevented rescue of LTP. In contrast to previous work using shRNA-mediated knockdown of LRRTM1,2, KO of these proteins at mature synapses also caused a decrease in AMPA receptor-mediated, but not NMDA receptor-mediated, synaptic transmission and had no detectable effect on presynaptic function. Imaging of recombinant photoactivatable AMPA receptor subunit GluA1 in the dendritic spines of cultured neurons revealed that it was less stable in the absence of LRRTM1,2. These results illustrate the advantages of conditional genetic deletion experiments for elucidating the function of endogenous synaptic proteins and suggest that LRRTM1,2 proteins help stabilize synaptic AMPA receptors at mature spines during basal synaptic transmission and LTP.