In developing brains, axons exhibit remarkable precision in selecting synaptic partners among many non-partner cells. Evolutionarily conserved teneurins are transmembrane proteins that instruct synaptic partner matching. However, how intracellular signaling pathways execute teneurins’ functions is unclear. Here, we use in situ proximity labeling to obtain the intracellular interactome of a teneurin (Ten-m) in the Drosophila brain. Genetic interaction studies using quantitative partner matching assays in both olfactory receptor neurons (ORNs) and projection neurons (PNs) reveal a common pathway: Ten-m binds to and negatively regulates a RhoGAP, thus activating the Rac1 small GTPases to promote synaptic partner matching. Developmental analyses with single-axon resolution identify the cellular mechanism of synaptic partner matching: Ten-m signaling promotes local F-actin levels and stabilizes ORN axon branches that contact partner PN dendrites. Combining spatial proteomics and high-resolution phenotypic analyses, this study advanced our understanding of both cellular and molecular mechanisms of synaptic partner matching.

在大脑发育过程中，轴突在许多非伙伴细胞中选择突触伙伴方面表现出非凡的精确度。进化上保守的 teneurins 是指导突触伙伴匹配的跨膜蛋白。然而，细胞内信号通路如何执行 tenurins 的功能尚不清楚。在这里，我们使用原位邻近标记来获得果蝇大脑中 teneurin (Ten-m) 的细胞内相互作用组。在嗅觉受体神经元 (ORN) 和投射神经元 (PN) 中使用定量伴侣匹配测定进行的遗传相互作用研究揭示了一个共同的途径：Ten-m 结合并负向调节 RhoGAP，从而激活 Rac1 小 GTP 酶以促进突触伴侣匹配。单轴突分辨率的发育分析确定了突触伙伴匹配的细胞机制：10-m 信号传导促进局部 F-肌动蛋白水平并稳定接触伙伴 PN 树突的 ORN 轴突分支。这项研究结合了空间蛋白质组学和高分辨率表型分析，增进了我们对突触伙伴匹配的细胞和分子机制的理解。