Cytoplasmic protein tyrosine phosphatase nonreceptor type 11 (PTPN11) and Drosophila homolog Corkscrew (Csw) regulate the mitogen-activated protein kinase (MAPK) pathway via a conserved autoinhibitory mechanism. Disease-causing loss-of-function (LoF) and gain-of-function (GoF) mutations both disrupt this autoinhibition to potentiate MAPK signaling. At the Drosophila neuromuscular junction glutamatergic synapse, LoF/GoF mutations elevate transmission strength and reduce activity-dependent synaptic depression. In both sexes of LoF/GoF mutations, the synaptic vesicles (SV)–colocalized synapsin phosphoprotein tether is highly elevated at rest, but quickly reduced with stimulation, suggesting a larger SV reserve pool with greatly heightened activity-dependent recruitment. Transmission electron microscopy of mutants reveals an elevated number of SVs clustered at the presynaptic active zones, suggesting that the increased vesicle availability is causative for the elevated neurotransmission. Direct neuron-targeted extracellular signal-regulated kinase (ERK) GoF phenocopies both increased local presynaptic MAPK/ERK signaling and synaptic transmission strength in mutants, confirming the presynaptic regulatory mechanism. Synapsin loss blocks this elevation in both presynaptic PTPN11 and ERK mutants. However, csw null mutants cannot be rescued by wild-type Csw in neurons: neurotransmission is only rescued by expressing Csw in both neurons and glia simultaneously. Nevertheless, targeted LoF/GoF mutations in either neurons or glia alone recapitulate the elevated neurotransmission. Thus, PTPN11/Csw mutations in either cell type are sufficient to upregulate presynaptic function, but a dual requirement in neurons and glia is necessary for neurotransmission. Taken together, we conclude that PTPN11/Csw acts in both neurons and glia, with LoF and GoF similarly upregulating MAPK/ERK signaling to enhance presynaptic Synapsin-mediated SV trafficking.

细胞质蛋白酪氨酸磷酸酶非受体 11 型 (PTPN11) 和果蝇同源物 Corkscrew (Csw) 通过保守的自抑制机制调节丝裂原激活蛋白激酶 (MAPK) 通路。引起疾病的功能丧失 (LoF) 和功能获得 (GoF) 突变都会破坏这种自身抑制，从而增强 MAPK 信号传导。在果蝇神经肌肉接头谷氨酸能突触，LoF/GoF 突变提高了传输强度并减少了活动依赖性突触抑制。在 LoF/GoF 突变的两性中，突触小泡 (SV) 共定位突触蛋白磷蛋白链在休息时高度升高，但随着刺激迅速降低，这表明存在更大的 SV 储备池，并且大大增强了活动依赖性募集。突变体的透射电子显微镜显示，聚集在突触前活性区的 SV 数量增加，表明囊泡可用性的增加是神经传递增加的原因。直接神经元靶向细胞外信号调节激酶 (ERK) GoF 表型均增加了突变体中的局部突触前 MAPK/ERK 信号传导和突触传递强度，证实了突触前调节机制。突触蛋白损失阻止了突触前 PTPN11 和 ERK 突变体的这种升高。然而，csw无效突变体不能被神经元中的野生型 Csw 拯救：神经传递只能通过在神经元和神经胶质细胞中同时表达 Csw 来拯救。然而，神经元或神经胶质细胞中的靶向 LoF/GoF 突变重现了神经传递的升高。因此，任一细胞类型中的 PTPN11/Csw 突变都足以上调突触前功能，但神经元和神经胶质细胞的双重要求对于神经传递是必要的。综上所述，我们得出结论，PTPN11/Csw 在神经元和神经胶质细胞中起作用，LoF 和 GoF 类似地上调 MAPK/ERK 信号传导，以增强突触前突触蛋白介导的 SV 运输。