神经回路的形成需要细胞表面蛋白的广泛相互作用以将轴突引导到其正确的目标神经元。粘附G蛋白偶联受体latrophilin-2(Lphn2)与其伴侣teneurin-3的跨细胞相互作用通过相互排斥指示海马网络的精确组装。Lphn2在远端CA1神经元中充当排斥受体,将其轴突引导到近端下膜,并作为近端下膜中的排斥配体,将近端CA1轴突引导至远端下膜。目前尚不清楚Lphn2介导的细胞内信号是否需要其在任一情况下的作用。这里,我们显示Lphn2在异源细胞中与Gα12/13偶联;这种偶联通过栓系激动剂的组成型暴露而增加。Lphn2系链激动剂区的特定突变破坏其G蛋白偶联和自身蛋白水解裂解,而突变自身蛋白水解裂解位点可以防止裂解,但保留了功能性束缚激动剂。使用体内错误表达测定法,我们证明了野生型Lphn2将近端CA1轴突误导到近端下膜,并且Lphn2束缚激动剂活性是其作为轴突排斥受体的作用所必需的。相比之下,Lphn2作为下膜靶神经元中的排斥配体的作用既不需要束缚激动剂活性,也不需要自身蛋白水解。因此,束缚激动剂活性是Lphn2介导的神经回路组装所必需的。
允许动物感知和与环境相互作用的复杂大脑回路在发育早期开始形成。在此期间,神经元延伸纤维状突起以建立精确的布线模式。进入纤维和靶细胞表面的各种类型的蛋白质确保只有正确的伴侣会连接在一起。例如,Latrophilin-2,是海马中形成精确连接所必需的神经元表面蛋白,对记忆很重要的大脑区域。穿过某些神经元的膜,它作为信号发送配体来引导传入的纤维,携带Latrophilin-2的神经元会排斥显示某些蛋白质伴侣的细胞的投射。同时,Latrophilin-2还允许神经元通过与称为G蛋白的细胞内信号蛋白一起工作来接收化学信号,这有助于在细胞之间传递信息。尚不清楚这种作为信号受体的作用如何参与发育过程中海马的布线。为了探索这个问题,皮德里克,Perry-Hauser等人。研究了Latrophilin-2对通常不携带该蛋白的小鼠海马神经元连接模式的影响。将Latrophilin-2引入这些“近端CA1细胞”会使它们远离通常的伴侣-除非Latrophilin-2被改变以使其无法与G蛋白相互作用。相比之下,迫使CA1细胞的连接伴侣展示正常或改变版本的Latrophilin-2不会干扰充当排斥配体的蛋白质。一起来看,这些结果表明,Latrophilin-2通过G蛋白发出信号的能力对于试图将其纤维投射到其他细胞上的神经元很重要,但当Latrophilin-2作用于引导来自其他神经元的传入纤维时并不重要。这些结果表明,根据上下文,单个蛋白质可以通过充当信号接收受体和信号发送配体来塑造神经回路。在未来,皮德里克,Perry-Hauser等人。希望他们的发现将为神经发育障碍中大脑的布线如何中断提供新的思路。
The formation of neural circuits requires extensive interactions of cell-surface proteins to guide axons to their correct target neurons. Trans-cellular interactions of the adhesion G protein-coupled receptor
latrophilin-2 (Lphn2) with its partner teneurin-3 instruct the precise assembly of hippocampal networks by reciprocal repulsion. Lphn2 acts as a repulsive receptor in distal CA1 neurons to direct their axons to the proximal subiculum, and as a repulsive ligand in the proximal subiculum to direct proximal CA1 axons to the distal subiculum. It remains unclear if Lphn2-mediated intracellular signaling is required for its role in either context. Here, we show that Lphn2 couples to Gα12/13 in heterologous cells; this coupling is increased by constitutive exposure of the tethered agonist. Specific mutations of Lphn2\'s tethered agonist region disrupt its G protein coupling and autoproteolytic cleavage, whereas mutating the autoproteolytic cleavage site alone prevents cleavage but preserves a functional tethered agonist. Using an in vivo misexpression assay, we demonstrate that wild-type Lphn2 misdirects proximal CA1 axons to the proximal subiculum and that Lphn2 tethered agonist activity is required for its role as a repulsive receptor in axons. By contrast, neither tethered agonist activity nor autoproteolysis were necessary for Lphn2\'s role as a repulsive ligand in the subiculum target neurons. Thus, tethered agonist activity is required for Lphn2-mediated neural circuit assembly in a context-dependent manner.
The complex brain circuits that allow animals to sense and interact with their environment start to form early during development. Throughout this period, neurons extend fiber-like projections to establish precise wiring patterns. Various types of proteins at the surface of both incoming fibers and target cells ensure that only the right partners will connect together.
Latrophilin-2, for example, is a neuronal surface protein essential for the formation of accurate connections in the hippocampus, a brain region important for memory. Studded through the membrane of certain neurons, it acts as a signal-sending ligand to direct incoming fibers, with neurons that carry Latrophilin-2 repelling projections from cells that display certain protein partners. At the same time, Latrophilin-2 also allows neurons to receive chemical signals by working with intracellular signaling proteins known as G proteins, which help to relay information between cells. It remained unclear how this role as a signalling receptor participates in the wiring of the hippocampus during development. To explore this question, Pederick, Perry-Hauser et al. examined the impact of Latrophilin-2 on the connection patterns of mouse hippocampal neurons that do not normally carry this protein. Introducing
Latrophilin-2 into these ‘proximal CA1 cells’ misdirected them away from their usual partners – unless
Latrophilin-2 was altered so that it could not interact with G proteins. In contrast, forcing the connecting partners of CA1 cells to display normal or altered versions of Latrophilin-2 did not interfere with the protein acting as a repulsive ligand. Taken together, these results suggest that the ability of
Latrophilin-2 to signal through G proteins is important for neurons that are attempting to project their fibers onto other cells, but not important when Latrophilin-2 acts in targets to direct incoming fibers from other neurons. These results show that a single protein can shape neural circuits by acting both as a signal-receiving receptor and a signal-sending ligand depending on the context. In the future, Pederick, Perry-Hauser et al. hope that their findings will shed new light on how the wiring of the brain is disrupted in neurodevelopmental disorders.