Burdina Nele, Liebsch Filip, Macha Arthur, Gil Joaquín Lucas Ortuño, Frommelt Pia, Rais Irina, Basler Fabian, Pöpsel Simon, Schwarz Guenter
Department of Chemistry and Biochemistry, Institute of Biochemistry, University of Cologne, Cologne, Germany.
Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital, University of Cologne, Cologne, Germany.
J Neurochem. 2025 Aug;169(8):e70169. doi: 10.1111/jnc.70169.
Gephyrin is the main scaffolding protein at inhibitory synapses, clustering glycine and GABA receptors. At specific GABAergic synapses, the nucleotide exchange factor collybistin recruits gephyrin to the postsynaptic membrane via interaction with phosphoinositides. However, the molecular mechanisms underlying the formation, maintenance, and regulation of collybistin-dependent gephyrin clusters remain poorly understood. This study sheds light on the molecular mechanism of gephyrin cluster formation on the basis of gephyrin self-oligomerization induced by collybistin, leading to the formation of a high-molecular weight (> 5 MDa) gephyrin-collybistin complex, which is regulated in two ways: First, plasma-membrane phosphoinositides promote complex formation, demonstrating their critical role in membrane targeting and stabilization of gephyrin-collybistin clusters at postsynaptic sites. Second, gephyrin phosphorylation at Ser325 abolishes complex formation with collybistin, thus impairing collybistin-dependent gephyrin clustering at GABAergic synapses. Collectively, our data demonstrate a molecular mechanism for synaptic clustering of gephyrin, which involves collybistin- and phosphoinositide-dependent formation of high-molecular weight gephyrin oligomers.
桥连蛋白是抑制性突触处的主要支架蛋白，可聚集甘氨酸和γ-氨基丁酸（GABA）受体。在特定的GABA能突触中，核苷酸交换因子结肠直肠癌缺失蛋白通过与磷酸肌醇相互作用，将桥连蛋白募集到突触后膜。然而，结肠直肠癌缺失蛋白依赖性桥连蛋白簇的形成、维持和调控的分子机制仍知之甚少。本研究基于结肠直肠癌缺失蛋白诱导的桥连蛋白自寡聚化，揭示了桥连蛋白簇形成的分子机制，导致形成高分子量（>5 MDa）的桥连蛋白-结肠直肠癌缺失蛋白复合物，其调控方式有两种：第一，质膜磷酸肌醇促进复合物形成，表明它们在突触后位点桥连蛋白-结肠直肠癌缺失蛋白簇的膜靶向和稳定中起关键作用。第二，桥连蛋白第325位丝氨酸的磷酸化消除了与结肠直肠癌缺失蛋白的复合物形成，从而损害了GABA能突触处结肠直肠癌缺失蛋白依赖性桥连蛋白的聚集。总体而言，我们的数据证明了桥连蛋白突触聚集的分子机制，这涉及结肠直肠癌缺失蛋白和磷酸肌醇依赖性的高分子量桥连蛋白寡聚体的形成。
