Myosin Va, a Novel Interaction Partner of STXBP1, Is Required to Transport Syntaxin1A to the Plasma Membrane

• Published in: Neuroscience 2023-08, Vol.524, p.256-268
• Main Authors: Taura, Yoshihiro, Tozawa, Takenori, Fujimoto, Takahiro, Ichise, Eisuke, Chiyonobu, Tomohiro, Itoh, Kyoko, Iehara, Tomoko
• Format: Article
• Language: English
• Subjects: Animals; Brain Diseases - genetics; Cell Membrane - metabolism; membrane trafficking; Mice; Munc18 Proteins - genetics; Munc18 Proteins - metabolism; myosin Va; Neurons - metabolism; RNA Interference; STXBP1 encephalopathy; syntaxin-binding protein1; syntaxin1a
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2023.05.031

•A novel interaction partner of STXBP1, Myosin Va, was identified.•Myosin Va showed tight association with STXBP1S rather than STXBP1L.•STXBP1 and Myosin Va were co-expressed at tip of the neurites in primary hippocampal neurons.•STXBP1 and Myosin Va were required for membrane trafficking of Syntaxin1A. Syntaxin-binding protein 1 (STXBP1, also known as Munc18-1) regulates exocytosis as a chaperone protein of Syntaxin1A. The haploinsufficiency of STXBP1 causes early infantile-onset developmental and epileptic encephalopathy, known as STXBP1 encephalopathy. Previously, we reported impaired cellular localization of Syntaxin1A in induced pluripotent stem cell-derived neurons from an STXBP1 encephalopathy patient harboring a nonsense mutation. However, the molecular mechanism of abnormal Syntaxin1A localization in the haploinsufficiency of STXBP1 remains unknown. This study aimed to identify the novel interacting partner of STXBP1 involved in transporting Syntaxin1A to the plasma membrane. Affinity purification coupled with mass spectrometry analysis identified a motor protein Myosin Va as a potential binding partner of STXBP1. Co-immunoprecipitation analysis of the synaptosomal fraction from the mouse and tag-fused recombinant proteins revealed that the STXBP1 short splice variant (STXBP1S) interacted with Myosin Va in addition to Syntaxin1A. These proteins colocalized at the tip of the growth cone and axons in primary cultured hippocampal neurons. Furthermore, RNAi-mediated gene silencing in Neuro2a cells showed that STXBP1 and Myosin Va were required for membrane trafficking of Syntaxin1A. In conclusion, this study proposes a potential role of STXBP1 in the trafficking of the presynaptic protein Syntaxin1A to the plasma membrane in conjunction with Myosin Va.