TY - JOUR TI - Rabphilin 3A binds the N-peptide of SNAP-25 to promote SNARE complex assembly in exocytosis AU - Li, Tianzhi AU - Cheng, Qiqi AU - Wang, Shen AU - Ma, Cong A2 - Pfeffer, Suzanne R VL - 11 PY - 2022 DA - 2022/09/29 SP - e79926 C1 - eLife 2022;11:e79926 DO - 10.7554/eLife.79926 UR - https://doi.org/10.7554/eLife.79926 AB - Exocytosis of secretory vesicles requires the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins and small GTPase Rabs. As a Rab3/Rab27 effector protein on secretory vesicles, Rabphilin 3A was implicated to interact with SNAP-25 to regulate vesicle exocytosis in neurons and neuroendocrine cells, yet the underlying mechanism remains unclear. In this study, we have characterized the physiologically relevant binding sites between Rabphilin 3A and SNAP-25. We found that an intramolecular interplay between the N-terminal Rab-binding domain and C-terminal C2AB domain enables Rabphilin 3A to strongly bind the SNAP-25 N-peptide region via its C2B bottom α-helix. Disruption of this interaction significantly impaired docking and fusion of vesicles with the plasma membrane in rat PC12 cells. In addition, we found that this interaction allows Rabphilin 3A to accelerate SNARE complex assembly. Furthermore, we revealed that this interaction accelerates SNARE complex assembly via inducing a conformational switch from random coils to α-helical structure in the SNAP-25 SNARE motif. Altogether, our data suggest that the promotion of SNARE complex assembly by binding the C2B bottom α-helix of Rabphilin 3A to the N-peptide of SNAP-25 underlies a pre-fusion function of Rabphilin 3A in vesicle exocytosis. KW - exocytosis KW - SNARE KW - Rabphilin 3A KW - SNAP-25 KW - conformational change JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -