title: SNAP23/25 and VAMP2 mediate exocytic event of transferrin receptor-containing recycling vesicles.
abstract: We recently showed that Rab11 is involved not only in formation of recycling vesicles containing the transferrin (Tfn)-transferrin receptor (TfnR) complex at perinuclear recycling endosomes but also in tethering of recycling vesicles to the plasma membrane (PM) in concert with the exocyst tethering complex. We here aimed at identifying SNARE proteins responsible for fusion of Tfn-TfnR-containing recycling vesicles with the PM, downstream of the exocyst. We showed that exocyst subunits, Sec6 and Sec8, can interact with SNAP23 and SNAP25, both of which are PM-localizing Qbc-SNAREs, and that depletion of SNAP23 and/or SNAP25 in HeLa cells suppresses fusion of Tfn-TfnR-containing vesicles with the PM, leading to accumulation of the vesicles at the cell periphery. We also found that VAMP2, an R-SNARE, is colocalized with endocytosed Tfn on punctate endosomal structures, and that its depletion in HeLa cells suppresses recycling vesicle exocytosis. These observations indicate that fusion of recycling vesicles with the PM downstream of the exocyst is mediated by SNAP23/25 and VAMP2, and provide novel insight into non-neuronal roles of VAMP2 and SNAP25.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Kubo
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Minako
authors.initials: M
authors.lastname: Kobayashi
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Nozaki
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Chikako
authors.initials: C
authors.lastname: Yagi
authors.affiliation: Division of Molecular Biology, Tottori University School of Life Science, Yonago, Tottori 683-8503, Japan.
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Hatsuzawa
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Katoh
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Hye-Won
authors.initials: HW
authors.lastname: Shin
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Senye
authors.initials: S
authors.lastname: Takahashi
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan kazunaka@pharm.kyoto-u.ac.jp.
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Nakayama
keywords: Exocyst; Exocytosis; Recycling endosome; SNAP23; SNAP25; Transferrin receptor; VAMP2