Phosphorylated septin 3 delocalizes from the spine base and facilitates endoplasmic reticulum extension into spines via myosin-Va. - Ageta-Ishihara, Natsumi; Mizukami, Masato; Kinoshita, Itsuki; Asami, Yurika; Nishioka, Tomoki; Bito, Haruhiko; Kaibuchi, Kozo; Kinoshita, Makoto (Molecular Brain, 2025)