title: Phospholipase C-related catalytically inactive protein (PRIP) controls KIF5B-mediated insulin secretion.
abstract: We previously reported that phospholipase C-related catalytically inactive protein (PRIP)-knockout mice exhibited hyperinsulinemia. Here, we investigated the role of PRIP in insulin granule exocytosis using Prip-knockdown mouse insulinoma (MIN6) cells. Insulin release from Prip-knockdown MIN6 cells was higher than that from control cells, and Prip knockdown facilitated movement of GFP-phogrin-labeled insulin secretory vesicles. Double-immunofluorescent staining and density step-gradient analyses showed that the KIF5B motor protein co-localized with insulin vesicles in Prip-knockdown MIN6 cells. Knockdown of GABAA-receptor-associated protein (GABARAP), a microtubule-associated PRIP-binding partner, by Gabarap silencing in MIN6 cells reduced the co-localization of insulin vesicles with KIF5B and the movement of vesicles, resulting in decreased insulin secretion. However, the co-localization of KIF5B with microtubules was not altered in Prip- and Gabarap-knockdown cells. The presence of unbound GABARAP, freed either by an interference peptide or by Prip silencing, in MIN6 cells enhanced the co-localization of insulin vesicles with microtubules and promoted vesicle mobility. Taken together, these data demonstrate that PRIP and GABARAP function in a complex to regulate KIF5B-mediated insulin secretion, providing new insights into insulin exocytic mechanisms.
authors.affiliation: Department of Cellular and Molecular Pharmacology, Division of Basic Life Sciences, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8553, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Asano
authors.affiliation: Laboratory of Molecular and Cellular Biophysics, Research Institute for Electronic Science, Hokkaido University, Sapporo 001-0020, Japan.
authors.forename: Tomomi
authors.initials: T
authors.lastname: Nemoto
authors.affiliation: Department of Cellular and Molecular Pharmacology, Division of Basic Life Sciences, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8553, Japan.
authors.forename: Tomoya
authors.initials: T
authors.lastname: Kitayama
authors.affiliation: Department of Cellular and Molecular Pharmacology, Division of Basic Life Sciences, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8553, Japan.
authors.forename: Kae
authors.initials: K
authors.lastname: Harada
authors.affiliation: Department of Cellular and Molecular Pharmacology, Division of Basic Life Sciences, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8553, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Cellular and Molecular Pharmacology, Division of Basic Life Sciences, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8553, Japan.
authors.forename: Kana
authors.initials: K
authors.lastname: Harada
authors.affiliation: Laboratory of Biomembranes, Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, Tokyo 162-8640, Japan.
authors.forename: Isei
authors.initials: I
authors.lastname: Tanida
authors.affiliation: Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Hirata
authors.affiliation: Department of Cellular and Molecular Pharmacology, Division of Basic Life Sciences, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8553, Japan tkanema2@hiroshima-u.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kanematsu
keywords: GABARAP; Insulin secretion; KIF5B; PRIP; Vesicle transport