title: KRAS-induced actin-interacting protein is required for the proper localization of inositol 1,4,5-trisphosphate receptor in the epithelial cells.
abstract: Three inositol 1,4,5-trisphosphate receptor (IP(3)R) subtypes are differentially expressed among tissues and function as the Ca(2+) release channel on specialized endoplasmic reticulum (ER) membranes. The proper subcellular localization of IP(3)R is crucial for its proper function, but this molecular mechanism is unclear. KRAS-induced actin-interacting protein (KRAP) was originally identified as a cancer-related molecule, and is involved in the regulation of whole-body energy homeostasis and pancreatic exocrine system. We herein identified IP(3)R as an associated molecule with KRAP in vivo, and the association was validated by the co-immunoprecipitation and confocal immunostaining studies in mouse tissues including liver and pancreas. The association of KRAP with IP(3)R was also observed in the human epithelial cell lines including HCT116, HeLa and HEK293 cells. Intriguingly, KRAP interacts with distinct subtypes of IP(3)R in a tissue-dependent manner, i.e. IP(3)R1 and IP(3)R2 in the liver and IP(3)R2 and IP(3)R3 in the pancreas. The NH(2)-terminal amino acid residues 1-610 of IP(3)R are critical for the association with KRAP and KRAP-IP(3)R complex resides in a specialized ER but not a typical reticular ER. Furthermore, the localization of particular IP(3)R subtypes in tissues from KRAP-deficient mice is obviously disturbed, i.e. IP(3)R1 and IP(3)R2 in the liver and IP(3)R2 and IP(3)R3 in the pancreas. These findings demonstrate that KRAP physically associates with IP(3)R and regulates the proper localization of IP(3)R in the epithelial cells in vivo and cultured cells, and might shed light on the Ca(2+) signaling underlying physiological cellular programs, cancer development and metabolism-related diseases.
authors.affiliation: Department of Cell Biology, Faculty of Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Fujimoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Machida
authors.forename: Yoko
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Tsunoda
authors.forename: Keiko
authors.initials: K
authors.lastname: Doi
authors.forename: Takeharu
authors.initials: T
authors.lastname: Ota
authors.forename: Tadashi
authors.initials: T
authors.lastname: Okamura
authors.forename: Masahide
authors.initials: M
authors.lastname: Kuroki
authors.forename: Senji
authors.initials: S
authors.lastname: Shirasawa
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D010179:Pancreas / Q000378:metabolism; D014018:Tissue Distribution
chemical_list: D053496:Inositol 1,4,5-Trisphosphate Receptors; C557477:KRAP protein, mouse; D008840:Microfilament Proteins; D002118:Calcium