title: Effect of ionomycin on interaction of calnexin with vesicular stomatitis virus glycoprotein is cell type-specific.
abstract: Ionomycin is a calcium ionophore that induces release of calcium ions (Ca(2+)) from cellular storage to cytoplasm and Ca(2+) influx from the outside of the cell. We investigated the effect of ionomycin on endoplasmic reticulum (ER)-Golgi transport in the vesicular stomatitis virus glycoprotein (VSV-G) system. Ionomycin inhibited transport of VSV-G in a concentration-dependent manner in baby hamster kidney (BHK) cells and HeLa cells. Half-maximum inhibition was observed at 5 μM. The inhibitory effect of ionomycin was not dependent on the cytoplasmic portion. Chelation of Ca(2+) in culture medium did not affect transport efficiency, but co-incubation with ionomycin completely shut off transport. These findings highlight the importance of Ca(2+) release from cellular storage. Because the inhibitory effect of ionomycin was expected to be dependent on mutual interaction of VSV-G and the ER chaperone calnexin, we further investigated interaction kinetics. In HeLa cells but not BHK cells the interaction of VSV-G and calnexin was prolonged in the presence of ionomycin. Taken together, the present results indicate that, by releasing Ca(2+) from cellular storage, ionomycin inhibits ER-Golgi transport by interfering with the release of VSV-G from calnexin in HeLa cells. A mechanism of cell type-dependent ER-Golgi transport regulation was revealed.
authors.affiliation: Department of Pathology, Nihon University School of Dentistry.
authors.forename: Michisato
authors.initials: M
authors.lastname: Okudera
authors.forename: Takahiro
authors.initials: T
authors.lastname: Gojoubori
authors.forename: Ichiro
authors.initials: I
authors.lastname: Tsujino
authors.forename: Masatake
authors.initials: M
authors.lastname: Asano
mesh_terms: D000818:Animals; D037281:Calnexin / Q000378:metabolism*; D002460:Cell Line; D006224:Cricetinae; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology*; D054243:Vesicular Stomatitis / Q000378:metabolism*; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: D006023:Glycoproteins; D014764:Viral Proteins; D037281:Calnexin; D015759:Ionomycin