title: RIG1 suppresses Ras activation and induces cellular apoptosis at the Golgi apparatus.
abstract: Retinoid-inducible gene 1 encodes RIG1 is a growth regulator, which inhibits the pathways of the RAS/mitogen-activated protein kinases by suppressing the activation of RAS. Confocal microscopic analysis demonstrated that RIG1 is localized in the endoplasmic reticulum (ER) and Golgi apparatus in HtTA cervical cancer cells. Carboxyterminal-deleted RIG1 targeted to the Golgi or ER was constructed and validated. The activation of HRAS was inhibited by 25.1% or 81.4% in cells cotransfected with wild-type or Golgi-targeted RIG1, respectively. Expression of wild-type or Golgi-targeted RIG1 for 24 h induced cellular apoptosis in HtTA cells, as assessed by MTT assay, the release of lactate dehydrogenase, and chromatin condensation. In contrast, ER-targeted RIG1 and carboxyterminal-deleted RIG1 (RIG1DeltaC) exhibited no activity. Caspase-2, -3, and -9 were activated following the expression of wild-type and Golgi-targeted RIG1. Although the caspase-3 inhibitor Z-DEVD-FMK partially or completely reversed the cell death induced by wild-type or Golgi-targeted RIG1, it did not prevent the anti-RAS effect of RIG1. In conclusion, the proapoptotic and anti-RAS activities of RIG1 are primarily associated with the Golgi localization of the protein. The proapoptotic activities of RIG1 are mediated through the activation of caspase-2 and -3 and are independent of its effect on RAS.
authors.affiliation: Graduate Institute of Life Sciences, National Defense Medical Center, and Department of Medical Education and Research, Buddhist Tzu Chi General Hospital, 289 Jianguo Road, Xindian City, Taipei, Taiwan, ROC.
authors.forename: Fu-Ming
authors.initials: FM
authors.lastname: Tsai
authors.forename: Rong-Yaun
authors.initials: RY
authors.lastname: Shyu
authors.forename: Shun-Yuan
authors.initials: SY
authors.lastname: Jiang
mesh_terms: D017209:Apoptosis; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D016283:Proto-Oncogene Proteins p21(ras) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000378:metabolism*
chemical_list: D061945:Caspase Inhibitors; C437968:PLAAT4 protein, human; D018168:Receptors, Retinoic Acid; D004815:Epidermal Growth Factor; D020169:Caspases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)