title: The nuclear localization of SET mediated by impalpha3/impbeta attenuates its cytosolic toxicity in neurons.
abstract: SET is a multi-functional protein in proliferating cells. Some of the proposed functions of SET suggest an important nuclear role. However, the nuclear import pathway of SET is also unknown and the function of SET in neurons is unclear. Presently, using cortical neurons, we report that the nuclear import of SET is mediated by an impalpha/impbeta-dependent pathway. Nuclear localization signal, (168)KRSSQTQNKASRKR(181), in SET interacts with impalpha3, which recruits impbeta to form a ternary complex, resulting in efficient transportation of SET into nucleus. By in vitro nuclear import assay based on digitonin-permeabilized neurons, we further demonstrated that the nuclear import of SET relies on Ran GTPase. We provide evidence that this nuclear localization of SET is important in neuronal survival. Under basal conditions, SET is predominately nuclear. However, upon death induced by genotoxic stress, endogenous SET decreases in the nucleus and increases in the cytoplasm. Consistent with a toxic role of SET in the cytoplasm, targeted expression of SET to the cytoplasm exacerbates death compared to wild type SET expression which is protective following DNA damage. Taken together, our results indicate that SET is imported into the nucleus through its association with impalpha3/impbeta, and that localization of SET is important in regulation of neuronal death.
authors.affiliation: Institute of Molecular and Cell Biology, Proteos, Singapore, Singapore. dqu@uottawa.ca
authors.forename: Dianbo
authors.initials: D
authors.lastname: Qu
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jing
authors.initials: J
authors.lastname: Ma
authors.forename: Ke
authors.initials: K
authors.lastname: Guo
authors.forename: Rong
authors.initials: R
authors.lastname: Li
authors.forename: Yijun
authors.initials: Y
authors.lastname: Yin
authors.forename: Xinmin
authors.initials: X
authors.lastname: Cao
authors.forename: David S
authors.initials: DS
authors.lastname: Park
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity; D003600:Cytosol / Q000378:metabolism; D004268:DNA-Binding Proteins; D018014:Gene Transfer Techniques; D056488:Histone Chaperones; D006801:Humans; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity; D028901:alpha Karyopherins / Q000378:metabolism*; D028961:beta Karyopherins / Q000378:metabolism*
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D056488:Histone Chaperones; C513473:SET protein, human; D014157:Transcription Factors; D028901:alpha Karyopherins; D028961:beta Karyopherins; C523975:importin alpha 3, mouse