title: Signal peptide peptidase-mediated nuclear localization of heme oxygenase-1 promotes cancer cell proliferation and invasion independent of its enzymatic activity.
abstract: Heme oxygenase-1 (HO-1) is a heme-degrading enzyme anchored in the endoplasmic reticulum by a carboxyl-terminal transmembrane segment (TMS). HO-1 is highly expressed in various cancers and its nuclear localization is associated with the progression of some cancers. Nevertheless, the mechanism underlying HO-1 nuclear translocation and its pathological significance remain elusive. Here we show that the signal peptide peptidase (SPP) catalyzes the intramembrane cleavage of HO-1. Coexpression of HO-1 with wild-type SPP, but not a dominant-negative SPP, promoted the nuclear localization of HO-1 in cells. Mass spectrometry analysis of cytosolic HO-1 isolated from HeLa cells overexpressing HO-1 and SPP revealed two adjacent intramembrane cleavage sites located after S275 and F276 within the TMS. Mutations of S275F276 to A275L276 significantly hindered SPP-mediated HO-1 cleavage and nuclear localization. Nuclear HO-1 was detected in A549 and DU145 cancer cell lines expressing high levels of endogenous HO-1 and SPP. SPP knockdown or inhibition significantly reduced nuclear HO-1 localization in A549 and DU145 cells. The positive nuclear HO-1 stain was also evident in lung cancer tissues expressing high levels of HO-1 and SPP. Overexpression of a truncated HO-1 (t-HO-1) lacking the TMS in HeLa and H1299 cells promoted cell proliferation and migration/invasion. The effect of t-HO-1 was not affected by a mutation in the catalytic site. However, blockade of t-HO-1 nuclear localization abolished t-HO-1-mediated effect. The tumorigenic effect of t-HO-1 was also demonstrated in the mouse model. These findings disclose that SPP-mediated intramembrane cleavage of HO-1 promotes HO-1 nuclear localization and cancer progression independent of HO-1 enzymatic activity.
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
authors.forename: F-F
authors.initials: FF
authors.lastname: Hsu
authors.affiliation: 1] Graduate Institute of Clinical Medicine, Taipei Medical University, Taipei, Taiwan [2] Cancer Center, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan.
authors.forename: C-T
authors.initials: CT
authors.lastname: Yeh
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
authors.forename: Y-J
authors.initials: YJ
authors.lastname: Sun
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
authors.forename: M-T
authors.initials: MT
authors.lastname: Chiang
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
authors.forename: W-M
authors.initials: WM
authors.lastname: Lan
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
authors.forename: F-A
authors.initials: FA
authors.lastname: Li
authors.affiliation: Cancer Center, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan.
authors.forename: W-H
authors.initials: WH
authors.lastname: Lee
authors.affiliation: Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
authors.forename: L-Y
authors.initials: LY
authors.lastname: Chau
mesh_terms: D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism*; D049109:Cell Proliferation; D006367:HeLa Cells; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry; D051379:Mice; D009361:Neoplasm Invasiveness; D009369:Neoplasms / Q000378:metabolism* / Q000473:pathology
chemical_list: C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; D016282:Aspartic Acid Endopeptidases; C460085:signal peptide peptidase