A serine protease inhibitor prevents endoplasmic reticulum stress-induced cleavage but not transport of the membrane-bound transcription factor ATF6.
Mammalian cells express several transcription factors embedded in the endoplasmic reticulum (ER) as transmembrane proteins that are activated by proteolysis, and two types of these proteins have been extensively investigated. One type comprises the sterol regulatory element-binding proteins (SREBP-1 and SREBP-2). The other type comprises the activating transcription factors 6 (ATF6alpha and ATF6beta), which are activated in response to ER stress. It was shown previously that both SREBP and ATF6 are cleaved sequentially first by the Site-1 protease (serine protease) and then by the Site-2 protease (metalloprotease) (Ye, J., Rawson, R. B., Komuro, R., Chen, X., Dave, U. P., Prywes, R., Brown, M. S., and Goldstein, J. L. (2000) Mol. Cell 6, 1355-1364). In this study, we examined various protease inhibitors and found that 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF), a serine protease inhibitor, prevented ER stress-induced cleavage of ATF6alpha and ATF6beta, resulting in inhibition of transcriptional induction of ATF6-target genes. AEBSF also inhibited production of the mature form of SREBP-2 that was induced in response to sterol depletion, and appeared to directly prevent cleavage of ATF6alpha and ATF6beta by inhibiting Site-1 protease. As the Site-1 protease is localized in the Golgi apparatus, both SREBP and ATF6 must relocate to the Golgi apparatus to be cleaved. We showed here that AEBSF treatment had little effect on ER stress-induced translocation of ATF6 from the ER to the Golgi apparatus, but blocked nuclear localization of ATF6. These results indicate that the transport of ATF6 from the ER to the Golgi apparatus and that from the Golgi apparatus to the nucleus are distinct steps that can be distinguished by treatment with AEBSF.
Okada
Tetsuya
T
Graduate School of Biostudies, Kyoto University, Kyoto 606-8304, Japan.
Haze
Kyosuke
K
Nadanaka
Satomi
S
Yoshida
Hiderou
H
Seidah
Nabil G
NG
Hirano
Yuko
Y
Sato
Ryuichiro
R
Negishi
Manabu
M
Mori
Kazutoshi
K
D051702:Activating Transcription Factor 6; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004229:Dithiothreitol / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006056:Golgi Apparatus / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D043484:Proprotein Convertases; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology*; D051780:Sterol Regulatory Element Binding Protein 1; D051782:Sterol Regulatory Element Binding Protein 2; D013450:Sulfones / Q000494:pharmacology*; D019284:Thapsigargin / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism*
C497111:ATF6 protein, human; D051702:Activating Transcription Factor 6; D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C497387:SREBF1 protein, human; C497390:SREBF2 protein, human; D015842:Serine Proteinase Inhibitors; D051780:Sterol Regulatory Element Binding Protein 1; D051782:Sterol Regulatory Element Binding Protein 2; D013450:Sulfones; D014157:Transcription Factors; C002010:4-(2-aminoethyl)benzenesulfonylfluoride; D019284:Thapsigargin; D043484:Proprotein Convertases; D012697:Serine Endopeptidases; C115575:membrane-bound transcription factor peptidase, site 1; D004229:Dithiothreitol