Geranylgeranylacetone, an inducer of the 70-kDa heat shock protein (HSP70), elicits unfolded protein response and coordinates cellular fate independently of HSP70.
Geranylgeranylacetone (GGA), an antiulcer agent, has the ability to induce 70-kDa heat shock protein (HSP70) in various cell types and to protect cells from apoptogenic insults. However, little is known about effects of GGA on other HSP families of molecules. We found that, at concentrations >/=100 microM, GGA caused selective expression of 78-kDa glucose-regulated protein (GRP78), an HSP70 family member inducible by endoplasmic reticulum (ER) stress, without affecting the level of HSP70 in various cell types. Induction of ER stress by GGA was also evidenced by expression of another endogenous marker, CCAAT/enhancer-binding protein-homologous protein (CHOP); decreased activity of ER stress-responsive alkaline phosphatase; and unfolded protein response (UPR), including activation of the activating transcription factor 6 (ATF6) pathway and the inositol-requiring ER-to-nucleus signal kinase 1-X-box-binding protein 1 (IRE1-XBP1) pathway. Incubation of mesangial cells with GGA caused significant apoptosis, which was attenuated by transfection with inhibitors of caspase-12 (i.e., a dominant-negative mutant of caspase-12 and MAGE-3). Dominant-negative suppression of IRE1 or XBP1 significantly attenuated apoptosis without affecting the levels of CHOP and GRP78. Inhibition of c-Jun NH(2)-terminal kinase, the molecule downstream of IRE1, by 1,9-pyrazoloanthrone (SP600125) did not improve cell survival. Blockade of ATF6 by 4-(2-aminoethyl) benzenesulfonyl fluoride enhanced apoptosis by GGA, and it was correlated with attenuated induction of both GRP78 and CHOP. Overexpression of GRP78 or dominant-negative inhibition of CHOP significantly attenuated GGA-induced apoptosis. These results suggested that GGA triggers both proapoptotic (IRE1-XBP1, ATF6-CHOP) and antiapoptotic (ATF6-GRP78) UPR and thereby coordinates cellular fate even without induction of HSP70.
Endo
Satoshi
S
Department of Molecular Signaling, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Shimokato 1110, Chuo, Yamanashi 409-3898, Japan.
Hiramatsu
Nobuhiko
N
Hayakawa
Kunihiro
K
Okamura
Maro
M
Kasai
Ayumi
A
Tagawa
Yasuhiro
Y
Sawada
Norifumi
N
Yao
Jian
J
Kitamura
Masanori
M
D051702:Activating Transcription Factor 6 / Q000378:metabolism; D000818:Animals; D000897:Anti-Ulcer Agents / Q000494:pharmacology*; D017209:Apoptosis; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D004224:Diterpenes / Q000494:pharmacology*; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D050883:HSC70 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D018832:Molecular Chaperones / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D017510:Protein Folding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D000071701:Regulatory Factor X Transcription Factors; D051742:Transcription Factor CHOP / Q000378:metabolism; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1
D051702:Activating Transcription Factor 6; D000897:Anti-Ulcer Agents; D004268:DNA-Binding Proteins; D004224:Diterpenes; D000091342:Endoplasmic Reticulum Chaperone BiP; D050883:HSC70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D008565:Membrane Proteins; D018832:Molecular Chaperones; D009687:Nuclear Proteins; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605544:Xbp1 protein, mouse; C000605545:Xbp1 protein, rat; D051742:Transcription Factor CHOP; D017346:Protein Serine-Threonine Kinases; C031049:geranylgeranylacetone