ATF6B (ATF6-beta) activates chaperones

Stable Identifier
R-HSA-8874177
Type
Pathway
Species
Homo sapiens
ReviewStatus
3/5
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Like its homolog ATF6 (reviewed in Fox and Andrew 2015), ATF6B is activated by cleavage in response to endoplasmic reticulum (ER) stress (Haze et al. 2001). In unstressed cells, ATF6B spans the ER membrane where its lumenal domain probably forms a complex with HSPA5 (BiP, GRP78). During ER stress, HSPA5 dissociates from ATF6B exposing Golgi localization signals in the lumenal domain of ATF6B and causing ATF6B to traffic to the Golgi membrane. The Golgi-resident proteases MBTPS1 (S1P) and MBTPS2 (S2P) cleave ATF6B and release the cytoplasmic domain, which contains a transcription activation domain, a bZIP dimerization domain, and a nuclear localization signal (Haze et al. 2001). N-glycosylation in the lumenal domain of ATF6B is required for cleavage (Guan et al. 2009). The cytoplasmic fragment traffics to the nucleus where it acts as a weak transcription activator (Haze et al. 2001). By forming heterodimers with the strong activator ATF6, ATF6B acts as an inhibitory modulator of ATF6 (Thuerauf et al. 2004, Thuerauf et al. 2007).
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