Trafficking of the bZIP transmembrane transcription factor CREB-H into alternate pathways of ERAD and stress-regulated intramembrane proteolysis.
CREB-H is an ATF6-related, transmembrane transcription factor that, in response to endoplasmic reticulum (ER)-associated stress, is cleaved by Golgi proteases and transported to the nucleus to effect appropriate adaptive responses. We characterize the ER processing and turnover of CREB-H with results which have important implications for ER stress regulation and signalling. We show that CREB-H is glycosylated and demonstrate that both the ER and nuclear forms of CREB-H have short half-lives. We also show that CREB-H is subject to cycles of retrotranslocation, deglycosylation and degradation through the ER-associated degradation (ERAD) pathway. Proteasome inhibition resulted in accumulation of a cytosolic intermediate but additionally, in contrast to inhibition of glycosylation, promoted specific cleavage of CREB-H and nuclear transport of the N-terminal-truncated product. Our data indicate that under normal conditions CREB-H is transported back from the ER to the cytosol, where it is subject to ERAD, but under conditions that repress proteasome function or promote load CREB-H is diverted from this pathway instead undergoing cleavage and nuclear transport. Finally, we identify a cytoplasmic determinant involved in CREB-H ER retention, deletion of which results in constitutive Golgi transport and corresponding cleavage. We present a model where cellular stresses may be sensed at different levels by different members of the basic and leucine zipper domain transmembrane proteins.
Bailey
Daniel
D
Marie Curie Research Institute, The Chart, Oxted, Surrey, RH8 0TL, UK.
Barreca
Cristina
C
Marie Curie Research Institute, The Chart, Oxted, Surrey, RH8 0TL, UK.
O'Hare
Peter
P
Marie Curie Research Institute, The Chart, Oxted, Surrey, RH8 0TL, UK.
D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism*; D002522:Chlorocebus aethiops; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D008954:Models, Biological; D008969:Molecular Sequence Data; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
C500051:Creb3l3 protein, mouse; D017362:Cyclic AMP Response Element-Binding Protein; D007976:Leupeptins; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde