DNAJB12 and DNJB14 are non-redundant Hsp40 redox chaperones involved in endoplasmic reticulum protein reflux

• Published in: Biochimica et biophysica acta. General subjects Vol. 1868; no. 1; p. 130502
• Main Authors: Purificação, Aline Dias da, Debbas, Victor, Tanaka, Leonardo Yuji, Gabriel, Gabriele Verônica de Mello, Wosniak Júnior, João, De Bessa, Tiphany Coralie, Garcia-Rosa, Sheila, Laurindo, Francisco Rafael Martins, Oliveira, Percillia Victoria Santos
• Format: Journal Article
• Language: English
• Published: Netherlands 01.01.2024
• Subjects: disulfides; endoplasmic reticulum; gene expression; heat; heat-shock protein 40; proteasome endopeptidase complex; sulfenic acids; thiols; unfolded protein response; DNAJB12; DNAJB14; ER protein reflux; Endoplasmic reticulum stress
• ISSN: 0304-4165; 1872-8006; 1872-8006
• DOI: 10.1016/j.bbagen.2023.130502

The endoplasmic reticulum (ER) transmembrane chaperones DNAJB12(B12) and DNAJB14(B14) are cofactors that cooperate with cytosolic Heat Shock-70 protein (HSC70) facilitating folding/degradation of nascent membrane proteins and supporting the ER-membrane penetration of viral particles. Here, we assessed structural/functional features of B12/B14 with respect to their regulation by ER stress and their involvement in ER stress-mediated protein reflux. We investigated the effect of Unfolded Protein Response(UPR)-eliciting drugs on the expression/regulation of B12-B14 and their roles in ER-to-cytosol translocation of Protein Disulfide Isomerase-A1(PDI). We show that B12 and B14 are similar but do not seem redundant. They share predicted structural features and show high homology of their cytosolic J-domains, while their ER-lumen DUF1977 domains are quite dissimilar. Interactome analysis suggested that B12/B14 associate with different biological processes. UPR activation did not significantly impact on B12 gene expression, while B14 transcripts were up-regulated. Meanwhile, B12 and B14 (33.4 kDa isoform) protein levels were degraded by the proteasome upon acute reductive challenge. Also, B12 degradation was impaired upon sulfenic-acid trapping by dimedone. We originally report that knockdown of B12/B14 and their cytosolic partner SGTA in ER-stressed cells significantly impaired the amount of the ER redox-chaperone PDI in a cytosolic-enriched fraction. Additionally, B12 but not B14 overexpression increased PDI relocalization in non-stressed cells. Our findings reveal that B12/B14 regulation involves thiol redox processes that may impact on their stability and possibly on physiological effects. Furthermore, we provide novel evidence that these proteins are involved in UPR-induced ER protein reflux.