Structural transitions modulate the chaperone activities of Grp94

• 成果类型: Article
• 署名作者: Amankwah, Yaa S.; Fleifil, Yasmeen; Unruh, Erin; Collins, Preston; Wang, Yi; Vitou, Katherine; Bates, Alison; Obaseki, Ikponwmosa; Sugoor, Meghana; Alao, John Paul; Mccarrick, Robert M.; Gewirth, Daniel T.; Sahu, Indra D.; Li, Zihai; Lorigan, Gary. A.; Kravats, Andrea N.
• 署名单位: University System of Ohio; Miami University; University System of Ohio; Ohio State University; James Cancer Hospital & Solove Research Institute; University System of Ohio; Miami University; Hauptman Woodward Medical Research Institute
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-13503
• DOI: 10.1073/pnas.2309326121
• 发表日期: 2024-03-19
• 关键词: toll-like receptors; n-terminal domain; mitochondrial hsp90; master chaperone; escherichia-coli; client-binding; atp hydrolysis; closed state; protein; hsp70

摘要

Hsp90s are ATP- dependent chaperones that collaborate with co- chaperones and Hsp70s to remodel client proteins. Grp94 is the ER Hsp90 homolog essential for folding multiple secretory and membrane proteins. Grp94 interacts with the ER Hsp70, BiP, although the collaboration of the ER chaperones in protein remodeling is not well understood. Grp94 undergoes large - scale conformational changes that are coupled to chaperone activity. Within Grp94, a region called the pre - N domain suppresses ATP hydrolysis and conformational transitions to the active chaperone conformation. In this work, we combined in vivo and in vitro functional assays and structural studies to characterize the chaperone mechanism of Grp94. We show that Grp94 directly collaborates with the BiP chaperone system to fold clients. Grp94's pre - N domain is not necessary for Grp94-client interactions. The folding of some Grp94 clients does not require direct interactions between Grp94 and BiP in vivo, suggesting that the canonical collaboration may not be a general chaperone mechanism for Grp94. The BiP co- chaperone DnaJB11 promotes the interaction between Grp94 and BiP, relieving the pre - N domain suppression of Grp94's ATP hydrolysis activity. In structural studies, we find that ATP binding by Grp94 alters the ATP lid conformation, while BiP binding stabilizes a partially closed Grp94 intermediate. Together, BiP and ATP push Grp94 into the active closed conformation for client folding. We also find that nucleotide binding reduces Grp94's affinity for clients, which is important for productive client folding. Alteration of client affinity by nucleotide binding may be a conserved chaperone mechanism for a subset of ER chaperones. Significance Grp94 is a molecular chaperone in the endoplasmic reticulum that folds a range of client proteins. This study explored the chaperone mechanism of Grp94 and illustrates how Grp94 collaborates with another ER chaperone, BiP. Collaboration of the two chaperones is facilitated by a BiP cochaperone and requires ATP binding and hydrolysis by Grp94 and direct interactions with BiP. However, all clients do not require the direct BiP- Grp94 interaction for folding. BiP promotes dimer closure of Grp94 toward the active conformation, overcoming kinetic barriers imposed by Grp94's pre - N domain. Nucleotide binding reduces client interactions with Grp94 to enable refolding, which may represent a general chaperone mechanism. These studies improve our understanding of these ER chaperones and highlight diversity in chaperone mechanisms.