Regulated association of misfolded endoplasmic reticulum lumenal proteins with P58/DNAJc3

Abstract

P58/DNAJc3 defends cells against endoplasmic reticulum (ER) stress. Most P58 molecules are translocated into the ER lumen, and here we report selective and stable binding to misfolded proteins by P58's TPR-containing N-terminal domain. In vitro, too, P58 binds selectively to a model misfolded protein and challenge of that complex with physiological concentrations of the ER lumenal Hsp70-type chaperone BiP encourages disassembly. BiP-induced dissociation of P58 from its substrate depends on the presence of ATP and on interactions with P58's J-domain, which are mediated by invariant residues BiP R197 and P58 H422 . A functional J-domain also accelerates dissociation of P58 from a model substrate, VSV-G ts045 , on the latter's re-folding in vivo. However, J-domain binding can be separated from the ability to promote substrate dissociation by the mutant BiP E201G and a wild-type J-domain fused ectopically to P58 H422Q rescues the latter's inability to dissociate from substrate in response to BiP and ATP. These findings are consistent with a model whereby localized activation of the Hsp70-type partner is sufficient to promote substrate handover from the J-domain cochaperone.

Protein Folding and Quality Control in the ER

“…ERdj6, designated p58 IPK , was initially reported to negatively regulate PKR and PERK phosphorylation in the cytosol (Gale et al 1998;Yan et al 2002). However, it was later determined that ERdj6 is also localized to the ER by an ER-targeting signal and that ERdj6 binds to BiP through its J-domain or the tetratricopeptide (TPR) repeat domain and functions as a cochaperone (Rutkowski et al 2007;Petrova et al 2008). ERdj6 is most probably involved in the productive folding of newly synthesized proteins in the ER lumen.…”

Emerging features of ER resident J-proteins in plants

“…19 P58 IPK was later discovered to also be an ER resident protein that binds to unfolded proteins and acts as a co-chaperone for BiP. 20,21 Although P58 IPK binds to several unfolded proteins, modulation of P58 IPK level did not affect degradation of the unfolded proteins. 22 Binding of P58 IPK to unfolded proteins is BiP-independent, and BiP enhances release of P58 IPK from the unfolded proteins, implicating that P58 IPK may reduce the burden of unfolded proteins by upregulating protein folding in the ER lumen.…”

“…22 Binding of P58 IPK to unfolded proteins is BiP-independent, and BiP enhances release of P58 IPK from the unfolded proteins, implicating that P58 IPK may reduce the burden of unfolded proteins by upregulating protein folding in the ER lumen. 21 In plants, P58 IPK was first identified as an interactor with a virus-encoded ligand, TMV-P50. 23 P58 IPK silencing in tobacco and knockout of AtP58 IPK in Arabidopsis led to cell death upon infection with plant viruses, suggesting that plant P58 IPK has similar cytoplasmic functions to mammalian P58 IPK .…”

The α-Helical Structure of Prodomains Promotes Translocation of Intrinsically Disordered Neuropeptide Hormones into the Endoplasmic Reticulum

“…Because p58 IPK can interact with both the nascent chain and BiP (65,76), such interactions could impair productive translocation of IDPs into the ER lumen. Other translocon-associated proteins, such as Sec63 or Sec62, might be involved in such a pathway as well.…”