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HOP3, a member of the HOP family in Arabidopsis, interacts with BiP and plays a major role in the ER stress response
Author(s) -
FernándezBautista Nuria,
FernándezCalvino Lourdes,
Muñoz Alfonso,
Castellano M. Mar
Publication year - 2017
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/pce.12927
Subject(s) - unfolded protein response , endoplasmic reticulum , arabidopsis , tunicamycin , biology , microbiology and biotechnology , hsp90 , chaperone (clinical) , eukaryote , cyclic nucleotide binding domain , endoplasmic reticulum associated protein degradation , hsp70 , chemical chaperone , mutant , heat shock protein , biochemistry , peptide sequence , gene , medicine , pathology , genome
HSP70‐HSP90 organizing protein (HOP) is a well‐studied family of cytosolic cochaperones. However, the possible role of HOP during the endoplasmic reticulum (ER) stress response and the identity of its interactors within the ER were not previously addressed in any eukaryote. We have demonstrated that Arabidopsis HOP3, whose function was not studied before, interacts in vivo with cytosolic HSP90 and HSP70, and, unexpectedly, with binding immunoglobulin protein (BiP), a HSP70 ER‐resident protein. Although BiP lacks the domain described in other eukaryotes for HOP‐HSP70 binding, it interacts with HOP3 through a non‐canonical association to its nucleotide binding domain. Consistent with this interaction with BiP, HOP3 is partially localized at the ER. Moreover, HOP3 is induced both at transcript and protein levels by unfolded protein response (UPR) inducer agents by a mechanism dependent on inositol‐requiring enzyme 1 (IRE1). Importantly, hop3 loss‐of‐function mutants show a reduction in pollen germination and a hypersensitive phenotype in the presence of ER stress inducer agents, a phenotype that is reverted by the addition of the chemical chaperone tauroursodeoxycholic acid (TUDCA). All these data demonstrate, for the first time in any eukaryote, a main role of HOP as an important regulator of the ER stress response, a process intimately linked in plants to important specific developmental programs and to environmental stress sensing and response.