HOP3, a member of the HOP family in Arabidopsis, interacts with BiP and plays a major role in the ER stress response.
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.
Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Campus Montegancedo UPM, 28223, Pozuelo de Alarcón, Madrid, Spain.
Nuria
N
Fernández-Bautista
Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Campus Montegancedo UPM, 28223, Pozuelo de Alarcón, Madrid, Spain.
Lourdes
L
Fernández-Calvino
Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Campus Montegancedo UPM, 28223, Pozuelo de Alarcón, Madrid, Spain.
Alfonso
A
Muñoz
Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Campus Montegancedo UPM, 28223, Pozuelo de Alarcón, Madrid, Spain.
M Mar
http://orcid.org/0000-0003-0339-4247
MM
Castellano
D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D004229:Dithiothreitol / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D005810:Multigene Family; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D011485:Protein Binding / Q000187:drug effects; D000072417:Protein Domains; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D013655:Taurochenodeoxycholic Acid / Q000494:pharmacology; D014415:Tunicamycin / Q000494:pharmacology; D056811:Unfolded Protein Response / Q000187:drug effects
D029681:Arabidopsis Proteins; D002352:Carrier Proteins; C000625918:HOP3 protein, Arabidopsis; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D018832:Molecular Chaperones; D012333:RNA, Messenger; D014415:Tunicamycin; C077221:BIP protein, Arabidopsis; D013655:Taurochenodeoxycholic Acid; C031655:ursodoxicoltaurine; D004229:Dithiothreitol
DTT; HSP70-HSP90; TUDCA; UPR; cochaperone; pollen germination; tunicamycin