HOP3 is a new regulator of endoplasmic reticulum stress response

Proper protein folding in the ER is vital to maintain cellular homeostasis. In this sense, there is a growing interest in the identification, as in the case of AtHOP3, of new regulators in this process.


The endoplasmic reticulum (ER) is the organelle where the proteins that are transported to the membrane or secreted are folded. Under different abiotic and biotic stresses, as well as during specific plant developmental processes, the demand for protein folding in the ER is exceeded, leading to a high accumulation of misfolded proteins known as "ER stress”. This ER stress is toxic for the cell and should be alleviated in order to maintain protein homeostasis.

In this paper, we have described that Arabidopsis HOP3, which belong to the HSP70-HSP90 organizing protein family (HOP), interacts with an essential protein involved in protein folding in the ER, the chaperone BiP. In addition, we have demonstrated that HOP3 is induced in the presence of different ER-promoting agents and that hop3 mutants show a marked hypersensitivity to ER stress along with a decrease in pollen germination in vitro (a developmental process intimately linked to ER stress). These data among others demonstrate, for the first time in eukaryotes, that HOPs are involved in relieving ER stress.

Figure. hop3 mutant shows an increased hypersensibility to DTT (an ER-stress inducer agent). This phenotype is reverted in the complemented lines.


Original Paper:

Fernández-Bautista, N; Fernández-Calvino, L; Muñoz, A; Castellano, MM. 2017. "AtHOP3, a member of the HOP family in Arabidopsis, interacts with BiP and plays a major role in the ER stress response". Plant, Cell & Environment. DOI: 10.1111/pce.12927".