Functional Study of Endomembrane Proteins (EMPs) in Plants
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AbstractEndomembrane proteins (EMPs) constitute a 12-member protein family in Arabidopsis, which are the most abundant protein species in Golgi proteome1. We previously demonstrated that EMP12 localized in Golgi apparatus due to dual trafficking signals presented at the C-terminus: an ER (endoplasmic reticulum) export signal and a novel Golgi retention signal2,3. However, the functional roles of EMPs remain unknown in plants.
Here we present an update on the functional study of EMPs in plant. Recently, we identified an EMP knockout mutant, empx, which is sensitive to ER stress induced by tunicamycin and DTT treatments. Unfolded protein response (UPR) is one of the mechanisms that is activated to relieve the ER stress. UPR might be constitutively activated in the emp mutant because we observed that 1) under normal condition, BiP3, one of the UPR responsive genes, is up-regulated in empx vs. wild-type plant, and 2) bZIP28 is translocated into nucleus in empx under normal condition. We thus hypothesize that such constant activation is a result of insufficient chaperones maintained in ER to aid protein folding. Indeed, one of the chaperones, BiP, was found to be mislocalized from ER to post-ER compartments in empx. Since BiP is a HDEL protein, whose trafficking is regulated by the HDEL receptor ERD2, we looked at whether ERD2 trafficking is also affected in empx. Instead of localized mainly in the Golgi apparatus, ERD2 was found to be retained in the ER in empx. Here we provide a working model on how EMPs may be involved in UPR by regulating ERD2. This work is partially supported by grant from the Research Grants Council of Hong Kong (CUHK14130716, CUHK2/CRF/11G, C4011-14R, and AoE/M-05/12) to L.J.
All Author(s) ListKing Pong Leung, Ming Luo, Caiji Gao, Xiaoqiang Yao, Liwen Jiang
Name of ConferenceCold Spring Harbor Asia 2017 Conference on Plant Cell and Developmental Biology
Start Date of Conference22/05/2017
End Date of Conference26/05/2017
Place of ConferenceSuzhou
Country/Region of ConferenceChina
LanguagesEnglish-United States

Last updated on 2018-16-04 at 18:35