Conserved function of the lysine-based KXD/E motif in Golgi retention for endomembrane proteins among different organisms |
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| Authors: | Cheuk Hang Woo Caiji Gao Ping Yu Linna Tu Zhaoyue Meng David K Banfield Xiaoqiang Yao Liwen Jiang |
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| Institution: | RIKEN;aCentre for Cell and Developmental Biology and State Key Laboratory of Agrobiotechnology, School of Life Sciences, and;cSchool of Biomedical Sciences, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China;bDivision of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China;dCUHK Shenzhen Research Institute, Chinese University of Hong Kong, Shenzhen 518057, China |
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| Abstract: | We recently identified a new COPI-interacting KXD/E motif in the C-terminal cytosolic tail (CT) of Arabidopsis endomembrane protein 12 (AtEMP12) as being a crucial Golgi retention mechanism for AtEMP12. This KXD/E motif is conserved in CTs of all EMPs found in plants, yeast, and humans and is also present in hundreds of other membrane proteins. Here, by cloning selective EMP isoforms from plants, yeast, and mammals, we study the localizations of EMPs in different expression systems, since there are contradictory reports on the localizations of EMPs. We show that the N-terminal and C-terminal GFP-tagged EMP fusions are localized to Golgi and post-Golgi compartments, respectively, in plant, yeast, and mammalian cells. In vitro pull-down assay further proves the interaction of the KXD/E motif with COPI coatomer in yeast. COPI loss of function in yeast and plants causes mislocalization of EMPs or KXD/E motif–containing proteins to vacuole. Ultrastructural studies further show that RNA interference (RNAi) knockdown of coatomer expression in transgenic Arabidopsis plants causes severe morphological changes in the Golgi. Taken together, our results demonstrate that N-terminal GFP fusions reflect the real localization of EMPs, and KXD/E is a conserved motif in COPI interaction and Golgi retention in eukaryotes. |
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