期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2009
卷号：106
期号：32
页码：13612-13617
DOI：10.1073/pnas.0906144106
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Mammalian calreticulin (CRT) is a multifunctional Ca2+-binding protein involved in more than 40 cellular processes in various subcellular compartments, such as Ca2+ storage and protein folding in the endoplasmic reticulum (ER). CRT homologues were discovered in plants almost 15 years ago, and recent studies revealed that many plant species contain 2 or more CRTs that are members of 2 distinct families, the CRT1/2 family and the plant-specific CRT3 family. However, little is known about their physiological functions. Here we report ebs2 (EMS-mutagenized bri1 suppressor 2) as an allele-specific suppressor of bri1-9, a dwarf Arabidopsis mutant caused by retention of a defective brassinosteroid receptor in the ER. EBS2 encodes the Arabidopsis CRT3 that interacts with ER-localized bri1-9 in a glycan-dependent manner. Loss-of-function ebs2 mutations compromise ER retention of bri1-9 and suppress its dwarfism, whereas EBS2 over-expression enhances its dwarf phenotype. In contrast, mutations of 2 other CRTs or their membrane-localized homologues calnexins had little effect on bri1-9. A domain-swapping experiment revealed that the positively charged C-terminal tail of CRT3 is crucial for its "bri1-9-retainer" function. Our study revealed not only a functional role for a plant-specific CRT, but also functional diversity among the 3 Arabidopsis CRT paralogues.
关键词：BRI1 ; calnexin ; ER chaperone ; ER quality control ; UGGT
