title: The chloroplast protease subunit ClpP4 is a substrate of the E3 ligase AtCHIP and plays an important role in chloroplast function.
abstract: Animal CHIP proteins are chaperone-dependent E3 ubiquitin ligases that physically interact with Hsp70, Hsp90 and proteasome, promoting degradation of a selective group of non-native or damaged proteins in animal cells. The plant CHIP-like protein, AtCHIP, also plays important roles in protein turnover metabolism. AtCHIP interacts with a proteolytic subunit, ClpP4, of the chloroplast Clp protease in vivo, and ubiquitylates ClpP4 in vitro. The steady-state level of ClpP4 is reduced in AtCHIP-overexpressing plants under high-intensity light conditions, suggesting that AtCHIP targets ClpP4 for degradation and thereby regulates the Clp proteolytic activity in chloroplasts under certain stress conditions. Overexpression of ClpP4 in Arabidopsis leads to chlorotic phenotypes in transgenic plants, and chloroplast structures in the chlorotic tissues of ClpP4-overexpressing plants are abnormal and largely devoid of thylakoid membranes, suggesting that ClpP4 plays a critical role in chloroplast structure and function. As AtCHIP is a cytosolic protein that has been shown to play an important role in regulating an essential chloroplast protease, this research provides new insights into the regulatory networks controlling protein turnover catabolism in chloroplasts.
authors.affiliation: Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409, USA.
authors.forename: Guoxin
authors.initials: G
authors.lastname: Shen
authors.forename: Juqiang
authors.initials: J
authors.lastname: Yan
authors.forename: Vijaya
authors.initials: V
authors.lastname: Pasapula
authors.forename: Jinhua
authors.initials: J
authors.lastname: Luo
authors.forename: Cixin
authors.initials: C
authors.lastname: He
authors.forename: Adrian K
authors.initials: AK
authors.lastname: Clarke
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D049071:Endopeptidase Clp / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D046529:Microscopy, Electron, Transmission; D030821:Plants, Genetically Modified; D011485:Protein Binding; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
chemical_list: D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases; D049071:Endopeptidase Clp