The E3 ligase AtCHIP ubiquitylates FtsH1, a component of the chloroplast FtsH protease, and affects protein degradation in chloroplasts.
The Arabidopsis E3 ligase AtCHIP was found to interact with FtsH1, a subunit of the chloroplast FtsH protease complex. FtsH1 can be ubiquitylated by AtCHIP in vitro, and the steady-state level of FtsH1 is reduced in AtCHIP-over-expressing plants under high-intensity light conditions, suggesting that the ubiquitylation of FtsH1 by AtCHIP might lead to the degradation of FtsH1 in vivo. Furthermore, the steady-state level of another subunit of the chloroplast FtsH protease complex, FtsH2, is also reduced in AtCHIP-over-expressing plants under high-intensity light conditions, and FtsH2 interacts physically with AtCHIP in vivo, suggesting the possibility that FtsH2 is also a substrate protein for AtCHIP in plant cells. A substrate of FtsH protease in vivo, the photosystem II reaction center protein D1, is not efficiently removed by FtsH in AtCHIP-over-expressing plants under high-intensity light conditions, supporting the assumption that FtsH subunits are substrates of AtCHIP in vivo, and that AtCHIP over-expression may lead to a reduced level of FtsH in chloroplasts. AtCHIP interacts with cytosolic Hsp70 and the precursors of FtsH1 and FtsH2 in the cytoplasm, and Hsp70 also interacts with FtsH1, and these protein-protein interactions appear to be increased under high-intensity light conditions, suggesting that Hsp70 might be partly responsible for the increased degradation of the substrates of Hsp70, such as FtsH1 and FtsH2, in AtCHIP-over-expressing plants under high-intensity light conditions. Therefore, AtCHIP, together with Hsp70, may play an important role in protein quality control in chloroplasts.
Shen
Guoxin
G
Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409, USA.
Adam
Zach
Z
Zhang
Hong
H
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D016923:Cell Death / Q000528:radiation effects; D002736:Chloroplasts / Q000201:enzymology* / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D008027:Light; D045726:Metalloproteases / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D020798:Two-Hybrid System Techniques; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination
D029681:Arabidopsis Proteins; D018840:HSP70 Heat-Shock Proteins; D045332:Photosystem II Protein Complex; C511865:CHIP protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases; C525055:FtsH1 protein, Arabidopsis; D045726:Metalloproteases