Regulation of the Arabidopsis GSK3-like kinase BRASSINOSTEROID-INSENSITIVE 2 through proteasome-mediated protein degradation.
Glycogen synthase kinase 3 (GSK3) is a unique serine/threonine kinase that is implicated in a variety of cellular processes and is regulated by phosphorylation or protein-protein interaction in animal cells. BIN2 is an Arabidopsis GSK3-like kinase that negatively regulates brassinosteroid (BR) signaling. Genetic studies suggested that BIN2 is inhibited in response to BR perception at the cell surface to relieve its inhibitory effects on downstream targets; however, little is known about biochemical mechanisms of its inhibition. Here, we show that BIN2 is regulated by proteasome-mediated protein degradation. Exogenous application of a BR biosynthesis inhibitor and an active BR increased and decreased the amount of BIN2 proteins, respectively. Interestingly, the gain-of-function bin2-1 mutation significantly stabilizes BIN2, making it unresponsive to BR-induced BIN2 depletion. Exogenous application of different plant growth hormones revealed that BIN2 depletion is specifically induced by BR through a functional BR receptor, while treatment of a proteasome inhibitor, MG132, not only prevented the BR-induced BIN2 depletion but also nullified the inhibitory effect of BR on the BIN2 kinase activity. Taken together, our results strongly suggest that proteasome-mediated protein degradation constitutes an important regulatory mechanism for restricting the BIN2 activity.
Peng
Peng
P
Department of Molecular, Cellular and Development Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA.
Yan
Zhenyan
Z
Zhu
Yongyou
Y
Li
Jianming
J
D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D004355:Drug Stability; D004795:Enzyme Stability; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017930:Genes, Reporter; D014644:Genetic Variation; D038362:Glycogen Synthase Kinase 3 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics; D007976:Leupeptins / Q000494:pharmacology; D016296:Mutagenesis; D009154:Mutation; D010641:Phenotype; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction
D029681:Arabidopsis Proteins; D038362:Glycogen Synthase Kinase 3; D049452:Green Fluorescent Proteins; D007976:Leupeptins; D046988:Proteasome Endopeptidase Complex; D011494:Protein Kinases; D011994:Recombinant Proteins; C448985:At4g18710 protein, Arabidopsis; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde