Inhibition of protein synthesis by TOR inactivation revealed a conserved regulatory mechanism of the BiP chaperone in Chlamydomonas

Diaz-Troya, S. and Perez-Perez, M. E. and Perez-Martin, M. and Moes, S. and Jeno, P. and Florencio, F. J. and Crespo, J. L.. (2011) Inhibition of protein synthesis by TOR inactivation revealed a conserved regulatory mechanism of the BiP chaperone in Chlamydomonas. Plant Physiology , 157 (2). pp. 730-741.

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The target of rapamycin (TOR) kinase integrates nutritional and stress signals to coordinately control cell growth in all eukaryotes. TOR associates with highly conserved proteins to constitute two distinct signaling complexes termed TORC1 and TORC2. Inactivation of TORC1 by rapamycin negatively regulates protein synthesis in most eukaryotes. Here, we report that down-regulation of TOR signaling by rapamycin in the model green alga Chlamydomonas reinhardtii resulted in pronounced phosphorylation of the endoplasmic reticulum chaperone BiP. Our results indicated that Chlamydomonas TOR regulates BiP phosphorylation through the control of protein synthesis, since rapamycin and cycloheximide have similar effects on BiP modification and protein synthesis inhibition. Modification of BiP by phosphorylation was suppressed under conditions that require the chaperone activity of BiP, such as heat shock stress or tunicamycin treatment, which inhibits N-linked glycosylation of nascent proteins in the endoplasmic reticulum. A phosphopeptide localized in the substrate-binding domain of BiP was identified in Chlamydomonas cells treated with rapamycin. This peptide contains a highly conserved threonine residue that might regulate BiP function, as demonstrated by yeast functional assays. Thus, our study has revealed a regulatory mechanism of BiP in Chlamydomonas by phosphorylation/dephosphorylation events and assigns a role to the TOR pathway in the control of BiP modification.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Services Biozentrum > Mass Spectrometry (Jenö)
UniBasel Contributors:Jenö, Paul and Moes, Suzanne
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Society of Plant Biologists
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:30 Nov 2017 08:08
Deposited On:30 Nov 2017 08:08

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