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Identification of a TOR-regulated phosphoproteome and the regulation of cellular protein synthesis

ABSTRACT: We describe an in depth analysis in fission yeast of changes in the phosphoproteome after inhibition of the TOR protein kinases. A total of 756 phosphosites on 316 proteins showed significant and rapid changes in phosphorylation levels after TOR kinase inhibition when the rate of protein synthesis reduced by 90%. These proteins were involved in a range of cellular processes including 4 that featured strongly: signalling-related processes, translation, cell polarity and actin cytoskeletal organisation, and vesicle-mediated transport and autophagy. We propose that these processes have major roles in TOR regulated cellular growth control. We also show that the S6 protein kinases have no role in immediate TOR regulated cellular protein synthesis, but in contrast there is a role for Tif471, the translation initiation factor homologue of eIF4G. This protein becomes rapidly phosphorylated after TORC1 inhibition in particular, but if that phosphorylation is prevented, as demonstrated by mutations on the specific phosphosites, the inhibition of protein synthesis rate is reduced. We propose that this factor is a downstream target of the TOR pathway, with a role in partially regulating global cellular protein synthesis.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Schizosaccharomyces Pombe 972h-

SUBMITTER: Andrew Jones

LAB HEAD: Paul Nurse

PROVIDER: PXD023664 | Pride | 2021-07-09

REPOSITORIES: Pride

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