A phospho-proteomic screen identifies novel S6K1 and mTORC1 substrates revealing additional complexity in the signaling network regulating cell growth

Katarzyna Jastrzebski; Katherine M Hannan; Colin M House; Sandy S-C Hung; Richard B Pearson; Ross D Hannan

doi:10.1016/j.cellsig.2011.03.016

A phospho-proteomic screen identifies novel S6K1 and mTORC1 substrates revealing additional complexity in the signaling network regulating cell growth

Cell Signal. 2011 Aug;23(8):1338-47. doi: 10.1016/j.cellsig.2011.03.016. Epub 2011 Apr 1.

Authors

Katarzyna Jastrzebski¹, Katherine M Hannan, Colin M House, Sandy S-C Hung, Richard B Pearson, Ross D Hannan

Affiliation

¹ Research Division, Peter MacCallum Cancer Centre, Melbourne, Locked Bag 1, A'Beckett Street, Victoria 8006, Australia.

PMID: 21440620
DOI: 10.1016/j.cellsig.2011.03.016

Abstract

S6K1, a critical downstream substrate of mTORC1, has been implicated in regulating protein synthesis and a variety of processes that impinge upon cell growth and proliferation. While the role of the cytoplasmic p70(S6K1) isoform in the regulation of translation has been intensively studied, the targets and function of the nuclear p85(S6K1) isoform remain unclear. Therefore, we carried out a phospho-proteomic screen to identify novel p85(S6K1) substrates. Four novel putative p85(S6K1) substrates, GRP75, CCTβ, PGK1 and RACK1, and two mTORC1 substrates, ANXA4 and PSMA6 were identified, with diverse roles in chaperone function, ribosome maturation, metabolism, vesicle trafficking and the proteasome, respectively. The chaperonin subunit CCTβ was further investigated and the site of phosphorylation mapped to serine 260, a site located in the chaperonin apical domain. Consistent with this domain being involved in folding substrate interactions, we found that phosphorylation of serine 260 modulates chaperonin folding activity.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Amino Acid Sequence
Animals
Annexin A4 / metabolism
Cell Growth Processes
Cell Line
Chaperonin Containing TCP-1 / chemistry
Chaperonin Containing TCP-1 / metabolism
HSP70 Heat-Shock Proteins / metabolism
Humans
Mechanistic Target of Rapamycin Complex 1
Membrane Proteins / metabolism
Mice
Molecular Sequence Data
Multiprotein Complexes
Neuropeptides / metabolism
Phosphoglycerate Kinase / metabolism
Phosphorylation
Proteasome Endopeptidase Complex / metabolism
Proteins / metabolism*
Proteins / physiology
Proteomics*
RNA Interference
RNA, Small Interfering
Receptors for Activated C Kinase
Ribosomal Protein S6 Kinases, 70-kDa / antagonists & inhibitors
Ribosomal Protein S6 Kinases, 70-kDa / genetics
Ribosomal Protein S6 Kinases, 70-kDa / metabolism*
Signal Transduction*
Substrate Specificity
TOR Serine-Threonine Kinases

Substances

Annexin A4
CCT2 protein, human
HSP70 Heat-Shock Proteins
Membrane Proteins
Multiprotein Complexes
Neuropeptides
Proteins
RACK1 protein, mouse
RNA, Small Interfering
Receptors for Activated C Kinase
glucose-regulated proteins
Mechanistic Target of Rapamycin Complex 1
Ribosomal Protein S6 Kinases, 70-kDa
TOR Serine-Threonine Kinases
Pgk1 protein, mouse
Phosphoglycerate Kinase
PSMA6 protein, mouse
Proteasome Endopeptidase Complex
Chaperonin Containing TCP-1