Mammalian target of rapamycin complex 1 (mTORC1) plays a role in pasteurella multocida toxin (PMT)-induced protein synthesis and proliferation in swiss 3T3 cells

Hammou Oubrahim, Allison Wong, Brenda A. Wilson, P. Boon Chock

Research output: Contribution to journalArticlepeer-review

Abstract

Pasteurella multocida toxin (PMT) is a potent mitogen known to activate several signaling pathways via deamidation of a conserved glutamine residue in the subunit of heterotrimeric G-proteins. However, the detailed mechanism behind mitogenic properties ofPMTis unknown. Herein, we show thatPMT induces protein synthesis, cell migration, and proliferation in serum-starved Swiss 3T3 cells. Concomitantly PMT induces phosphorylation of ribosomal S6 kinase (S6K1) and its substrate, ribosomal S6 protein (rpS6), in quiescent 3T3 cells. The extent of the phosphorylation is time and PMT concentration dependent, and is inhibited by rapamycin and Torin1, the two specific inhibitors of the mammalian target of rapamycin complex 1 (mTORC1). Interestingly, PMT-mediated mTOR signaling activation was observed in MEF WT but not in Gαq/11 knock-out cells. These observations are consistent with the data indicating that PMT-induced mTORC1 activation proceeds via the deamidation of Gαq/11, which leads to the activation of PLCβ to generate diacylglycerol and inositol trisphosphate, two known activators of the PKC pathway. Exogenously added diacylglycerol or phorbol 12-myristate 13-acetate, known activators of PKC, leads to rpS6 phosphorylation in a rapamycin- dependent manner. Furthermore, PMT-induced rpS6 phosphorylation is inhibited by PKC inhibitor, Gö6976. Although PMT induces epidermal growth factor receptor activation, it exerts no effect on PMT-induced rpS6 phosphorylation. Together, our findings reveal for the first time that PMT activates mTORC1 through the Gαq/11/PLCβ/PKC pathway. The fact that PMT-induced protein synthesis and cell migration is partially inhibited by rapamycin indicates that these processes are in part mediated by the mTORC1 pathway.

Original languageEnglish (US)
Pages (from-to)2805-2815
Number of pages11
JournalJournal of Biological Chemistry
Volume288
Issue number4
DOIs
StatePublished - Jan 25 2013

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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