p70S6K is regulated by Focal Adhesion Kinase and is required for Src-selective autophagy

Emma Sandilands, Christina Schoenherr, Margaret Frame

Research output: Contribution to journalArticlepeer-review

Abstract

Here we report that Focal Adhesion Kinase (FAK) is required for optimal signalling to the Akt-p70S6K-S6 pathway in squamous cell carcinoma cells (SCCs). Specifically, in SCCs that are genetically deficient for FAK, there is reduced phosphorylation of Akt, p70S6K and S6, and signalling to Akt-p70S6K-S6 is more sensitive to inhibition by multiple agents that suppress the pathway. By contrast, mTOR is unaffected. Indeed, pharmacological agents that inhibit the Akt-p70S6K-S6 pathway, and PDK1 that lies upstream of Akt, also impair the autophagic targeting of activated c-Src (p-Src) in FAK deficient cells. This is associated with loss of a complex between p-Src and the autophagy protein LC3, a biochemical surrogate of impaired Src-selective autophagy. In keeping with a vital role for p70S6K, inhibition by a selective inhibitor and specific siRNA also impaired Src-selective autophagy. Finally, components of the PDK1-Akt-p70S6K signalling pathway were co-located with p-Src at autophagosomes, and Src and p70S6K co-exist in the same biochemical complex. We therefore deduce that the FAK-regulated signalling module PDK1-Akt-p70S6K that controls Src’s intracellular trafficking operates at Src-containing autophagosomes.
Original languageEnglish
JournalCellular Signalling
Volume27
Issue number9
Early online date9 Jun 2015
DOIs
Publication statusPublished - Sep 2015

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