The mTOR-FAK mechanotransduction signaling axis for focal adhesion maturation and cell proliferation

Fan Yen Lee, Yen Yi Zhen, Chun Man Yuen, Raymond Fan, Yen Ta Chen, Jiunn Jye Sheu, Yi Ling Chen, Ching Jen Wang, Cheuk Kwan Sun*, Hon Kan Yip

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

40 Scopus citations

Abstract

Background: Mechanotransduction (MTD) is an important physiopathological signalling pathway associated with cardiovascular disease such as hypertension. Phosphorylation of focal adhesion kinase (FAK) is a MTDsensing protein. This study tested the hypothesis that mTOR-FAK MTD signaling axis was crucial for focal adhesion (FA) maturation and cell proliferation. Methods: Shock-wave was adopted as a tool for MTD and mTOR-FAK signaling. Results: After demonstrating a failure in FAK phosphorylation after microfilament depolymerization, we attempted to identify the upstream regulator out of three kinases known to be activated in pressure-stimulated MTD [i.e., GSK-3β, Akt, and mTORC1 (mammalian target of rapamycin complex 1)]. Of the three specific inhibitors, only rapamycin, an inhibitor of mTORC1, was found to inhibit FAK phosphorylation, suggesting that mTORC1 is the upstream regulator in shock-wave-elicited FAK phosphorylation. Moreover, mTOR and its readout protein S6K were found to be activated by shock-wave stimulation. On the other hand, microscopic examination revealed not only MTD-induced increase in the number of actin stress fibers, but also alternative subcellular localization of mTORC1 as vesicle-like inclusions on microfilaments. Besides, rapamycin was found to destruct the granular pattern of mTORC1, while dissociation between F-actin and mTORC1 was noted after cytochalasin D administration. Since mTORC1 and FAK are essential for cell proliferation, we performed proliferation assay for mesenchymal stem cell (MSC) with and without shockwave administration/rapamycin treatment/FAK depletion. The results demonstrated significant enhancement of cell proliferation after shock-wave stimulation but remarkable suppression after rapamycin and siFAK treatment. Conclusion: Our findings suggest not only a co-ordinated regulation of FAK phosphorylation by mTORC1 and microfilaments, but also the participation of mTORC1-FAK signalling in MSC proliferation.

Original languageEnglish
Article numberAJTR0031248
Pages (from-to)1603-1617
Number of pages15
JournalAmerican Journal of Translational Research
Volume9
Issue number4
StatePublished - 2017

Bibliographical note

Publisher Copyright:
© 2017, E-Century Publishing Corporation. All rights reserved.

Keywords

  • Cell proliferation
  • Focal adhesion kinase
  • Mammalian target of rapamycin complex 1
  • Shock wave

Fingerprint

Dive into the research topics of 'The mTOR-FAK mechanotransduction signaling axis for focal adhesion maturation and cell proliferation'. Together they form a unique fingerprint.

Cite this