Effects of Ha-RasV12 and Caveolin-1 in cyclic stretch-induced alterations of cell perpendicular alignment cell height and cell survival in MDCK cells

Abstract

Mechanoresponse is different between normal cells and cancer cells We previously reported that cancer cells were not only softer than their normal cell type but also resistant to soft matrix-induced cell death so called loss of mechanosensing Contractile units (CUs) composed of focal adhesion complex and actomyosin subunits are crucial for providing local contraction in response to mechanical forces It has been demonstrated that loss of mechanosensing in cancer cells may be due to disfunction of CUs In order to examine whether cancer cells may respond to mechanical stretch differently from normal cells we applied a dynamic cyclic stretch force on MK4 cells harboring inducible Ha-RasV12 overexpression system The results showed that Ha-RasV12 overexpressing cells lost stretch-induced perpendicular alignment To investigate the role of CUs in stretch induced perpendicular alignment we tested the effects of myosin II inhibitor caveolin-1 (Cav-1) knockdown and FAK inhibitor The results showed that inhibition of myosin II activity and FAK phosphorylation suppressed perpendicular alignment after stretch Knockdown of Cav1 did not ameliorate stretch-induced perpendicular alignment but instead promoted perpendicular alignment In contrast overexpression of Cav1 enhanced actin belt constriction and increased the cell height suggesting that Cav1 functioned predominantly in adherens junction during stretch and FA might be the mechanosensor to change the cell orientation To investigate whether cyclic stretch exerted effects on cell growth we checked cell proliferation and apoptosis The results showed that cyclic stretch triggered cell apoptosis in Ha-RasV12 overexpressing cells but not normal cells Moreover cyclic stretch induced phosphorylation of JNK was observed only at the cell confluency indicating junctional CUs and FA-dominated CUs might influenced the cell survival differently Taken together cellular contractility is important for the maintenance of cells during dynamic stretching leading to cell orientation change Cyclic stretch promotes normal cell proliferation but triggers transformed cell apoptosis

Date of Award	2019
Original language	English
Supervisor	Ming-Jer Tang (Supervisor)