Purchase this article with an account.
M. Filla, M. Schwinn, A. Nosie, R. Clark, D. Peters; β3 Integrin Signaling Is Involved In Dexamethasone-induced Cross-linked Actin Network (CLAN) Formation In Human Trabecular Meshwork (HTM) Cells. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4656.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To determine if cross-linked actin networks (CLANs) induced by dexamethasone (DEX) in human trabecular meshwork (HTM) cells are structurally similar to those formed following β3 integrin activation and involve αvβ3 integrin signaling.
Two HTM cell strains and the immortalized TM-1 cell line overexpressing αvβ3 integrin were used. DEX- or ethanol-pre-treated HTM cells were treated with cycloheximide to block de novo protein synthesis prior to being re-plated on fibronectin with or without β3 integrin-activating mAb AP-5. Fluorescence microscopy was used to identify phalloidin-labeled CLANs and to ascertain the presence of α-actinin, PIP2 and syndecan-4 within them. β3 integrin signaling involvement was determined using a PI3-kinase (LY294002) or Rac1/Trio (NSC23766) inhibitor. αvβ3 integrin expression levels and the β3 integrin activation state were determined by FACS analysis and fluorescence microscopy.
CLANs induced by either DEX or activating β3 integrin contained syndecan-4, PIP2, and α-actinin. PI3-kinase inhibition did not affect DEX-induced CLAN formation while Rac1/Trio inhibition decreased the percentage of CLAN-positive cells by 80%. In contrast, inhibition of PI3-kinase or Rac1/Trio decreased β3 integrin-induced CLAN formation in the presence of DEX. DEX pre-treatment increased β3 integrin-induced CLAN formation ~ 6-fold and the level of αvβ3 integrin expression and activation 3-fold relative to control cells. Focal adhesions containing activated β3 integrin also increased ~ 5-fold in DEX-treated cells. Finally, the overexpression of αvβ3 integrin in TM-1 cells increased CLAN formation 2-fold.
DEX-induced CLAN formation in HTM cells involved αvβ3 integrin activation and the Rac1/Trio signaling pathway previously shown to be associated with αvβ3-induced CLAN formation. Together these data suggest that steroid-induced CLAN formation may involve enhanced β3 integrin signaling in HTM cells possibly via an inside-out signaling mechanism. However, we can not exclude a role for β1 integrin signaling.
This PDF is available to Subscribers Only