YAP/TAZ mediate TGFβ2-induced Schlemm’s canal cell dysfunction

Abstract

Purpose: Elevated transforming growth factor beta2 (TGFβ2) levels in the aqueous humor have been linked to glaucomatous outflow tissue dysfunction. Potential mediators of dysfunction are the transcriptional co-activators, Yes-associated protein (YAP) and transcriptional coactivator with PDZ binding motif (TAZ). However, the molecular underpinnings of YAP/TAZ modulation in SC cells under glaucomatous conditions are not well understood. Here, we investigate how TGFβ2 regulates YAP/TAZ activity in human SC (HSC) cells using biomimetic extracellular matrix (ECM) hydrogels, and examine whether pharmacologic YAP/TAZ inhibition would attenuate TGFβ2-induced HSC cell dysfunction. Methods: Primary HSC cells were seeded atop photocrosslinked ECM hydrogels, made of collagen type I, elastin-like polypeptide and hyaluronic acid, or encapsulated within the hydrogels. Changes in actin cytoskeleton, YAP/TAZ activity, ECM production, phospho-myosin light chain levels, and hydrogel contraction were assessed. Results: TGFβ2 significantly increased YAP/TAZ nuclear localization in HSC cells, which was prevented by either filamentous (F)-actin relaxation or depolymerization. Pharmacologic YAP/TAZ inhibition using verteporfin decreased fibronectin expression and reduced actomyosin cytoskeletal rearrangement in HSC cells induced by TGFβ2. Similarly, verteporfin significantly attenuated TGFβ2-induced HSC cell-encapsulated hydrogel contraction. Conclusions: Our data provide evidence for a pathologic role of aberrant YAP/TAZ signaling in HSC cells under simulated glaucomatous conditions, and suggest that pharmacologic YAP/TAZ inhibition has promising potential to improve outflow tissue dysfunction.

YAP/TAZ inactivation with simvastatin attenuates glucocorticoid-induced human trabecular meshwork cell dysfunction

“…The transcriptional coactivators YAP and TAZ dynamically shuttle between the cytoplasm and nucleus to regulate gene expression; increased nuclear YAP/TAZ localization principally indicates enhanced transcriptional activity 54 . Our recent studies on human TM and Schlemm's canal cells support this notion in ocular cells 15,55 . Moreover, the mevalonate pathway was shown to promote YAP/TAZ nuclear accumulation and activity in non-ocular cells 40 ; therefore, we hypothesized that simvastatin decreases glucocorticoid-induced pathologic YAP/TAZ nuclear localization and signaling in HTM cells.…”

Targeting YAP mechanosignaling to ameliorate stiffness-induced Schlemm’s canal cell pathobiology

“…Experiments using human donor eye tissue were approved by the SUNY Upstate Medical University Institutional Review Board (protocol #1211036) and performed in accordance with the tenets of the Declaration of Helsinki for the use of human tissue. Primary human SC cells were isolated from ostensibly normal donor corneal rims discarded after transplant surgery, as recently described (31), and cultured according to established protocols (33). Four normal, previously characterized (31) SC cell strains (HSC01, HSC02, HSC03, HSC09) were used in the present study (Table . 1).…”

“…Primary human SC cells were isolated from ostensibly normal donor corneal rims discarded after transplant surgery, as recently described (31), and cultured according to established protocols (33). Four normal, previously characterized (31) SC cell strains (HSC01, HSC02, HSC03, HSC09) were used in the present study (Table . 1). All SC cell strains were characterized based upon their typical spindlelike elongated cell morphology, expression of vascular endothelial-cadherin and fibulin-2, and lack of myocilin induction following exposure to dexamethasone (31).…”

“…Four normal, previously characterized (31) SC cell strains (HSC01, HSC02, HSC03, HSC09) were used in the present study (Table . 1). All SC cell strains were characterized based upon their typical spindlelike elongated cell morphology, expression of vascular endothelial-cadherin and fibulin-2, and lack of myocilin induction following exposure to dexamethasone (31). Different combinations of SC cell strains were used per experiment depending on cell availability, and all studies were conducted between cell passage 3-6.…”

“…A recent genome-wide association study further identified YAP1 among previously unknown open-angle glaucoma-risk loci (30), suggesting a potential causal association with outflow dysfunction. To examine this specifically, we recently linked glaucoma-like SC cell dysfunction directly with aberrant YAP activity using transforming growth factor beta2 as disease stimulus (31). However, the role of YAP mechanosignaling in SC cell pathobiology in response to ECM stiffening remains poorly understood.…”