Existence of the Canonical Wnt Signaling Pathway in the Human Trabecular Meshwork

Mao, Weiming; Millar, J. A.; Wang, Wan Heng; Silverman, Sean; Liu, Yang; Wordinger, Robert J.; Rubin, Jeffrey S.; Pang, Iok Hou; Clark, Abbot F.

doi:10.1167/iovs.12-9664

Cited by 70 publications

(102 citation statements)

References 38 publications

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“…The Wnt signaling pathway, an important pathway in glaucoma, 43,71 is also influenced by YAP/TAZ. The results from the present study also implicate substratum stiffness in Wnt regulation.…”

Section: Discussionmentioning

confidence: 99%

“…These data were consistent with previous reports of SFRP-1 being overexpressed in glaucomatous HTM cells and increased expression resulting in elevated IOP. 43,71 TAZ, also upregulated on pathomimetic substrates, has been identified as a Wnt antagonist. 41 Our results suggest that the overexpression of SFRP-1 and TAZ in cells cultured on pathomimetic substrates inhibits Wnt signaling in glaucoma.…”

Section: Discussionmentioning

confidence: 99%

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Role of Substratum Stiffness in Modulating Genes Associated with Extracellular Matrix and Mechanotransducers YAP and TAZ

Raghunathan

Morgan

Dreier

et al. 2013

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. Primary open-angle glaucoma is characterized by increased resistance to aqueous humor outflow and a stiffer human trabecular meshwork (HTM). Two Yorkie homologues, Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif, encoded by WWTR1 (TAZ), are mechanotransducers of the extracellular-microenvironment and coactivators of transcription. Here, we explore how substratum stiffness modulates the YAP/TAZ pathway and extracellular matrix genes in HTM cells and how this may be play a role in the onset and progression of glaucoma.METHODS. HTM cells from normal donors were cultured on hydrogels mimicking the stiffness of normal (5 kPa) and glaucomatous (75 kPa) HTM. Changes in expression of YAP/ TAZ related genes and steroid responsiveness were determined. Additionally, transglutaminase-2 expression was determined after YAP silencing.RESULTS. YAP and TAZ are both expressed in human trabecular meshwork cells. In vitro, YAP and TAZ were inversely regulated by substratum stiffness. YAP and 14-3-3r were downregulated to different extents on stiffer substrates; TAZ, tissue transglutaminase (TGM2), and soluble frizzled-related protein-1 (sFRP-1) were significantly upregulated. CTGF expression appeared to be altered differentially by both YAP and TAZ. Myocilin and angiopoietin-like 7 expression in response to dexamethasone was more pronounced on stiffer substrates. We demonstrated a direct effect by YAP on TGM2 when YAP was silenced by small interfering RNA.CONCLUSIONS. The expression of YAP/TAZ and ECM-relatedgenes is impacted on physiologically relevant substrates. YAP was upregulated in cells on softer substrates. Stiffer substrates resulted in upregulation of canonical Wnt modulators, TAZ and sFRP-1, and thus may influence the progression of glaucoma. These results demonstrate the importance of YAP/TAZ in the HTM and suggest their role in glaucoma. (Invest Ophthalmol Vis Sci.

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“…The Wnt signaling pathway, an important pathway in glaucoma, 43,71 is also influenced by YAP/TAZ. The results from the present study also implicate substratum stiffness in Wnt regulation.…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Role of Substratum Stiffness in Modulating Genes Associated with Extracellular Matrix and Mechanotransducers YAP and TAZ

Raghunathan

Morgan

Dreier

et al. 2013

Invest. Ophthalmol. Vis. Sci.

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“…25 It is likely that in this experiment, as the authors interpret, the very low Wnt induction in cells of the outflow facility was due to low transfection efficiencies. Although the presence of the Wnt pathway in the trabecular meshwork has been demonstrated, 26,27 newer designs overcoming transfection barriers are needed to ascertain the correlation of myocilin with this pathway in the trabecular meshwork.…”

Section: Microarraysmentioning

confidence: 99%

The Effects of Myocilin Expression on Functionally Relevant Trabecular Meshwork Genes: A Mini-Review

Borrás

2014

Journal of Ocular Pharmacology and Therapeutics

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Myocilin is a secreted glaucoma-associated protein, specifically induced by dexamethasone in human trabecular meshwork cells, where it was discovered. Myocilin is expressed in several tissues of the body, but it causes disease only in the eye. The protein contains two domains: an N-terminal region with significant homologies to nonmuscle myosin, and a C-terminal region, which is similar to the olfactomedin proteins. Forty percent of myocilin undergoes an intracellular endoproteolytic cleavage by calpain II, a calcium-dependent cysteine protease, which releases the 2 domains. The protein is known to interact with intracellular and extracellular matrix proteins, and some is released into the extracellular space associated with exosomes. Myocilin mutations are linked to glaucoma and induce elevated intraocular pressure. Most of the glaucoma-causative mutations map to the olfactomedin domain, which appears to be a critical domain for the function of the protein. Myocilin mutants are misfolded, aggregate in the endoplasmic reticulum, and are not secreted. Overexpression of myocilin and of its mutants in primary human trabecular meshwork cells triggers changes in the expression of numerous genes, many of which have been known to be involved in mechanisms important for the physiology and pathology of the tissue.Here we review recent studies from our laboratory and those of others that deal with trabecular meshwork genes, which are altered by the overexpression of wild-type and glaucoma-causative mutant myocilin genes.

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“…Wnt can activate multiple signaling pathways, including a canonical β-catenin-mediated pathway and multiple non-canonical pathways (Clevers, 2006; Freese et al, 2010; Macdonald and He, 2012; Yu and Virshup, 2014). However, it appears that the non-canonical pathways are not involved in IOP regulation and that the effect is not specific to SFRP1, as another antagonist of canonical Wnt pathway (Dickkopf-related protein 1) had similar effects (Mao et al, 2012). These two studies provide firm support for a critical role of canonical Wnt antagonism in IOP regulation and OAG.…”

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confidence: 99%

Wnt inhibition induces persistent increases in intrinsic stiffness of human trabecular meshwork cells

Morgan

Raghunathan

Chang

et al. 2015

Experimental Eye Research

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Wnt antagonism has been linked to glaucoma and intraocular pressure regulation, as has increased stiffness of human trabecular meshwork (HTM) tissue. We have shown culturing HTM cells on substrates that mimic the elevated stiffness of glaucomatous tissue leads to elevated expression of the Wnt antagonist secreted frizzled related protein 1 (SFRP1), suggesting a linkage between SFRP1 and HTM mechanobiology. In this study, we document biomechanical consequences of Wnt antagonism on HTM cells. Cells were treated with the Wnt antagonists (SFRP1, KY02111, and LGK-974) for 8 days and allowed to recover for 4 days. After recovery, intrinsic cell stiffness and activation of the Wnt pathway via β-catenin staining and blotting were assayed. Basal cell stiffness values were 3.71±0.37, 4.33±3.07, and 3.07± kPa (median±S.D.) for cells derived from 3 donors. Cell stiffness increased after 0.25 μg/mL (4.32±5.12, 8.86±8.51, 4.84±3.15 kPa) and 0.5 μg/mL (16.75±5.59, 13.18±7.99, and 8.54±5.77 kPa) SFRP1 treatment. Stiffening was observed after 10μM KY02111 (10.72±5.63 and 6.57±5.53 kPa) as well as LGK-974 (9.60±7.41 and 11.40±9.24 kPa) treatment compared with controls (3.79±1.01 and 5.16±2.14 kPa). Additionally, Wnt inhibition resulted in decreased β-catenin staining and increased phosphorylation at threonine 41 after recovery. In conclusion, this work demonstrates a causal relationship between Wnt inhibition and cell stiffening. Additionally, these findings suggest transient Wnt inhibition resulted in durable modulation of the mechanical phenotype of HTM cells. When placed in context with previous results, these findings provide a causal link between Wnt antagonism and cell stiffness and suggest a feedback loop contributing to glaucoma progression.

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Existence of the Canonical Wnt Signaling Pathway in the Human Trabecular Meshwork

Abstract: There is a canonical Wnt signaling pathway in the TM, and this canonical Wnt pathway, but not the noncanonical Wnt signaling pathway, regulates IOP.

Cited by 70 publications

References 38 publications

Role of Substratum Stiffness in Modulating Genes Associated with Extracellular Matrix and Mechanotransducers YAP and TAZ

Role of Substratum Stiffness in Modulating Genes Associated with Extracellular Matrix and Mechanotransducers YAP and TAZ

The Effects of Myocilin Expression on Functionally Relevant Trabecular Meshwork Genes: A Mini-Review

Wnt inhibition induces persistent increases in intrinsic stiffness of human trabecular meshwork cells

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