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Vertebrate Lonesome Kinase Regulated Extracellular Matrix Protein Phosphorylation, Cell Shape, and Adhesion in Trabecular Meshwork Cells.

ABSTRACT: Glaucoma, a leading cause of irreversible blindness, is commonly associated with elevated intraocular pressure (IOP) due to impaired aqueous humor (AH) drainage through the trabecular meshwork (TM). Although dysregulated production and organization of extracellular matrix (ECM) is presumed to increase resistance to AH outflow and elevate IOP by altering TM cell contractile and adhesive properties, it is not known whether regulation of ECM protein phosphorylation via the secretory vertebrate lonesome kinase (VLK) influences TM cellular characteristics. Here, we tested this possibility. Experiments carried out in this study reveal that the 32?kDa protein is a prominent VLK isoform detectable in lysates and conditioned media (CM) of human TM cells. Increased levels of VLK were observed in CM of TM cells subjected to cyclic mechanical stretch, or treated with dexamethasone, TGF-?2, and TM cells expressing constitutively active RhoA GTPase. Downregulation of VLK expression in TM cells using siRNA decreased tyrosine phosphorylation (TyrP) of ECM proteins and focal adhesions, and induced changes in cell shape in association with reduced levels of actin stress fibers and phospho-paxillin. VLK was also demonstrated to regulate TGF-?2-induced TyrP of ECM proteins. Taken together, these results suggest that VLK secretion can be regulated by external cues, intracellular signal proteins, and mechanical stretch, and VLK can in turn regulate TyrP of ECM proteins secreted by TM cells and control cell shape, actin stress fibers, and focal adhesions. These observations indicate a potential role for VLK in homeostasis of AH outflow and IOP, and in the pathobiology of glaucoma. J. Cell. Physiol. 232: 2447-2460, 2017. © 2016 Wiley Periodicals, Inc.

SUBMITTER: Maddala R

PROVIDER: S-EPMC5462548 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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Vertebrate Lonesome Kinase Regulated Extracellular Matrix Protein Phosphorylation, Cell Shape, and Adhesion in Trabecular Meshwork Cells.

Maddala Rupalatha R Skiba Nikolai P NP Rao Ponugoti Vasantha PV

Journal of cellular physiology 20170327 9

Glaucoma, a leading cause of irreversible blindness, is commonly associated with elevated intraocular pressure (IOP) due to impaired aqueous humor (AH) drainage through the trabecular meshwork (TM). Although dysregulated production and organization of extracellular matrix (ECM) is presumed to increase resistance to AH outflow and elevate IOP by altering TM cell contractile and adhesive properties, it is not known whether regulation of ECM protein phosphorylation via the secretory vertebrate lone ...[more]

PMID: 27591737

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Project description:PurposeThe purpose of this study was to determine whether genipin-induced crosslinked cell-derived matrix (XCDM) precipitates fibrotic phenotypes in human trabecular meshwork (hTM) cells by dysregulating β-catenin and Yes-associated protein (YAP)/ transcriptional coactivator with PDZ-binding motif (TAZ) signaling pathways.MethodsCell-derived matrices were treated with control or genipin for 5 hours to obtain respective uncrosslinked (CDM) and XCDMs and characterized. hTM cells were seeded on these matrices with/without Wnt pathway modulators in serum-free media for 24 hours. Elastic modulus, gene, and protein (whole cell and subcellular fractions) expressions of signaling mediators and targets of Wnt/β-catenin and YAP/TAZ pathways were determined.ResultsAt the highest genipin concentration (10% XCDM), XCDM had increased immunostaining of N-ε(γ-glutamyl)-lysine crosslinks, appeared morphologically fused, and was stiffer (5.3-fold, P < 0.001). On 10% XCDM, hTM cells were 7.8-fold (P < 0.001) stiffer, total β-catenin was unchanged, pβ-catenin was elevated, and pGSK3β was suppressed. Although 10% XCDM had no effect on cytoplasmic β-catenin levels, it reduced nuclear β-catenin, cadherin 11, and key Wnt target genes/proteins. The 10% XCDM increased total TAZ, decreased pTAZ, and increased cytoplasmic TAZ levels in hTM cells. The 10% XCDM increased total YAP, reduced nuclear YAP levels, and critical YAP/TAZ target genes/proteins. Wnt activation rescued hTM cells from 10% XCDM-induced stiffening associated with increased nuclear β-catenin.ConclusionsIncreased cytoplasmic TAZ may inhibit β-catenin from its nuclear shuttling or regulating cadherin 11 important for aqueous homeostasis. Elevated cytoplasmic TAZ may inhibit YAP's probable homeostatic function in the nucleus. Together, TAZ's cytoplasmic localization may be an important downstream event of how increased TM extracellular matrix (ECM) crosslinking may cause increased stiffness and ocular hypertension in vivo. However, Wnt pathway activation may ameliorate ocular hypertensive phenotypes induced by crosslinked ECM.

Dataset Information

Vertebrate Lonesome Kinase Regulated Extracellular Matrix Protein Phosphorylation, Cell Shape, and Adhesion in Trabecular Meshwork Cells.

Publications

Vertebrate Lonesome Kinase Regulated Extracellular Matrix Protein Phosphorylation, Cell Shape, and Adhesion in Trabecular Meshwork Cells.

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