Control of Trabecular Meshwork Cytoskeleton

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The long-term objective of this grant is to identify how to modulate αvβ3 integrin signaling pathways in order to develop therapeutic targets to control intraocular pressure (IOP) in glaucoma. The glaucomas, which lead to irreversible loss of retinal ganglion cells, affect approximately 67 million people worldwide. They are commonly associated with elevated levels of intraocular pressure (IOP) due to a reduction in aqueous humor outflow from the trabecular meshwork (TM). One of the major risk factors that has emerged as an important regulatory mechanism for outflow facility is the actin cytoskeleton. It controls a number of key biological processes involved in maintaining normal outflow facility including contractility, phagocytosis, and deposition of the extracellular matrix. Integrins play a central role in regulating these cytoskeleton-mediated activities and our studies suggest that dysregulation of the αvβ3 integrin causes the major phenotypic changes associated with glaucoma including decreased phagocytosis, increased extracellular matrix deposition, CLAN formation and an elevation in IOP. We propose that this integrin is activated in glaucoma by elevated levels of TGFβ2 or following treatments with glucocorticoids, like dexamethasone (DEX). In this grant, we plan to use RNAseq studies to identify the factors upregulated by DEX or TGFβ2 that activate αvβ3 integrin and proximity ligation assays to determine if these factors are associated with the integrin adhesome. We also plan to demonstrate that an NRON/NFAT complex controls DEX-induced activation of αvβ3 integrin and the secondary glucocorticoid response involved in steroid-induced glaucoma. Finally, we plan to show that the responses to DEX (ECM formation, IOP elevation, and outflow facility) are affected by the activated state of αvβ3 integrin in vivo, not just its expression level. To test this last hypothesis we plan to use a tamoxifen inducible CreERcag-β3 integrinflox/flox mouse to knock down αvβ3 integrin expression in the mouse TM. Adenoviral (Ad5) vectors expressing 3 different activated states of αvβ3 integrin (wildtype, inactive and constitutively active) will be used to alter the activity levels of αvβ3 integrins in vivo. The proposed studies are the first to demonstrate that changes in a specific integrin signaling pathway can affect IOP, outflow facility, and ECM formation in vivo. They will enhance our understanding of how integrin signaling events are controlled in the TM and how this affects the cytoskeletal events (ECM deposition, cell contractility and phagocytosis) that regulate outflow facility. Understanding how integrins contribute to the regulation of these processes is important because it will enable us to provide new therapeutic targets to regulate the cytoskeleton in order to restore homeostasis and decrease IOP.