ABSTRACT Glaucoma, a leading cause of irreversible blindness in the world, affects more than 285,000 U.S. veterans. Elevated intraocular pressure (IOP) is associated with both development and progression of primary open angle glaucoma, and IOP is the only modifiable risk factor for the disease. However, the mechanisms causing elevated IOP remain poorly understood. Trabecular meshwork cells are critical to maintaining a normal aqueous fluid flow and IOP. In other tissues, such as the kidney, bones and cartilage, the primary cilia play a mechanosensory role in fluid flow. Here, we will explore the potential of cilia in trabecular meshwork cells to serve a mechanosensory role in the eye. In our previous funding cycle, we demonstrated that phosphoinositide lipids within primary cilia are an important regulator of eye pressure. We showed that phosphoinositide lipids within primary cilia are tightly controled and that dysregulation produces elevated eye pressure. Using optogenetic techniques, we targeted delivery of inositol enzymes to subcompartments within trabecular meshwork cells to demonstrate their function in regulating IOP. Mutations in OCRL, an inositol polyphosphate 5-phosphatase, cause congenital glaucoma. We further identified a novel link between signaling by cilia phosphoinositides and autophagy and lysosomal function. Here, we build on our strong preliminary evidence of the power of optogenetic tools to develop a new optogenetic regulator for eye pressure based on OptoXRchimeric G-protein coupled-receptor (GRCR) that has been shown to stimulate outflow facility. We hypothesize that optogenetically regulated GRCR and phosphoinositide signaling within trabecular meshwork cells will stimulate aqueous outflow. In Aim 1, we will determine whether reduction of IOP by GPR18 agonist PSBKD107 depends on primary cilia signaling. In Aim 2, we will determine whether chimeric OptoXR-GPR18 will improve outflow facility. In Aim 3, we will determine whether GPR18 levels are reduced in trabecular meshwork of open angle glaucoma patients. The proposed research is expected to have a significant impact on the understanding of mechanosensation of eye pressure in mammals, which will facilitate the discovery of new therapies for open angle glaucoma and other forms of glaucoma. Ultimately, the knowledge obtained from this project will lead to novel therapeutic compounds for the many veterans suffering from vision loss.