Abstract
Purpose :
The trabecular pathway maintains intraocular pressure (IOP) by regulating resistance to aqueous humor (AH) outflow. However, our understanding of the molecular mechanisms regulating the barrier activity of trabecular meshwork (TM) is limited. This study aimed to highlight shared cell adhesive properties between TM cells and podocytes relevant to their filtration and barrier activities.
Methods :
We employed a proteomics approach to identify major cell adhesive proteins in normal and dexamethasone-treated human TM cells. The distribution patterns and phosphorylation statuses of selected cell adhesive proteins were evaluated in human TM cells under normal conditions and Abl kinase inhibition through immunofluorescence and immunoblot analyses.
Results :
This study identified various cell adhesive proteins (cell-ECM and cell-cell) not previously described in human TM cells. Notably, several of these identified proteins in TM cells are known as preferred proteins in kidney podocytes, crucial for the filtration barrier activity of podocyte slit diaphragms. Intriguingly, glucocorticoids induce actin cytoskeletal crosslinking and stress fibers in both TM cells and podocytes, enhancing barrier activity. Additionally, the Abl kinase inhibitor, known to disrupt podocyte barrier activity by reducing cell adhesive interactions in slit diaphragms, was found to increase AH outflow and reduce IOP. Moreover, mutations in LMX1b, a LIM domain-containing transcription factor that regulates the expression of various cytoskeletal and cell adhesive proteins in podocytes, have been associated with glaucoma and elevated IOP in humans.
Conclusions :
This study reveals the expression of various podocyte-preferred cell adhesive proteins in human TM cells involved in filtration barrier activity, partly regulated by the LMX1b transcription factor. Importantly, variants and mutations in LMX1b impair podocyte filtration barrier activity, and lead to glaucoma with increased IOP, indicating the role of LMX1b regulated cell adhesive proteins in TM and in maintaining IOP homeostasis. Interestingly, TM cells and podocytes appear to share physiological functions influenced by common attributes of actin cytoskeleton and cell adhesive interactions.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.