Advanced glycation end products (AGEs) have an important role in diabetic complications, with many responses mediated through AGE-receptors. The current study has investigated the binding and uptake of AGEs by retinal microvascular endothelium in an attempt to understand the nature of AGE-interaction with receptors on the cell surface. There has been special emphasis placed on the R1, R2, and R3 components of AGE-receptor complex (AGE-RC) and their localization to caveolin-rich membrane domains. Retinal microvascular endothelial cells (RMECs) were exposed to either AGE-modified BSA (AGE-BSA) or native BSA conjugated to colloidal gold (gAGE, gBSA) for various time periods, fixed, and processed for transmission electron microscopy (TEM). Localization of AGE-RC components in caveolae was investigated using confocal microscopy and ultrastructural immunogold labeling. Caveolae were extracted from RMECs using differential Triton X-100 solubility, and Western analysis was conducted to test for caveolae enrichment and the presence of AGE-RC complex components. Ligand blots determined 125I-AGE-BSA binding to caveolae-enriched extracts. Colloidal gold conjugates of AGE-BSA bound to caveolae and were internalized to be trafficked to lysosomal-like compartments. AGE-receptor complex components were significantly enriched within caveolae. The data suggest that AGEs interact with their receptors within caveolae. It is significant that the AGE-R complex localizes to these organelles, because this may have implications for AGE binding, internalization, signal transduction, and the modulation of AGE-receptor-mediated vascular cell dysfunction.
ABSTRACT. The objectives of this study were to investigate the distributions of abnormally expressed optineurin (OPTN) proteins in retinal ganglion cells (RGC5s) of transgenic rats and their effects on subcellular morphological structures. Green fluorescent protein labeled EGFP wildtype (OPTN WT ), E50K mutant type (OPTN E50K ), and OPTN siRNA (si-OPTN) eukaryotic expression plasmids were constructed and transfected into RGC5s. Intracellular structures were labeled with organelle specific fluorescent dyes. Construct localization and cell morphologies were visualized by confocal fluorescence microscopy. OPTN WT was observed to be distributed as fine punctate fluorescent particles in the cytoplasm around the nucleus, along with exhibiting nuclear expression. OPTN E50K exhibited similar distribution but with non-uniform fluorescence particle size. si-OPTN distribution was similar to that of EGFP: uniform across the cytoplasm and nucleus. Compared with the negative control group, OPTN WT , and OPTN E50K and to a lesser degree pEGFP-transfected cells exhibited fracture and loss of myofilament proteins and mitochondrial swelling and cytoplasmic accumulation, along with abnormal lysosomal distribution and increased volume, and Golgi fragmentation. However, si-OPTN transfected cells exhibited no significant damage. Therefore, we demonstrated that the E50K mutation disrupts the uniformity of OPTN protein distribution upon exogenous overexpression. Furthermore, these results suggested that si-OPTN transfection, and thus potentially OPTN knockdown, did not impact subcellular morphology of RGC5 cells, whereas transfection, especially when combined with wild-type or mutant OPTN expression, led to substantial abnormalities in subcellular morphological structures. These findings lay a foundation for further research into the function of the OPTN protein.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.