November 1, 2017 at 10:30 pm

MCB 7410 Seminar | Revealing the Novel Biomarkers in Exosomal Proteome of Age-related Macular Degeneration, Nov. 7

The MCB 7410 Seminar features Quyen (Jason) Luong discussing “Revealing the Novel Biomarkers in Exosomal Proteome of Age-related Macular Degeneration” on Tuesday, Nov. 7, at 4:35 p.m. in Porter 104.

Luong is a graduate student in Biological Sciences Department and the Molecular and Cellular Biology program.

Refreshments are provided.

Abstract: Age-related macular degeneration (AMD) is a disease of the eyes that affect individuals above the age of 50. Currently, 1.75 million people are living with AMD in the US. Due to the aging population, this number is projected to increase by 50%, to approximately 3 million people in 2020. AMD affects the central vision, specifically the macular region of the retina (light sensitive tissue) in the back of the eye. Due to old age and accumulation of oxidative stress over the years, extracellular deposits build up between the retinal pigment epithelium (RPE) and the posterior choroid vascular layer. This thickens the separation between RPE and the nutrient source, impairing the diffusion process and leading to the death of RPE cells. Two types of RPE can occur, dry (thinning of RPE due to death of RPE cells), and wet (scarring of macula due to increase presence of leaky vessels). Without proper treatment and early detection, both types lead to debilitating consequences and severe vision loss. Since the completion of the genome project and the increase of genomics research, scientists have turned toward finding the magic protein marker that could indicate the onset of diseases. Proteomics has been utilized to search for new biomarkers for disease prevention. Blood protein analyses yielded inaccurate and insensitive results to diseases, leading to the quest of more specific markers. Secretory proteins in the local tissues have become a new interest in such discovery. These secretory proteins can be released into the extracellular space via exosomes. These extracellular vehicles have been found to be in numerous bodily fluid, to contain various content (RNAs, miRNAs, proteins, etc.), and to participate in variety of functions (programmed cell death, tumor-environment interactions, etc.). Exosomal proteins in ocular fluids have also been studied in glaucoma, cataracts, and AMD. To specifically search for a novel AMD biomarker, Kang et al. obtained exosomal proteins from aqueous humor of the eye from 26 patients with the diseases as well as from RPE cell lines (ARPE-19) and profiled these proteins using liquid-chromotography- electrospraying ionizing-tandam mass spectrometry (LC-ESI-MS/MS). This technique is powerful to identify specific protein content within the exosomes. After performing whole-proteomics profiling of these exosomal proteins, comparing them to the profiles of the controls, and searching against previously published data and databases, the authors identified targeted proteins for further analyses using the liquid chromatography-multiple reaction monitoring (LC-MRM). Two criteria were used to select proteins for LC-MRM analyses: proteins must be in the exosomes of ARPE-19 and aqueous humor, and the peptides must be frequently observed in MS. Six proteins were analyzed: actin, myosin-9, Hsp70, cathepsin D, cytokeratin 8 and 14. From the six proteins, cathepsin D and cytokeratin 8 are increased in aqueous humor of AMD patients (indicated by Western blot) and have essential roles in the pathophysiology of AMD, with cytokeratin 8 being a better indicator protein from area-under-curve (AUC) analyses (AUC=0.929). Post-treatment analyses of these proteins show variable results, indicating a variable responses to anti-VEGF treatment of wet AMD. Combining proteomics-based characterization with the understanding of pathophysiology of AMD and patients’ responses, we are one-step closer to finding a target-based therapy and personalized medicine. Future studies with larger sample size is needed to confirm the potential biomarkers to help prevent the progression of AMD.

Kang GY et al. Exosomal proteins in the aqueous humor as novel biomarkers in patients with neovascular age-related macular degeneration. J. Proteome Res. 13:581-595. 2014.

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