Researchers at the National Institutes of Health (NIH) have identified AKT2 as a potential therapeutic target for dry age-related macular degeneration (AMD). The study, published in Nature Communications, reveals that alterations in AKT2 affect lysosome function, leading to the formation of drusen, a hallmark of dry AMD. This discovery offers a promising avenue for developing treatments for this currently untreatable condition.
The Role of Lysosomes in AMD
Lysosomes, the cell's waste disposal system, are crucial for maintaining the health of the retina. Retinal pigment epithelium (RPE) cells support the retina's neurons by providing nutrients and removing waste. Dysfunction in this waste removal process leads to the accumulation of drusen, characteristic deposits in dry AMD. Despite extensive research, the mechanisms behind drusen formation have remained largely unknown.
AKT2 and Lysosome Dysfunction
The researchers investigated the role of AKT2, a signaling protein, in RPE cells. By manipulating AKT2 expression in mice, they found that overexpression of AKT2 led to lysosome dysfunction and the development of dry AMD symptoms, including RPE degeneration. Similar features were observed in RPE cells from human donors with AMD and in RPE cells generated from patient stem cells.
Kapil Bharti, Ph.D., co-head of the Ocular Stem Cell & Translational Research (OSCTR) Section at NIH's National Eye Institute, stated, "This study's findings form the basis for a possible future treatment for dry AMD, for which no therapy currently exists."
Genetic Risk Factor and AKT2
Further analysis revealed that RPE cells from donors with the CFH Y402H gene variant, which increases AMD risk, exhibited greater AKT2 expression, functionally defective lysosomes, and drusen deposits. This suggests a direct link between a known genetic risk factor for AMD and AKT2-mediated lysosome dysfunction.
Implications for Therapy
These findings suggest that targeting the AKT2/SIRT5/TFEB pathway could represent a novel therapeutic approach for dry AMD. Ruchi Sharma, Ph.D., co-head of the OSCTR Section, had previously developed an AMD patient stem cell-derived RPE model, which facilitated this research. The current study builds upon this earlier work, providing a deeper understanding of the molecular mechanisms underlying dry AMD and paving the way for the development of targeted therapies.
AMD is a leading cause of vision loss in the United States, affecting the macula, the central part of the retina responsible for sharp, central vision. Currently, there are no effective treatments for dry AMD, highlighting the urgent need for new therapeutic strategies.
