Addressing the Link Between Impairment in Phagosome Degradation and AMD

The goal of this project is to identify what POS phagosome stages and at what time of the day are more impacted during phagosomal degradation in AMD. In Aim 1, I will test which stages of POS phagosome degradation are most impacted in cultures of human RPE cells carrying the AMD risk alleles. These studies will allow me to test in detail for defects in phagosome maturation and resolve which part of the degradation pathway impacts phagosome maturation. In Aim 2, I will assess which stages of POS phagosome maturation are most impacted, according to the daily cycle, in two in vivo mouse models (Klc1-/- and Elovl4-TG2 mice), in which there is an overall delay in POS phagosome degradation and which possess macular degeneration-like pathology.

Every day, small pieces of the photoreceptor outer segments are phagocytosed and then degraded by the Retinal Pigment Epithelial (RPE) cells. It is known that in some macular dystrophies (MDs) the degradation process is impaired and that that leads to the accumulation of undigested material in the RPE, what affects the whole retinal health. However, we still do not know precisely how both processes are related.

Historically, phagosome degradation has been assumed to be directly coupled with ingestion. However, in recent experiments we have detected that the maturation rate of specific phagosome stages varies according to time of day, and independently of each other. We think that some of these stages might be more affected than others in MDs, what could lead to the accumulation of those specific maturation stages at unusual times of the day and to the buildup of undigested material in the RPE cells.

Therefore, I propose to investigate the maturation rate and the accumulation of specific phagosome stages in vitro in MDs RPE cell models in comparison to cells from healthy patients. Second, I will study the maturation rate and the accumulation of the specific phagosome stages during the daily cycle in murine models that develop an MD-like pathology. These studies will provide a paradigm shift in our identification and understanding of the etiology of MDs and could be key for the development of new strategies to stop or prevent them.

Phagosome degradation is impaired in AMD, what leads to the accumulation of RPE deposits. However, the precise mechanism by which this happens is still unknown.

Previously, I have developed a way to identify different phagosome stages during the maturation process. Also, I have found that the maturation rate between these stages varies throughout the daily cycle. Therefore, in this project I will combine both findings to analyze what phagosome maturation stages are more impacted in AMD cells and according to the daily cycle.

Once the study is complete we will have more precise information about this mechanism that is impaired in AMD. We will also know if it is more affected at specific times of the day. This could help us to develop ways to ameliorate the impacted process.