Lamp1 non-cell autonomous regulation of endolysosomal acidification

Abstract

Many neurodegenerative disorders have been linked to a disruption in the endolysosomal pathway. They are characterized by an accumulation of insoluble protein aggregates, caused by a disruption in proteostasis. Lysosomes have a major role in proteostasis due to their role in cellular catabolism and as signaling hubs that regulate nutritional signaling. A dysfunction in the lysosomal pathway causes a disruption in the breakdown of proteins within the cell, leading to an accumulation of protein aggregates. Protein aggregates can accumulate as a result of a change in the pH of the lysosome, adversely affecting the optimal function of acid hydrolases which serve to cleave and degrade proteins.• The Jenny lab focuses on the role of lysosome associated membrane protein Lamp1 in the regulation of pH within the endolysosomal compartment. Lamp1 deficient Drosophila larvae showed an increase in the number of acidic vesicles found in the cells of fat bodies, as indicated by lysotracker staining. The Jenny Lab has hypothesized that Lamp1 plays a role in the regulation of pH within the endolysosomal system. Additionally, preliminary mosaic analysis suggests a non-cell autonomous function of Lamp1. The mechanism of this non-cell autonomy is currently unknown. We hypothesize that Lamp1 mediates a non-cell autonomous communication regulating endolysosomal acidification between Drosophila fat bodies and other tissues such as the brain.• To analyze changes in the number of acidic vesicles based on genotype, we dissected 3rd instar larval fat body cells, stained them with lysotracker, and imaged them using the apotome microscope. These images were then quantified using the SparQ plug-in in Fiji. Additionally, antibody staining technique was performed to measure Lamp1 expression in the brain and fat body cells of different genotypes. • Our results showed that there is a decrease in the number of acidic vesicles in fat body cells upon specifically rescuing Lamp1 in the brain. Additionally, we did not detect Lamp1 protein in the fat body cells of Lamp1 brain rescue. Together, these data support that having Lamp1 expression in the brain alone is sufficient to prevent the increase of acidic vesicles in the fat bodies. This suggests that there is non-cell autonomous communication between the fat bodies and brain mediated by Lamp1. Additionally, while analyzing lysotracker images and quantifications, we have seen that there is variation in the number of acidic vesicles found in the fat body cells of the Lamp1 brain rescue. This suggests that there is a partial rescue of Lamp1 in the fat bodies of the Lamp1 brain rescue genotype. Further research is required to confirm non-cell autonomous communication between other tissues in the larva and fat bodies. This research will contribute to the overall understanding of the endolysosomal pathway and the biology of neurodegenerative diseases.