LAMP2, or lysosomal-associated membrane protein 2, is a well-recognized mediator of autolysosome maturation. It is involved in the autophagy-lysosomal protein degradation pathway, which is crucial for many cellular processes. Mutations in the LAMP2 gene can lead to various diseases, highlighting its biological importance. Genetic models, such as knockout (KO) mouse models, have been instrumental in studying its function [1,2,4].

In thymic stromal cells, genetic inactivation of Lamp2 specifically impairs the development of CD4 T cells that completed positive selection, due to defects in autophagy in lamp2-deficient cortical thymic epithelial cells (cTECs) which are linked to alterations in MHC II processing [1]. In mice, Lamp2 deficiency also leads to age-dependent autofluorescence abnormalities of the fundus, thickening of Bruch's membrane, and the formation of basal laminar deposits, similar to histopathological changes in age-related macular degeneration (AMD) [6]. Moreover, in engineered azacytidine (Aza)-resistant MDS cell lines, LAMP2 deficiency is responsible for Aza resistance and hypersensitivity to lysosome and autophagy inhibitors [3]. Mutations in the LAMP2 gene cause Danon disease in humans, and LAMP2-deficient mice replicate symptoms of Danon patients, including accumulation of autophagic vacuoles in heart and skeletal muscle [4,5].

In conclusion, LAMP2 plays essential roles in autophagy, T-cell development, and lysosomal function. Studies using KO mouse models have revealed its significance in diseases such as Danon disease, AMD, and in the response to drugs like azacytidine in MDS/AML. Understanding LAMP2 function provides insights into the underlying mechanisms of these diseases and may offer potential therapeutic targets.

References:

1. Rodrigues, Pedro M, Sousa, Laura G, Perrod, Chiara, Saftig, Paul, Alves, Nuno L. 2022. LAMP2 regulates autophagy in the thymic epithelium and thymic stroma-dependent CD4 T cell development. In Autophagy, 19, 426-439. doi:10.1080/15548627.2022.2074105. https://pubmed.ncbi.nlm.nih.gov/35535798/

2. Shalata, Adel, Bar-Shai, Marina, Hadid, Yarin, Ben-Yosef, Tamar, Yaniv, Liat. 2023. Danon Disease: Entire LAMP2 Gene Deletion with Unusual Clinical Presentation-Case Report and Review of the Literature. In Genes, 14, . doi:10.3390/genes14081539. https://pubmed.ncbi.nlm.nih.gov/37628591/

3. Dubois, Alix, Furstoss, Nathan, Calleja, Anne, Auberger, Patrick, Robert, Guillaume. 2019. LAMP2 expression dictates azacytidine response and prognosis in MDS/AML. In Leukemia, 33, 1501-1513. doi:10.1038/s41375-018-0336-1. https://pubmed.ncbi.nlm.nih.gov/30607021/

4. Eskelinen, Eeva-Liisa. 2006. Roles of LAMP-1 and LAMP-2 in lysosome biogenesis and autophagy. In Molecular aspects of medicine, 27, 495-502. doi:. https://pubmed.ncbi.nlm.nih.gov/16973206/

5. Bottillo, Irene, Giordano, Carla, Cerbelli, Bruna, d'Amati, Giulia, Grammatico, Paola. 2016. A novel LAMP2 mutation associated with severe cardiac hypertrophy and microvascular remodeling in a female with Danon disease: a case report and literature review. In Cardiovascular pathology : the official journal of the Society for Cardiovascular Pathology, 25, 423-31. doi:10.1016/j.carpath.2016.07.005. https://pubmed.ncbi.nlm.nih.gov/27497751/

6. Notomi, Shoji, Ishihara, Kenji, Efstathiou, Nikolaos E, Kroemer, Guido, Vavvas, Demetrios G. 2019. Genetic LAMP2 deficiency accelerates the age-associated formation of basal laminar deposits in the retina. In Proceedings of the National Academy of Sciences of the United States of America, 116, 23724-23734. doi:10.1073/pnas.1906643116. https://pubmed.ncbi.nlm.nih.gov/31699817/