Lysosomal transmembrane protein 5: Impact on immune cell function and implications for immune-related deficiencies.

Lysosomal transmembrane protein 5 (LAPTM5) is a lysosomal-associated protein that interacts with surface receptors on various immune cells, including B cells, T cells, macrophages and dendritic cells. Dysregulated expression of LAPTM5 is implicated in the development of multiple immune system-related diseases. In the context of tumors, elevated LAPTM5 levels in immune cells are associated with decreased cell membrane levels of T cell receptors (TCR) or B cell receptors (BCR), leading to impaired antigen presentation and immune escape, thereby promoting tumor progression. Besides, LAPTM5 is critical for inducing non-apoptotic cell death in tumor parenchymal cells since its downregulation leads to inhibition of the cell death pathway in the tumor parenchyma and subsequent enhanced tumorigenesis. LAPTM5 also affects the cell cycle as the elevated LAPTM5 expression in solid tumors causes its inability to block the G0/G1 stage. In non-solid tumors, abnormal LAPTM5 expression disrupts blood cell development and causes irregular proliferation. Furthermore, in the nervous system, aberrant LAPTM5 expression in microglia is correlated with Alzheimer's disease severity. In this context, further preclinical research is essential to validate LAPTM5 as a potential target for diagnosis, therapy, and prognosis in immune-related disorders and tumors. This review summarized the current insights into LAPTM5's role in tumors and immune-related deficits, highlighting its potential as a valuable biomarker and therapeutic target.