Lysosomal protein transmembrane 4 alpha (LAPTM4A)

Lysosomal protein transmembrane 4 alpha (LAPTM4A) is a membrane protein characterized by four transmembrane domains, primarily localized to lysosomes and endosomes[1][5][6][7]. Although its exact physiological function remains to be fully determined in humans, mouse studies and sequence homology suggest that LAPTM4A plays a role in transporting small molecules, including nucleosides and their derivatives, between the cytosol and the lumen of intracellular vesicles such as endosomes and lysosomes[5][6]. LAPTM4A contains conserved sorting signals required for its proper targeting to the lysosomal compartment, specifically two tandemly arranged tyrosine-based motifs[1]. Overexpression of LAPTM4A can modulate cellular sensitivity to chemotherapeutic agents, antibiotics, and other amphipathic solutes, indicating a potential but not fully established role in multidrug resistance pathways, although this is more definitive for its paralog LAPTM4B[1][6]. LAPTM4A is considered a potential therapeutic target as a transporter relevant to endo-lysosomal function, but there are currently no specific drugs or biomarkers directly targeting this protein reported in the available literature[5][6]. Note: Most cancer-related and detailed signaling pathway roles (e.g., in EGFR trafficking and PI3K/AKT/mTOR signaling) have been described for *LAPTM4B*, a closely related paralog, not LAPTM4A. Some database and literature entries conflate the two; data here is specific to LAPTM4A except as noted[3][5][6].

Other names

Lysosomal-associated transmembrane protein 4AKIAA0108LAPTM4MBNTMTRPUNQ1846/PRO3574HUMORF13Membrane nucleoside transporter