Lysosomal-associated transmembrane protein 4B (LAPTM4B)

Lysosomal-associated transmembrane protein 4B (LAPTM4B) is an integral membrane protein primarily localized to the lysosomal and late endosomal membrane, encoded by the LAPTM4B gene on chromosome 8q22.1. It contains four transmembrane domains and is expressed as two main isoforms—LAPTM4B-35 and LAPTM4B-24—due to alternative translation initiation. LAPTM4B is involved in multiple cellular processes, including regulation of lysosomal function, autophagy induction, and modulation of cell proliferation, invasion, and metastasis. LAPTM4B is upregulated in various solid tumors, promotes chemoresistance (notably to anthracyclines), resists apoptosis, and amplifies EGFR and mTORC1 signaling, making it a candidate therapeutic target and prognostic biomarker in cancer. Overexpression is associated with poor clinical outcomes across several malignancies. LAPTM4B protein also modulates exosome secretion and the intracellular trafficking of specific proteins and lipids, further influencing tumor cell behavior and communication.

Other names

Lysosomal protein transmembrane 4 betaPSEC0001LC27Lysosome-associated transmembrane protein 4-betaLAPTM4betalysosomal-associated protein transmembrane 4 betaLAPTM4B-35LAPTM4B-24

LAPTM4B contributes to anthracycline resistance by sequestering drugs in cytoplasm and reducing DNA damage. It promotes EGFR signaling by blocking lysosomal degradation of EGFR, amplifying proliferative and survival signals. It also enhances mTORC1 activation through recruitment of leucine transporters, promoting cell growth and survival.