LAPTM4B

Lysosomal-associated protein transmembrane 4B is required for optimal lysosomal function. It blocks EGF-stimulated EGFR intraluminal sorting and degradation. Conversely by binding with the phosphatidylinositol 4, 5-bisphosphate, it regulates its PIP5K1C interaction, inhibits HGS ubiquitination and relieves LAPTM4B inhibition of EGFR degradation. It recruits SLC3A2 and SLC7A5 (the Leu transporter) to the lysosome, promoting entry of leucine and other essential amino acid (EAA) into the lysosome, stimulating activation of proton-transporting vacuolar (V)-ATPase protein pump (V-ATPase) and hence mTORC1 activation. It plays a role as negative regulator of TGFB1 production in regulatory T cells. It binds ceramide and facilitates its exit from late endosome in order to control cell death pathways.

Full Name

lysosomal-associated protein transmembrane 4B

Function

Required for optimal lysosomal function (PubMed:21224396).
Blocks EGF-stimulated EGFR intraluminal sorting and degradation. Conversely by binding with the phosphatidylinositol 4,5-bisphosphate, regulates its PIP5K1C interaction, inhibits HGS ubiquitination and relieves LAPTM4B inhibition of EGFR degradation (PubMed:25588945).
Recruits SLC3A2 and SLC7A5 (the Leu transporter) to the lysosome, promoting entry of leucine and other essential amino acid (EAA) into the lysosome, stimulating activation of proton-transporting vacuolar (V)-ATPase protein pump (V-ATPase) and hence mTORC1 activation (PubMed:25998567).
Plays a role as negative regulator of TGFB1 production in regulatory T cells (PubMed:26126825).
Binds ceramide and facilitates its exit from late endosome in order to control cell death pathways (PubMed:26280656).

Biological Process

Endosome organizationManual Assertion Based On ExperimentIMP:UniProtKB
Endosome transport via multivesicular body sorting pathwayManual Assertion Based On ExperimentIDA:UniProtKB
Negative regulation of lysosomal protein catabolic processManual Assertion Based On ExperimentIMP:UniProtKB
Negative regulation of transforming growth factor beta1 productionManual Assertion Based On ExperimentIDA:UniProtKB
Regulation of lysosomal membrane permeabilityManual Assertion Based On ExperimentIMP:UniProtKB
Regulation of lysosome organizationManual Assertion Based On ExperimentIMP:UniProtKB

Cellular Location

Endomembrane system
Late endosome membrane
Cell membrane
Cell projection
Lysosome membrane
Endosome membrane
Endosome, multivesicular body membrane
Endosome, multivesicular body lumen

PTM

Undergoes proteolytic cleavage following delivery to the lysosomes.
Ubiquitinated by NEDD4.