The ubiquitin ligase Deltex‐3L regulates endosomal sorting of the G protein‐coupled receptor CXCR4 (1066.18)

Abstract

G protein‐coupled receptor (GPCR) sorting into the degradative pathway is important for attenuating signaling. Upon agonist activation of the chemokine receptor CXCR4, a GPCR, it is rapidly ubiquitinated, internalized to endosomes and sorted to lysosomes via the endosomal sorting complex required for transport (ESCRT) pathway. ESCRT‐0 ubiquitination is linked to the efficiency with which CXCR4 is sorted for lysosomal degradation, however mechanistic insight is lacking. Here, we show for the first time that the RING‐domain E3 ubiquitin ligase Deltex‐3‐like (DTX3L) mediates CXCR4 sorting from early endosomes to lysosomes. Using several biochemical and immunochemical techniques including fixed cell confocal immunofluoresence microscopy, co‐immunoprecipitation and in vitro ubiquitination assays, we show that DTX3L localizes to early endosomes upon CXCR4 activation and interacts directly with and inhibits the activity of the E3 ubiquitin ligase atrophin‐1 interacting protein 4 (AIP4). This serves to limit the extent to which ESCRT‐0 is ubiquitinated and is able to sort CXCR4 for lysosomal degradation. Therefore we have defined a novel role for DTX3L in GPCR endosomal sorting and propose that DTX3L may play a broad role in endosomal sorting. In addition, our data reveal an unprecedented link between two distinct E3 ubiquitin ligases to control the activity of the ESCRT machinery.Grant Funding Source: GM075159