Characterisation of novel protein ‘WDR98/RMC1’ and its role in lysosome biology

Following the results from a pilot study indicating the interaction of endosomal maturation proteins MON1B and CCZ1 with the uncharacterised protein ‘WDR98/RMC1’, this potentially new protein complex was investigated further. Literature research and bioinformatics revealed the highly evolutionarily conserved nature of WDR98 and also its unique C-terminal ‘MIC’ domain (the N-terminal containing the common protein binding platform domain WD40). Immunoprecipitation methods were used to confirm the, then novel, interaction of WDR98 with MON1B and CCZ1 individually. Furthermore, it was discovered that the WD40 domain is alone capable of eliciting binding between these proteins. Though reported elsewhere that WDR98 was able to bind to RAB5 and RAB7 in a whole-lysate context, we are confident that WDR98 is unable to bind to either RAB in isolation in vitro. Immunofluorescence was utilised to localise WDR98 to endosomes both early (RAB5) and late (RAB7) and lysosomes (LGP120), specifically those most active around the nuclear periphery. WDR98 was not seen to localise to autophagosomes (LC3). Both the WD40 and MIC domains also localised to lysosomes individually. This, along with recent literature, indicates an important role for WDR98 in protein trafficking, specifically endosomal maturation and lysosome biology. In addition, its potential role in disease and the emerging disease-contribution of the lysosome, particularly concerning cancer, renders this protein an exciting discovery, with potential as a target for future investigations.