title: Evidence for recycling of invariant surface transmembrane domain proteins in African trypanosomes.
abstract: Intracellular trafficking is a vital component of both virulence mechanisms and drug interactions in Trypanosoma brucei, the causative agent of human African trypanosomiasis and n'agana of cattle. Both maintaining the surface proteome composition within a life stage and remodeling the composition when progressing between life stages are important features of immune evasion and development for trypanosomes. Our recent work implicates the abundant transmembrane invariant surface glycoproteins (ISGs) in the uptake of first-line therapeutic suramin, suggesting a potential therapeutic route into the cell. RME-8 is a mediator of recycling pathways in higher eukaryotes and is one of a small cohort of intracellular transport gene products upregulated in mammal-infective trypanosomes, suggesting a role in controlling the copy number of surface proteins in trypanosomes. Here we investigate RME-8 function and its contribution to intracellular trafficking and stability of ISGs. RME-8 is a highly conserved protein and is broadly distributed across multiple endocytic compartments. By knockdown we find that RME-8 is essential and mediates delivery of endocytic probes to late endosomal compartments. Further, we find ISG accumulation within endosomes, but that RME-8 knockdown also increases ISG turnover; combined with previous data, this suggests that it is most probable that ISGs are recycled, and that RME-8 is required to support recycling.
authors.affiliation: Department of Pathology, University of Cambridge, Cambridge, United Kingdom.
authors.forename: V Lila
authors.initials: VL
authors.lastname: Koumandou
authors.forename: Cordula
authors.initials: C
authors.lastname: Boehm
authors.forename: Katy A
authors.initials: KA
authors.lastname: Horder
authors.forename: Mark C
authors.initials: MC
authors.lastname: Field
mesh_terms: D000818:Animals; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D014346:Trypanosoma brucei brucei / Q000166:cytology / Q000378:metabolism*
chemical_list: D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D015800:Protozoan Proteins; D034741:RNA, Small Interfering; C074692:ISG65 protein, Trypanosoma brucei; C074691:ISG75 protein, Trypanosoma brucei