The single ENTH-domain protein of trypanosomes; endocytic functions and evolutionary relationship with epsin.
Epsin N-terminal homology (ENTH) domains occur in proteins of either the epsin or epsin-related (epsinR) form. They principally function in clathrin-mediated trafficking and membrane deformation. Both epsin and epsinR possess clathrin-binding motifs, but only epsin incorporates a ubiquitin-interaction motif (UIM). To better understand the origins of ENTH-domain proteins and their functions, we performed detailed comparative genomics and phylogenetics on the epsin family. The epsin ENTH-UIM configuration is an architecture restricted to yeast and animals. Further, we undertook functional analysis in Trypanosoma brucei (T. brucei), a divergent organism possessing a single ENTH-domain protein (TbEpsinR). TbEpsinR has a cellular location similar to both epsin and epsinR at plasma membrane clathrin budding sites and endosomal compartments, and associates with clathrin, as demonstrated by coimmunoprecipitation. Knockdown of TbEpsinR leads to a significant decrease in the intracellular pools of multiple surface antigens, without affecting bulk membrane internalization. Therefore, despite lacking the UIM, TbEpsinR maintains a similar role to metazoan epsin in endocytosis and participates as a clathrin-associated adaptor. We suggest that recruitment of a UIM to the ENTH-domain proteins was not essential for participation in endocytosis of ubiquitylated molecules, and is presumably a specific innovation restricted to higher eukaryotes.
Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QP, UK.
Carme
C
Gabernet-Castello
Joel B
JB
Dacks
Mark C
MC
Field
D033942:Adaptor Proteins, Vesicular Transport / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D002966:Clathrin / Q000378:metabolism; D003208:Concanavalin A / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism / Q000648:ultrastructure; D023281:Genomics; D006801:Humans; D007150:Immunohistochemistry; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D014168:Transferrin / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000166:cytology / Q000235:genetics* / Q000378:metabolism
D033942:Adaptor Proteins, Vesicular Transport; D002966:Clathrin; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D014168:Transferrin; C114154:epsin; D003208:Concanavalin A