The single ENTH-domain protein of trypanosomes; endocytic functions and evolutionary relationship with epsin

Traffic. 2009 Jul;10(7):894-911. doi: 10.1111/j.1600-0854.2009.00910.x. Epub 2009 Mar 17.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Vesicular Transport / classification
  • Adaptor Proteins, Vesicular Transport / genetics*
  • Adaptor Proteins, Vesicular Transport / metabolism
  • Amino Acid Sequence
  • Animals
  • Biological Evolution*
  • Clathrin / metabolism
  • Concanavalin A / metabolism
  • Endocytosis / physiology*
  • Endosomes / metabolism
  • Endosomes / ultrastructure
  • Genomics
  • Humans
  • Immunohistochemistry
  • Microscopy, Immunoelectron
  • Molecular Sequence Data
  • Phylogeny
  • Protein Structure, Tertiary
  • Protozoan Proteins / classification
  • Protozoan Proteins / genetics*
  • Protozoan Proteins / metabolism
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Sequence Alignment
  • Transferrin / metabolism
  • Trypanosoma brucei brucei / cytology
  • Trypanosoma brucei brucei / genetics*
  • Trypanosoma brucei brucei / metabolism


  • Adaptor Proteins, Vesicular Transport
  • Clathrin
  • Protozoan Proteins
  • Recombinant Fusion Proteins
  • Transferrin
  • epsin
  • Concanavalin A