Trypanosoma brucei metacaspase 4 is a pseudopeptidase and a virulence factor

William R Proto, Esther Castanys-Munoz, Alana Black, Laurence Tetley, Catherine X Moss, Luiz Juliano, Graham H Coombs, Jeremy C Mottram

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

Metacaspases are caspase family cysteine peptidases found in plants, fungi and protozoa, but not mammals. Trypanosoma brucei is unusual in having five metacaspases (MCA1-MCA5) of which MCA1 and MCA4 have active site substitutions, making them possible non-enzymatic homologues. Here we demonstrate that recombinant MCA4 lacks detectable peptidase activity, despite maintaining a functional peptidase structure. MCA4 is expressed primarily in the bloodstream form of the parasite and associates with the flagellar membrane via dual myristoylation/palmitoylation. Loss of function phenotyping revealed critical roles for MCA4; rapid depletion by RNAi caused lethal disruption to the parasite's cell cycle, yet the generation of MCA4 null mutant parasites (mca4) was possible. mca4 had normal growth in axenic culture, but markedly reduced virulence in mice. Further analysis revealed that MCA4 is released from the parasite and is specifically processed by MCA3, the only metacaspase that is both palmitoylated and enzymatically active. Accordingly we have identified that the multiple metacaspases in T. brucei form a membrane-associated proteolytic cascade to generate a pseudopeptidase virulence factor.
Original languageEnglish
JournalJournal of Biological Chemistry
Early online date23 Sep 2011
DOIs
Publication statusPublished - 2011

Keywords

  • trypanosoma brucei
  • metacaspase 4
  • pseudopeptidase
  • virulence
  • cysteine peptidase
  • caspase family
  • parasite

Fingerprint Dive into the research topics of 'Trypanosoma brucei metacaspase 4 is a pseudopeptidase and a virulence factor'. Together they form a unique fingerprint.

Cite this