Trypanosoma brucei Metacaspase 4 Is a Pseudopeptidase and a Virulence Factor
| Autor: | Esther Castanys-Munoz, Laurence Tetley, Alana Black, William R. Proto, Jeremy C. Mottram, Luiz Juliano, Graham H. Coombs, Catherine X. Moss |
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| Přispěvatelé: | Univ Glasgow, Universidade Federal de São Paulo (UNIFESP), Univ Strathclyde |
| Rok vydání: | 2011 |
| Předmět: |
Enzyme Mutation
Pseudopeptidase Virulence Factors Lipoylation Trypanosoma brucei brucei Cysteine Peptidase Protozoan Proteins Virulence Trypanosoma brucei Microbiology Biochemistry Virulence factor Mice 03 medical and health sciences Palmitoylation Virulence Factor parasitic diseases Animals Secretion Molecular Biology 030304 developmental biology Myristoylation 0303 health sciences biology 030302 biochemistry & molecular biology Cell Biology biology.organism_classification Caspase Cysteine protease Metacaspase 3. Good health Cell biology Parasite Flagella Caspases Cysteine Protease Caspase Family |
| Zdroj: | The Journal of Biological Chemistry Repositório Institucional da UNIFESP Universidade Federal de São Paulo (UNIFESP) instacron:UNIFESP |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.m111.292334 |
| Popis: | Background: Metacaspases are multifunctional cysteine peptidases. Results: Trypanosoma brucei metacaspase 4 is a catalytically inactive metacaspase homologue required for parasite virulence, which interacts with an active parasite metacaspase during release from the cell. Conclusion: Metacaspase 4 is a pseudopeptidase virulence factor. Significance: Extracellular release and proteolytic processing provide novel insights into metacaspase function. 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 (Δmca4) was possible. Δmca4 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. |
| Databáze: | OpenAIRE |
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