A Function for a Specific Zinc Metalloprotease of African Trypanosomes

Autor: Keiko Otsu, Paul M. Grandgenett, Helen R Wilson, John E. Donelson, Mary E. Wilson
Jazyk: angličtina
Rok vydání: 2007
Předmět:
lcsh:Immunologic diseases. Allergy
Proteases
Eukaryotes
medicine.medical_treatment
Cellular differentiation
Immunology
Trypanosoma brucei brucei
Gene Dosage
Protozoan Proteins
Antigens
Protozoan
Trypanosoma brucei
Glycosylphosphatidylinositol Diacylglycerol-Lyase
Biochemistry
Microbiology
law.invention
Cell Line
03 medical and health sciences
law
Virology
parasitic diseases
Genetics
medicine
Animals
Gene
lcsh:QH301-705.5
Molecular Biology
030304 developmental biology
0303 health sciences
Life Cycle Stages
Protease
biology
Phosphatidylinositol Diacylglycerol-Lyase
030302 biochemistry & molecular biology
Metalloendopeptidases
biology.organism_classification
Leishmania
Molecular biology
3. Good health
Infectious Diseases
lcsh:Biology (General)
Trypanosoma
Recombinant DNA
Metalloproteases
Parasitology
lcsh:RC581-607
Gene Deletion
Variant Surface Glycoproteins
Trypanosoma
Research Article
Zdroj: PLoS Pathogens
PLoS Pathogens, Vol 3, Iss 10, Pp 1432-1445 (2007)
ISSN: 1553-7374
1553-7366
Popis: The Trypanosoma brucei genome encodes three groups of zinc metalloproteases, each of which contains ∼30% amino acid identity with the major surface protease (MSP, also called GP63) of Leishmania. One of these proteases, TbMSP-B, is encoded by four nearly identical, tandem genes transcribed in both bloodstream and procyclic trypanosomes. Earlier work showed that RNA interference against TbMSP-B prevents release of a recombinant variant surface glycoprotein (VSG) from procyclic trypanosomes. Here, we used gene deletions to show that TbMSP-B and a phospholipase C (GPI-PLC) act in concert to remove native VSG during differentiation of bloodstream trypanosomes to procyclic form. When the four tandem TbMSP-B genes were deleted from both chromosomal alleles, bloodstream B −/− trypanosomes could still differentiate to procyclic form, but VSG was removed more slowly and in a non-truncated form compared to differentiation of wild-type organisms. Similarly, when both alleles of the single-copy GPI-PLC gene were deleted, bloodstream PLC −/− cells could still differentiate. However, when all the genes for both TbMSP-B and GPI-PLC were deleted from the diploid genome, the bloodstream B −/− PLC −/− trypanosomes did not proliferate in the differentiation medium, and 60% of the VSG remained on the cell surface. Inhibitors of cysteine proteases did not affect this result. These findings demonstrate that removal of 60% of the VSG during differentiation from bloodstream to procyclic form is due to the synergistic activities of GPI-PLC and TbMSP-B.
Author Summary African trypanosomes cause sleeping sickness, a fatal disease of humans and livestock in Africa. During their life cycle, these protozoan parasites cycle between the bloodstream of mammals and tsetse flies. Their two main developmental stages are the bloodstream form and the procyclic form in the tsetse fly. Bloodstream trypanosomes thwart their host's immune response by periodically switching their major surface protein, the variant surface glycoprotein (VSG). When bloodstream trypanosomes are ingested by a tsetse fly, they must quickly shed the VSG and replace it with an unrelated invariant protein more suited to their survival as procyclic organisms in the fly midgut. Here, we examine the mechanisms used by trypanosomes to remove the VSG during their differentiation from bloodstream to procyclic form in culture. We deleted the genes for one of the trypanosome's protease enzymes from the trypanosome genome and found that bloodstream trypanosomes could still differentiate to the procyclic form, but VSG removal was diminished. Deleting the genes for a phospholipase enzyme had a similar effect—they could still differentiate but VSG removal was impaired. When the genes for both the protease and the phospholipase were deleted, bloodstream trypanosomes could not differentiate to the procyclic form, they retained about 60% of the VSG on their surface, and they died in the differentiation medium. These results highlight the synergistic roles of these two enzymes in the differentiation process.
Databáze: OpenAIRE
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