G21/G translocation chromosome in a boy with mongolism

The genome of the African trypanosome Trypanosoma brucei (Tb) contains at least three gene families (TbMSP-A, -B, and -C) encoding homologues of the abundant major surface protease (MSP, previously called GP63), which is found in all Leishmania species. TbMSP-B mRNA occurs in both procyclic and bloodstream trypanosomes, whereas TbMSP-A and -C mRNAs are detected only in bloodstream organisms. RNA interference (RNAi)-mediated gene silencing was used to investigate the function of TbMSP-B protein. RNAi directed against TbMSP-B but not TbMSP-A ablated the steady state TbMSP-B mRNA levels in both procyclic and bloodstream cells but had no effect on the kinetics of cultured trypanosome growth in either stage. Procyclic trypanosomes have been shown previously to have an uncharacterized cell surface metalloprotease activity that can release ectopically expressed surface proteins. To determine whether TbMSP-B is responsible for this release, transgenic variant surface glycoprotein 117 (VSG117) was expressed constitutively in T. brucei procyclic TbMSP-RNAi cell lines, and the amount of surface VSG117 was determined using a surface biotinylation assay. Ablation of TbMSP-B but not TbMSP-A mRNA resulted in a marked decrease in VSG release with a concomitant increase in steady state cell-associated VSG117, indicating that TbMSP-B mediates the surface protease activity of procyclic trypanosomes. This finding is consistent with previous pharmacological studies showing that peptidomimetic collagenase inhibitors block release of transgenic VSG from procyclic trypanosomes and are toxic for bloodstream but not procyclic organisms.

Section: )supporting

confidence: 85%

mentioning

confidence: 99%

Expression and Function of the Trypanosoma brucei Major Surface Protease (GP63) Genes

LaCount

Gruszynski²,

Grandgenett

et al. 2003

“…Leishmania gp63 is involved in the binding of the parasite to and intracellular survival within host macrophages (5,(12)(13)(14). Upon inoculation into the mammalian host by their sandfly vector, infective flagellated promastigotes are exposed to a variety of antimicrobial factors, some of which may be inactivated by gp63.…”

mentioning

confidence: 99%

Extracellular Release of the Glycosylphosphatidylinositol (GPI)-linked Leishmania Surface Metalloprotease, gp63, Is Independent of GPI Phospholipolysis

McGwire¹,

O'Connell²,

Chang³

et al. 2002

107

The major zinc metalloprotease of Leishmania (gp63), an important determinant of parasite virulence, is attached to the parasite surface via a glycosylphosphatidylinositol anchor. Here we report the spontaneous release of proteolytically active gp63 from a number of Leishmania isolates, causing cutaneous and visceral disease. To investigate the mechanism(s) of gp63 release, we transfected a gp63-deficient variant of Leishmania amazonensis with constructs expressing gp63 and various mutants thereof. Surprisingly, approximately half of wild type gp63 was found in the culture supernatant 12 h post-synthesis. Biochemical analysis of the extracellular gp63 revealed two forms of the protein, one that is released from the cell surface, and another, that apparently is directly secreted. Release of cell surface gp63 was significantly reduced when the proteolytic activity of the protein was inactivated by site-specific mutagenesis or inhibited by zinc chelation, suggesting that release involves autoproteolysis. The extracellular gp63 does not contain a glycosylphosphatidylinositol moiety or ethanolamine, indicating that phospholipolysis is not involved in the release process. Release of gp63 is also independent of glycosylation. The finding of proteolytically active, extracellular gp63 produced by multiple Leishmania isolates suggests a potential role of the extracellular enzyme in substrate degradation relevant to their survival in both the mammalian host and the insect vector.

“…The mechanism of this increase is not known. These data further suggest (18). ␣-Tubulin was used as a loading control.…”

Section: Knockdown Of Par1 In Macrophages Prevented Leishmania-inducementioning

confidence: 65%

Mechanism of Down-regulation of RNA Polymerase III-transcribed Non-coding RNA Genes in Macrophages by Leishmania

Rana

Misra

Mittal

et al. 2011

The parasitic protozoan Leishmania invades mammalian macrophages to establish infection. We reported previously that Leishmania manipulates the expression of several noncoding RNA genes (e.g. Alu RNA, B1 RNA, and signal recogni- into the micromolar range, thereby activating the Ca 2؉ -dependent protease -calpain. -Calpain then degraded TFIIIC110 to inhibit the expression of the selected ncRNA genes. Avirulent stocks of Leishmania not expressing surface gp63 failed to down-regulate ncRNAs in the exposed macrophages. Inhibition of PAR1 or calpain 1 in macrophages made them resistant to Leishmania infection. These data suggest that macrophage PAR1 and calpain 1 are potential drug targets against leishmaniasis.