UniProt release 15.6
Published July 28, 2009
Microsporidian polar tube: a molecular syringe in UniProtKB/Swiss-Prot
Microsporidia are ubiquitous, obligate intracellular spore-forming fungal parasites which infect a wide range of invertebrates and vertebrates. They are common pathogens responsible for opportunistic infections in immunodeficient humans, such as HIV-infected patients or patients being treated with immunosuppressive drugs. The most common microsporidian associated with AIDS is Enterocytozoon bieneusi which induces chronic diarrhea in HIV-infected individuals. However, since no animal model for E.bieneusi is available, most of the experimental studies on microsporidia have been carried out on Encephalitozoon cuniculi. This microsporidium, which commonly infects rodents, has also been reported to infect humans. Its complete proteome is available in UniProtKB.
Microsporidia are primitive organisms lacking fundamental organelles found in other eukaryotes, such as stacked Golgi apparatus, peroxisomes or mitochondria. However, they have a mitochondrial relic organelle called the mitosome which does not contain any DNA. As a result, to persist in the environment, they have to parasitize the cells of higher organisms.
How do they achieve their goal? The microsporidian intracellular developmental cycle leads to a terminal sporogenic phase producing small spores which are critical for their host-to-host transmission. The unicellular spores have a resistant wall protecting a mononucleate or binucleate sporoplasm (the infectious apparatus of the spore) and an extrusion apparatus consisting of a single polar tube with an anterior attachment complex. Once the target cell is recognized, the polar tube acts as a syringe: it pierces the host cell membrane and rapidly "injects" the sporoplasm into the host cell.
3 polar tube proteins have been identified: PTP1, PTP2, and PTP3. The major polar tube protein, PTP1, accounts for at least 70% of the mass of the polar tube. Before the polar tube can act, the spore has to recognize the host cell and stick to its surface. This role is played by EnP1, which is involved in the adhesion of spores to host cell surface glycoaminoglycans. Orthologous proteins have been identified: EnP1, PTP1 and PTP2 in Encephalitozoon intestinalis and PTP1 and PTP2 in Encephalitozoon hellem. These 2 microsporidian species infect man and cause intestinal infections keratoconjunctivitis, and respiratory infections.
All these infectious proteins are available in UniProtKB with the following accession numbers:
Cross-references to CTD
Cross-references have been added to the Comparative Toxicogenomics Database, which elucidates molecular mechanisms by which environmental chemicals affect human disease. Chemical-gene/protein interactions and chemical- and gene-disease relationships are curated from the published literature, and integrated with diverse data to facilitate environmental health research.
CTD is available at http://ctd.mdibl.org/.
The format of the explicit links in the flat file is:
|Resource identifier||NCBI geneID.|
Q9YIC3: DR CTD; 395652; -.
Cross-references to Ensembl
We have changed the format of the cross-reference lines to Ensembl. The DR Ensembl lines have been extended in order to include identifiers for transcripts and peptides.
|Resource identifier||Ensembl unique identifier for a transcript.|
|Optional information 1||Ensembl unique identifier for a protein.|
|Optional information 2||Ensembl unique identifier for a gene.|
|Optional information 3||Species name.|
O43462: DR Ensembl; ENST00000379484; ENSP00000368798; ENSG00000012174; Homo sapiens.
Changes concerning keywords