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A Cryptosporidium parvum genomic region encoding hemolytic activity
M I Steele1, T L Kuhls, K Nida
1Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City 73126, USA.
Abstract:
Successful parasitization by Cryptosporidium parvum requires multiple disruptions in both host and protozoan cell membranes as cryptosporidial sporozoites invade intestinal epithelial cells and subsequently develop into asexual and sexual life stages. To identify cryptosporidial proteins which may play a role in these membrane alterations, hemolytic activity was used as a marker to screen a C. parvum genomic expression library. A stable hemolytic clone (H4) containing a 5.5-kb cryptosporidial genomic fragment was identified. The hemolytic activity encoded on H4 was mapped to a 1-kb region that contained a complete 690-bp open reading frame (hemA) ending in a common stop codon. A 21-kDa plasmid-encoded recombinant protein was expressed in maxicells containing H4. Subclones of H4 which contained only a portion of hemA did not induce hemolysis on blood agar or promote expression of the recombinant protein in maxicells. Reverse transcriptase-mediated PCR analysis of total RNA isolated from excysted sporozoites and the intestines of infected adult mice with severe combined immunodeficiency demonstrated that hemA is actively transcribed during the cryptosporidial life cycle.
Insights
Researchers identified a Cryptosporidium parvum protein, hemA, essential for host cell invasion. This protein
Area of Science:
- Parasitology
- Molecular Biology
- Cell Biology
Background:
- Cryptosporidium parvum infection requires host and parasite cell membrane disruption for invasion and development.
- Identifying parasite proteins involved in membrane alteration is crucial for understanding pathogenesis.
Purpose of the Study:
- To screen for Cryptosporidium parvum proteins involved in host cell membrane disruption.
- To identify and characterize a specific protein responsible for hemolytic activity.
Main Methods:
- Screening of a C. parvum genomic expression library using hemolytic activity as a marker.
- Mapping of hemolytic activity to a specific gene (hemA) and characterization of its encoded protein.
- Analysis of hemA transcription in different life cycle stages and infected hosts.
Main Results:
- A hemolytic clone (H4) containing a 5.5-kb genomic fragment was identified.
- Hemolytic activity was mapped to a 690-bp open reading frame, hemA, encoding a 21-kDa protein.
- hemA was found to be actively transcribed in excysted sporozoites and in infected mouse intestines.
Conclusions:
- The hemA gene encodes a protein crucial for Cryptosporidium parvum's hemolytic activity.
- This protein likely plays a significant role in the membrane disruptions necessary for parasite invasion and development.
- hemA represents a potential target for therapeutic interventions against cryptosporidiosis.
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