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Histoplasma acquisition of calcium and expression of CBP1 during intracellular parasitism
Author(s) -
West Batanghari Janet,
Deepe George S.,
Di Cera Enrico,
Goldman William E.
Publication year - 1998
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1998.00697.x
Subject(s) - biology , microbiology and biotechnology , histoplasma , calcium , yeast , calcium in biology , intracellular , biochemistry , histoplasma capsulatum , immunology , histoplasmosis , organic chemistry , chemistry
A highly adapted parasite of macrophages, the yeast phase of Histoplasma capsulatum , survives and proliferates within phagolysosomes, while the mycelial phase exists only as a saprophyte in the soil. We have shown previously that these two phases of Histoplasma differ in their calcium requirements for growth and in the production of a released calcium‐binding protein (CBP). Cloning and sequencing the CBP1 gene revealed two introns, a putative signal peptide and potential calcium‐binding sites. We also evaluated CBP1 expression by reverse transcription–polymerase chain reaction (RT–PCR) of yeasts grown in broth culture and within two host cell types, a macrophage‐like cell line and respiratory epithelial cells. H . capsulatum yeasts expressed CBP1 in all of these settings. Splenocytes from mice immunized with H . capsulatum yeasts responded to purified CBP in proliferation assays, providing evidence for the production of CBP during the infection of mammalian hosts. In addition, after H . capsulatum yeasts were subjected to a calcium‐free shock, exogenously added CBP allowed yeasts to incorporate more calcium than yeasts incubated without added CBP. These results suggest that CBP may function to provide yeasts with calcium when they are in a low‐calcium environment, such as the phagolysosomal compartment within macrophages.