Histoplasma capsulatum encodes a dipeptidyl peptidase active against the mammalian immunoregulatory peptide, substance P.
The pathogenic fungus Histoplasma capsulatum secretes dipeptidyl peptidase (Dpp) IV enzyme activity and has two putative DPPIV homologs (HcDPPIVA and HcDPPIVB). We previously showed that HcDPPIVB is the gene responsible for the majority of secreted DppIV activity in H. capsulatum culture supernatant, while we could not detect any functional contribution from HcDPPIVA. In order to determine whether HcDPPIVA encodes a functional DppIV enzyme, we expressed HcDPPIVA in Pichia pastoris and purified the recombinant protein. The recombinant enzyme cleaved synthetic DppIV substrates and had similar biochemical properties to other described DppIV enzymes, with temperature and pH optima of 42 degrees C and 8, respectively. Recombinant HcDppIVA cleaved the host immunoregulatory peptide substance P, indicating the enzyme has the potential to affect the immune response during infection. Expression of HcDPPIVA under heterologous regulatory sequences in H. capsulatum resulted in increased secreted DppIV activity, indicating that the encoded protein can be expressed and secreted by its native organism. However, HcDPPIVA was not required for virulence in a murine model of histoplasmosis. This work reports a fungal enzyme that can function to cleave the immunomodulatory host peptide substance P.
Cooper
Kendal G
KG
Department of Medical Microbiology and Immunology, University of Wisconsin, Madison, Wisconsin, United States of America.
Zarnowski
Robert
R
Woods
Jon P
JP
D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D003001:Cloning, Molecular; D017931:DNA Primers; D018819:Dipeptidyl Peptidase 4 / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D004195:Disease Models, Animal; D004795:Enzyme Stability; D005260:Female; D006658:Histoplasma / Q000201:enzymology* / Q000472:pathogenicity; D006660:Histoplasmosis / Q000382:microbiology; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D051379:Mice; D008810:Mice, Inbred C57BL; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D013373:Substance P / Q000378:metabolism*; D013696:Temperature; D014774:Virulence
D017931:DNA Primers; D011994:Recombinant Proteins; D013373:Substance P; D018819:Dipeptidyl Peptidase 4