Paracoccidioides brasiliensis expresses both glycosylphosphatidylinositol-anchored proteins and a potent phospholipase C.
This study reports, for the first time, the detection of glycosylphosphatidylinositol (GPI) membrane anchors in proteins of a pathogenic fungus, Paracoccidioides brasiliensis. Taking into account that fungal antigens are found in the sera of paracoccidioidiomycosis patients and that cleavage of this glycolipid by phospholipases is a means of selective protein release, the presence of an enzyme with this property has also been investigated. Using a methodological approach in which the proteins were immobilized on nitrocellulose, treated with phospholipase C of Trypanosoma brucei and then probed with antibodies which recognize the 1,2-cyclic-phosphate inositol moiety formed as a reaction product in proteins bearing the glycolipid anchor, it was possible to detect a major glycoprotein in the 80- to 90-kDa range, as well as two other minor species of 66 and 43 kDa. All of them bind to Concanavalin-A and are also substrates of a very potent fungal phospholipase C which is inhibited by p-chloromercuri-phenylsulfonic acid and is insensitive to EDTA. The integrity of glycosylphosphatidylinositol anchors in proteins of P. brasiliensis is impaired by 0.1 M NaOH, a finding indicative of a diacyl glycerolipid moiety which is quite surprising since it is, with the exception of African trypanosomes surface proteins and Torpedo acetylcholinesterase, an uncommon feature among GPIs in general. The present findings may have implications in the pathology of paracoccidiodomycosis.
Heise
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Department of Microbiology, Immunology and Parasitology, Escola Paulista de Medicina, São Paulo, Brazil.
Travassos
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LR
de Almeida
M L
ML
D004075:Diglycerides / Q000737:chemistry; D005656:Fungal Proteins / Q000737:chemistry; D006023:Glycoproteins / Q000737:chemistry; D017261:Glycosylphosphatidylinositols / Q000302:isolation & purification*; D010228:Paracoccidioides / Q000737:chemistry* / Q000201:enzymology; D010738:Type C Phospholipases / Q000302:isolation & purification*
D004075:Diglycerides; D005656:Fungal Proteins; D006023:Glycoproteins; D017261:Glycosylphosphatidylinositols; D010738:Type C Phospholipases