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Fusobacterium nucleatum is a Gram-negative anaerobe associated with various human infections, including periodontal diseases and preterm birth. A novel FadA adhesin was recently identified for host-cell binding. It consists of 129 amino acid residues, with an 18-amino acid signal peptide. Expression of FadA in Escherichia coli enhanced bacterial binding to host epithelial and endothelial cells. In both E. coli and F. nucleatum, FadA exists in two forms, the intact pre-FadA and the secreted mature FadA (mFadA), with pre-FadA anchored in the inner membrane and mFadA secreted outside the bacteria. Pre-FadA and mFadA formed high Mr complexes. When each form was purified to a single species, mFadA was soluble at neutral pH, whereas pre-FadA was insoluble. Pre-FadA became soluble when mixed with mFadA or under acidic pH. When fluorescence-labeled mFadA alone was added to the epithelial cells, no binding was detected. However, when mixed with nonlabeled pre-FadA, binding and invasion of mFadA into epithelial cells was observed. FadA is a unique bacterial adhesin/invasin in that it utilizes its own two forms for both structural and functional purposes. The pre-FadA-mFadA complex is probably anchored in the inner membrane and protrudes through the outer membrane. Internalization of the pre-FadA-mFadA ensures invasion of the bacteria into the host cells. [ABSTRACT FROM AUTHOR]

Chronic wasting disease (CWD), a transmissible prion disease that affects elk and deer, poses new challenges to animal and human health. Although the transmission of CWD to humans has not been proven, it remains a possibility. If this were to occur, it is important to know whether the ‘acquired’ human prion disease would show a phenotype including the scrapie prion protein (PrPSc) features that differ from those associated with human sporadic prion disease. In this study, we have compared the pathological profiles and PrPSc characteristics in brains of CWD-affected elk and deer with those in subjects with sporadic Creutzfeldt-Jakob disease (CJD), as well as CJD-affected subjects who might have been exposed to CWD, using histopathology, immunohistochemistry, immunoblotting, conformation stability assay, and N-terminal protein sequencing. Spongiform changes and intense PrPSc staining were present in several brain regions of CWD-affected animals. Immunoblotting revealed three proteinase K (PK)-resistant bands in CWD, representing different glycoforms of PrPSc. The unglycosylated PK-resistant PrPSc of CWD migrated at 21 kDa with an electrophoretic mobility similar to that of type 1 human PrPSc present in sporadic CJD affecting subjects homozygous for methionine at codon 129 (sCJDMM1). N-terminal sequencing showed that the PK cleavage site of PrPSc in CWD occurred at residues 82 and 78, similar to that of PrPSc in sCJDMM1. Conformation stability assay also showed no significant difference between elk CWD PrPSc and the PrPSc species associated with sCJDMM1. However, there was a major difference in glycoform ratio of PrPSc between CWD and sCJDMM1 affecting both subjects potentially exposed to CWD and non-exposed subjects. Moreover, PrPSc of CWD exhibited a distinct constellation of glycoforms distinguishable from that of sCJDMM1 in two-dimensional immunoblots. These findings underline the importance of detailed PrPSc characterization in trying to detect novel forms of acquired prion disease. [ABSTRACT FROM AUTHOR]

The central event in the pathogenesis of prion diseases, a group of fatal, transmissible neurodegenerative disorders including Creutzfeldt-Jakob disease (CJD) in humans, is the conversion of the normal or cellular prion protein (PrP[sup C]) into the abnormal or scrapie isoform (PrP[sup Sc]). The basis of the PrP[sup C] to PrP[sup Sc] conversion is thought to involve the diminution of α-helical domains accompanied by the increase of β structures within the PrP molecule. Consequently, treatment of PrP[sup Sc] with proteinase K (PK) generates a large PK-resistant C-terminal core fragment termed PrP27-30 that in human prion diseases has a gel mobility of ∼19-21 kDa for the unglycosylated form, and a ragged N terminus between residues 78 and 103. PrP27-30 is considered the pathogenic and infectious core of PrP[sup Sc]. Here we report the identification of two novel PK-resistant, but much smaller C-terminal fragments of PrP (PrP-CTF 12/13) in brains of subjects with sporadic CJD. PrP-CTF 12/13, like PrP27-30, derive from both glycosylated as well as unglycosylated forms. The unglycosylated PrPCTF 12/13 migrate at 12 and 13 kDa and have the N terminus at residues 162/167 and 154/156, respectively. Therefore, PrP-CTF12/13 are 64-76 amino acids N-terminally shorter than PrP27-30 and are about half of the size of PrP27-30. PrP-CTF12/13 are likely to originate from a subpopulation of PrP[sup Sc] distinct from that which generates PrP27-30. The finding of PrP-CTF12/13 in CJD brains widens the heterogeneity of the PK-resistant PrP fragments associated with prion diseases and may provide useful insights toward the understanding of the PrP[sup Sc] structure and its formation. [ABSTRACT FROM AUTHOR]