CapA, an Autotransporter Protein ofCampylobacter jejuni, Mediates Association with Human Epithelial Cells and Colonization of the Chicken Gut

Abstract

Two putative autotransporter proteins, CapA and CapB, were identified in silico from the genome sequence of Campylobacter jejuni NCTC11168. The genes encoding each protein contain homopolymeric tracts, suggestive of phase variation mediated by a slipped-strand mispairing mechanism; in each case the gene sequence contained frameshifts at these positions. The C-terminal two-thirds of the two genes, as well as a portion of the predicted signal peptides, were identical; the remaining N-terminal portions were gene specific. Both genes were cloned and expressed; recombinant polypeptides were purified and used to raise rabbit polyclonal monospecific antisera. Using immunoblotting, expression of the ca.116-kDa CapA protein was demonstrated for in vitro-grown cells of strain NCTC11168, for 4 out of 11 recent human fecal isolates, and for 2 out of 8 sequence-typed strains examined. Expression of CapB was not detected for any of the strains tested. Surface localization of CapA was demonstrated by subcellular fractionation and immunogold electron microscopy. Export of CapA was inhibited by globomycin, reinforcing the bioinformatic prediction that the protein is a lipoprotein. A capA insertion mutant had a significantly reduced capacity for association with and invasion of Caco-2 cells and failed to colonize and persist in chickens, indicating that CapA plays a role in host association and colonization by Campylobacter. In view of this demonstrated role, we propose that CapA stands for Campylobacter adhesion protein A.

CmeR Functions as a Pleiotropic Regulator and Is Required for Optimal Colonization of Campylobacter jejuni In Vivo

“…The identified genes encode membrane transporters (Cj0035c, Cj0366c, Cj0561c, and Cj1619), proteins involved in C 4 -dicarboxylate transport or utilization and metabolism (Cj0087, Cj0088, Cj0671, Cj0437, Cj0264c, and Cj0119), enzymes for capsular polysaccharide biosynthesis (Cj1424c, Cj1426c, Cj1427c, Cj1428c, Cj1429c, Cj1430c, and Cj1432c), periplasmic proteins or lipoproteins (Cj0089, Cj0091, Cj0092, Cj0628/Cj0629, and Cj0854c), a putative transcriptional factor (Cj1563c, a MerR homolog), a putative iron-binding protein (Cj0241c), a putative purine nucleoside triphosphate pyrophosphatase (Cj1374c), and hypothetical proteins (Cj0040 and Cj0583). Cj0628 and Cj0629 were originally annotated as two separate genes (32), but recent work showed that these two genes form a single ORF encoding an autotransporter protein (2). Differential expression of the identified genes in 11168W7 and 11168W7⌬cmeR.…”

Campylobacter jejuni response to human mucin MUC2: modulation of colonization and pathogenicity determinants

“…Adherence involves different types of lectin-like molecules attaching to their corresponding glycosylated receptors on the epithelial cells (Guerry et al, 2002). Major outermembrane proteins such as the putative rod-shapedetermining protein MreB, the putative periplasmic protein MreC and C. jejuni lipoprotein JlpA play important roles in bacterial adhesion (Ashgar et al, 2007;del Rocio Leon-Kempis et al, 2006;Jin et al, 2003;Kakuda & DiRita, 2006;Karlyshev et al, 2000;Konkel et al, 1997;Linton et al, 2000;Mamelli et al, 2006;McSweegan & Walker, 1986;Monteville & Konkel, 2002;Moser et al, 1997;Pei & Blaser, 1993). The genes encoding these three proteins were upregulated in response to MUC2.…”

Molecular mechanisms and biological role ofCampylobacter jejuniattachment to host cells

“…CapA mutant showed decreased adherence to human Caco-2 cells and also low colonisation efficiency in chicks [25]. In another study, mutation of capA also showed decreased adherence to chicken epithelial cells in vitro, although it did not result in a reduced ability of mutants to colonise chicks (47%) [17].…”

“…According to Sanger Institute annotation capB gene was assigned two pairs of ORFs, in the same way as capA. In contrast to CapA, playing a role in adhesion to cultured cells, no expression of CapB was detected [25]. Due to high level of amino acid sequence similarity between the two proteins, CapB might also be considered a putative adhesin.…”

“…CapA is an autotransporter lipoprotein reported to be involved in C. jejuni adherence to host cells [25]. CapA mutant showed decreased adherence to human Caco-2 cells and also low colonisation efficiency in chicks [25].…”