Neisseria gonorrhoeae PilV, a type IV pilus-associated protein essential to human epithelial cell adherence

Abstract

Type IV pili (Tfp) of Neisseria gonorrhoeae, the Gram-negative etiologic agent of gonorrhea, facilitate colonization of the human host. Tfp are assumed to play a key role in the initial adherence to human epithelial cells by virtue of the associated adhesin protein PilC. To examine the structural and functional basis for adherence in more detail, we identified potential genes encoding polypeptides sharing structural similarities to PilE (the Tfp subunit) within the N. gonorrhoeae genome sequence database. We show here that a fiber subunit-like protein, termed PilV, is essential to organelle-associated adherence but dispensable for Tfp biogenesis and other pilus-related phenotypes, including autoagglutination, competence for natural transformation, and twitching motility. The adherence defect in pilV mutants cannot be attributed to reduced levels of piliation, defects in fiber anchoring to the bacterial cell surface, or to unstable pilus expression related to organelle retraction. PilV is expressed at low levels relative to PilE and copurifies with Tfp fibers in a PilC-dependent fashion. Purified Tfp from pilV mutants contain PilC adhesin at reduced levels. Taken together, these data support a model in which PilV functions in adherence by promoting the functional display of PilC in the context of the pilus fiber.

Type IV Pilin Proteins: Versatile Molecular Modules

“…N. meningitidis can bind to and traverse both epithelial and endothelial cell layers, in a T4P-dependent manner (376), and it recruits a variety of host proteins to do its bidding. The bacteria bind to cells and form microcolonies in a manner that requires retractable T4P and the noncore minor pilins PilV and PilX, as well as the pilus-associated PilC1 and PilC2 proteins (63,111,225,283,287,288,362,415).…”

“…However, Neisseria pili were also recently shown by a number of investigators to contain minor pilins, whose low abundance relative to that of the major subunit does not necessarily reflect their important contributions to pilus function and pathogenicity (63,154,175,248,283,415,416). To determine whether the level of protein diversity among minor pilins was lower than that among major pilins, and thus whether they would potentially make better vaccine candidates, Cehovin et al (88) examined the prevalence and sequence similarity among specific minor pilin genes in a large set of pathogenic isolates of N. meningitidis.…”

Intestinal adherence associated with type IV pili of enterohemorrhagic Escherichia coli O157:H7

“…TFP are important virulence factors in many pathogenic Gram-negative bacteria, as they mediate adherence to eukaryotic cells and host colonization and are associated with other phenomena related to pathogenicity, including bacterial aggregation, biofilm formation, DNA binding and uptake, and twitching motility (36)(37)(38)(39)(40)(41). So far, TFP have not been observed in AE-producing EHEC O157:H7.…”

Specific DNA recognition mediated by a type IV pilin

“…(i) ComP is one of three minor (low abundance) pilins in pathogenic Neisseria species (with PilV and PilX) that modulate Tfp-mediated properties without affecting Tfp biogenesis (19)(20)(21)(22). ComP has a prominent role in competence (20,21) at the level of DNA uptake (23).…”