The PilC adhesin of the Neisseria type IV pilus – binding specificities and new insights into the nature of the host cell receptor

Abstract

SummaryType IV pili of Neisseria gonorrhoeae and Neisseria meningitidis mediate the first contact to human mucosal epithelial cells, an interaction which is also critical for the interaction with vascular endothelial cells. The PilC proteins have been characterized as the principal pilus-associated adhesin. Here we show that PilC2 exhibits a defined cell and tissue tropism, as it binds to human epithelial and endothelial cell lines, but not to human T cells or fibroblasts. Piliated gonococci and PilC2 exhibit similar patterns of binding to human epithelial and endothelial cells, supporting the function of PilC as the key pilus adhesin. Although CD46 has previously been suggested to be a pilus receptor, several observations indicate that neisserial type IV pili and the pilus adhesin PilC2 interact with epithelial cells in a CD46 independent manner. Biochemical approaches were used to characterize the nature of host cell factors mediating binding of piliated gonococci and PilC2 protein. Our data indicate that the putative host cell receptor for gonococcal pili and the PilC2 pilus adhesin is a surface protein. Glycostructures were found to not be involved in binding. Moreover, we observed the uptake of purified PilC2 protein together with its receptor via receptor-mediated endocytosis and subsequent receptor re-exposure on the cell surface. Our data support the existence of a specific pilus receptor and provide intriguing information on the nature of the receptor.

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).…”

Concepts and Mechanisms: Crossing Host Barriers

“…Critical bacterial components have been discovered by screening random mutant libraries (Badger et al 2000;Doran et al 2005), analyzing bacterial transcription profiles during infection (Dietrich et al 2003;Teng et al 2005), and using bioinformatic approaches for whole genome comparisons (Uchiyama et al 2009;van Sorge et al 2009;Tazi et al 2010). Bacterial pili, or fimbriae, have emerged as a common class of adhesins used by many meningeal pathogens, such as E. coli K1 (Teng et al 2005), GBS (Maisey et al 2007;van Sorge et al 2009), and N. meningitides (Kirchner and Meyer 2005) to initiate attachment to brain endothelium. Other well-characterized or recently described bac- terial components such as CbpA and NanA, a surface anchored sialidase, in S. pneumonia (Ring et al 1998;Uchiyama et al 2009), lipoteichoic acid and HvgA in GBS (Doran et al 2005;Tazi et al 2010), type1 fimbriae, OmpA and ibeA/B in E. coli K1 (Prasadarao et al 1999a,b;Teng et al 2005), promote brain endothelial cell attachment and subsequent cellular penetration.…”

Humanized Mouse Model to Study Bacterial Infections Targeting the Microvasculature

“…Many aspects of infection have been studied in vitro including bacterial adhesion, host cell response as well as cytokine response [6][7][8][9] . Type IV pili (Tfp) have been implicated as the major adhesion organelle for N. meningitidis on both epithelial and endothelial cells 10 …”