Gonococcal Phospholipase D Modulates the Expression and Function of Complement Receptor 3 in Primary Cervical Epithelial Cells

Abstract

CR3-mediated endocytosis is a primary mechanism by which Neisseria gonorrhoeae elicits membrane ruffling and cellular invasion of the cervical epithelia. Our data indicate that, upon infection of cervical epithelia, N. gonorrhoeae specifically releases proteins, including a phospholipase D (PLD) homolog, which facilitate membrane ruffling. To elucidate the function of gonococcal PLD in infection of the cervical epithelia, we constructed an N. gonorrhoeae PLD mutant. By comparative association and/or invasion assays, we demonstrated that PLD mutant gonococci are impaired in their ability to adhere to and to invade primary cervical cells. This defect can be rescued by the addition of supernatants obtained from wild-type-infected cell monolayers but not by exogenously added Streptomyces PLD. The decreased level of total cell association (i.e., adherence and invasion) observed for mutant gonococci is, in part, attributed to the inability of these bacteria to recruit CR3 to the cervical cell surface with extended infection. Using electron microscopy, we demonstrate that gonococcal PLD may be necessary to potentiate membrane ruffling and clustering of gonococci on the cervical cell surface. These data may be indicative of the inability of PLD mutant gonococci to recruit CR3 to the cervical cell surface. Alternatively, in the absence of gonococcal PLD, signal transduction events required for CR3 clustering may not be activated. Collectively, our data indicate that PLD augments CR3-mediated gonococcus invasion of and survival within cervical epithelia.Neisseria gonorrhoeae is a strict human pathogen, which causes the sexually transmitted disease gonorrhea. This organism possesses multiple mechanisms by which it is able to colonize its sole human host and which are dependent upon the particular microenvironment of the infection site. In this respect, the gonococcus senses its particular microenvironment and adjusts its mode of pathogenicity accordingly. Several gonococcal constituents are implicated to play a role in its pathogenicity, including lipooligosaccharide (LOS), porin, pilus, and the opacity-associated outer membrane proteins. Invasion of male urethral epithelial cells is mediated by LOS, the terminal galactose of which serves as a ligand for the asialoglycoprotein receptor (ASGP-R) (15). An intimate association between the gonococcal and host cell membranes precedes clathrin-dependent endocytosis (15). In contrast, complement (CЈ) receptor type 3 (CR3)-mediated endocytosis is a primary mechanism by which N. gonorrhoeae invades primary human cervical epithelial cells (8). This process is dependent upon the cooperative binding of (gonococcus-bound, host-derived) iC3b, gonococcal porin, and gonococcal pilus to the I domain of CR3 (7, 9). Engagement of CR3 results in membrane ruffling (8) and internalization of gonococci in macropinosomes (10).Our studies show that ruffling induced by gonococci during cervical cell infection is delayed from the onset of infection by 60 to 90 min (10). The onset of ruffling can be ...

Construction and Characterization of a Derivative of Neisseria gonorrhoeae Strain MS11 Devoid of All opa Genes

“…Gonococci appear to enter HEC-1-B cells as individual bacteria and then replicate in the cells to produce intracellular inclusions of bacteria (39). Although gonococcal microcolonies are able to interact with and induce membrane ruffling on epithelial cells (14), the bulk of the vacuoles containing intracellular gonococci rarely contain more than a few bacteria (19,30). This suggests that the clumping of gonococci is actually a deterrent to cellular invasion.…”

Bacterial Sphingomyelinases and Phospholipases as Virulence Factors

“…Furthermore, NgPLD also modulates host cell signaling by binding directly to the PH domain of the Akt kinase, which results in its activation as well as in CR3 receptor translocation to the cell surface, promoting further N. gonorrhoeae uptake (285). Accordingly, an NgPLD-lacking mutant strain exhibited a decreased ability to invade primary cervical cells due to its impaired capacity to recruit CR3 to the cell surface and elicit membrane ruffles (284).…”

“…N. gonorrhoeae produces a PLD, designated NgPLD, which is necessary for efficient epithelial cell invasion (284). NgPLD-produced PA drives cell surface recruitment of CR3, membrane ruffling, and bacteria engulfment (284). Furthermore, NgPLD also modulates host cell signaling by binding directly to the PH domain of the Akt kinase, which results in its activation as well as in CR3 receptor translocation to the cell surface, promoting further N. gonorrhoeae uptake (285).…”

“…This bacterium is endocytosed by a clathrin-dependent mechanism or by complement receptor type 3 (CR3)-mediated endocytosis (284). N. gonorrhoeae produces a PLD, designated NgPLD, which is necessary for efficient epithelial cell invasion (284). NgPLD-produced PA drives cell surface recruitment of CR3, membrane ruffling, and bacteria engulfment (284).…”

“…gonorrhoeae, the causative agent of human gonorrhea, replicates within cervical and urethral epithelial cells (284). This bacterium is endocytosed by a clathrin-dependent mechanism or by complement receptor type 3 (CR3)-mediated endocytosis (284).…”