Mechanisms of Chlamydia trachomatis Entry into Nonphagocytic Cells

Abstract

The mechanisms of entry for the obligate intracellular bacterium C. trachomatis were examined by functional disruption of proteins essential for various modes of entry. RNA interference was used to disrupt proteins with established roles in clathrin-mediated endocytosis (clathrin heavy chain, dynamin-2, heat shock 70-kDa protein 8, Arp2, cortactin, and calmodulin), caveola-mediated endocytosis (caveolin-1, dynamin-2, Arp2, NSF, and annexin II), phagocytosis (RhoA, dynamin-2, Rac1, and Arp2), and macropinocytosis (Pak1, Rac1, and Arp2). Comparative quantitative PCR analysis was performed on small interfering RNA-transfected HeLa cells to accurately determine the extent of C. trachomatis entry after these treatments. Key structural and regulatory factors associated with clathrin-mediated endocytosis were found to be involved in Chlamydia entry, whereas those for caveola-mediated endocytosis, phagocytosis, and macropinocytosis were not. Thus, clathrin and its coordinate accessory factors were required for entry of C. trachomatis, although additional, uncharacterized mechanisms are also utilized.

Comparison of Chlamydia trachomatis serovar L2 growth in polarized genital epithelial cells grown in three-dimensional culture with non-polarized cells

“…This intriguing difference between strains may possibly be due to the recognition of and binding to different receptor molecules on host cell surfaces that, for serovar E, may be enriched or clustered in some regions or microdomains of polarized epithelial cell apical membranes, such as lipid rafts or caveolae, proposed to be involved in serovar E but not in serovar L2 entry [19,20]. Although their role in chlamydial entry is still controversial [21][22][23], it is an interesting possibility, as many pathogens are known to interact with these membrane microdomains and that receptor molecules, such as membrane-associated estrogen receptors that locate to caveolae, have been implicated in serovar E attachment/entry [11,24]. In contrast, initial interactions of serovar L2 EB with host cell surfaces may occur via recognition of a broader range of host molecules or molecules widely represented throughout cell surfaces, such as heparan sulfate proteoglycans [25], and/or via Tarp-mediated pedestallike formation [26,27], a phenomenon shown to be more prevalent for serovar L2 than with serovar D [26] or serovar E [28].…”

Dynamin- and Clathrin-Dependent Endocytosis in African Swine Fever Virus Entry

“…Two complementary approaches were used to disrupt dynamin-dependent endocytosis: use of dominant negative mutant K44A (14) and of dynasore, a specific and widely used chemical inhibitor of dynamin GTPase activity (1,(23)(24)(25). Transient expression of the K44A mutant significantly inhibited transferrin uptake and ASFV infection (about 50%) compared to wild-type dynamin or GFP alone.…”

Chlamydial Intracellular Survival Strategies

“…The actin rearrangements that occur during entry are transient and may be terminated by secreted chlamydial effectors such as CT166, which glucosylates Rac1 (Thalmann et al 2010), or CT694, which interacts and colocalizes with AHNAK, an actin-binding protein (Hower et al 2009). Additional host factors that contribute to uptake into nonphagocytic cells include clathrin (Boleti et al 1999;Hybiske and Stephens 2007a) and cholesterol-rich microdomains (Norkin et al 2001;Jutras et al 2003;Stuart et al 2003;Gabel et al 2004). …”