(D) Cy2-SitC-His was incorporated into TLR2-deficient MKs

(D) Cy2-SitC-His was incorporated into TLR2-deficient MKs. with TLR2, is definitely internalized by sponsor cells, induces proinflammatory cytokines, and activates intracellular build up of TLR2. Acknowledgement of intruding pathogens is the first step of sponsor defense. The innate immune response is definitely capable of realizing microbes and provides a first line of defense to the host. It is mediated in part by pattern acknowledgement receptors (PRRs), including Toll-like receptors (TLRs), that specifically identify microbe-associated molecular patterns (MAMPs) derived from microorganisms (2). TLR2 has been shown to play a crucial role in the host response toStaphylococcus aureus(47). It appears to AQ-13 dihydrochloride be a receptor for various structurally unrelated MAMPs, e.g., lipoproteins (27,39), glycolipids from spirochetes, lipoarabinomannan from mycobacteria, porins fromNeisseria(45), lipoteichoic acid (LTA) (32,40), and peptidoglycan (PGN) (1,4,12,20,33). However, an increasing quantity of studies suggest that bacterial lipoproteins are the major, if not single, TLR2-activating molecules of Gram-positive bacteria (18,27,43,48,52). The N termini of bacterial lipoproteins contain a uniqueS-diacylglyceryl cysteine moiety. InEscherichia coliand other Gram-negative bacteria, as well as in mycobacterial and spirochetal species, an additional acyl group is usually linked to the amino group of this cysteine (16), resulting in the formation of triacylated membrane anchor structures. Lipoproteins are synthesized as preproteins with a distinct type II signal sequence containing a conserved lipobox consensus AQ-13 dihydrochloride motif (28). In theS. aureusgenome, more than 50 genes contain the type II signal sequence common for lipoproteins. Some of them have been annotated as substrate binding components of ABC transporters that are involved in nutrient and iron acquisition, and one of the predominant lipoproteins is usually SitC (43). SitC is usually part of the iron transporter SitABC (10). Until now, only synthetic lipoprotein analogs, such asN-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-(R)-cyste- inyl-(lysyl)3-lysine (Pam3Cys; tripalmitoyl cysteinyl) lipopeptide, Pam3CSK4(adapted from theEscherichia coliBraun’s lipoprotein), and dipalmitoyl MALP-2 (macrophage-activating lipopeptide 2 kDa) fromMycoplasma fermentans(31), have Rabbit Polyclonal to GPRIN2 been shown to mimic the proinflammatory properties of bacterial lipoproteins (46). This led to a model in which triacylated lipopeptides signal through TLR2/TLR1 heterodimers, whereas diacylated lipopeptides signal through TLR2/TLR6 heterodimers. Indeed, the structure of TLR1/TLR2 heterodimers with Pam3CSK4suggests that both AQ-13 dihydrochloride receptors are involved in binding the lipopeptide (24). On the other hand, activation of TLR1- and TLR6-deficient mice with di- and triacylated lipopeptides (e.g., Pam2CSK4and Pam3CGNNDESNISFKEK) revealed that neither TLR1 nor TLR6 was necessary for activation (8). Whether lipoproteins ofS. aureusare di- or triacylated is still not clear. Gram-negative bacteria possess anN-acyltransferase (Lnt) that transfers an acyl group to the amino group of theS-diacylated cysteine residue, yielding a triacylated (N-acylated,S-diacylated) lipoprotein. However, an Lnt homolog has not been found in Gram-positive bacteria such as staphylococci. Therefore, it was assumed that this lipoproteins inS. aureuswere diacylated. Indeed, N-terminal analysis of anS. aureuslipoprotein (SAOUHSC_02699) revealed that it is diacylated (48). However, it has also been reported that purified SitC (another lipoprotein) is usually triacylated (27). Even though major role of lipoproteins in TLR2 activation seems to be established, detailed information on molecular lipoproteins interacting with TLR2 in host cells is still unclear. In this study, the interaction of the staphylococcal lipoprotein SitC with TLR2 of main murine keratinocytes (MKs) was AQ-13 dihydrochloride examined. We show that SitC colocalizes specifically with TLR2 and stimulates proinflammatory cytokines and intracellular TLR2 expression. == MATERIALS AND METHODS == == Bacterial strains, growth media, and plasmids. == S. aureusSA113,S. aureus(pTX30SitC-his), andStaphylococcus carnosusRKET(pPSHG5His6mSHL) AQ-13 dihydrochloride were used in this study. Strains were grown aerobically at 37C in basal medium (BM) with the supplements indicated in Table1. == TABLE 1. == Strains used in this study.