Structural requirements of muramylpeptides for induction of Toll-like receptor 2-mediated NF-κB activation in CHO cells

Abstract

We previously demonstrated that Gram-positive bacteria activated immune cells via CD14 and Toll-like receptor 2 (TLR2). Although peptidoglycan, a major constituent of the bacterial cell wall, substituted for whole organisms, the essential structure of muramylpeptides required to stimulate the cells is not clear. We further investigated the critical determinant for recognition by CD14 and TLR2. Chinese hamster ovary (CHO) fibroblasts, which do not express a functional TLR2 transcript, were transfected with TLR2 or TLR4. These cells were exposed to freeze-dried Staphylococcus epidermidis and were subsequently subjected to the pro-inflammatory transcription factor nuclear factor-kappaB (NF-kappaB)-dependent CD25 expression assay. Heterologous expression of human TLR2, but not TLR4, in CHO cells conferred immune responsiveness to freeze-dried S. epidermidis. A preparation of peptidoglycan from S. epidermidis substituted for whole organisms. Staphylococcus aureus lytic enzyme-digested product (SEPS) from peptidoglycan retained the activity, but hydrolysis of the glycan backbone in SEPS by M-1 endo-N-acetylmuramidase resulted in loss of the activity. These findings showed that cellular activation by Gram-positive cell wall components was mediated by TLR2, but not TLR4, and indicated that the glycan backbone of peptidoglycan is critical for TLR2-mediated NF-kappaB activation.

Priming of human oral epithelial cells by interferon-γ to secrete cytokines in response to lipopolysaccharides, lipoteichoic acids and peptidoglycans

“…aureus PGN-and soluble PGN, SEPS-induced IL-8 secretion was clearly inhibited by anti-TLR2 MAb, in accordance with previous reports [13][14][15]50]. Although MDP is the minimal structure essential for the bioactivities of PGN, its signalling in relation to TLRs has not been elucidated.…”

Surface Calreticulin Mediates Muramyl Dipeptide-induced Apoptosis in RK13 Cells

“…For example, the binding of the muramyl moiety of L,D-MDP to the tryptophan region of the 5-hydroxytryptamine binding site on myelin basic protein, luteinizing hormone-releasing hormone, and melanocyte-stimulating hormone-adrenocorticotropic hormone plays a key role in inducing antibodies to self-proteins that are produced during autoimmune disease (15,16). In contrast, some biological effects of MDP (and PG) depend on the stereoisomeric configuration of the dipeptide moiety of L,D-MDP and its interaction with a cellular protein (5)(6)(7)(8)(9)(10)(11)(12)(13)(14). For example, the apoptogenic activity of L,D-MDP in rabbit kidney RK 13 cells is dependent on the interaction of the dipeptide moiety of L,D-MDP with CRT (5, 12), a multifunctional protein with chaperone function (17)(18)(19).…”

“…or living organisms such as edema, fever, loss of appetite, meningitis, arthritis, and uveitis (5)(6)(7)(8)(9)(10)(11)(12)(13)(14).…”

Study of the Relationship between Changes in Lactic Acid Bacterial Cell Components and Stimulation of IL-12 Production under Salt-Stressed Conditions

“…33) The polymer peptidoglycan of Staphylococcus epidermidis is mediated by TLR2, but the monomer peptidoglycan have no activity. 34) KKM122 cells grown in a medium containing Penicillin G showed weaker IL-12 activities (Fig. 5).…”