Giving Gold Wings: Ultrabright and Fragmentation Free Mass Spectrometry Reporters for Barcoding, Bioconjugation Monitoring, and Data Storage.

The widespread application of laser desorption/ionization mass spectrometry (LDI-MS) highlights the need for a bright and multiplexable labeling platform. While ligand-capped Au nanoparticles (AuNPs) have emerged as a promising LDI-MS contrast agent, the predominant thiol ligands suffer from low ion yields and extensive fragmentation. In this work, we develop a N-heterocyclic carbene (NHC) ligand platform that enhances AuNP LDI-MS performance. NHC scaffolds are tuned to generate barcoded AuNPs which, when benchmarked against thiol-AuNPs, are bright mass tags and form unfragmented ions in high yield. To illustrate the transformative potential of NHC ligands, the mass tags were employed in three orthogonal applications: monitoring a bioconjugation reaction, performing multiplexed imaging, and storing and reading encoded information. These results demonstrate that NHC-nanoparticle systems are an ideal platform for LDI-MS and greatly broaden the scope of nanoparticle contrast agents.

Does implant placement using a minimally invasive technique increase early failures among trainees at an academic center?

PURPOSE: This study aims to identify whether dental implants placed using a flapless technique have a higher early failure rate, defined as failure within 6 months of placement, compared to implants placed with flap elevation when a surgical guide is not used. METHODS: A retrospective cohort study was conducted to evaluate implants placed with either flapless (FL) or mucoperiosteal flap (MF) surgery between 2006 and 2012 at the Philadelphia VA Medical Center (PVAMC). Implant status after FL or MF surgery was assessed using dental encounter and radiographs at subsequent follow-up appointments to assess for early implant failures within 6 months of implant placement. RESULTS: The FL technique was used to place 89 implants in 38 subjects, while the MF technique was used to place 381 implants in 139 subjects. Early failure occurred in 37 implants, of which 13 occurred in the FL group and 24 occurred in the MF group. FL surgery was found to be associated with a 265% increase in early implant failure (OR 2.653; 95% CL 1.287-5.469) and was statistically significant (p = 0.0064). Residents were over 200% more likely to have an early implant failure when using the FL technique (OR 2.314; 95% CL 1.112-4.816), CONCLUSIONS: Analysis revealed flapless implant placement was associated with higher early implant failure rates. In addition, early failures were more likely to occur when residents placed an implant using the flapless technique. While FL surgery can result in long-term success, it is a more technique-sensitive approach that requires greater clinical skill and stricter case selection to perform.

Are proton pump inhibitors associated with implant failure and peri-implantitis?

OBJECTIVE: Proton pump inhibitors (PPIs) may be linked to implant failure by affecting bone metabolism and osseointegration. This study evaluated how PPIs influence long-term implant failure and peri-implantitis in PPI users and nonusers. STUDY DESIGN: This was a retrospective cohort study of patients treated at the Philadelphia Veterans Affairs Medical Center between 2006 and 2013. The primary predictor variable was PPI use. Outcome variables were long-term implant failure and the presence of peri-implantitis. Data gathered included demographic characteristics, medical comorbidities, implant location, and dimensions. Multivariate regression models measured independent factor associations. The final study cohort contained 933 implants placed in 284 patients. A total of 323 (32.6%) implants were placed in patients with ongoing PPI use. PPI users were less likely to smoke (22.1% vs 31.9%; P < .01) and use illicit drugs (5.0% vs 9.7%; P = .01) and more likely to have undergone prior bone grafting (18.3% vs 12.9%; P = .03). RESULTS: PPI use lost significance after controlling for confounding factors and was not an independent predictor of implant failure (odds ratio [OR], 0.801; 95% confidence interval [CI], 0.56-1.15; P = .24) or peri-implantitis (OR, 0.801; 95% CI, 0.56-1.15; P = .24). CONCLUSIONS: Our study found no independent associations between PPI use and implant failure or peri-implantitis. Contrary to published literature, PPIs may not influence implant health.

Synergistic and additive interactions between receptor signaling networks drive the regulatory T cell versus T helper 17 cell fate choice.

CD4+ T cells differentiate into subsets that promote immunity or minimize damage to the host. T helper 17 cells (Th17) are effector cells that function in inflammatory responses. T regulatory cells (Tregs) maintain tolerance and prevent autoimmunity by secreting immunosuppressive cytokines and expressing check point receptors. While the functions of Th17 and Treg cells are different, both cell fate trajectories require T cell receptor (TCR) and TGF-ß receptor (TGF-ßR) signals, and Th17 polarization requires an additional IL-6 receptor (IL-6R) signal. Utilizing high-resolution phosphoproteomics, we identified that both synergistic and additive interactions between TCR, TGF-ßR, and IL-6R shape kinase signaling networks to differentially regulate key pathways during the early phase of Treg versus Th17 induction. Quantitative biochemical analysis revealed that CD4+ T cells integrate receptor signals via SMAD3, which is a mediator of TGF-ßR signaling. Treg induction potentiates the formation of the canonical SMAD3/4 trimer to activate a negative feedback loop through kinases PKA and CSK to suppress TCR signaling, phosphatidylinositol metabolism, and mTOR signaling. IL-6R signaling activates STAT3 to bind SMAD3 and block formation of the SMAD3/4 trimer during the early phase of Th17 induction, which leads to elevated TCR and PI3K signaling. These data provide a biochemical mechanism by which CD4+ T cells integrate TCR, TGF-ß, and IL-6 signals via generation of alternate SMAD3 complexes that control the development of early signaling networks to potentiate the choice of Treg versus Th17 cell fate.

Probing N-Heterocyclic Carbene Surfaces with Laser Desorption Ionization Mass Spectrometry.

The proliferation of N-heterocyclic carbene (NHC) self-assembled monolayers (SAMs) on gold surfaces stems from their exceptional stability compared to conventional thiol-SAMs. The prospect of biological applications for NHC-SAMs on gold shows the need for biocompatible techniques (e.g., large biomolecule detection and high throughput) that assesses SAM molecular composition. Herein, we demonstrate that laser desorption ionization mass spectrometry (LDI-MS) is a powerful and facile probe of NHC surface chemistry. LDI-MS of prototypical imidazole-NHC- and benzimidazole-NHC-functionalized AuNPs yields exclusively [NHC2Au]+ ions and not larger gold clusters. Employing benzimidazole-NHC isotopologues, we explore how monolayers pack on a single AuNP and the lability of the NHCs once ligated. Quantitative analysis of the homoleptic and heteroleptic [NHC2Au]+ ions is performed by comparing to a binomial model representative of a randomized monolayer. Lastly, the reduction of nitro-NHC-AuNPs to amine-NHC-AuNPs is tracked via LDI-MS signals, illustrating the ability of LDI-MS to probe postsynthetic modifications of the anchored NHCs, which is critical for current and future applications of NHC surfaces.

Does alcohol consumption protect against late dental implant failures?

PURPOSE: Social factors have been implicated in the development of peri-implant pathologies, including implant failure. This study aims to investigate whether alcohol consumption affects late dental implant failures. METHODS: A retrospective cohort study evaluated implants placed between 2006 and 2012 at the Philadelphia Veterans Affairs Medical Center. The primary predictor variable was alcohol consumption, measured as nonconsumption and mild, moderate, and heavy consumption. The primary outcome variable was late dental implant failure. Univariate, bivariate, and multivariate statistics were applied, with P < .05 used to define statistical significance. RESULTS: Our cohort consisted of 103 patients and 295 implants with a 5-year minimum follow-up. Most patients were male (93%) with an average age of 60 at the time of implant placement. Late implant failure was associated with 30 implants. Compared to nonconsumption, mild consumption was associated with a 75% decrease in late implant failure (P = .0494), moderate consumption was associated with a 60% decrease (P = .3826), and heavy consumption was associated with a 200% increase (P < .1782). Compared to mild consumption, heavy consumption was associated with an 847% increase in late failure (P = .0135). CONCLUSIONS: Results from this retrospective cohort analysis suggest that mild alcohol consumption is associated with a decrease in late dental implant failures.

Hygiene Recall in Diabetic and Nondiabetic Patients: A Periodic Prognostic Factor in the Protection Against Peri-Implantitis?

PURPOSE: Diabetes mellitus is associated with an increased risk of poor outcomes with dental implant placement. This study aims to identify if frequency of hygiene visits is a protective factor for the development of peri-implantitis in diabetic patients. METHODS: A retrospective cohort design was conducted on patients presenting for dental implant placement at the Philadelphia Veterans Affairs (VA) Medical Center from 2006 to 2012. The primary predictor variable was hygiene frequency, recorded as either infrequent, annual (7-12 month recall), or biannual (≤6-month recall). The number of months between implant placement and the presence of peri-implantitis was the primary outcome (time-to-peri-implantitis) variable, which was assessed on a subject level and adjusted for clustered, correlated multiple implants on the same subject. Additional variables were greater than or equal to 60 years of age, male gender, smokers, short implant length, diabetes, uncontrolled diabetes, and removable prostheses. Descriptive, univariate, and Cox proportional hazards regression statistics were computed to measure associations with peri-implantitis with P ≤ .05 used to define statistical significance. RESULTS: The study sample was composed of 286 patients. In total, 748 implants were placed. Subjects greater than or equal to 60 years of age were 2 times more likely to develop peri-implantitis (hazards ratio (HR) = 2.015, 95% Cl (0.985-4.119), P = .0549). Subjects receiving implant-supported removable prostheses were 2.3 times more likely to develop peri-implantitis (HR = 2.315, 95% CI (1.006-5.327), P = .0485). With each hygiene visit, patients' risk of developing peri-implantitis decreased 20% (HR = 0.805, 95% Cl (0.394-1.647), P = .5528). In addition, diabetic patients were 49% more likely to develop peri-implantitis (HR = 1.491, 95% CI (0.758-2.936), P = .2475) than nondiabetic patients. CONCLUSIONS: Diabetic patients may be at increased risk for the development of peri-implantitis and an increased frequency of hygiene visits may reduce peri-implant diseases.

Prophylactic Activation of Shh Signaling Attenuates TBI-Induced Seizures in Zebrafish by Modulating Glutamate Excitotoxicity through Eaat2a.

Approximately 2 million individuals experience a traumatic brain injury (TBI) every year in the United States. Secondary injury begins within minutes after TBI, with alterations in cellular function and chemical signaling that contribute to excitotoxicity. Post-traumatic seizures (PTS) are experienced in an increasing number of TBI individuals that also display resistance to traditional anti-seizure medications (ASMs). Sonic hedgehog (Shh) is a signaling pathway that is upregulated following central nervous system damage in zebrafish and aids injury-induced regeneration. Using a modified Marmarou weight drop on adult zebrafish, we examined PTS following TBI and Shh modulation. We found that inhibiting Shh signaling by cyclopamine significantly increased PTS in TBI fish, prolonged the timeframe PTS was observed, and decreased survival across all TBI severities. Shh-inhibited TBI fish failed to respond to traditional ASMs, but were attenuated when treated with CNQX, which blocks ionotropic glutamate receptors. We found that the Smoothened agonist, purmorphamine, increased Eaat2a expression in undamaged brains compared to untreated controls, and purmorphamine treatment reduced glutamate excitotoxicity following TBI. Similarly, purmorphamine reduced PTS, edema, and cognitive deficits in TBI fish, while these pathologies were increased and/or prolonged in cyclopamine-treated TBI fish. However, the increased severity of TBI phenotypes with cyclopamine was reduced by cotreating fish with ceftriaxone, which induces Eaat2a expression. Collectively, these data suggest that Shh signaling induces Eaat2a expression and plays a role in regulating TBI-induced glutamate excitotoxicity and TBI sequelae.

Transforming growth factor ß (TGF-ß) receptor signaling regulates kinase networks and phosphatidylinositol metabolism during T-cell activation.

The cytokine content in tissue microenvironments shapes the functional capacity of a T cell. This capacity depends on the integration of extracellular signaling through multiple receptors, including the T-cell receptor (TCR), co-receptors, and cytokine receptors. Transforming growth factor ß (TGF-ß) signals through its cognate receptor, TGFßR, to SMAD family member proteins and contributes to the generation of a transcriptional program that promotes regulatory T-cell differentiation. In addition to transcription, here we identified specific signaling networks that are regulated by TGFßR. Using an array of biochemical approaches, including immunoblotting, kinase assays, immunoprecipitation, and flow cytometry, we found that TGFßR signaling promotes the formation of a SMAD3/4-protein kinase A (PKA) complex that activates C-terminal Src kinase (CSK) and thereby down-regulates kinases involved in proximal TCR activation. Additionally, TGFßR signaling potentiated CSK phosphorylation of the P85 subunit in the P85-P110 phosphoinositide 3-kinase (PI3K) heterodimer, which reduced PI3K activity and down-regulated the activation of proteins that require phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3) for their activation. Moreover, TGFßR-mediated disruption of the P85-P110 interaction enabled P85 binding to a lipid phosphatase, phosphatase and tensin homolog (PTEN), aiding in the maintenance of PTEN abundance and thereby promoting elevated PtdIns(4,5)P2 levels in response to TGFßR signaling. Taken together, these results highlight that TGF-ß influences the trajectory of early T-cell activation by altering PI3K activity and PtdIns levels.

Is Alcohol Consumption Associated With Protection Against Peri-Implantitis? A Retrospective Cohort Analysis.

PURPOSE: Recent studies have pointed to the effects of social factors on the health of dental implants. We investigated whether varying levels of alcohol consumption will influence the health of dental implants and associated peri-implant inflammation. PATIENTS AND METHODS: A retrospective cohort study was performed to evaluate implants placed from 2006 to 2012 at the Philadelphia Veteran's Affairs Medical Center. Alcohol consumption was gathered from the health maintenance records within 3 months of implant placement and served as the predictor variable. Analysis was performed at follow-up visits for the presence of the outcome variable, peri-implantitis, which was assessed at an implant level. A multivariable generalized estimating equation logistic regression model was constructed, and a Wald test was used to analyze the statistical significance of each parameter. The results were interpreted as an odds ratio estimate, including the 95% confidence interval. Descriptive statistics were used to compute and analyze the data, with P < .05 used to define statistical significance. RESULTS: Demographically, our cohort consisted mainly of male patients (92%), with an average age of 60 years at implant placement. The mean interval to peri-implantitis was 30 ± 25 months. Peri-implantitis occurred most frequently within 2 years of implant placement. The incidence of peri-implantitis was greatest among heavy alcohol consumers (42%) and lowest among mild and moderate consumers (12 and 6%, respectively). Compared with no consumption, mild alcohol consumption was associated with a 47% decrease in peri-implantitis (P < .0223) and moderate consumption was associated with a 75% decrease (P < .0250). Heavy consumption was associated with a nearly threefold increase in peri-implantitis (P < .0001). CONCLUSIONS: The results from our retrospective cohort analysis revealed that mild to moderate alcohol consumption is associated with a lower rate of peri-implantitis. However, heavy consumption was associated with an increase in the incidence of peri-implantitis among patients with dental implants.

Slt, MltD, and MltG of Pseudomonas aeruginosa as Targets of Bulgecin A in Potentiation of ß-Lactam Antibiotics.

The interplay between the activities of lytic transglycosylases (LTs) and penicillin-binding proteins (PBPs) is critical for the health of the bacterial cell wall. Bulgecin A (a natural-product inhibitor of LTs) potentiates the activity of ß-lactam antibiotics (inhibitors of PBPs), underscoring this intimate mechanistic interdependence. Bulgecin A in the presence of an appropriate ß-lactam causes bulge deformation due to the formation of aberrant peptidoglycan at the division site of the bacterium. As Pseudomonas aeruginosa, a nefarious human pathogen, has 11 LT paralogs, the answer as to which LT activity correlates with ß-lactam potentiation is important and is currently unknown. Growth of P. aeruginosa PAO1 strains harboring individual transposon-insertion mutants at each of the 11 genes for LTs, in the presence of the ß-lactam antibiotic ceftazidime or meropenem, implicated the gene products of slt, mltD, and mltG (of the 11), in bulge formation and potentiation. Hence, the respective enzymes would be the targets of inhibition by bulgecin A, which was indeed documented. We further demonstrated by imaging in real time and by SEM that cell lysis occurs by the structural failure of this bulge. Upon removal of the ß-lactam antibiotic prior to lysis, P. aeruginosa experiences delayed recovery from the elongation and bulge phenotype in the presence of bulgecin A. These observations argue for a collaborative role for the target LTs in the repair of the aberrant cell wall, the absence of activities of which in the presence of bulgecin A results in potentiation of the ß-lactam antibiotic.

Siderophore Conjugates of Daptomycin are Potent Inhibitors of Carbapenem Resistant Strains of Acinetobacter baumannii.

Development of resistance to antibiotics is a major medical problem. One approach to extending the utility of our limited antibiotic arsenal is to repurpose antibiotics by altering their bacterial selectivity. Many antibiotics that are used to treat infections caused by Gram-positive bacteria might be made effective against Gram-negative bacterial infections, if they could circumvent permeability barriers and antibiotic deactivation processes associated with Gram-negative bacteria. Herein, we report that covalent attachment of the normally Gram-positive-only antibiotic, daptomycin, with iron sequestering siderophore mimetics that are recognized by Gram-negative bacteria, provides conjugates that are active against virulent strains of Acinetobacter baumannii, including carbapenemase and cephalosporinase producers. The result is the generation of a new set of antibiotics designed to target bacterial infections that have been designated as being of dire concern.

A Synthetic Dual Drug Sideromycin Induces Gram-Negative Bacteria To Commit Suicide with a Gram-Positive Antibiotic.

Many antibiotics lack activity against Gram-negative bacteria because they cannot permeate the outer membrane or suffer from efflux and, in the case of ß-lactams, are degraded by ß-lactamases. Herein, we describe the synthesis and studies of a dual drug conjugate (1) of a siderophore linked to a cephalosporin with an attached oxazolidinone. The cephalosporin component of 1 is rapidly hydrolyzed by purified ADC-1 ß-lactamase to release the oxazolidinone. Conjugate 1 is active against clinical isolates of Acinetobacter baumannii as well as strains producing large amounts of ADC-1 ß-lactamase. Overall, the results are consistent with siderophore-mediated active uptake, inherent activity of the delivered dual drug, and in the presence of ß-lactamases, intracellular release of the oxazolidinone upon cleavage of the cephalosporin to allow the freed oxazolidinone to inactivate its target. The ultimate result demonstrates that Gram-positive oxazolidinone antibiotics can be made to be effective against Gram-negative bacteria by ß-lactamase triggered release.

TCR Signal Strength Regulates Akt Substrate Specificity To Induce Alternate Murine Th and T Regulatory Cell Differentiation Programs.

The Akt/mTOR pathway is a key driver of murine CD4+ T cell differentiation, and induction of regulatory T (Treg) cells results from low TCR signal strength and low Akt/mTOR signaling. However, strong TCR signals induce high Akt activity that promotes Th cell induction. Yet, it is unclear how Akt controls alternate T cell fate decisions. We find that the strength of the TCR signal results in differential Akt enzymatic activity. Surprisingly, the Akt substrate networks associated with T cell fate decisions are qualitatively different. Proteomic profiling of Akt signaling networks during Treg versus Th induction demonstrates that Akt differentially regulates RNA processing and splicing factors to drive T cell differentiation. Interestingly, heterogeneous nuclear ribonucleoprotein (hnRNP) L or hnRNP A1 are Akt substrates during Treg induction and have known roles in regulating the stability and splicing of key mRNAs that code for proteins in the canonical TCR signaling pathway, including CD3ζ and CD45. Functionally, inhibition of Akt enzymatic activity results in the dysregulation of splicing during T cell differentiation, and knockdown of hnRNP L or hnRNP A1 results in the lower induction of Treg cells. Together, this work suggests that a switch in substrate specificity coupled to the phosphorylation status of Akt may lead to alternative cell fates and demonstrates that proteins involved with alternative splicing are important factors in T cell fate decisions.

Orbital, Mediastinal and Cervicofacial Subcutaneous Emphysema after Dental Rehabilitation in a Pediatric Patient.

Subcutaneous emphysema is a rare possible complication of dental procedures. The majority of the dental literature describes cases of localized areas of subcutaneous emphysema following various dental procedures, with a large number of these cases seen following intraoral surgical procedures. Classically, subcutaneous emphysema occurs within minutes to hours after conclusion of dental procedures and is commonly misdiagnosed as either an allergic reaction or acute post-operative swelling. This case report describes a four-year-old male who underwent dental rehabilitation for routine restorative dentistry without extractions under general anesthesia. He subsequently developed extensive subcutaneous emphysema involving the right periorbital region, cervicofacial spaces, and caudal extension to include the superior aspect of the mediastinum. The purpose of this report was to provide a brief review of the prior literature on the subject, report on the case, and review the management for patients with subcutaneous emphysema.

Structure and compatibility of a magnesium electrolyte with a sulphur cathode.

Magnesium metal is an ideal rechargeable battery anode material because of its high volumetric energy density, high negative reduction potential and natural abundance. Coupling Mg with high capacity, low-cost cathode materials such as electrophilic sulphur is only possible with a non-nucleophilic electrolyte. Here we show how the crystallization of the electrochemically active species formed from the reaction between hexamethyldisilazide magnesium chloride and aluminum trichloride enables the synthesis of a non-nucleophilic electrolyte. Furthermore, crystallization was essential in the identification of the electroactive species, [Mg(2)(µ-Cl)(3)·6THF](+), and vital to improvements in the voltage stability and coulombic efficiency of the electrolyte. X-ray photoelectron spectroscopy analysis of the sulphur electrode confirmed that the electrochemical conversion between sulphur and magnesium sulfide can be successfully performed using this electrolyte.

Zwint-1 is a novel Aurora B substrate required for the assembly of a dynein-binding platform on kinetochores.

Aurora B (AurB) is a mitotic kinase responsible for multiple aspects of mitotic progression, including assembly of the outer kinetochore. Cytoplasmic dynein is an abundant kinetochore protein whose recruitment to kinetochores requires phosphorylation. To assess whether AurB regulates recruitment of dynein to kinetochores, we inhibited AurB using ZM447439 or a kinase-dead AurB construct. Inhibition of AurB reduced accumulation of dynein at kinetochores substantially; however, this reflected a loss of dynein-associated proteins rather than a defect in dynein phosphorylation. We determined that AurB inhibition affected recruitment of the ROD, ZW10, zwilch (RZZ) complex to kinetochores but not zwint-1 or more-proximal kinetochore proteins. AurB phosphorylated zwint-1 but not ZW10 in vitro, and three novel phosphorylation sites were identified by tandem mass spectrometry analysis. Expression of a triple-Ala zwint-1 mutant blocked kinetochore assembly of RZZ-dependent proteins and induced defects in chromosome movement during prometaphase. Expression of a triple-Glu zwint-1 mutant rendered cells resistant to AurB inhibition during prometaphase. However, cells expressing the triple-Glu mutant failed to satisfy the spindle assembly checkpoint (SAC) at metaphase because poleward streaming of dynein/dynactin/RZZ was inhibited. These studies identify zwint-1 as a novel AurB substrate required for kinetochore assembly and for proper SAC silencing at metaphase.

Absorption spectrum, mass spectrometric properties, and electronic structure of 1,2-benzoquinone.

Absorption spectrophotometric and mass spectrometric properties of 1,2-benzoquinone, prepared in aqueous solution by the hexachloroiridate(IV) oxidation of catechol and isolated by HPLC, are reported. Its absorption spectrum has a broad moderately intense band in the near UV with an extinction coefficient of 1370 M(-1)cm(-1) at its 389 nm maximum. The oscillator strength of this band contrasts with those of the order-of-magnitude stronger approximately 250 nm bands of most 1,4-benzoquinones. Gaussian analysis of its absorption spectrum indicates that it also has modestly intense higher energy bands in the 250-320 nm region. In atmospheric pressure mass spectrometric studies 1,2-benzoquinone exhibits very strong positive and negative mass 109 signals that result from the addition of protons and hydride ions in APCI and ESI ion sources. It is suggested that the hydride adduct is formed as the result of the highly polar character of ortho-quinone. On energetic collision the hydride adduct loses an H atom to produce the 1,2-benzosemiquinone radical anion. The present studies also show that atmospheric pressure mass spectral patterns observed for catechol are dominated by signals of 1,2-benzoquinone resulting from oxidation of catechol in the ion sources. Computational studies of the electronic structures of 1,2-benzoquinone, its proton and hydride ion adducts, and 1,2-benzosemiquinone radical anion are reported. These computational studies show that the structures of the proton and hydride adducts are similar and indicate that the hydride adduct is the proton adduct of a doubly negatively charged 1,2-benzoquinone. The contrast between the properties of 1,2- and 1,4-benzoquinone provides the basis for considerations on the effects of conjugation in aromatic systems.

Mycobacterium avium glycopeptidolipids require specific acetylation and methylation patterns for signaling through toll-like receptor 2.

Toll-like receptors (TLRs) recognize pathogen-associated molecules and play a vital role in promoting an immune response against invading microbes. TLR2, one of the key members of the TLR family, recognizes a wide variety of microbial products, including lipoproteins and lipopeptides, from a number of pathogens. Recent studies from our laboratory indicate that glycopeptidolipids (GPLs), a major surface component of Mycobacterium avium and other non-tuberculosis mycobacteria, are ligands for TLR2. However, the molecular requirements necessary for the GPL-TLR2 interaction were not defined in this report. In the present study we isolated different GPL species from M. avium, and using mass spectrometry and NMR analyses, characterized the molecular requirements of the GPL-TLR2 interaction. Interestingly, the extent of the respective acetylation and methylation of the 6-deoxytalose and rhamnose contained within the core GPL structure dictated whether the GPL signaled through TLR2. These experiments illustrate how subtle changes in a complex TLR2 ligand can alter its affinity for this important receptor, and suggest that M. avium could potentially modify its GPL structure to limit its interaction with TLR2.