Regulatory T (Treg) cells, which maintain immune homeostasis and self-tolerance, form an immunological synapse (IS) with antigen-presenting cells (APCs). However, signaling events at the Treg cell IS ...remain unknown. Here we show that the kinase PKC-η associated with CTLA-4 and was recruited to the Treg cell IS. PKC-η-deficient Treg cells displayed defective suppressive activity, including suppression of tumor immunity but not of autoimmune colitis. Phosphoproteomic and biochemical analysis revealed an association between CTLA-4-PKC-η and the GIT2-αPIX-PAK complex, an IS-localized focal adhesion complex. Defective activation of this complex in PKC-η-deficient Treg cells was associated with reduced depletion of CD86 from APCs by Treg cells. These results reveal a CTLA-4-PKC-η signaling axis required for contact-dependent suppression and implicate this pathway as a potential cancer immunotherapy target.
Abstract
In Singapore, 9.03 million doses of the mRNA COVID-19 vaccines by Pfizer-BioNTech and Moderna have been administered, and 4.46 million people are fully vaccinated. An additional 87,000 ...people have been vaccinated with vaccines in World Health Organization’s Emergency Use Listing. The aim of this review is to explore the reported cardiac adverse events associated with different types of COVID-19 vaccines. A total of 42 studies that reported cardiac side effects after COVID-19 vaccination were included in this study. Reported COVID-19 vaccine-associated cardiac adverse events were mainly myocarditis and pericarditis, most commonly seen in adolescent and young adult male individuals after mRNA vaccination. Reports of other events such as acute myocardial infarction, arrhythmia and stress cardiomyopathy were rare. Outcomes of post-vaccine myocarditis and pericarditis were good. Given the good vaccine efficacy and the high number of cases of infection, hospitalisation and death that could potentially be prevented, COVID-19 vaccine remains of overall benefit, based on the current available data.
Protein kinase C-θ (PKCθ) is a member of the novel PKC subfamily known for its selective and predominant expression in T lymphocytes where it regulates essential functions required for T cell ...activation and proliferation. Our previous studies provided a mechanistic explanation for the recruitment of PKCθ to the center of the immunological synapse (IS) by demonstrating that a proline-rich (PR) motif within the V3 region in the regulatory domain of PKCθ is necessary and sufficient for PKCθ IS localization and function. Herein, we highlight the importance of Thr
-Pro residue in the PR motif, the phosphorylation of which is key in the activation of PKCθ and its subsequent IS localization. We demonstrate that the phospho-Thr
-Pro motif serves as a putative binding site for the peptidyl-prolyl
isomerase (PPIase), Pin1, an enzyme that specifically recognizes peptide bonds at phospho-Ser/Thr-Pro motifs. Binding assays revealed that mutagenesis of PKCθ-Thr
-to-Ala abolished the ability of PKCθ to interact with Pin1, while Thr
replacement by a Glu phosphomimetic, restored PKCθ binding to Pin1, suggesting that Pin1-PKCθ association is contingent upon the phosphorylation of the PKCθ-Thr
-Pro motif. Similarly, the Pin1 mutant, R
A, failed to associate with PKCθ, suggesting that the integrity of the Pin1 N-terminal WW domain is a requisite for Pin1-PKCθ interaction.
docking studies underpinned the role of critical residues in the Pin1-WW domain and the PKCθ phospho-Thr
-Pro motif, to form a stable interaction between Pin1 and PKCθ. Furthermore, TCR crosslinking in human Jurkat T cells and C57BL/6J mouse-derived splenic T cells promoted a rapid and transient formation of Pin1-PKCθ complexes, which followed a T cell activation-dependent temporal kinetic, suggesting a role for Pin1 in PKCθ-dependent early activation events in TCR-triggered T cells. PPIases that belong to other subfamilies, i.e., cyclophilin A or FK506-binding protein, failed to associate with PKCθ, indicating the specificity of the Pin1-PKCθ association. Fluorescent cell staining and imaging analyses demonstrated that TCR/CD3 triggering promotes the colocalization of PKCθ and Pin1 at the cell membrane. Furthermore, interaction of influenza hemagglutinin peptide (HA
)-specific T cells with antigen-fed antigen presenting cells (APCs) led to colocalization of PKCθ and Pin1 at the center of the IS. Together, we point to an uncovered function for the Thr
-Pro motif within the PKCθ-V3 regulatory domain to serve as a priming site for its activation upon phosphorylation and highlight its tenability to serve as a regulatory site for the Pin1
isomerase.
Pseudomonas aeruginosa is a dreaded pathogen in many clinical settings. Its inherent and acquired antibiotic resistance thwarts therapy. In particular, derepression of the AmpC β-lactamase is a ...common mechanism of β-lactam resistance among clinical isolates. The inducible expression of ampC is controlled by the global LysR-type transcriptional regulator (LTTR) AmpR. In the present study, we investigated the genetic and structural elements that are important for ampC induction. Specifically, the ampC (PampC) and ampR (PampR) promoters and the AmpR protein were characterized. The transcription start sites (TSSs) of the divergent transcripts were mapped using 5′ rapid amplification of cDNA ends-PCR (RACE-PCR), and strong σ54 and σ70 consensus sequences were identified at PampR and PampC, respectively. Sigma factor RpoN was found to negatively regulate ampR expression, possibly through promoter blocking. Deletion mapping revealed that the minimal PampC extends 98 bp upstream of the TSS. Gel shifts using membrane fractions showed that AmpR binds to PampC in vitro whereas in vivo binding was demonstrated using chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR). Additionally, site-directed mutagenesis of the AmpR helix-turn-helix (HTH) motif identified residues critical for binding and function (Ser38 and Lys42) and critical for function but not binding (His39). Amino acids Gly102 and Asp135, previously implicated in the repression state of AmpR in the enterobacteria, were also shown to play a structural role in P. aeruginosa AmpR. Alkaline phosphatase fusion and shaving experiments suggest that AmpR is likely to be membrane associated. Lastly, an in vivo cross-linking study shows that AmpR dimerizes. In conclusion, a potential membrane-associated AmpR dimer regulates ampC expression by direct binding.
Cell population density-dependent regulation of gene expression is an important determinant of bacterial pathogenesis. Staphylococci have two quorum-sensing (QS) systems. The accessory gene regulator ...(
agr) is genus specific and uses a post-translationally modified peptide as an autoinducing signal. In the pathogens
Staphylococcus aureus and
Staphylococcus epidermidis,
agr controls the expression of a series of toxins and virulence factors and the interaction with the innate immune system. However, the role of
agr during infection is controversial. A possible second QS system of staphylococci,
luxS, is found in a variety of Gram-positive and Gram-negative bacteria. Importantly, unlike many QS systems described in Gram-negative bacteria,
agr and
luxS of staphylococci reduce rather than induce biofilm formation and virulence during biofilm-associated infection.
agr enhances biofilm detachment by up-regulation of the expression of detergent-like peptides, whereas
luxS reduces cell-to-cell adhesion by down-regulating expression of biofilm exopolysaccharide. Significant QS activity in staphylococci is observed for actively growing cells at a high cell density, such as during the initial stages of an infection and under optimal environmental conditions. In contrast, the metabolically quiescent biofilm mode of growth appears to be characterized by an overall low activity of the staphylococcal QS systems. It remains to be shown whether QS control in staphylococci represents a promising target for the development of novel antibacterial agents.
Cardiac sarcoma attached to pacemaker lead Sia, Ching‐Hui; Goh, Fang Qin; Kong, William Kok‐Fai ...
Journal of cardiac surgery,
20/May , Volume:
35, Issue:
5
Journal Article
Peer reviewed
Open access
Background and Aim
Cardiac sarcoma is a rare condition and may mimic atrial myxoma. We present a case report of a man with a cardiac sarcoma.
Method
Case report presentation.
Results
A 68‐year‐old ...man with a permanent pacemaker presented to us with a 4‐month history of breathlessness. Echocardiography revealed a large right atrial mass adherent to the pacemaker lead and a provisional diagnosis of atrial myxoma was made based on echocardiographic appearance. A 60 x 30 x 30 mm irregular lobulated tumour was surgically resected from the right atrium. Upon histopathologic examination, the tumour was consistent with an undifferentiated pleomorphic sarcoma.
Conclusion
Cardiac sarcomas have an extremely poor prognosis and more unfortunately this man developed a surgical site infection and died of acute mediastinitis. We discuss the presentation, imaging and current surgical approaches to cardiac sarcoma. Curative treatment is currently limited for this disease.
We reported that protein kinase C-η (PKCη) forms a novel (to our knowledge) signaling complex with the checkpoint inhibitory protein CTLA-4 in regulatory T cells (Tregs). This complex is required for ...the contact-dependent suppressive activity of Tregs, including suppression of antitumor immunity. However, the importance of PKCη in protective immunity mediated by T effector cells remains unclear. We used mice with germline or conditional Treg-specific deletion of
, the PKCη-encoding gene, to explore CD8
T cell-dependent antiviral immunity using the lymphocytic choriomeningitis virus Armstrong strain acute infection model as well as the in vitro activation of murine or human CD8
T cells. Five days following infection, germline
mice displayed enhanced viral clearance compared with control mice. Similarly,
Treg-specific conditional knockout mice also showed improved viral clearance and displayed enhanced expression of granzyme B and IFN-γ by both virus-specific and total CD8
T cells, demonstrating that enhanced viral clearance in germline
mice is caused by PKCη deficiency in Tregs and the resulting functional defect of
Tregs. In addition, purified
mouse CD8
T cells as well as
knockdown human CD8
T cells displayed intact, or even enhanced, T cell activation in vitro as measured by proliferation and expression of granzyme B and IFN-γ. Thus, global PKCη deletion does not impair overall CD8
T cell-mediated immunity, including antiviral immunity, implying that selective pharmacological PKCη inhibition could be safely used in vivo to inhibit undesired contact-dependent suppression by Tregs and, thus, enhance tumor-specific and, likely, virus-specific immunity.
Purpose
The purpose of this study was to develop a simple and effective percutaneous approach to create tricuspid regurgitation in swine.
Methods
Eleven pigs (71.68 ± 7.70 kg, 3 male) were involved ...in this study. A grasping forceps was introduced into the right ventricle through a steerable sheath under fluoroscopic guidance and used to disrupt the tricuspid valve apparatus by avulsing leaflet or chordae tendineae repeatedly. Transthoracic echocardiography and right ventricular angiography were used to evaluate the degree of tricuspid regurgitation created.
Results
Ten of the 11 pigs (90.91%) achieved severe tricuspid regurgitation and 1 (9.09%) obtained moderate tricuspid regurgitation immediately after the procedure. Heart rate of the pigs significantly increased immediately after tricuspid regurgitation creation compared to baseline (88.64 ± 23.24 vs. 76.00 ± 15.30 bpm,
P
= 0.02), but recovered to normal level at one month follow-up (77.09 ± 11.97 bpm,
P
= 0.85). The right atrium, tricuspid valve annulus, and right ventricle dilated obviously one month after tricuspid regurgitation creation (dimension changes: 3.01 ± 0.35 vs. 3.56 ± 0.40 cm,
P
= 0.02; 2.92 ± 0.36 vs. 3.37 ± 0.39 cm,
P
= 0.01; 3.06 ± 0.42 vs. 3.60 ± 0.47 cm,
P
= 0.03 respectively). Autopsy findings showed that rupture of leaflet and/or chordae tendineae finally led to the tricuspid regurgitation.
Conclusions
Severe tricuspid regurgitation can be created by a simple and effective percutaneous approach with a grasping forceps in swine model and right heart dilation can be observed consistently at one-month follow-up. This model will be valuable in pre-clinical studies for developing new tricuspid valve repair or replacement technique to treat severe tricuspid regurgitation.
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