The E3 Ubiquitin Protein Ligase LINCR Amplifies the TLR-Mediated Signals through Direct Degradation of MKP1

Toll-like receptors (TLRs) induce innate immune responses through activation of intracellular signaling pathways, such as MAP kinase and NF-κB signaling pathways, and play an important role in host defense against bacterial or viral infections. Meanwhile, excessive activation of TLR signaling leads to a variety of inflammatory disorders, including autoimmune diseases. TLR signaling is therefore strictly controlled to balance optimal immune response and inflammation. However, its balancing mechanisms are not fully understood. In this study, we identified the E3 ubiquitin ligase LINCR/ NEURL3 as a critical regulator of TLR signaling. In LINCR-deficient cells, the sustained activation of JNK and p38 MAPKs induced by the agonists for TLR3, TLR4, and TLR5, was clearly attenuated. Consistent with these observations, TLR-induced production of a series of inflammatory cytokines was significantly attenuated, suggesting that LINCR positively regulates innate immune responses by promoting the activation of JNK and p38. Interestingly, our further mechanistic study identified MAPK phosphatase-1 (MKP1), a negative regulator of MAP kinases, as a ubiquitination target of LINCR. Thus, our results demonstrate that TLRs fine-tune the activation of MAP kinase pathways by balancing LINCR (the positive regulator) and MKP1 (the negative regulator), which may contribute to the induction of optimal immune responses.

LLPS of SQSTM1/p62 and NBR1 as outcomes of lysosomal stress response limits cancer cell metastasis

Liquid droplet has emerged as a flexible intracellular compartment that modulates various cellular processes. Here, we uncover an antimetastatic mechanism governed by the liquid droplets formed through liquid-liquid phase separation (LLPS) of SQSTM1/p62 and neighbor of BRCA1 gene 1 (NBR1). Some of the tyrosine kinase inhibitors (TKIs) initiated lysosomal stress response that promotes the LLPS of p62 and NBR1, resulting in the spreading of p62/NBR1 liquid droplets. Interestingly, in the p62/NBR1 liquid droplet, degradation of RAS-related C3 botulinum toxin substrate 1 was accelerated by cellular inhibitor of apoptosis protein 1, which limits cancer cell motility. Moreover, the antimetastatic activity of the TKIs was completely overridden in p62/NBR1 double knockout cells both in vitro and in vivo. Thus, our results demonstrate a function of the p62/NBR1 liquid droplet as a critical determinant of cancer cell behavior, which may provide insight into both the clinical and biological significance of LLPS.

Tryptophan-Starved Human Cells Overexpressing Tryptophanyl-tRNA Synthetase Enhance High-Affinity Tryptophan Uptake via Enzymatic Production of Tryptophanyl-AMP

Our previous study demonstrated that L-tryptophan (Trp)-depleted cells display a marked enhancement in Trp uptake facilitated by extracellular tryptophanyl-tRNA synthetase (TrpRS). Here, we show that Trp uptake into TrpRS-overexpressing cells is also markedly elevated upon Trp starvation. These findings indicate that a Trp-deficient condition is critical for Trp uptake, not only into cells to which TrpRS protein has been added but also into TrpRS-overexpressing cells. We also show that overexpression of TrpRS mutants, which cannot synthesize tryptophanyl-AMP, does not promote Trp uptake, and that inhibition of tryptophanyl-AMP synthesis suppresses this uptake. Overall, these data suggest that tryptophanyl-AMP production by TrpRS is critical for high-affinity Trp uptake.

LPE growth of Tb3Al5O12:Ce single crystalline film converters for WLED application

Efficient phosphor converters for white LEDs based on TbAG:Ce single crystalline films, LPE grown onto YAG substrates, is developed. The film-substrate interface of TbAG:Ce SCF/YAG epitaxial structures was studied using high-resolution STEM images.

Tryptophan Depletion Modulates Tryptophanyl-tRNA Synthetase-Mediated High-Affinity Tryptophan Uptake into Human Cells

The novel high-affinity tryptophan (Trp)-selective transport system is present at elevated levels in human interferon-γ (IFN-γ)-treated and indoleamine 2,3-dioxygenase 1 (IDO1)-expressing cells. High-affinity Trp uptake into cells results in extracellular Trp depletion and immune suppression. We have previously shown that both IDO1 and tryptophanyl-tRNA synthetase (TrpRS), whose expression levels are increased by IFN-γ, have a crucial function in high-affinity Trp uptake into human cells. Here, we aimed to elucidate the relationship between TrpRS and IDO1 in high-affinity Trp uptake. We demonstrated that overexpression of IDO1 in HeLa cells drastically enhances high-affinity Trp uptake upon addition of purified TrpRS protein to uptake assay buffer. We also clarified that high-affinity Trp uptake by Trp-starved cells is significantly enhanced by the addition of TrpRS protein to the assay buffer. Moreover, we showed that high-affinity Trp uptake is also markedly elevated by the addition of TrpRS protein to the assay buffer of cells overexpressing another Trp-metabolizing enzyme, tryptophan 2,3-dioxygenase (TDO2). Taken together, we conclude that Trp deficiency is crucial for high-affinity Trp uptake mediated by extracellular TrpRS.

Topological Kagome Magnet Co3Sn2S2 Thin Flakes with High Electron Mobility and Large Anomalous Hall Effect

Magnetic Weyl semimetals attract considerable interest not only for their topological quantum phenomena but also as an emerging materials class for realizing quantum anomalous Hall effect in the two-dimensional limit. A shandite compound Co₃Sn₂S₂ with layered kagome-lattices is one such material, where vigorous efforts have been devoted to synthesize the two-dimensional crystal. Here, we report a synthesis of Co₃Sn₂S₂ thin flakes with a thickness of 250 nm by chemical vapor transport method. We find that this facile bottom-up approach allows the formation of large-sized Co₃Sn₂S₂ thin flakes of high-quality, where we identify the largest electron mobility (∼2600 cm² V^-1 s^-1) among magnetic topological semimetals, as well as the large anomalous Hall conductivity (∼1400 Ω^-1 cm^-1) and anomalous Hall angle (∼32%) arising from the Berry curvature. Our study provides a viable platform for studying high-quality thin flakes of magnetic Weyl semimetal and stimulate further research on unexplored topological phenomena in the two-dimensional limit.

Pro-apoptotic functions of TRAF2 in p53-mediated apoptosis induced by cisplatin

Tumor necrosis factor receptor-associated factor 2 (TRAF2) is an essential component of tumor necrosis factor-α (TNF-α) signaling that regulates nuclear factor-κB (NF-κB) and c-Jun N-terminal kinase (JNK) pathways, and compelling evidence has demonstrated that TRAF2 suppresses TNF-α-induced cytotoxicity. On the other hand, it has been reported that oxidative stress-induced cytotoxicity is potentiated by TRAF2, indicating that TRAF2 both positively and negatively regulates stress-induced cytotoxicity in a context-specific manner. However, the causal role of TRAF2 in DNA damage response (DDR) remains to be explored. In this study, we assessed the function of TRAF2 in DDR induced by cisplatin, a representative DNA-damaging agent, and found that TRAF2 exerts pro-apoptotic activity through p53-dependent mechanisms at least in human fibrosarcoma cell line HT1080. TRAF2 deficient cells exhibit significant resistance to cell death induced by cisplatin, accompanied by the reduction of both p53 protein level and caspase-3 activation. Moreover, cisplatin-induced JNK activation was attenuated in TRAF2-deficient cells, and pharmacological inhibition of JNK signaling suppressed p53 stabilization. These results suggest that TRAF2 promotes p53-dependent apoptosis by activating the JNK signaling cascade in HT1080 cells. Thus, our data demonstrate a novel function of TRAF2 in cisplatin-induced DDR as a pro-apoptotic protein.

Non-canonical functions of human cytoplasmic tyrosyl-, tryptophanyl- and other aminoacyl-tRNA synthetases

Aminoacyl-tRNA synthetases catalyze the aminoacylation of their cognate tRNAs. Here we review the accumulated knowledge of non-canonical functions of human cytoplasmic aminoacyl-tRNA synthetases, especially tyrosyl- (TyrRS) and tryptophanyl-tRNA synthetase (TrpRS). Human TyrRS and TrpRS have an extra domain. Two distinct cytokines, i.e., the core catalytic "mini TyrRS" and the extra C-domain, are generated from human TyrRS by proteolytic cleavage. Moreover, the core catalytic domains of human TyrRS and TrpRS function as angiogenic and angiostatic factors, respectively, whereas the full-length forms are inactive for this function. It is also known that many synthetases change their localization in response to a specific signal and subsequently exhibit alternative functions. Furthermore, some synthetases function as sensors for amino acids by changing their protein interactions in an amino acid-dependent manner. Further studies will be necessary to elucidate regulatory mechanisms of non-canonical functions of aminoacyl-tRNA synthetases in particular, by analyzing the effect of their post-translational modifications.

Interaction of Np(v) with borate in alkaline, dilute-to-concentrated, NaCl and MgCl2 solutions

The formation of sparingly soluble ternary Na/Mg–Np(v)–borate(s) solid phases in alkaline, dilute-to-concentrated, NaCl and MgCl₂ solutions is confirmed by a multimethod experimental approach.

Pro-caspase-3 protects cells from polymyxin B-induced cytotoxicity by preventing ROS accumulation

Polymyxin B (PMB), a last-line antibiotic used against antibiotic-resistant superbugs, causes undesirable cytotoxic side effects. However, its mechanisms remain unknown. In this study, we unexpectedly found that caspase-3, a main executor of apoptosis, plays a protective role in PMB-induced cytotoxicity. Caspase-3 knockout (KO) cells exhibited higher susceptibility to PMB-induced cytotoxicity compared with wild-type (WT) cells, accompanied by increased levels of reactive oxygen species (ROS). Interestingly, co-treatment with the antioxidant N-acetylcysteine (NAC) rescued cell viability to a similar extent as WT cells. Furthermore, PMB failed to facilitate the processing of inactive caspase-3 (pro-caspase-3) into active forms, suggesting that pro-caspase-3 nonenzymatically suppresses PMB-driven ROS accumulation and its cytotoxicity. Thus, our findings that demonstrate the potential ability of PMB to stimulate ROS generation, but which is normally masked by pro-caspase-3-dependent mechanisms, may provide novel insights into the mechanisms of PMB-induced side effects.

Tryptophanyl-tRNA synthetase mediates high-affinity tryptophan uptake into human cells

The tryptophan (Trp) transport system has a high affinity and selectivity toward Trp, and has been reported to exist in both human and mouse macrophages. Although this system is highly expressed in interferon-γ (IFN-γ)-treated cells and indoleamine 2,3-dioxygenase 1 (IDO1)-expressing cells, its identity remains incompletely understood. Tryptophanyl-tRNA synthetase (TrpRS) is also highly expressed in IFN-γ-treated cells and also has high affinity and selectivity for Trp. Here, we investigated the effects of human TrpRS expression on Trp uptake into IFN-γ-treated human THP-1 monocytes or HeLa cells. Inhibition of human TrpRS expression by TrpRS-specific siRNAs decreased and overexpression of TrpRS increased Trp uptake into the cells. Of note, the TrpRS-mediated uptake system had more than hundred-fold higher affinity for Trp than the known System L amino acid transporter, promoted uptake of low Trp concentrations, and had very high Trp selectivity. Moreover, site-directed mutagenesis experiments indicated that Trp- and ATP-binding sites, but not tRNA-binding sites, in TrpRS are essential for TrpRS-mediated Trp uptake into the human cells. We further demonstrate that the addition of purified TrpRS to cell culture medium increases Trp uptake into cells. Taken together, our results reveal that TrpRS plays an important role in high-affinity Trp uptake into human cells.

Treatment of mediastinitis arising after replacement of the ascending aorta

Mediastinitis due to graft infection is a serious and potentially lethal complication associated with replacement of the ascending aorta. We present the case of a 67-year-old man with this condition for the aneurysm and chronic dissection. Mediastinitis and sepsis were diagnosed and debridement, irrigation with povidone solution and omental transposition were performed successfully. Continuous closed irrigation prior to omental transposition without replacement of the infected graft is useful for treating mediastinitis after ascending aortic or arch replacement.

[A case of quadricuspid aortic valve associated with mitral regurgitation]

A case of a 60-year-old man associated with quadricuspid aortic valve and mitral regurgitation is reported. The aortic valve consisted of three larger cusps and a small accessory cusp situated between the right and the non-coronary cusps. The aortic regurgitation resulted from malcoaptation of the four cusps and the mitral regurgitation resulted from annulus dilatation and thickening of the anterior leaflet. The surgical treatment was performed successfully by the aortic and mitral valve replacements with St. Jude Medical valves. The patient is doing well fifteen months postoperatively. Sixteen Japanese cases of quadricuspid aortic valve which were corrected surgically are reviewed.

[A case who developed mechanical pulsus alternans after Bentall's operation for annuloaortic ectasia]

Left ventricular pulsus alternans developed immediately after Bentall's operation in a 37-year-old patient with Marfan's syndrome accompanied by severe left heart failure due to annuloaortic ectasia. Echocardiographic examination suggested that this symptom was caused by alternating contractility based on left ventricular myocardial failure. Left heart failure disappeared early after operation, but pulsus alternans persisted until 7 months after operation, when EDVI decreased from 225 ml/m2 to 113 ml/m2.

[Successful repair of an acute type A dissection during pregnancy]

We report a successful repair of an acute type-A aortic dissection during pregnancy. A 29-year-old pregnant woman in the 32 weeks of gestation with Marfan Syndrome was admitted to our hospital for the treatment of anterior chest and back pains. An urgent aortogram through pulmonary artery revealed an aortic dissection beginning from the ascending aorta to the aortic bifurcation. On the following day, an emergent Cesarean section was performed and a baby weighing 1944 g was delivered. Thereafter, cardiopulmonary bypass was instituted and the ascending aorta was opened. An intimal tear was found 2 cm above the aortic valve. The dissected space was closed with reinforcement of Teflon felt strip. A Dacron gusset was sutured to restore aortic continuity. During the weaning from the CPB, a retrograde aortic dissection developed and the heart became arrested. Therefore we immediately converted the aortic perfusion cannula from the right external iliac artery to graft of the ascending aorta, and the operation was completed successfully with a good recovery of the heart. The mother and her child have been alive and well for 3 years and 5 months after the operation.

[Subdural hematoma following surgery of an aneurysm of the diverticulum of the ductus arteriosus with partial cardiopulmonary bypass]

The patient was a 72-year-old man, who had an aneurysm of the descending thoracic aorta with left recurrent laryngeal nerve palsy identified by preoperative examination. Thoracotomy revealed an aneurysm of a diverticulum of the ductus arteriosus measuring 2.7 X 3.4 cm. The aneurysm was excised under partial cardiopulmonary bypass and the defect of the aortic wall was repaired with a Dacron patch. Two days after surgery, he developed mild deterioration of consciousness and right hemiparesis. An acute subdural hematoma which covered the left frontal, parietal, and temporal lobes was found by CT examination. Craniotomy was performed 16 days after the previous surgery, and 100 g of hematoma was removed. Following craniotomy, complete recovery of cerebral function was observed. This appears to be a valuable report of a patient who developed acute subdural hematoma following surgery of aneurysms of the descending thoracic aorta with partial cardiopulmonary bypass.

[Successful mitral valve replacement for infective endocarditis in pregnancy]

A 27 weeks' pregnant women exhibited infective endocarditis due to alpha-streptococcus. As echocardiography showed vegetations on both mitral leaflets, cesarean section was performed at 35 weeks' gestation and a healthy male infant weighing 2,430 g was delivered. Antibiotic therapy was continued for fever after the cesarean section but macrohematuria and Osler's nodes developed. Emergency mitral valve replacement was performed successfully despite the presence of active infective endocarditis. She was discharged after completion of a 10-week course of antibiotic therapy.

[Effects of cardioplegic solutions on coronary artery and myocardium--comparison of the glucose-insulin-potassium solution and the St. Thomas' Hospital cardioplegic solution]

Effects of two cardioplegic solutions on coronary artery and myocardium were experimentally investigated in three types of preparations. In the isolated perfused guinea pig heart, infusion of Glucose-Insulin-Potassium (GIK) solution (37 degrees C) caused contraction of coronary artery, whereas the St. Thomas' Hospital cardioplegic solution (37 degrees C) produced vasodilation. At the end of 30 minutes reperfusion after continuous infusion of cardioplegic solution, the St. Thomas' Hospital cardioplegic solution produced a greater recovery of cardiac function than GIK solution. In the isolated pig coronary artery, vasoconstriction caused by high potassium content was diminished by addition of magnesium in concentration dependent manner. In the electrophysiological examination, the membrane potential of the guinea pig papillary muscle was recorded by means of conventional glass microelectrodes. Though GIK solution produced greater depolarization of resting membrane potential than the St. Thomas' Hospital cardioplegic solution, effects of the two different cardioplegic solution was not so different after reperfusion of Tyrode solution. The St. Thomas' Hospital cardioplegic solution resulted in greater recovery of contracting activity after reperfusion than GIK solution. These data suggest that GIK solution causes coronary vasoconstriction and has deleterious effects on myocardium and that the St. Thomas' Hospital cardioplegic solution has a vasodilating action and produced a greater myocardial protection than GIK solution.

Functional and metabolic protection of the neonatal myocardium from ischemia. Insufficient protection by cardioplegia

The effects of ischemia and cardiac arrest by cardioplegia on the mechanical function and energy metabolism of the ventricular myocardium of the neonatal guinea pig were investigated in the isolated perfused heart preparation and compared with these effects in the adult guinea pig. Whereas reperfusion after ischemia resulted in better recovery of mechanical function and a higher adenosine triphosphase content in the neonatal myocardium than in the adult, recovery from cardiac arrest induced by St. Thomas' Hospital cardioplegic solution was not as good in the neonatal myocardium as in the adult. Contracture developed in the neonatal myocardium on administration of the cardioplegic solution, but did not in the adult. This was considered to be the reason that the protective effect of the cardioplegic solution was inferior in the neonatal myocardium to that in the adult.

Difference in the mechanical response to a cardioplegic solution observed between the neonatal and the adult guinea pig myocardium

We attempted in two types of preparations to delinate the difference in responses to St. Thomas' Hospital cardioplegic solution between the neonatal and the adult guinea pig myocardium. Isolated guinea pig hearts were perfused with Langendorff's method and the tension of the papillary muscle of the right ventricle was recorded. Continuous infusion of St. Thomas' Hospital cardioplegic solution (37 degrees C) for 30 minutes resulted in a significantly higher elevation of the resting tension (development of contracture) in the neonatal myocardium than in the adult. The recovery of normal contractile tension after the resumption of perfusion with normal Krebs-Ringer bicarbonate solution was smaller in the neonate with increases in the myocardial water and calcium contents. The membrane potential of the papillary muscle preparation was recorded by means of conventional glass microelectrodes. There was no significant difference in the control values of the resting membrane potential and in the degree of depolarization during exposure to St. Thomas' Hospital cardioplegic solution between the neonate and the adult. Thus the greater elevation of the resting tension produced in the neonatal myocardium by St. Thomas' Hospital cardioplegic solution was not due to a greater depolarization of the surface membrane.

Successful resection of cardiac fibroma with ventricular tachycardia

A 22-year-old male was admitted to Niigata University Hospital complaining of palpitation. Echocardiogram, cineangiogram, and Holter electrocardiogram revealed a cardiac fibroma complicated by ventricular tachycardia (VT). The tumor extended from the interventricular septum to the anterior surface of the left ventricle, and an electrophysiological study demonstrated that the focus of the VT was situated at the tumor. The tumor was excised successfully. The patient is doing well two years after operation without any antiarrhythmic drugs, and VT has not recurred.