Differential global structural changes in the core particle of yeast and mouse proteasome induced by ligand binding

Two clusters of configurations of the main proteolytic subunit β5 were identified by principal component analysis of crystal structures of the yeast proteasome core particle (yCP). The apo-cluster encompasses unliganded species and complexes with nonpeptidic ligands, and the pep-cluster comprises complexes with peptidic ligands. The murine constitutive CP structures conform to the yeast system, with the apo-form settled in the apo-cluster and the PR-957 (a peptidic ligand) complex in the pep-cluster. In striking contrast, the murine immune CP classifies into the pep-cluster in both the apo and the PR-957–liganded species. The two clusters differ essentially by multiple small structural changes and a domain motion enabling enclosure of the peptidic ligand and formation of specific hydrogen bonds in the pep-cluster. The immune CP species is in optimal peptide binding configuration also in its apo form. This favors productive ligand binding and may help to explain the generally increased functional activity of the immunoproteasome. Molecular dynamics simulations of the representative murine species are consistent with the experimentally observed configurations. A comparison of all 28 subunits of the unliganded species with the peptidic liganded forms demonstrates a greatly enhanced plasticity of β5 and suggests specific signaling pathways to other subunits.Among the many factors involved in protein degradation through the ubiquitin-proteasome pathway, the core particle (CP) 20S proteasome plays the key role of the protease component. With the regulatory particle (RP), it forms a complex that selectively degrades ubiquitin-protein conjugates (1, 2). The CP in eukaryotes is a multisubunit complex composed of four stacked heptameric rings: two identical outer rings formed by seven different α subunits and two identical inner rings formed by seven different β subunits. The α_1–7β_1–7β_1–7α_1–7 organization defines a cylindrical structure (3). The α-rings control substrate entry into the lumen of the particle, where it is processed at the peptidolytic active centers, which are located at the inner walls of the β rings, specifically at subunits β1, β2, and β5. These active subunits are characterized by an N-terminal Thr residue. The other four β subunits have unprocessed N-terminal propeptides and are enzymatically inactive.All three active subunits share a common peptide hydrolyzing mechanism with two main steps (4): (i) the positioning of the substrate peptide in the active site by antiparallel alignment in between segments 47–49 and 21 of the active β subunits and (ii) peptide bond cleavage initiated by a nucleophilic attack of the hydroxyl group of the N-terminal Thr1 on the carbonyl carbon atom of the scissile peptide. Sequence diversity among β subunits endows them with distinctive structural features and different specificity pockets (S1, S2, S3, etc.) where the substrate side chains (P1, P2, P3, etc.) are bound (5). Consequently, the correlation of structural features of the S1 pockets with the distinctive cleavage products has led to the association of β1, β2, and β5 with caspase-like, trypsin-like, and chymotrypsin-like activities, respectively (6).The catalytically active subunits are substituted in immune cells of vertebrate organisms by the immune β-subunits β1i, β2i, and β5i as part of an adaptive immune response. These substitutions cause substantial functional differences between the constitutive (cCP) and immuno (iCP) species, reflected in higher yield of peptides that are recognized by the major histocompatibility complex (MHC) class I generated by iCP (7). Additionally, it has been observed that iCP achieves higher degradation rates than cCP, in both in vitro and cellular assays (8–13).Some sequence variations between the constitutive and immune subunits provide explanations to the observed catalytic differences. Most conspicuously, and first seen in the eukaryotic proteasome crystal structure from yeast (yCP) (3) and confirmed by the murine constitutive and immune CP structures (mcCP and miCP) (14), Arg45 of the β1 subunit, located at the base of the S1 pocket, is replaced by leucine in β1i, thereby causing a specific change of the electrostatic milieu, in line with the observed low postacidic activity of the iCP (15).Despite the high sequence similarity between β5 subunits of mcCP and miCP including identical active sites, a peptidic α-β-epoxyketone inhibitor, PR-957, showed higher affinity to iCP by one order of magnitude. The structural comparison of cCP and iCP in their apo and PR-957 liganded states suggested an explanation. On binding of PR-957, the cCP β5 backbone displays significant deformations, whereas the iCP β5 backbone remains unchanged. This observation, together with our experience in constructing β5 models for virtual screening purposes, prompted us to reinvestigate the vast amount of structural data for yCP by a procedure that facilitates discovery of global changes: principal component analysis (PCA).We focus our study on the β5 subunit, because β5 inactivation in yeast renders a lethal phenotype (16) and therefore β5 harbors an essential enzymatic activity, and because almost all crystallographically defined complexes are liganded at their β5 active site.Here we present a detailed investigation of the wealth of yeast and mouse proteasome ligand complex structures that led us to embark on structural comparisons beyond the immediate vicinity of the ligands to obtain a view of the global response of the core particle of yeast and mouse proteasome to complex formation. This study (i) is evidence of the structural plasticity of the β, specifically β5, subunits; (ii) offers perspectives for the analysis of the structure-function relationship of the CP; and (iii) provides an aid for the design and development of ligands as drugs for this intensively studied target for cancer and autoimmune diseases.     

Radical Resection for Second EGFR-mutated Primary Lung Cancer Following Immune Checkpoint Inhibitor Monotherapy for Stage IV Lung Adenocarcinoma

A 78-year-old woman with multiple lung nodules, epithelial growth factor receptor (EGFR) exon 20 insertion mutations, and diagnosed with advanced lung adenocarcinoma (cT4N3M1a, stage IVA), was referred to our hospital. She received immune checkpoint inhibitor (ICI) therapy. The therapy showed remarkable antitumor effects; only a single nodule remained in the right upper lobe. The nodule was diagnosed as adenocarcinoma through a biopsy. We subsequently performed right upper lobectomy for multiple primary lung cancer (MPLC). The surgical specimen contained EGFR exon 19 deletion mutations and not exon 20 insertion mutations.     

The closing survival gap after liver transplantation for hepatocellular carcinoma in the United States

BackgroundSocio-economic inequalities among different racial/ethnic groups have increased in many high-income countries. It is unclear, however, whether increasing socio-economic inequalities are associated with increasing differences in survival in liver transplant (LT) recipients.MethodsAdults undergoing first time LT for hepatocellular carcinoma (HCC) between 2002 and 2017 recorded in the Scientific Registry of Transplant Recipients (SRTR) were included and grouped into three cohorts. Patient survival and graft survival stratified by race/ethnicity were compared among the cohorts using unadjusted and adjusted analyses.ResultsWhite/Caucasians comprised the largest group (n=9,006, 64.9%), followed by Hispanic/Latinos (n=2,018, 14.5%), Black/African Americans (n=1,379, 9.9%), Asians (n=1,265, 9.1%) and other ethnic/racial groups (n=188, 1.3%). Compared to Cohort I (2002-2007), the 5-year survival of Cohort III (2012-2017) increased by 18% for Black/African Americans, by 13% for Whites/Caucasians, by 10% for Hispanic/Latinos, by 9% for patients of other racial/ethnic groups and by 8% for Asians (All P values<0.05). Despite Black/African Americans experienced the highest survival improvement, their overall outcomes remained significantly lower than other ethnic∕racial groups (adjusted HR for death=1.20; 95%CI 1.05-1.36; P=0.005; adjusted HR for graft loss=1.21; 95%CI 1.08-1.37; P=0.002).ConclusionThe survival gap between Black/African Americans and other ethnic/racial groups undergoing LT for HCC has significantly decreased over time. However, Black/African Americans continue to have the lowest survival among all racial/ethnic groups.     

Role of hylan G-F 20 in treatment of osteoarthritis of the hip joint

OBJECTIVE: To study the efficacy of hylan G-F 20 in the treatment of osteoarthritis (OA) of the hip joint. DESIGN: Prospective within-group study. SETTING: Musculoskeletal rehabilitation clinic. PARTICIPANTS: Twenty-two patients (25 hips) with hip joint OA who had failed to find pain relief from conservative methods such as physical therapy, exercises, and steroid injections. Demographics included 14 men and 11 women (mean age, 56.4y), 21 of whom had mild to moderate OA and 4 of whom had severe OA of the hips. INTERVENTION: Each hip joint was injected with 2mL of hylan G-F 20 at 2, 3, and 4 weeks and fluoroscopic lavage with 100mL of normal saline at week 1. All patients had standard hip exercise regimen after the injection. MAIN OUTCOME MEASURES: American Academy of Orthopaedic Surgeons (AAOS) Lower Limb Core Scale score and visual numeric pain score. RESULTS: At 1-year follow-up, the AAOS Lower Limb Core Scale score improved from a preinjection mean of 44.2 to a follow-up mean of 86.1 (P<.05). The mean visual numeric pain score improved from a preinjection mean of 8.7 (range, 6.4-10) to a follow-up mean of 2.3 (range, 0-7.2). The overall success rate was 84%. In patients with mild to moderate OA, the mean pain score decreased from a preinjection value of 7.8 to a follow-up value of 1.7. The success rate was 90.5% in that subgroup. In patients with severe OA, the mean pain score decreased from a preinjection value of 9.1 to a follow-up value of 3.8. The success rate was 50% in that subgroup. There were no complications related to the injection. CONCLUSION: Use of hylan G-F 20 injection is a viable option for treatment of mild to moderate OA of the hip joint.     

A cluster analysis model for caries risk assessment

Cluster analysis was applied to determine, the natural grouping of individuals, among sixty 8-10-year-old children, and to identify the most significant set of markers for risk assessment. The risk clusters were obtained with initial clinical and bacteriological measurements including dmf + DMFS, active caries, mutans streptococci and lactobacilli counts in plaque or saliva on two media, and Snyder's test results. The morbidity clusters were constructed with the final clinical indexes and incidence after 18 months (dependent variables). A risk cluster was identified that included the following significant initial variables; dmf + DMFS, active caries, counts of mutans streptococci from plaque on TSY20B and lactobacilli in saliva, and Snyder's test results. This set of markers identified 86% of the children at high risk who developed high morbidity, as well as 94% of children in the low-risk cluster who developed low or no caries. The results of this investigation provide the basis to develop a system for caries risk assessment.     

Effects of antihypertensives on plasma lipids and lipoprotein metabolism

There is good epidemiologic evidence that hypertension is associated with a high risk of cardiovascular disease. However, primary intervention trials have failed to demonstrate that a reduction in blood pressure in hypertensive patients reduces morbidity and mortality from cardiac events. Since various antihypertensive drugs adversely affect lipoprotein metabolism, these drugs may increase associated coronary risk and offset the beneficial effects of lowering blood pressure. This article reviews the effects of various antihypertensive drugs on plasma lipids, lipoproteins, and apolipoproteins. They can be summarized as follows: thiazide-type diuretics cause a marked elevation of plasma triglycerides and very low-density lipoprotein (VLDL) and minor increases in total cholesterol and low-density lipoprotein (LDL), but have little effects on high-density lipoprotein (HDL). The nonselective β-blockers do not significantly affect total cholesterol and LDL, but increase total triglycerides and VLDL and decrease HDL. The changes in plasma lipids and lipoproteins caused by cardioselective β-blockers and β-blockers with intrinsic sympathomimetic activity are qualitatively similar but less pronounced. Calcium antagonists and angiotensin-converting enzyme inhibitors appear to have no significant effects on plasma lipids. α₁-inhibitors reduce total triglycerides, total cholesterol, VLDL, and LDL and increase HDL. The possible mechanisms by which antihypertensive drugs affect cellular lipid metabolism (e.g., LDL receptor, lipid synthesis, lipoprotein lipase, lecithin cholesteryl acyltransferase, acylcholesteryl acyltransferase, and cholesteryl ester hydrolase) are described. The clinical significance of changes in blood lipids and cellular lipid metabolism caused by antihypertensive drugs is not yet totally clear. Nevertheless, before antihypertensive drug treatment is initiated, blood lipid levels should be measured to identify preexisting hyperlipidemia. Blood lipoprotein levels should be monitored during long-term antihypertensive therapy to reconsider the therapeutic regimen if adverse lipid changes are observed.     

20(S)-原人参二醇氨基酸衍生物的合成

目的对20（S）-原人参二醇进行结构修饰,合成其氨基酸衍生物,从而提高药物的水溶性。方法以二环己基碳化二亚胺为催化剂、吡啶为溶剂进行反应,合成20（S）-原人参二醇的氨基酸衍生物。结果得到20（S）-原人参二醇的氨基酸衍生物14个,其结构通过1H-NMR、13C-NMR图谱进行确证,同时总结了20（S）-原人参二醇的氨基酸衍生物的合成规律。结论本方法合成工艺简单易行,操作简便,适合工业化生产,所得产物的水溶性较合成前有所提高,有利于提高生物利用度。     

白细胞介素-20与急性缺血性脑卒中的关系

急性缺血性脑卒中（acute ischemic stroke, AIS）是最常见的卒中类型,致残致死率高,在其病理生理过程中,炎症反应发挥着重要作用。白细胞介素（interleukin, IL）-20通过促进炎症反应、促进血管生成,参与类风湿性关节炎、银屑病、癌症、动脉粥样硬化等疾病的发生发展。在中枢神经系统中,IL-20参与神经炎症反应,当脑组织缺氧可上调体内IL-20水平,诱导相关促炎性因子表达,从而促进炎症反应,加重AIS。该文根据近几年国内外相关研究,从炎症反应与AIS的关系以及IL-20的来源、作用机制、IL-20在中枢神经系统疾病中的作用等方面进行综述,探讨IL-20与AIS的关系,为预测AIS的发展、预后,以及AIS的治疗提供参考。 [国际神经病学神经外科学杂志, 2023, 50(4): 76-79]