褐飞虱G蛋白β亚基基因的功能分析

【目的】本研究旨在鉴定褐飞虱Nilaparvata lugens G蛋白β亚基基因(NlGβ)并分析其功能,以期为基于RNAi技术防治褐飞虱提供潜在的新靶标基因。【方法】利用PCR克隆并验证褐飞虱NlGβ的编码序列(coding sequence,CDS)并进行生物信息学分析;基于褐飞虱不同发育阶段(卵、1-5龄若虫和雌雄成虫)和成虫不同组织(头、足、肠道、表皮、脂肪体、雌性生殖系统和雄性生殖系统)转录组表达谱分析NlGβ的时空表达模式;通过对2和5龄褐飞虱若虫进行显微注射dsRNA沉默NlGβ,观测个体和雌性生殖系统表型,统计存活率、单雌产卵量和卵孵化率,利用透射电子显微镜技术观察侧输卵管膨大区。【结果】褐飞虱NlGβ(GenBank登录号:XP_022200908.1)的CDS长948 bp,NlGβ蛋白包含7个WD40结构域和4个WD_REPEATS_1基序,是一个较为保守的蛋白,除了直翅目昆虫外,来源于其他昆虫目中的NlGβ同源蛋白能很好地聚集在同一簇进化分支上。NlGβ的表达量在1-3龄若虫期呈现周期性变化,在5龄雌若虫和雌成虫中的表达量高于5龄雄若虫和雄成虫中的;NlGβ在成虫不同组织中都表达,但在脂肪体中表达量最高,在雌性生殖系统中的表达量高于雄性生殖系统中的。沉默褐飞虱2龄若虫NlGβ,出现蜕皮困难的现象,导致存活率较ds GFP对照组显著降低;沉默褐飞虱5龄若虫NlGβ,雌成虫腹部异常膨大,卵巢发育畸形,单雌产卵量较对照组显著下降,卵无法孵化,侧输卵管膨大区内分泌物增加,上皮细胞发生降解。【结论】NlGβ与褐飞虱的生长发育和雌虫的繁殖密切相关。

Structure and Function of ε-Subunit of ATP Synthase in Higher Plant Chloroplast

The ε-subunit is the smallest subunit of chloroplast ATP synthase, and is known to inhibit ATPase activity in isolated CF1-ATPase. As a result ε is sometimes called an inhibitory subunit. In addition, and perhaps more importantly, the ε -subunit is essential for the coupling of proton translocation to ATP synthesis (as proton gate). The relation between the structure and function of ε -subunit of ATP synthase in higher plant chloroplast has been studied by molecular biological methods such as site-directed mu-tagenesis and truncations for C- or N-terminus of ε -subunit. The results showed that: (1) Thr42 of ε-subunit is important for its structure and function; (2) compared with the ε-subunit in E.coli, the ε-subunit of chloroplast ATP synthase is more sensitive to C- or N-terminus truncations.

Na^+/K^+-ATPase α-subunit in swimming crab Portunus trituberculatus: molecular cloning, characterization, and expression under low salinity stress

Na^＋/K^＋-ATPases are membrane-associated enzymes responsible for the active transport of Na^＋ and K^＋ ions across cell membranes, generating chemical and electrical gradients. These enzymes＇ α-subunit provides catalytic function, binding and hydrolyzing ATP, and itself becoming phosphorylated during the transport cycle. In this study, Na^＋/K^＋-ATPase α-subunit eDNA was cloned from gill tissue of the swimming crab Portunus trituberculatus by reverse-transcription polymerase chain reaction （RT-PCR） and rapid amplification of eDNA end methods. Analysis of the nucleotide sequence revealed that the eDNA had a full-length of 3 833 base pairs （bp）, with an open reading frame of 3 120 bp, 5＇ untranslated region （UTR） of 317 bp, and 3＇ UTR of 396 bp. The sequence encoded a 1 039 amino acid protein with a predicted molecular weight of 115.57 kDa and with estimated pI of 5.21. It was predicted here to possess all expected features of Na^＋/K^＋-ATPase members, including eight transmembrane domains, putative ATP-binding site, and phosphorylation site. Comparison of arnino acid sequences showed that the P. tritubereulatus α-subunit possessed an overall identity of 75%-99% to that of other organisms. Phylogenetic analysis revealed that this α-subunit was in the same category as those of crustaceans. Quantitative real-time RT-PCR analysis indicated that this α-subunit＇s transcript were most highly expressed in gill and lowest in muscle. RT-PCR analysis also revealed that α-subunit expression in crab gill decreased after 2 and 6 h, but increased after 12, 24, 48, and 72 h. In addition, α-subunit expression in hepatopancreas of crab decreased after 2-72 h. These facts indicated that the crab＇s Na^＋/K^＋-ATPase α-subunit was potentially involved in the observed acute response to low salinity stress.

No association of G-protein beta polypeptide 3 polymorphism with irritable bowel syndrome: Evidence from a meta-analysis

AIM: To clarify the associations between G-protein beta polypeptide 3 (GNB3) C825T polymorphism and risk of the irritable bowel syndrome (IBS) by a meta-analysis.

Genetic predisposition to essential hypertension in a Mongolian population Detecting the C825T polymorphism of the G-protein beta 3 subunit gene

BACKGROUND： The prevalences of hypertension, cerebrovascular diseases, etc. are higher in Mongolian population because of the influence of various factors including genetics, geography, diet, etc. Therefore, it is helpful for prevention to develop researches on the genetics of various diseases including hypertension in Mongolian population. OBJECTIVE： To analyze the association between C825T polymorphisms of G-protein beta 3 subunit gene （GNB3）, the important candidate gene of various disease of cardiovascular system, and Mongolian patients with essential hypertension. DESIGN： A comparative observation. SETTINGS： Department of Neurology, the First Affiliated Hospital of Inner Mongolia Medical College; Wulate Houqi Red Cross Society. PARTICIPANTS： Totally 267 Mongolian residents, whose blood relations of 3 generations were all Mongolians, were selected from Wulate Houqi, Inner Mongolia. The patients were screened based on the diagnostic standard of hypertension set by WHO in 1999, and the enrolled subjects were divided into two groups according to the level of blood pressure： ① Normal blood pressure group （n =124）： 64 males and 60 females, systolic blood pressure （SBP） 〈 140 mm Hg （1 mm Hg=0.133 kPa）, diastolic blood pressure （DBP） 〈 90 mm Hg;②Essential hypertension group （n =143）： 71 males and 72 females, including 60 patients with simple high SBP （SBP ranged 145 to 195 mm Hg, whereas DBP 〈 90 mm Hg）. METHODS： Peripheral venous blood （5 mL） was drawn from all the subjects, the genome DNA was extracted, and the polymorphisms of the GNB3 C825T genotype were detected with the Sequenom system. Polyrnerase chain reaction （PCR） experiment and SNP detection were performed in Beijing Huada gene laboratory. Then the univariate analysis of variance was applied in the sample comparison among groups, and the chi-square test was used to compare the genotypes and allele frequencies. The odd ratio （OR） and 95% confidence interval （CI） were calculated. MAIN OUTCOME MEASURES： The distributions of GNB3 C825T genotypes and alleles were observed. RESULTS： All the 267 Mongolian subjects were involved in the analysis of results.① GNB3 C825T genotypes： In Mongolian population, the frequencies of CC, CT and TT genotypes at GNB3 C825T site in the essential hypertension group （48%, 41%, 11%） were not obvious different from those in the normal blood pressure group （43%, 47%, 10%, x^2 =0.162, P =0.688; OR：1.176, 95%CI： 0.533- 2.592）, whereas there were also no obvious differences between the simple high SBP group （57%, 35%, 8%） and the normal blood pressure group （x^2 =0.733, P =0.392; OR：1.957, 95%CI： 0.623- 6.143）. ②GNB3 C825T alleles： In Mongolian population, The frequencies of C and T alleles in the essential hypertension group （69%, 31%） were not obviously different from those in the normal blood pressure group （67%, 33%, x^2 =0.094, P = 0.759; OR：0.945, 95%CI：0.657 - 1.358）, whereas there were also no obvious differences between the simple high SBP group （74%, 26%） and the normal blood pressure group （ x^2 =2.133, P =0.144; OR：0.697, 95%CI： 0.428- 1.133）. CONCLUSION： GNB3 C825T site may be not a genetic marker of essential hypertension and simple high SBP in Mongolian population.

G-protein coupled receptors and synaptic plasticity in sleep deprivation

Insufficient sleep has been correlated to many physiological and psychoneurological disorders.Over the years,our understanding of the state of sleep has transcended from an inactive period of rest to a more active state involving important cellular and molecular processes.In addition,during sleep,electrophysiological changes also occur in pathways in specific regions of the mammalian central nervous system(CNS).Activity mediated synaptic plasticity in the CNS can lead to long-term and sometimes permanent strengthening and/or weakening synaptic strength affecting neuronal network behaviour.Memory consolidation and learning that take place during sleep cycles,can be affected by changes in synaptic plasticity during sleep disturbances.G-protein coupled receptors(GPCRs),with their versatile structural and functional attributes,can regulate synaptic plasticity in CNS and hence,may be potentially affected in sleep deprived conditions.In this review,we aim to discuss important functional changes that can take place in the CNS during sleep and sleep deprivation and how changes in GPCRs can lead to potential problems with therapeutics with pharmacological interventions.

New insights into sodium transport regulation in the distal nephron:Role of G-protein coupled receptors

The renal handling of Na^+ balance is a major determinant of the blood pressure(BP) level. The inability of the kidney to excrete the daily load of Na+ represents the primary cause of chronic hypertension. Among the different segments that constitute the nephron, those present in the distal part(i.e., the cortical thick ascending limb, the distal convoluted tubule, the connecting and collecting tubules) play a central role in the fine-tuning of renal Na^+ excretion and are the target of many different regulatory processes that modulate Na^+ retention more or less efficiently. G-protein coupled receptors(GPCRs) are crucially involved in this regulation and could represent efficient pharmacological targets to control BP levels. In this review, we describe both classical and novel GPCR-dependent regulatory systems that have been shown to modulate renal Na^+ absorption in the distal nephron. In addition to the multiplicity of the GPCR that regulate Na^+ excretion, this review also highlights the complexity of these different pathways, and the connections between them.

Isoleucine, an Essential Amino Acid, Induces the Expression of Human <i>β</i>Defensin 2 through the Activation of the G-Protein Coupled Receptor-ERK Pathway in the Intestinal Epithelia

Anti-microbial peptides are essential for the intestinal innate immunity that protects the intestinal epithelia from attacks by foreign pathogens. Human β-defensin (HBD) is one of the pivotal anti-microbial peptides that are expressed in the colonic epithelia. This study investigated the effect and the signaling mechanism of inducible β-defensin HBD2 by an essential amino acid, isoleucine (Ile) in colonic epithelial cells. Here we examined the expression level of HBD2 on induction of Ile in epithelial cells, and checked this pathway. HBD2 mRNA was induced by co-incubation with IL-1α and Ile in Caco2 cells, but not by Ile alone. An inhibitor of either ERK or Gi, a subunit of G-proteins, reduced the induction of HBD2 mRNA by Ile. The treatment with Ile also increased the intracellular calcium ion concentration, thus suggesting that the GPCR and ERK signaling pathway mediate the effects of Ile. These results indicate that an essential amino acid, Ile, enhances the expression of an inducible β-defensin, namely HBD2, by IL-1α through the activation of GPCRs and ERK signaling pathway. The administration of Ile may therefore represent a possible option to safely treat intestinal inflammation.

ATP Synthase β-subunit Abnormality in Pancreas Islets of Rats with Polycystic Ovary Syndrome and Type 2 Diabetes Mellitus

This study investigated the abnormal expression of ATP synthase β-subunit（ATPsyn-β） in pancreas islets of rat model of polycystic ovary syndrome（PCOS） with type 2 diabetes mellitus（T2DM）,and the secretion function changes after up-regulation of ATP5 b.Sixty female SD rats were divided into three groups randomly and equally.The rat model of PCOS with T2 DM was established by free access to the high-carbohydrate/high-fat diet,subcutaneous injections of DHEA,and a single injection of streptozotocin.The pancreas was removed for the detection of the ATPsyn-β expression by immunohistochemical staining,Western blotting and reverse transcription-PCR（RT-PCR）.The pancreas islets of the rats were cultured,isolated with collagenase Ⅴ and purified by gradient centrifugation,and the insulin secretion after treatment with different glucose concentrations was tested.Lentivirus ATP5 b was successfully constructed with the vector of GV208 and transfected into the pancreas islets for the over-expression of ATPsyn-β.The insulin secretion and intracellular ATP content were determined after transfection of the PCOS-T2 DM pancreas islets with Lenti-ATP5 b.The results showed that the expression of ATPsyn-β protein and m RNA was significantly decreased in the pancreas of PCOS-T2 DM rats.The ATP content in the pancreas islets was greatly increased and the insulin secretion was improved after the up-regulation of ATPsyn-β in the pancreas islets transfected with lenti-ATP5 b.These results indicated that for PCOS,the ATPsyn-β might be one of the key factors for the attack of T2 DM.

G-protein β subunit AGB1 positively regulates salt stress tolerance in Arabidopsis

The heterotrimeric GTP-binding proteins（G-proteins） in eukaryotes consisted of α, β and γ subunits and are important in molecular signaling by interacting with G-protein-coupled receptors（GPCR）, on which to transduce signaling into the cytoplast through appropriate downstream effectors. However, downstream effectors regulated by the G-proteins in plants are currently not well defined. In this study, the transcripts of AGB1, a G protein β subunit gene in Arabidopsis were found to be down-regulated by cold and heat, but up-regulated by high salt stress treatment. AGB1 mutant（agb1-2） was more sensitive to high salt stress than wild-type（WT）. Compared with WT, the cotyledon greening rates, fresh weight, root length, seedling germination rates and survival rates decreased more rapidly in agb1-2 along with increasing concentrations of Na Cl in normal（MS） medium. Physiological characteristic analysis showed that compared to WT, the contents of chlorophyll, relative proline accumulation and peroxidase（POD） were reduced, whereas the malonaldehyde（MDA） content and concentration ratio of Na＋/K＋ were increased in agb1-2 under salt stress condition. Further studies on the expression of several stress inducible genes associated with above physiological processes were investigated, and the results revealed that the expressions of genes related to proline biosynthesis, oxidative stress response, Na＋ homeostasis, stress- and ABAresponses were lower in agb1-2 than in WT, suggesting that those genes are possible downstream genes of AGB1 and that their changed expression plays an important role in determining phenotypic and physiologic traits in agb1-2. Taken together, these findings indicate that AGB1 positively regulates salt tolerance in Arabidopsis through its modulation of genes transcription related to proline biosynthesis, oxidative stress, ion homeostasis, stress- and ABA-responses.

Pathogenicity Assay for <i>Cochliobolus heterostrophus</i>G-Protein and MAPK Signaling Deficiency Strains

Cochliobolus heterostrophus is an agriculturally important and emerging model pathogen for studying the signaling hierarchies' role during the maize host colonization. In particular, G-protein and MAPK-linked pathways are playing a major role during pathogenesis. Although gene disruption studies are an efficient way of identifying the role of these cascades, differentiating between the mutant strains’ virulence ability may become an intricate task. For example, in C. heterostrophus, mutants in a G-protein α subunit gene, cga1, are defective in mating and appressorium formation, but unlike mutants in homologous genes in other fungal pathogens, the cga1 mutants remained highly virulent to corn under some host physiological conditions. Here, we used the cga1 strain as a model for developing an in vivo sensitive and accurate pathogenicity assay. A detailed and well controlled analysis of wild type (WT) and cga1 pathogenic behavior revealed that detached leaves are significantly more vulnerable to the disease than intact ones. In intact leaves, cga1 mutants were less infective of maize under most conditions. This difference was maximized when the first seedling leaf was chosen for inoculation and when the infected leaves, with spores or mycelia fragments droplets, were incubated for a period of four days. This optimal condition set enabled us to classify the C. heterostrophus G-protein signaling mutants deficient in α, β or both subunits in order of decreasing virulence: WT > cga1> cgb1> cga1 cgb1. The method presented proved to be accurate and sensitive enough to identify even slight variations in virulence. Moreover, it could be modified for use in studies of other foliar phytoparasitic fungi.

Association between G-protein β3 subunit gene and isolated systolic blood pressure elevation of greater than 130 mmHg: A large-scale cross-sectional study in the Japanese population

AIM To investigate whether GNB3 C825 T single nucleotide polymorphism(SNP) contributes to systolic blood pressure(SBP) ≥ 130 mmH g in a large-scale cross-sectional study among the Japanese population with diastolic blood pressure(DBP) < 85 mmH g. METHODS We analyzed 11008 Japanese subjects, including 2797 cases(SBP ≥ 130 and DBP < 85 mmH g) who were not taking anti-hypertensive medication and 8211 controls(SBP < 130 and DBP < 85 mmH g), all of whom enrolled in the genome banking project of the 21 st Century COE(Center of Excellence) Program at Jichi Medical University. Subjects were divided into four groups according to gender(male and female) and age(≤ 49 years and ≥ 50 years). GNB3 gene polymorphism was determined using the TaqM an probe method. We compared the frequencies of alleles and genotypes between cases and controls by chi-squared test. The strength of the associations was estimated by odds ratios(ORs) and 95%CI by using logistic regression analysis. The ORs were adjusted for age and body mass index. RESULTS Allele and genotype distributions significantly differed between cases and controls only in males aged ≤ 49 years. Compared to the CC genotype, a significant OR was obtained in the TT genotype among males aged ≤ 49 years.CONCLUSION This study indicates that the TT genotype of the GNB3 C825 T SNP may contribute to SBP elevation of greater than 130 mmH g compared to the CC genotype in Japanese males aged ≤ 49 years.

Effect of Allelic Variation of β-conglycinin α-subunit Locus cgy-2 on Soybean(Glycine max) Quality Ⅰ. Evaluation of Free Amino Acid Content

The effects of the deficiency of the allergenicα-subunit on soybean amino acid(AA)composition were studied using the cultivar Dongnong 47(DN47)as a genetic background.The near-isogenic line(NIL)NIL-DN47-Δα of DN47,with an introgression of theα-null trait allele from the high protein donor parent RiB,was created by marker assisted background selection and used to investigate the AA content and nutritional quality.The contents of crude protein,the total AAs,the total essential amino acids(EAAs)and sulfur-containing(Met and Cys)AAs increased by 4.11%,4.16%,5.20% and 11.96%,respectively in NIL-DN47-Δα compared with DN47.Analyses of the total EAAs(TEAAs)and the EAA index(EAAI)revealed that both parameters in NIL-DN47-Δα were higher than those in DN47.The null-allele of theα-subunit positively affected the AA scores.The quantitative changes in free AAs(FAAs)in the developing seeds of NIL-DN47-Δα and DN47 were compared as of 15 days after flowering(DAF)until maturity.The results showed that the total FAA content in NIL-DN47-Δα was significantly higher than that in the DN47 throughout the late maturation stage(40-60 DAF)of seeds.The high concentration of the FAAs in cgy-2 mutant seeds was a consequence of the high rates of synthesis and/or accumulation of individual FAAs during seed maturation where 25 DAF was an important turning point in the accumulation of the FAAs.The FAA contents of single soybeanα-null,double(α+α′)and triple(α+α′+group I)-null mutant combination lines were investigated.In all of these combinations,introduction of the cgy-2 gene invariably raised the FAA content of mature seeds above that of the DN47.In summary,the enhanced protein quality in cgy-2 mutants resulted from several factors.(1)There was a general increase in the contents of most AAs and FAAs in NIL-DN47-Δα.(2)The induced synthesis of free Arg contributed effectively to the high FAAs of various storage-protein-deficiency mutants.For example,in the S2(null α,group I),the free Arg content was seven times as much as that of DN47,accounting for more than half of the total FAA content in the seed.(3)The increase of sulfur-containing AAs in theα-null type NIL mainly resulted from elevated Met content.These data suggested that the cgy-2 mutation might improve the protein quality of soybean seeds and that lacked of the allergenicα-subunit resulted in increased the FAA content.

The Study on Immuno-response and Antisera Properties of Recombinant β-subunit of Human Chorionic Gonadotropin in C57 Black Mouse

In this study, the immuno-response of recombinant hCG-β and natural hCGβ was comparatively investigated by using Freund's adjuvant. The results showed that, the properties and merits of the antibodies elicited by both kinds of hCG-β were similar. The antisera had high affinity for binding with hCG (Kαγβ≈5.86×108/mol/L, Kαβ≈8.18×108/mol/L), and were found to be effective in inhibiting the binding of 125I-hCG to receptors in rat testes. Results also indicated that, similar to the antisera induced by natural hCG-β, the recombinant hCG-β induced antisera had capacity of neutralizing the biological activities of hCG. Recombinant hCG-β could be used as an immunogen for contraceptive vaccine.

Insights into the structural biology of G-protein coupled receptors impacts drug design for central nervous system neurodegenerative processes

In the last few years, there have been important new insights into the structural biology of G-protein coupled receptors. It is now known that allosteric binding sites are involved in the affinity and selec- tivity of ligands for G-protein coupled receptors, and that signaling by these receptors involves both G-protein dependent and independent pathways. The present review outlines the physiological and pharmacological implications of this perspective for the design of new drugs to treat disorders of the central nervous system. Specifically, new possibilities are explored in relation to allosteric and or- thosteric binding sites on dopamine receptors for the treatment of Parkinson＇s disease, and on muscarinic receptors for Alzheimer＇s disease. Future research can seek to identify ligands that can bind to more than one site on the same receptor, or simultaneously bind to two receptors and form a dimer. For example, the design of bivalent drugs that can reach homo/hetero-dimers of D2 dopa- mine receptor holds promise as a relevant therapeutic strategy for Parkinson＇s disease. Regarding the treatment of Alzheimer＇s disease, the design of dualsteric ligands for mono-oligomeric mus- carinic receptors could increase therapeutic effectiveness by generating potent compounds that could activate more than one signaling pathway.

Progress of CACNA1S Gene and Hypokalemic Periodic Paralysis

CACNA1 S gene is the gene encoding L-type calcium channel αa-subunit. CACNA1 S gene mutations can cause hypokalemic periodic pa- ralysis （HOKPP）. The related research speculated that CACNA1 S gene was the candidate genes which affect meat quality traits. In the present ar- ticle, the biological characteristics of CACNA1 S gene, structure, genetic diseases and the research development were respectively reviewed so as to provide a reference for further research.

海马脑片CA1中间神经元α7尼古丁受体亚型的功能研究

目的利用膜片钳全细胞记录方法研究α7尼古丁受体亚型的功能特点。方法实验在急性制备的海马脑片CA1中间神经元上进行;α7尼古丁受体亚型可被局部高压微量喷射的高浓度的胆碱特异性激活,膜片钳全细胞记录方法用于判断神经元类型并记录膜电流变化。结果中间神经元的动作电位发放频率较均匀,基本无适应性;其膜上的α7尼古丁受体亚型可被胆碱特异性激活,产生强大的持续时间短暂的内向离子流,该离子流可被MLA(一种α7尼古丁受体亚型的抑制剂)完全阻断。结论采用药理学和膜片钳技术相结合的方法可对α7尼古丁受体亚型的功能特点进行有效研究。

Rck of Salmonella enterica, subspecies enterica serovar Enteritidis, mediates Zipper-like internalization

Salmonella can invade non-phagocytic cells through its type Ⅲ secretion system （T3SS-1）, which induces a Trigger entry process. This study showed that Salmonella enterica, subspecies enterica serovar Enteritidis can also invade cells via the Rck outer membrane protein. Rck was necessary and sufficient to enable non-invasive E. coli and Rckcoated beads to adhere to and invade different cells. Internalization analysis of latex beads coated with different Rck peptides showed that the peptide containing amino acids 140-150 promoted adhesion, whereas amino acids between 150 and 159 modulated invasion. Expression of dominant-negative derivatives and use of specific inhibitors demonstrated the crucial role of small GTPases Racl and Cdc42 in activating the Arp2/3 complex to trigger formation of actin-rich accumulation, leading to Rck-dependent internalization. Finally, scanning and transmission electron microscopy with Rck-coated beads and E. coli expressing Rck revealed microvillus-like extensions that formed a Zipper-like structure, engulfing the adherent beads and bacteria. Overall, our results provide new insights into the Salmonella T3SS-independent invasion mechanisms and strongly suggest that Rck induces a Zipper-like entry mechanism. Consequently, Salmonella seems to be the first bacterium found to be able to induce both Zipper and Trigger mechanisms to invade host cells.

Catalytic domain of PDC-E2 contains epitopes recognized by antimitochondrial antibodies in primary biliary cirrhosis

AIM:To search for further immunodominant peptides of the pyruvate dehydrogenase complex E2-component (PDC-E2) recognized by antimitochondrial antibodies (AMA) in primary biliary cirrhosis (PBC). METHODS:Sera from 95 patients with PBC were tested by enzyme-linked immunosorbent assay against 33 synthetic overlapping peptides (25 amino acids; aa) covering the entire length of the E2-subunit of PDC-E2. Furthermore,the inner lipoyl peptide 167-184 was used in an unlip oylated and a lipoylated form as well as coupled to ovalbumin. Sera from 11 AMA negative/ANA posit ive PBC patients,63 patients with other liver disorders and 22 healthy blood donors served as controls.RESULTS:Of the 95 PBC-sera,74% reacted with the peptide 475-499 and 58% with the pept ide 407-431 located within the catalytic domain of PDC-E2. Patients with other disorders or healthy controls were positive in only up to 18%. Antibodies to the unlipoylatedand lip oylated pept ide 167-184 within the inner lipoyl domain were found in only 5% and 11% of the PBC sera,respectively; using ovalbumin-coupled peptides,the incidence increased up to 57% (unlipoylated form). CONCLUSION:Peptides within the catalytic site of PDC-E2 rather than the previously reported lipoyl binding peptide 167-184 may represent major immunodomin ant epitopes recognized by AMA in PBC.

Novel mechanism of drug resistance to proteasome inhibitors in multiple myeloma

Multiple myeloma(MM) is a cancer caused by uncontrolled proliferation of antibody-secreting plasma cells in bone marrow, which represents the second most common hematological malignancy. MM is a highly heterogeneous disease and can be classified into a spectrum of subgroups based on their molecular and cytogenetic abnormalities. In the past decade, novel therapies, especially, the first-in-class proteasome inhibitor bortezomib, have been revolutionary for the treatment of MM patients. Despite these remarkable achievements, myeloma remains incurable with a high frequency of patients suffering from a relapse, due to drug resistance. Mutation in the proteasome β5-subunit(PSMB5) was found in a bortezomib-resistant cell line generated via long-term coculture with increasing concentrations of bortezomib in 2008, but their actual implication in drug resistance in the clinic has not been reported until recently. A recent study discovered four resistance-inducing PSMB5 mutations from a relapsed MM patient receiving prolonged bortezomib treatment. Analysis of the dynamic clonal evolution revealed that two subclones existed at the onset of disease, while the other two subclones were induced. Protein structural modeling and functional assays demonstrated that all four mutations impaired the binding of bortezomib to the 20 S proteasome, conferring different degrees of resistance. The authors further demonstrated two potential approaches to overcome drug resistance by using combination therapy for targeting proteolysis machinery independent of the 20 S proteasome.