A Phase I Clinical Study Comparing the Pharmacokinetics, Safety, and Immunogenicity of GB221 Injection and Trastuzumab (Herceptin®) in Healthy Chinese Adults.

BACKGROUND AND OBJECTIVE: GB221 is a recombinant humanized anti-HER2 monoclonal antibody. The purpose of this study was to evaluate the pharmacokinetic, safety, and immunogenicity of GB221 in healthy Chinese adults in comparison to trastuzumab (Herceptin®). METHODS: In this randomized, double-blind, parallel-group phase I clinical trial, 88 subjects were randomized 1:1 to receive a single intravenous infusion (90-100 min) of GB221 or trastuzumab (6 mg/kg). The primary pharmacokinetic parameters-maximum observed serum concentration (Cmax), area under the serum concentration-time curve from zero to the last quantifiable concentration at time t (AUC0-t), and area under the serum concentration-time curve from time zero to infinity (AUC0-∞)-of GB221 and trastuzumab were compared to establish whether the 90% confidence interval (CI) attained the 80-125% bioequivalence standard. Safety and immunogenicity were also evaluated. RESULTS: The GB221 group (n = 43) and the trastuzumab group (n = 44) showed similar pharmacokinetic characteristics. The geometric mean ratios (90% CI) of Cmax, AUC0-t, and AUC0-∞ between the two groups were 107.53% (102.25-113.07%), 108.31% (103.57-113.26%), and 108.34% (103.57-113.33%), respectively. The incidence of treatment-emergent adverse events (TEAEs) was 83.7% (36/43) of the subjects in the GB221 group and 95.5% (42/44) of the subjects in the trastuzumab group. No subjects withdrew from the trial due to TEAEs, and there were no occurrences of serious adverse events. All subjects tested negative for antidrug antibodies (ADA). CONCLUSION: GB221 demonstrated similar pharmacokinetics to trastuzumab and comparable safety and immunogenicity in healthy Chinese adults.

Pomalidomide combined with dexamethasone for the treatment of relapsed/refractory multiple myeloma: a systematic review and meta-analysis.

BACKGROUND: To evaluate the efficacy and safety of pomalidomide in combination treatment of relapsed/refractory multiple myeloma (RRMM). METHODS: Published clinical trials were searched in the Cochrane Library, PubMed, EMBASE to February 2023. The literature was screened and evaluated according to the inclusion criteria, and the data were analyzed by a random effect model. Overall response rate (ORR), overall survival (OS), progression-free survival (PFS) and full grade or ≥ 3 adverse events (AEs) were the outcomes. RESULTS: This study included 31 clinical trials, which included 4776 patients. The pooled ORR of the doublet regimens was 33.3% (95%CI: 27-39%) and the triplet regimens was 66% (95%CI: 58-74%). Among the 25 included studies, the median PFS was 8.29 months (95%CI: 7.27-9.31), and nine studies reported median OS of 19.43 months (95%CI: 14.56-24.30). In terms of safety, the most common hematologic AEs of grade ≥ 3 were neutropenia (41%) and anemia (20%); Non-hematologic AEs were pneumonia (14%) and infection/febrile neutropenia (14%). CONCLUSIONS: Pomalidomide combined treatment regimens have shown good clinical efficacy, especially in pomalidomide + dexamethasone combined with other drugs. In terms of safety, it's important to pay attention to the likelihood of hematological adverse events when used clinically. SYSTEMATIC REVIEW REGISTRATION: PROSPERO: CRD42023420644.

Triclosan induces earlier puberty onset in female mice via interfering with L-type calcium channels and activating Pik3cd.

Triclosan (TCS) is a broad-spectrum antibacterial chemical widely presents in people's daily lives. Epidemiological studies have revealed that TCS exposure may affect female puberty development. However, the developmental toxicity after low-dose TCS continuous exposure remains to be confirmed. In our study, 8-week-old ICR female mice were continuously exposed to TCS (30, 300, 3000 µg/kg/day) or vehicle (corn oil) from 2 weeks before mating to postnatal day 21 (PND 21) of F1 female mice, while F1 female mice were treated with TCS intragastric administration from PND 22 until PND 56. Vaginal opening (VO) observation, hypothalamic-pituitary-ovarian (HPO) axis related hormones and genes detection, and ovarian transcriptome analysis were carried out to investigate the effects of TCS exposure on puberty onset. Meanwhile, human granulosa-like tumor cell lines (KGN cells) were exposed to TCS to further explore the biological mechanism of the ovary in vitro. The results showed that long-term exposure to low-dose TCS led to approximately a 3-day earlier puberty onset in F1 female mice. Moreover, TCS up-regulated the secretion of estradiol (E2) and the expression of ovarian steroidogenesis genes. Notably, ovarian transcriptomes analysis as well as bidirectional validation in KGN cells suggested that L-type calcium channels and Pik3cd were involved in TCS-induced up-regulation of ovarian-related hormones and genes. In conclusion, our study demonstrated that TCS interfered with L-type calcium channels and activated Pik3cd to up-regulate the expression of ovarian steroidogenesis and related genes, thereby inducing the earlier puberty onset in F1 female mice.

First-in-human trial of SAR107375E, a novel small molecule anticoagulant with dual inhibition of factor Xa and factor IIa.

BACKGROUND: SAR107375E is a direct dual inhibitor of both Factor Xa and Factor IIa and has shown potent anticoagulation activity in vitro and animals. This study evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics of single ascending intravenous doses of SAR107375E in healthy Chinese adult subjects. METHODS: In this randomized, double-blind, placebo-controlled trial, 60 healthy Chinese adult subjects were administered intravenously single ascending doses (0.5, 1.5, 3.0, 5.0, 7.5, 10.0, 15.0, or 20.0 mg) of SAR107375E (N = 44) or placebo (N = 16). Plasma and urine concentrations of SAR107375E were measured and used to calculate pharmacokinetic parameters. Coagulation functions were measured and compared with baseline values. Treatment-emergent adverse events were recorded to evaluate safety. RESULTS: In plasma, from the 0.5 to 20.0 mg dose group, t1/2 is 1.51-4.00 h, Cmax is 59.05-1360 ug/L, and AUC0-t is 25.01-528.45 h*ug/L. And it shows dose proportionality in the 5.0-20.0 mg range. Activated partial thromboplastin time and Ecarin clotting time correlated linearly with drug plasma concentration. No serious adverse events were reported during the study. CONCLUSION: SAR107375E exhibits good safety and tolerability, predictable pharmacokinetics and pharmacodynamics. CLINICAL TRIAL REGISTRATION: www.chinadrugtrials.org.cn, identifier is CTR20211082.

Association between exposure to persistent organic pollutants and pubertal timing in boys and girls: A systematic review and meta-analysis.

In recent years, the phenomenon of abnormal pubertal timing in children has become increasingly common worldwide. Persistent organic pollutants (POPs) may be one of the risk factors contributing to this phenomenon, but the relationship between them is unclear based on current evidence. The purpose of this study was to determine the association of POPs exposure with pubertal timing in girls and boys by conducting a systematic review and meta-analysis. We searched PubMed and Embase databases for studies before June 1, 2023. Meta-analysis was performed by pooling relative risk (RR) or odds ratio (OR) or prevalence ratio (PR) or hazard ratio (HR) estimates with 95 % confidence intervals (CIs). Subgroup analysis, publication bias assessment and sensitivity analysis were also carried out. A total of 21 studies were included, involving 2479 boys and 8718 girls. The results of meta-analysis showed that exposure to POPs was significantly associated with delayed pubertal timing in girls (RR: 0.85; 95 % CI: 0.79-0.91; p < 0.001). There was no statistically significant association between exposure to POPs and pubertal timing in boys (RR: 1.18; 95 % CI: 0.99-1.40; p = 0.070). Subgroup analysis showed that there may be gender differences in the effects of exposure to POPs on pubertal timing. Our results suggested that exposure to POPs could delay pubertal timing in girls. However, based on current evidence, no significant association was found between POPs exposure and pubertal timing in boys.

Phase I, Randomized, Placebo-Controlled, Dose-Escalation Study of GB223, a Fully-Humanized Monoclonal Antibody to RANKL, in Healthy Chinese Adults.

BACKGROUND: GB223 is a novel, fully-humanized monoclonal antibody against the receptor activator of nuclear factor-kappa B ligand (RANKL). In this phase I study, the safety, tolerability, pharmacokinetics, pharmacodynamics, and immunogenicity of GB223 were investigated. PATIENTS AND METHODS: This was a randomized, double-blinded, placebo-controlled, single-dose escalation study conducted in 44 healthy Chinese adults. Participants were randomly assigned to receive a single subcutaneous injection dose of 7, 21, 63, 119, or 140 mg of GB223 (n = 34) or placebo (n = 10) and were followed up for 140-252 days. RESULTS: The results of noncompartmental analysis showed that GB223 was slowly absorbed after dosing, with a time to reach maximum concentration (Tmax) ranging from 5 to 11 days. Serum GB223 concentrations decreased slowly, with a long half-life ranging from 7.91 to 19.60 days. A two-compartment Michaelis-Menten model was found to best describe the pharmacokinetics of GB223, and the absorption rate of GB223 differed between males (0.0146 h-1) and females (0.0081 h-1). Serum C-terminal telopeptide of type I collagen decreased significantly postdose, and the inhibition lasted 42-168 days. No deaths or drug-related serious adverse events occurred. The most frequent adverse events were blood parathyroid hormone increased (94.1%), blood phosphorus decreased (67.6%) and blood calcium decreased (58.8%). In the GB223 group, 44.1% (15/34) of subjects were antidrug antibody positive after dosing. CONCLUSION: In this study, we demonstrated for the first time that a single subcutaneous injection of GB223, from 7 to 140 mg, is safe and well tolerated in healthy Chinese subjects. GB223 has a nonlinear pharmacokinetic profile, and sex was a potential covariate that may affect the absorption rate of GB223. CLINICAL TRIAL REGISTRATION: NCT04178044 and ChiCTR1800020338.

Toxicological effects, residue levels and risks of endocrine-disrupting chemicals in Chinese medicine: a review.

Traditional Chinese medicine (TCM) that is used worldwide possesses the satisfactory function of disease prevention, treatment and health care, and this natural medicine seems to be favored due to its low side effects. Endocrine disrupting chemicals (EDCs), which exist in all aspects of our lives, may interfere with the synthesis, action and metabolism of human sex steroid hormones, resulting in the development and fertility problems as well as obesity and the disturbance of energy homeostasis. From planting to processing, TCM may be polluted by various EDCs. Many studies pay attention to this problem, but there are still few reviews on the residues and toxicity risks of EDCs in TCM. In this paper, researches related to EDCs in TCM were screened. The possible contamination sources of TCM from planting to processing and its toxic effects were introduced. Moreover, the residues of metals, pesticides and other EDCs in TCM as well as the health risks of human exposure to EDCs through ingestion of TCM materials were reviewed.

Biosimilarity Assessment of the Biosimilar Teriparatide Candidate and the Reference Drug in Healthy Subjects.

SAL001, a recombinant form of parathyroid hormone, is a biosimilar drug to teriparatide and is planned to be used in osteoporosis treatment. A single-dose, randomized, open-label, 2-way crossover trial was conducted in healthy subjects to compare the pharmacokinetics (PK) and safety between SAL001 and the reference drug. Sixty-four subjects were enrolled in the study, and 61 subjects completed the study. In each period, 20 µg of the test or reference formulation was administered subcutaneously. SAL001 was administered by autoinjector pen, whereas the reference drug was administered by a self-matched injection pen. Serial blood samples were obtained for the analyses of PK and serum calcium concentration. Geometric mean ratios with 90%CIs for the maximum plasma concentration (Cmax ) and area under the plasma concentration-time curve (AUC) were estimated. The safety of these 2 formulations was also evaluated. Overall, the 90%CIs for the geometric mean ratios of Cmax , AUC from time 0 to the last quantifiable time point, and AUC from time 0 extrapolated to infinity of the test or reference product were within 80.0%-125.0% of biosimilarity criteria. Other PK parameters, serum calcium concentration, and safety profiles had no significant differences between the 2 formulations. SAL001 demonstrated PK similarity to the reference drug, and the serum calcium concentration and safety profiles of SAL001 were also considered comparable to the reference drug.

Relative deprivation and depressive symptoms among Chinese migrant children: The impacts of self-esteem and belief in a just world.

Background: Studies have shown that relative deprivation is a risk factor for depressive symptoms, but the underlying mechanisms are not yet clarified. Thus, this study formulated a moderated mediation model to investigate the mediating role of self-esteem and the moderating role of belief in a just world between relative deprivation and depressive symptoms among rural-to-urban migrant children. Methods: A sample of 1,076 Chinese migrant children (M age = 12.25 years, SD = 1.66) completed measurements of relative deprivation, self-esteem, belief in a just world, and depressive symptoms. Furthermore, the mediating mechanism and moderating effect of the study were explored with the SPSS PROCESS macro (Models 4 and 7). Results: The results showed a significant positive association between relative deprivation and depressive symptoms, with self-esteem partially mediating this association. Moreover, belief in a just world moderated the association between relative deprivation and self-esteem. Namely, the indirect effect of self-esteem was moderated by belief in a just world. Specifically, the mediating effect was stronger for migrant children with higher levels of belief in a just world. Conclusion: These findings broaden our knowledge of how and when relative deprivation influences depressive symptoms among migrant children. Therefore, appropriate measures should be taken to prevent and manage migrant children' depression and provide them with corresponding guidance. Some measures could be taken by schools and educators to help migrant children with high relative deprivation in improving their self-esteem and belief in a just world, such as self-reference tasks and psychological intervention programs.

Diverging targets mediate the pathological roleof miR-199a-5p and miR-199a-3p by promoting cardiac hypertrophy and fibrosis.

MicroRNA-199a-5p (miR-199a-5p) and -3p are enriched in the myocardium, but it is unknown whether miR-199a-5p and -3p are co-expressed in cardiac remodeling and what roles they have in cardiac hypertrophy and fibrosis. We show that miR-199a-5p and -3p are co-upregulated in the mouse and human myocardium with cardiac remodeling and in Ang-II-treated neonatal mouse ventricular cardiomyocytes (NMVCs) and cardiac fibroblasts (CFs). miR-199a-5p and -3p could aggravate cardiac hypertrophy and fibrosis in vivo and in vitro. PPAR gamma coactivator 1 alpha (Ppargc1a) and sirtuin 1 (Sirt1) were identified as target genes to mediate miR-199a-5p in promoting both cardiac hypertrophy and fibrosis. However, miR-199a-3p aggravated cardiac hypertrophy and fibrosis through targeting RB transcriptional corepressor 1 (Rb1) and Smad1, respectively. Serum response factor and nuclear factor κB p65 participated in the upregulation of miR-199a-5p and -3p in Ang-II-treated NMVCs and mouse CFs, and could be conversely elevated by miR-199a-5p and -3p. Together, Ppargc1a and Sirt1, Rb1 and Smad1 mediated the pathological effect of miR-199a-5p and -3p by promoting cardiac hypertrophy and fibrosis, respectively. This study suggests a possible new strategy for cardiac remodeling therapy by inhibiting miR-199a-5p and -3p.

MicroRNA-92b-3p suppresses angiotensin II-induced cardiomyocyte hypertrophy via targeting HAND2.

AIMS: The pathological cardiac hypertrophy will develop into heart failure, which has no effective treatment currently. Previous studies have proved that microRNAs (miRNAs) participate in the development of cardiac hypertrophy and regulate the pathological progress. In this study, we want to investigate the role of microRNA-92b-3p (miR-92b-3p) in cardiomyocyte hypertrophy and the mechanisms involved. MATERIALS AND METHODS: Neonatal mouse ventricular cells (NMVCs) were isolated from the hearts of 1-3-d-old newborn C57BL6 mice. The isolated NMVCs were induced hypertrophic phenotype by Angiotensin-II (Ang-II) and the cell size was examined by FITC-phalloidin staining assay. The expression of miR-92b-3p was determined by quantitative real-time PCR (qRT-qPCR). MRNA and protein level of ß-MHC, ACTA1 and HAND2 in NMVCs transfected with miR-92b-3p mimic and inhibition were assessed by RT-qPCR assay and western blot assay, respectively. Dual luciferase assay was used to verify the interaction between miR-92b-3p and the 3'-untranslated region (UTR) of HAND2 gene. KEY FINDINGS: MiR-92b-3p and HAND2 were significantly increased in Ang-II-induced NMVCs. Overexpression of miR-92b-3p can ameliorate Ang-II-induced cardiomyocyte hypertrophy. MiR-92b-3p negatively regulated HAND2 expression at the transcriptional level. Both miR-92b-3p mimic and HAND2 siRNA could efficiently inhibit Ang-II-induced hypertrophy in mouse cardiomyocytes. SIGNIFICANCE: MiR-92b-3p inhibits Ang-II-induced cardiomyocyte hypertrophy via targeting HAND2.

Targeting myocyte-specific enhancer factor 2D contributes to the suppression of cardiac hypertrophic growth by miR-92b-3p in mice.

The role of microRNA-92b-3p (miR-92b-3p) in cardiac hypertrophy was not well illustrated. The present study aimed to investigate the expression and potential target of miR-92b-3p in angiotensin II (Ang-II)-induced mouse cardiac hypertrophy. MiR-92b-3p was markedly decreased in the myocardium of Ang-II-infused mice and of patients with cardiac hypertrophy. However, miR-92b-3p expression was revealed increased in Ang-II-induced neonatal mouse cardiomyocytes. Cardiac hypertrophy was shown attenuated in Ang-II-infused mice received tail vein injection of miR-92b-3p mimic. Moreover, miR-92b-3p inhibited the expression of atrial natriuretic peptide (ANP), skeletal muscle α-actin (ACTA1) and ß-myosin heavy chain (MHC) in Ang-II-induced mouse cardiomyocytes in vitro. Myocyte-specific enhancer factor 2D (MEF2D), which was increased in Ang-II-induced mouse hypertrophic myocardium and cardiomyocytes, was identified as a target gene of miR-92b-3p. Functionally, miR-92b-3p mimic, consistent with MEF2D siRNA, inhibited cell size increase and protein expression of ANP, ACTA1 and ß-MHC in Ang-II-treated mouse cardiomyocytes. Taken together, we demonstrated that MEF2D is a novel target of miR-92b-3p, and attenuation of miR-92b-3p expression may contribute to the increase of MEF2D in cardiac hypertrophy.

Activation of miR-34a-5p/Sirt1/p66shc pathway contributes to doxorubicin-induced cardiotoxicity.

The molecular mechanisms underlying anthracyclines-induced cardiotoxicity have not been well elucidated. MiRNAs were revealed dysregulated in the myocardium and plasma of rats received Dox treatment. MicroRNA-34a-5p (miR-34a-5p) was verified increased in the myocardium and plasma of Dox-treated rats, but was reversed in rats received Dox plus DEX treatments. Human miR-34a-5p was also observed increased in the plasma of patients with diffuse large B-cell lymphoma after 9- and 16-week epirubicin therapy. Up-regulation of miR-34a-5p was observed in Dox-induced rat cardiomyocyte H9c2 cells. MiR-34a-5p could augment Bax expression, but inhibited Bcl-2 expression, along with the increases of the activated caspase-3 and mitochondrial potentials in H9C2 cells. MiR-34a-5p was verified to modulate Sirt1 expression post-transcriptionally. In parallel to Sirt1 siRNA, miR-34a-5p could enhance p66shc expression, accompanied by increases of Bax and the activated caspase-3 and a decrease of Bcl-2 in H9c2 cells. Moreover, enforced expression of Sirt1 alleviated Dox-induced apoptosis of H9c2 cells, with suppressing levels of p66shc, Bax, the activated caspase-3 and miR-34a-5p, and enhancing Bcl-2 expression. Therefore, miR-34a-5p enhances cardiomyocyte apoptosis by targeting Sirt1, activation of miR-34a-5p/Sirt1/p66shc pathway contributes to Dox-induced cardiotoxicity, and blockage of this pathway represents a potential cardioprotective effect against anthracyclines.

CircRNA_000203 enhances the expression of fibrosis-associated genes by derepressing targets of miR-26b-5p, Col1a2 and CTGF, in cardiac fibroblasts.

Circular RNAs (circRNAs) participate in regulating gene expression in diverse biological and pathological processes. The present study aimed to investigate the mechanism underlying the modulation of circRNA_000203 on expressions of fibrosis-associated genes in cardiac fibroblasts. CircRNA_000203 was shown upregulated in the diabetic mouse myocardium and in Ang-II-induced mouse cardiac fibroblasts. Enforced-expression of circRNA_000203 could increase expressions of Col1a2, Col3a1 and α-SMA in mouse cardiac fibroblasts. RNA pull-down and RT-qPCR assay indicated that circRNA_000203 could specifically sponge miR-26b-5p. Dual luciferase reporter assay revealed that miR-26b-5p interacted with 3'UTRs of Col1a2 and CTGF, and circ_000203 could block the interactions of miR-26b-5p and 3'UTRs of Col1a2 and CTGF. Transfection of miR-26b-5p could post-transcriptionaly inhibit expressions of Col1a2 and CTGF, accompanied with the suppressions of Col3a1 and α-SMA in cardiac fibroblasts. Additionally, over-expression of circRNA_000203 could eliminate the anti-fibrosis effect of miR-26b-5p in cardiac fibroblasts. Together, our results reveal that suppressing the function of miR-26b-5p contributes to the pro-fibrosis effect of circRNA_000203 in cardiac fibroblasts.

Targeting EZH1 and EZH2 contributes to the suppression of fibrosis-associated genes by miR-214-3p in cardiac myofibroblasts.

The role of microRNA-214-3p (miR-214-3p) in cardiac fibrosis was not well illustrated. The present study aimed to investigate the expression and potential target of miR-214-3p in angiotensin II (Ang-II)-induced cardiac fibrosis. MiR-214-3p was markedly decreased in the fibrotic myocardium of a mouse Ang-II infusion model, but was upregulated in Ang-II-treated mouse myofibroblasts. Cardiac fibrosis was shown attenuated in Ang-II-infused mice received tail vein injection of miR-214-3p agomir. Consistently, miR-214-3p inhibited the expression of Col1a1 and Col3a1 in mouse myofibroblasts in vitro. MiR-214-3p could bind the 3'-UTRs of enhancer of zeste homolog 1 (EZH1) and -2, and suppressed EZH1 and -2 expressions at the transcriptional level. Functionally, miR-214-3p mimic, in parallel to EZH1 siRNA and EZH2 siRNA, could enhance peroxisome proliferator-activated receptor-γ (PPAR-γ) expression and inhibited the expression of Col1a1 and Col3a1 in myofibroblasts. In addition, enforced expression of EZH1 and -2, and knockdown of PPAR-γ resulted in the increase of Col1a1 and Col3a1 in myofibroblasts. Moreover, the NF-κB signal pathway was verified to mediate Ang-II-induced miR-214-3p expression in myofibroblasts. Taken together, our results revealed that EZH1 and -2 were novel targets of miR-214-3p, and miR-214-3p might be one potential miRNA for the prevention of cardiac fibrosis.

Myocyte-specific enhancer factor 2C: a novel target gene of miR-214-3p in suppressing angiotensin II-induced cardiomyocyte hypertrophy.

The role of microRNA-214-3p (miR-214-3p) in cardiac hypertrophy was not well illustrated. The present study aimed to investigate the expression and potential target of miR-214-3p in angiotensin II (Ang-II)-induced mouse cardiac hypertrophy. In mice with either Ang-II infusion or transverse aortic constriction (TAC) model, miR-214-3p expression was markedly decreased in the hypertrophic myocardium. Down-regulation of miR-214-3p was observed in the myocardium of patients with cardiac hypertrophy. Expression of miR-214-3p was upregulated in Ang-II-induced hypertrophic neonatal mouse ventricular cardiomyocytes. Cardiac hypertrophy was attenuated in Ang-II-infused mice by tail vein injection of miR-214-3p. Moreover, miR-214-3p inhibited the expression of atrial natriuretic peptide (ANP) and ß-myosin heavy chain (MHC) in Ang-II-treated mouse cardiomyocytes in vitro. Myocyte-specific enhancer factor 2C (MEF2C), which was increased in Ang-II-induced hypertrophic mouse myocardium and cardiomyocytes, was identified as a target gene of miR-214-3p. Functionally, miR-214-3p mimic, consistent with MEF2C siRNA, inhibited cell size increase and protein expression of ANP and ß-MHC in Ang-II-treated mouse cardiomyocytes. The NF-κB signal pathway was verified to mediate Ang-II-induced miR-214-3p expression in cardiomyocytes. Taken together, our results revealed that MEF2C is a novel target of miR-214-3p, and attenuation of miR-214-3p expression may contribute to MEF2Cexpressionin cardiac hypertrophy.

Evolutionary pattern of rDNA following polyploidy in Leymus (Triticeae: Poaceae).

Ribosomal ITS polymorphism and its ancestral genome origin of polyploid Leymus were examined to infer the evolutionary outcome of rDNA gene following allopolyploid speciation and to elucidate the geographic pattern of ITS variation. The results demonstrated that different polyploids have experienced varying fates, including maintenance or homogenization of divergent arrays, occurrence of chimeric repeats and potential pseudogenes. Our data suggested that (1) the Ns, P/F, and St genomic types in Leymus were originated from Psathyrostachys, Agropyron/Eremopyrum, and Pseudoroegneria, respectively; (2) the occurrence of a higher proportion of Leymus species with predominant uniparental rDNA type might associate with the segmental allopolyploid origin, nucleolar dominance of alloploids, and rapid radiation of Leymus; (3) maintenance of multiple parental ITS types in allopolyploid might result from long generation times associated to vegetative multiplication, number and chromosomal location of ribosomal loci and/or recurrent hybridization; (4) the rDNA genealogical structure of Leymus species might associate with the geographic origins; and (5) ITS sequence clade shared by Leymus species from Central Asia, North America, and Nordic might be an outcome of ancestral ITS homogenization. Our results shed new light on understanding evolutionary outcomes of rDNA following allopolyploid speciation and geographic isolation.

The effect of hinge mutations on effector binding and domain rotation in Escherichia coli D-3-phosphoglycerate dehydrogenase.

D-3-phosphoglycerate dehydrogenase (EC 1.1.1.95) from Escherichia coli contains two Gly-Gly sequences that have been shown previously to have the characteristics of hinge regions. One of these, Gly(336)-Gly(337), is found in the loop between the substrate binding domain and the regulatory domain. Changing these glycine residues to valine affected the sensitivity of the enzyme to inhibition by L-serine but not the extent of inhibition. The decrease in sensitivity was caused primarily by a decrease in the affinity of the enzyme for L-serine. These mutations also affected the domain rotation of the subunits in response to L-serine binding. A major conclusion of this study was that it defines a minimal limit on the necessary conformational changes leading to inhibition of enzyme activity. That is, some of the conformational differences seen in the native enzyme upon L-serine binding are not critical for inhibition, whereas others are maintained and may play important roles in inhibition and cooperativity. The structure of G336V demonstrates that the minimal effect of L-serine binding leading to inhibition of enzyme activity requires a domain rotation of approximately only 6 degrees in just two of the four subunits of the enzyme that are oriented diagonally across from each other in the tetramer. Moreover the structures show that both pairs of Asn190 to Asn190 hydrogen bonds across the subunit interfaces are necessary for activity. These observations are consistent with the half-the-sites activity, flip-flop mechanism proposed for this and other similar enzymes and suggest that the Asn190 hydrogen bonds may function in the conformational transition between alternate half-the-site active forms of the enzyme.

Identification of amino acid residues contributing to the mechanism of cooperativity in Escherichia coli D-3-phosphoglycerate dehydrogenase.

L-Serine inhibits the catalytic activity of Escherichia coli D-3-phosphoglycerate dehydrogenase (PGDH) by binding to its regulatory domain. This domain is a member of the ACT domain family of regulatory domains that are modulated by small molecules. A comparison of the phi and psi torsional angle differences between the crystal structures of PGDH solved in the presence and in the absence of L-serine demonstrated a clustering of significant angle deviations in the regulatory domain. A similar clustering was not observed in either of the other two structural domains of PGDH. In addition, significant differences were also observed at the active site and in the Trp-139 loop. To determine if these residues were functionally significant and not just due to other factors such as crystal packing, mutagenic analysis of these residues was performed. Not unexpectedly, this analysis showed that residues that affected the kcat/Km were grouped around the active site and those that affected the serine sensitivity were grouped in the regulatory domain. However, more significantly, residues that affected the cooperativity of inhibition of activity were identified at both locations. These latter residues represent structural elements that participate in both the initial and the ultimate events of the transfer of cooperative behavior from the regulatory domain to the active site. As such, their identification will assist in the elucidation of the pathway of cooperative interaction in this enzyme as well as in the elucidation of the regulatory mechanism of the ACT domain in general.

D-3-Phosphoglycerate dehydrogenase from Mycobacterium tuberculosis is a link between the Escherichia coli and mammalian enzymes.

D-3-Phosphoglycerate dehydrogenase (PGDH) from Mycobacterium tuberculosis has been isolated to homogeneity and displays an unusual relationship to the Escherichia coli and mammalian enzymes. In almost all aspects investigated, the M. tuberculosis enzyme shares the characteristics of the mammalian PGDHs. These include an extended C-terminal motif, substrate inhibition kinetics, dependence of activity levels and stability on ionic strength, and the inability to utilize alpha-ketoglutarate as a substrate. The unique property that the M. tuberculosis enzyme shares with E. coli PGDH that it is very sensitive to inhibition by L-serine, with an I(0.5) = 30 microm. The mammalian enzymes are not inhibited by L-serine. In addition, the cooperativity of serine inhibition appears to be modulated by chloride ion, becoming positively cooperative in its presence. This is modulated by the gain of cooperativity in serine binding for the first two effector sites. The basis for the chloride modulation of cooperativity is not known, but the sensitivity to serine inhibition can be explained in terms of certain amino acid residues in critical areas of the structures. The differential sensitivity to serine inhibition by M. tuberculosis and human PGDH may open up interesting possibilities in the treatment of multidrug-resistant tuberculosis.