Biomedical subjects

Xue Zhang

Publications and source records attributed to Xue Zhang.

At least 19 recordsLinked to original sources

PubMed2026

Ancient DNA unveils distinctive ancestries in the Bronze and Iron Ages of East Tianshan.

The East Tianshan Mountains occupy a key corridor between Central and East Asia, but their population history remains poorly understood. Here we report genome-wide data from 135 ancient individuals from 11 archaeological sites. We identify a previously unrecognized Bronze Age admixture between populations related to Yellow River millet farmers and steppe pastoralists associated with the Chemurchek culture. In contrast, we find little genetic contribution from contemporaneous middle-to-late Bronze Age steppe pastoralists, despite their eastward expansion across the Eurasian Steppe. By the Iron Age, regional populations had become more heterogeneous, incorporating additional eastern and steppe-related sources while retaining variable contributions from Early Bronze Age groups. These results reveal sustained demographic interactions in eastern Central Asia nearly 1800 years preceding the establishment of the historic Silk Road.

DNA, Ancient↗

PubMed2026

Genomic insights into low-level rifampicin resistance mediated by borderline rpoB mutations in Mycobacterium tuberculosis: prevalence and phylogeny in Northeast China.

The emergence of low-level rifampicin (RIF) resistance in Mycobacterium tuberculosis poses a challenge to tuberculosis (TB) control, as it often leads to discordance between genotypic resistance detected by molecular assays (e.g., Xpert MTB/RIF) and phenotypic susceptibility in conventional drug susceptibility testing (DST). In this study, we performed whole-genome sequencing (WGS) on 17 clinical isolates from Changchun, Northeast China, which exhibited such discordance. All isolates harbored functional borderline mutations in the rpoB RRDR region, predominantly Leu452Pro and Leu430Pro (29% each), followed by His445Asn (18%). RIF minimum inhibitory concentration (MIC) values ranged from ≤0.25 to 1.0 mg/L, confirming low-level resistance. Notably, 53% (9/17) of the isolates were co-resistant to fluoroquinolones and 24% (4/17) to isoniazid (INH). According to WHO classification, 59% (10/17) were pre-extensively drug-resistant TB (Pre-XDR-TB) or multidrug-resistant TB (MDR-TB). Phylogenetic analysis revealed that 94% (16/17) belonged to the East Asian Beijing lineage (Lineage 2.2.1), with no evidence of recent local transmission. These findings underscore the complexity of low-level RIF resistance and its frequent association with broader drug resistance in a dominant lineage, highlighting the need for integrating MIC and WGS into diagnostic algorithms to guide appropriate treatment and surveillance.IMPORTANCEThe accurate detection of RIF resistance is critical for the management of TB, yet standard phenotypic methods often fail to identify strains with low-level resistance conferred by borderline rpoB mutations. This study provides the first genomic characterization of such discordant isolates in Northeast China, revealing a high prevalence of co-resistance to other key drugs and a strong association with the locally dominant Beijing lineage. The findings emphasize that reliance on phenotypic DST alone may lead to underestimation of drug resistance and inappropriate treatment, potentially contributing to the emergence and spread of Pre-XDR-TB and MDR-TB. Incorporating MIC determination and WGS into routine diagnostics could enhance detection, inform tailored therapy, and improve surveillance of these clinically significant strains.

Mycobacterium tuberculosis↗

PubMed2025

TRAIT: A Comprehensive Database for T-cell Receptor-antigen Interactions.

Comprehensive and integrated resources on interactions between T-cell receptors (TCRs) and antigens are still lacking for adoptive T-cell-based immunotherapies, highlighting a significant gap that must be addressed to fully understand the mechanisms of antigen recognition by T cells. In this study, we present the T-cell receptor-antigen interaction database (TRAIT), a comprehensive database that profiles the interactions between TCRs and antigens. TRAIT stands out due to its comprehensive description of TCR-antigen interactions by integrating sequences, structures, and affinities. It provides millions of experimentally validated TCR-antigen pairs, resulting in an exhaustive landscape of antigen-specific TCRs. Notably, TRAIT emphasizes single-cell omics as a major reliable data source for TCR-antigen interactions and includes millions of reliable non-interactive TCRs. Additionally, it thoroughly demonstrates the interactions between mutations of TCRs and antigens, thereby benefiting affinity optimization of engineered TCRs as well as vaccine design. TCRs on clinical trials are innovatively provided. With the significant efforts made toward elucidating the complex interactions between TCRs and antigens, TRAIT is expected to ultimately contribute superior algorithms and substantial advancements in the field of T-cell-based immunotherapies. TRAIT is freely accessible at https://pgx.zju.edu.cn/traitdb.

Receptors, Antigen, T-Cell↗

PubMed2006

Simultaneously inhibition of HIV and HBV replication through a dual small interfering RNA expression system.

Human immunodeficiency virus (HIV) is often acquired in individuals already infected with hepatitis B virus (HBV) as a result of shared routes of transmission. Since current options for the treatment of HIV and HBV infections are limited, there is an essential need for the development of effective therapies against HIV/HBV co-infections. RNA interference (RNAi) has been used as a powerful tool to silence genes in cells and animals. In this study, we developed a small interfering RNA generation system that expressed two different siRNAs to target the HBs gene of HBV and the gp120 gene of HIV in Bel-7402 and HEK293T cells, respectively. Our results demonstrated that the two siRNA molecules could simultaneously inhibit the expression of HBs and gp120 by 81% and 89%, respectively. In addition, dual siRNA molecules significantly decreased the production of HBs, and simultaneously inhibited the replication of HBV and HIV. This dual siRNA generation system not only proved to be a novel approach for studying functions of multiple genes simultaneously, but also provides a potential approach for the treatment and prevention of HIV and HBV co-infection.

Animals↗

PubMed2006

Inhibition of SARS-CoV gene expression by adenovirus-delivered small hairpin RNA.

OBJECTIVE: Severe acute respiratory syndrome (SARS) is a highly contagious and lethal disease caused by a new type of coronavirus, SARS-associated coronavirus (SARS-CoV). Currently, there is no efficient treatment and prevention for this disease. We constructed recombinant adenoviral vectors that can express shRNAs, which inhibited the expression of SARS-CoV genes effectively in mammalian cells. METHODS: In this study, we designed several plasmids that express small hairpin RNA molecules (shRNA) specifically targeting to the genes encoding for the SARS-CoV nucleocapsid (N) protein and envelope (E) protein, respectively. Effective shRNA molecules to the viral genes were screened and identified, and then constructed into adenovirus vectors. The effects of adenovirus-delivered small hairpin RNA on SARS-CoV gene expression were determined by RT-PCR, Western blot, and luciferase activity assays. RESULTS: The levels of viral mRNAs and viral proteins of the targets were significantly decreased or completely inhibited in cell lines after being infected with the recombinant adenoviruses that expressed specific shRNA molecules. CONCLUSIONS: Since many cell types can be efficiently infected by adenovirus, recombinant adenoviruses could serve as an alternative powerful tool for shRNA delivery and for gene suppression, especially when the targeted cells are resistant to transfection by DNA or RNA. With availability of high titers of adenoviruses and uniform and rapid infection, this approach would have foreseeable wide applications both in experimental biology and molecular medicine.

Adenoviridae↗

PubMed2006

Hydrogen bonding makes a difference in the rhodium-catalyzed enantioselective hydrogenation using monodentate phosphoramidites.

A new generation of monodentate phosphoramidite ligands bearing a primary amine moiety was found to display comparable or better efficiency than bisphosphines in the Rh-catalyzed asymmetric hydrogenation of challenging substrates, such as (Z)-methyl alpha-acetoxyacrylate or (E)-beta-aryl itaconate derivatives, affording the corresponding hydrogenation products with excellent enantioselectivities (up to >99% ee). The presence of intermolecular hydrogen bonding (HB) between two monodentate ligands in the catalyst was found to be critical for excellent catalyst performance. This finding provides a basis for design and development of further catalyst systems using this type of monodentate phosphoramidite ligands.

Catalysis↗

PubMed2006

Tumor suppressor PTEN affects tau phosphorylation: deficiency in the phosphatase activity of PTEN increases aggregation of an FTDP-17 mutant Tau.

BACKGROUND: Aberrant hyperphosphorylation of tau protein has been implicated in a variety of neurodegenerative disorders. Although a number of protein kinases have been shown to phosphorylate tau in vitro and in vivo, the molecular mechanisms by which tau phosphorylation is regulated pathophysiologically are largely unknown. Recently, a growing body of evidence suggests a link between tau phosphorylation and PI3K signaling. In this study, phosphorylation, aggregation and binding to the microtubule of a mutant frontal temporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) tau in the presence of tumor suppressor PTEN, a major regulatory component in PI3K signaling, were investigated. RESULTS: Phosphorylation of the human mutant FTDP-17 tau, T40RW, was evaluated using different phospho-tau specific antibodies in the presence of human wild-type or phosphatase activity null mutant PTEN. Among the evaluated phosphorylation sites, the levels of Ser214 and Thr212 phospho-tau proteins were significantly decreased in the presence of wild-type PTEN, and significantly increased when the phosphatase activity null mutant PTEN was ectopically expressed. Fractionation of the mutant tau transfected cells revealed a significantly increased level of soluble tau in cytosol when wild-type PTEN was expressed, and an elevated level of SDS-soluble tau aggregates in the presence of the mutant PTEN. In addition, the filter/trap assays detected more SDS-insoluble mutant tau aggregates in the cells overexpressing the mutant PTEN compared to those in the cells overexpressing wild-type PTEN and control DNA. This notion was confirmed by the immunocytochemical experiment which demonstrated that the overexpression of the phosphatase activity null mutant PTEN caused the mutant tau to form aggregates in the COS-7 cells. CONCLUSION: Tumor suppressor PTEN can alleviate the phosphorylation of the mutant FTDP-17 tau at specific sites, and the phosphatase activity null PTEN increases the mutant tau phosphorylation at these sites. The changes of the tau phosphorylation status by ectopic expression of PTEN correlate to the alteration of the mutant tau's cellular distribution. In addition, the overexpression of the mutant PTEN can increase the level of the mutant tau aggregates and lead to the formation of visible aggregates in the cells.

Journal Article↗

PubMed2006

A novel deletion in TNNI2 causes distal arthrogryposis in a large Chinese family with marked variability of expression.

Distal arthrogryposis (DA) is composed of a group of clinically and genetically heterogeneous disorders, characterized by multiple congenital contractures of the limbs. Point mutations in three genes encoding contractile fast-twitch myofibers, TPM2, TNNI2 and TNNT3, were recently identified in DA type 1 (DA1; MIM 108120) and DA type 2B (DA2B; MIM 601680). We have described a large Chinese DA family in which different individuals had phenotypes similar to DA1 or DA2B. To map the disease locus in this family, two-point linkage analysis was first performed using microsatellite markers selected from the genomic regions close to the TPM2, TNNI2/TNNT3 and TNNC2 genes. A positive LOD score of 3.61 at theta = 0 was obtained with the marker close to the TNNI2/TNNT3 genes, corresponding to the genetic mapping site of DA2B. Direct sequencing of the PCR-amplified DNA fragment spanning exon 8 of the TNNI2 gene showed a heterozygous deletion, c.523_525delAAG (p.K175del), in the proband. This novel mutation was confirmed to cosegregate with the DA phenotype in affected individuals but not detected in all unaffected individuals of the family and not in 50 healthy controls. In summary, we have found a novel TNNI2 mutation in a Chinese family with DA2B. Our work represents the first report on the link between TNNI2 and the DA phenotype in Chinese.

Arthrogryposis↗

PubMed2006

The role of Sp1 and Sp3 in the constitutive DPYD gene expression.

Dihydropyrimidine dehydrogenase (DPD), the initial and rate-limiting enzyme in the 5-fluorouracil (5-FU) catabolic pathway, has been implicated as one of the factors determining the efficacy and toxicity of the anticancer agent 5-FU. Studies have attributed variation in DPD activity partially to alterations at the transcriptional level of DPYD gene. We investigated the transcription factors implicated in the constitutive expression of DPYD by utilizing a 174-bp fragment of the DPYD promoter region in which three consensus Sp protein binding sites (SpA, SpB and SpC) were predicted. The binding of Sp1 and Sp3 transcription factors to this region was detected by electrophoretic mobility shift and chromatin immunoprecipitation assays. By ectopically expressing human Sp1 and Sp3 in Sp-deficient Drosophila S2 cells, we demonstrated that Sp1 is a strong activator, while Sp3 by its own is a weak activator of the DPYD promoter. Moreover, Sp3 may serve as a competitor of Sp1, thus decreasing the Sp1 induced promoter activity. SpA, SpB and SpC sites are all Sp1 inducible. In the full activation of the DPYD promoter in human cell lines, the SpB site is essential; the SpC site works cooperatively with SpB, while SpA has minor promoter activity. These studies provide further insight into the molecular mechanisms underlying the heterogeneity of DPD activity, and may facilitate the efficacy and safety of 5-FU-based chemotherapy.

Base Sequence↗

PubMed2006

Tumor-suppressor PTEN affects tau phosphorylation, aggregation, and binding to microtubules.

Neurofibrillary tangles (NFTs), consisting of abnormally hyperphosphorylated tau, are implicated in the pathogenesis of several neurodegenerative diseases including Alzheimer's disease (AD). The molecular mechanisms underlying the regulation of tau phosphorylation are largely unknown. While the PI3K/Akt pathway has been shown to regulate multiple cellular events pertinent to AD pathogenesis, potential functions of tumor suppressor phosphatase and tensin homologue deleted on chromosome 10 (PTEN) in AD pathogenesis have not been explored. Here, we examine the effects of PTEN on tau phosphorylation, its microtubule association and formation of aggregates, and consequentially neuronal morphology. In cultured cells, overexpression of wild-type (WT) PTEN alters tau phosphorylation at several sites, increases tau-microtubule association and decreases formation of tau aggregates. In addition, the phosphatase-null PTEN increases tau aggregation and impairs tau binding to microtubule and neurite outgrowth of neurons expressing the mutant PTEN. We also found a significant loss of PTEN in AD patient brains correlated with a dramatically increased concentration of phospho-tau at Ser-214 in NFTs. Together, our results demonstrate that PTEN regulates tau phosphorylation, binding to microtubules and formation of aggregates and neurite outgrowth. These findings suggest a link between malfunction of PTEN and tauopathy, and imply PTEN as a therapeutic target for tauopathy.

Alzheimer Disease↗

PubMed2006

Transcriptional regulation of APH-1A and increased gamma-secretase cleavage of APP and Notch by HIF-1 and hypoxia.

The proteolytic cleavage of Alzheimer beta-amyloid precursor protein (APP) and signaling receptor Notch is mediated by the PS/gamma-secretase complex, which consists of presenilins, nicastrin, APH-1, and PEN-2. Although the four components are known to coordinately regulate each other at the protein level, information regarding their transcription regulation is scarce. Here we characterized the 5'-flanking region of the human APH-1A gene and identified a 271-bp fragment containing the transcription initiation site for the promoter activity. Sequence analysis, mutagenesis, and gel shift studies revealed a binding of AP4 and HIF-1 to the promoter, which affects the promoter activity. Activation of HIF-1 by short-term NiCl2 treatments (a condition of chemical hypoxia) dramatically increased APH-1A mRNA and protein expression, accompanied by increased secretion of Abeta and decreased APP CTFs formation, indicative of an increase in gamma-secretase activity. NiCl2 treatments had little effect on APP and the other three components of the gamma-secretase complex. The cellular concentration of Notch intracellular domain (NICD) was also increased by the hypoxic treatment. Our results demonstrate that APH-1A expression and the gamma-secretase mediated Abeta and Notch NICD generation are regulated by HIF-1, and the specific control of APH-1A expression may imply physiological functions uniquely assigned to APH-1A.

Amyloid Precursor Protein Secretases↗

PubMed2006

Experimental and theoretical studies on the hydrogen-bond-promoted enantioselective hetero-Diels-Alder reaction of Danishefsky's diene with benzaldehyde.

The enantioselective hetero-Diels-Alder (HDA) reaction of Danishefsky's diene with benzaldehyde has been achieved catalytically by a series of alpha,alpha,alpha',alpha'-tetraaryl-1,3-dioxolane-4,5-dimethanol (TADDOL) derivatives through hydrogen-bonding activation, affording 2-phenyl-2,3-dihydro-4H-pyran-4-one after trifluoroacetic acid workup in moderate yield and good enantioselectivity. The alpha,alpha'-aryl substituents in the TADDOL molecules are found to exert a significant impact on both the activity and the enantioselectivity of the catalysis. In combination with the experimental investigations, the mechanism of the present reaction has also been studied theoretically using the ONIOM (B3LYP/6-31G:PM3) method with trans-1,3-dimethoxy-1,3-butadiene as the model for Danishefsky's diene. In agreement with the experimental findings, the calculation results indicate that this TADDOL-catalyzed HDA reaction proceeds via a concerted mechanism through an asynchronous and zwitterionic transition structure (TS). The carbonyl group of benzaldehyde is activated by forming an intermolecular hydrogen bond with one of the hydroxy groups of TADDOL. Meanwhile, the intramolecular hydrogen bond between the two hydroxy groups in TADDOL is found to facilitate the intermolecular hydrogen bonding with benzaldehyde. The sense of asymmetric induction is well-rationalized by the analysis of the relative energies of TADDOL-complexed TSs, while the different stereocontrol capabilities exhibited by TADDOLs in the reaction can be qualitatively established on the basis of the structural features of their corresponding TSs.

Alkenes↗

PubMed2006

Species-specific identification by inhibitor-controlled PCR of ruminant components contaminating industrial crude porcine heparin.

With the emergence of bovine spongiform encephalopathy, the source of pharmaceutical heparin is currently restricted to porcine intestinal mucosa. To control the species origin of industrial crude heparin, molecular biology methods relying on species-specific protein or DNA analysis should be developed to identify the ruminant components that might be contaminants in industrial crude porcine heparin (ICPH). Because heparin contained in ICPH is a strong PCR inhibitory substance, it is necessary to explore DNA extraction methods specific for ICPH and develop analysis methods that could monitor the presence of PCR inhibitory substances. In the present studies, DNA was extracted from ICPH by seven methods, and their abilities to remove the PCR inhibitory substances were compared using inhibitory-controlled PCR (IC-PCR). The results showed that, based on the optimization of the final concentration of the internal processing control (IPC), IC-PCR was a rapid, sensitive and efficient way to monitor the presence of PCR inhibitory substances contained in DNA extracted from ICPH, and only the agarose gel purification method could be used to completely eliminate the PCR inhibitory substances contained in ICPH.

Animals↗

PubMed2006

[A DNA duplication at chromosome 10q24.3 is associated with split-hand split-foot malformation in a Chinese family].

OBJECTIVE: To identify the disease-causing genetic alteration of split-hand/split-foot malformation (SHFM) in a Chinese family. METHODS: Three of the 5 affected individuals from a four-generation Chinese SHFM family were examined physically and radiologically. Peripheral blood samples were collected from Digital photographs of the malformed hands and feet were taken. Peripheral blood samples were collected from 2 affected individuals, and lymphocytes were isolated to undergo high resolution G-banding. Genomic DNA was extracted from the whole blood samples of 4 available family members, including the 3 affected individuals. All 16 exons and their flanking intronic sequences of the TP63 gene were amplified using polymerase chain reaction (PCR) and sequenced directly. Microsatellite markers from the five SHFM loci were analyzed in the available family members by PCR, polyacrylamide gel electrophoresis and silver staining. For semi-quantitative determination of the allele copy number, the polymorphic PCR-amplified fragments representing genetic markers from the SHFM3 locus at chromosome 10q24.3 were sequenced in the affected individuals using normal individuals with identical genotypes as controls. RESULTS: All 3 existing affected individuals showed absence of 3 radial fingers, 2 affected individuals had a deep central cleft and central ray deficiency in the feet, and 1 affected individual had a fibular monodactyli, all limb malformations being bilateral and consistent with the phenotype of typical SHFM. G-banding showed normal karyotypes in the 3 affected individuals and no visible cytogenetic abnormality was found. Moreover, no mutation was identified in the TP63 gene. While no haplotype sharing was observed in the markers from loci SHFM1, SHFM4 and SHFM5, potential haplotype sharing was detected in the markers from two loci, SHFM2 and SHFM3, indicating possible causative mutation at SHFM2 or SHFM3. Furthermore, obviously biased silver density toward the allele fragments shared by the 3 affected individuals was observed in the markers from the SHFM3 locus. Comparative sequencing showed roughly one-fold increase of fluorescent signal of the shared fragments in the affected individuals. These results suggested a large-scale DNA duplication within the SHFM3 locus. CONCLUSION: A large-scale DNA duplication within the SHFM3 locus at chromosome 10q24.3 has been identified as the pathogenic genetic change in Chinese patients with SHFM.

Base Sequence↗

PubMed2006

[Cloning and expression of human interleukin-26 in Escherichia coli].

To clone human interleukin-26 (hIL-26) and express it in E. coli efficiently. Two pairs of primers were synthesized according to the hIL-26 gene reported on GenBank. The hIL-26 gene was cloned by nest PCR following the first round RT-PCR from human peripherial blood monocytes total RNA, and then the PCR product was cloned into pMD18-T vector. Colony PCR, restriction analysis and sequence analysis showed that the gene cloned was the same as the reported hIL-26. The recombinant was cut with BamHI and EcoR I to obtain the hIL-26 fragment, and then the fragment was inserted into pBV220 which was cut with the same enzymes. The recombinant expression vector was induced to express hIL-26 at 42 degrees C, SDS-PAGE analysis showed that the recombinant protein accounted for up to 20% of the whole protein of E. coli, and the protein was also confirmed by Western blotting. Purity of the protein was found to be above 90% after purified with molecular sieve. After renaturalized with glutathione buffer, the promoting effect of it on the production of IFN-y in PBMC was detected by RT-PCR. A recombinant bacterial strain for expressing hIL-26 with biological activity was constructed successfully.

Cloning, Molecular↗

PubMed2006

pH-regulated Slo3 K+ channels: properties of unitary currents.

Here we have examined the voltage and pH dependence of unitary Slo3 channels and used analysis of current variance to define Slo3 unitary current properties over a broader range of voltages. Despite complexity in Slo3 channel openings that precludes simple definition of the unitary conductance, average current through single Slo3 channels varies linearly with voltage at positive activation potentials. Furthermore, the average Slo3 unitary current at a given activation potential does not change with pH. Consistent with macroscopic conductance estimates, the apparent open probability of Slo3 channel exhibits a pH-dependent maximum, with limiting values around 0.3 at the most elevated pH and voltage. Estimates of Slo3 conductance at negative potentials support a weaker intrinsic voltage dependence of gating than is observed for Slo1. For the pH-regulated Slo3 K(+) channel, the dependence of macroscopic conductance on pH suggests that the pH-sensitive mechanism regulates gating in an allosteric manner qualitatively similar to regulation of Slo1 by Ca(2+). Together, the results support the view that the regulation of macroscopic Slo3 currents by pH reflects regulation of gating equilibria, and not a direct effect of pH on ion permeation. Specifically, both voltage and pH regulate a closed-open conformational change in a largely independent fashion.

Animals↗

PubMed2006

Slo3 K+ channels: voltage and pH dependence of macroscopic currents.

The mouse Slo3 gene (KCNMA3) encodes a K(+) channel that is regulated by changes in cytosolic pH. Like Slo1 subunits responsible for the Ca(2+) and voltage-activated BK-type channel, the Slo3 alpha subunit contains a pore module with homology to voltage-gated K(+) channels and also an extensive cytosolic C terminus thought to be responsible for ligand dependence. For the Slo3 K(+) channel, increases in cytosolic pH promote channel activation, but very little is known about many fundamental properties of Slo3 currents. Here we define the dependence of macroscopic conductance on voltage and pH and, in particular, examine Slo3 conductance activated at negative potentials. Using this information, the ability of a Horrigan-Aldrich-type of general allosteric model to account for Slo3 gating is examined. Finally, the pH and voltage dependence of Slo3 activation and deactivation kinetics is reported. The results indicate that Slo3 differs from Slo1 in several important ways. The limiting conductance activated at the most positive potentials exhibits a pH-dependent maximum, suggesting differences in the limiting open probability at different pH. Furthermore, over a 600 mV range of voltages (-300 to +300 mV), Slo3 conductance shifts only about two to three orders of magnitude, and the limiting conductance at negative potentials is relatively voltage independent compared to Slo1. Within the context of the Horrigan-Aldrich model, these results indicate that the intrinsic voltage dependence (z(L)) of the Slo3 closed-open equilibrium and the coupling (D) between voltage sensor movement are less than in Slo1. The kinetic behavior of Slo3 currents also differs markedly from Slo1. Both activation and deactivation are best described by two exponential components, both of which are only weakly voltage dependent. Qualitatively, the properties of the two kinetic components in the activation time course suggest that increases in pH increase the fraction of more rapidly opening channels.

Allosteric Regulation↗

PubMed2006

Transcriptional regulation of PEN-2, a key component of the gamma-secretase complex, by CREB.

Gamma-secretase, which is responsible for the intramembranous cleavage of Alzheimer's beta-amyloid precursor protein (APP), the signaling receptor Notch, and many other substrates, is a multiprotein complex consisting of at least four components: presenilin (PS), nicastrin, APH-1, and PEN-2. Despite the fact that PEN-2 is known to mediate endoproteolytic cleavage of full-length PS and APH-1 and nicastrin are required for maintaining the stability of the complex, the detailed physiological function of each component remain elusive. Unlike that of PS, the transcriptional regulation of PEN-2, APH-1, and nicastrin has not been investigated. Here, we characterized the upstream regions of the human PEN-2 gene and identified a 238-bp fragment located 353 bp upstream of the translational start codon as the key region necessary for the promoter activity. Further analysis revealed a CREB binding site located in the 238-bp region that is essential for the transcriptional activity of the PEN-2 promoter. Mutation of the CREB site abolished the transcriptional activity of the PEN-2 promoter. Electrophoretic mobility shift assays and chromatin immunoprecipitation analysis showed the binding of CREB to the PEN-2 promoter region both in vitro and in vivo. Activation of the CREB transcriptional factor by forskolin dramatically promoted the expression of PEN-2 mRNA and protein, whereas the other components of the gamma-secretase complex remained unaffected. Forskolin treatment slightly increases the secretion of soluble APPalpha and Abeta without affecting Notch cleavage. These results demonstrate that expression of PEN-2 is regulated by CREB and suggest that the specific control of PEN-2 expression may imply additional physiological functions uniquely assigned to PEN-2.

Amyloid Precursor Protein Secretases↗