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Shi Y, Wu W, Chai Q, Li Q, Hou Y, Xia H, Ren B, Xu H, Guo X, Jin C, Lv M, Wang Z, Fu YX, Zhu M. LTβR controls thymic portal endothelial cells for haematopoietic progenitor cell homing and T-cell regeneration. Nat Commun 2016; 7:12369. [PMID: 27493002 PMCID: PMC4980457 DOI: 10.1038/ncomms12369] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 06/27/2016] [Indexed: 12/19/2022] Open
Abstract
Continuous thymic homing of haematopoietic progenitor cells (HPCs) via the blood is critical for normal T-cell development. However, the nature and the differentiation programme of specialized thymic endothelial cells (ECs) controlling this process remain poorly understood. Here using conditional gene-deficient mice, we find that lymphotoxin beta receptor (LTβR) directly controls thymic ECs to guide HPC homing. Interestingly, T-cell deficiency or conditional ablation of T-cell-engaged LTβR signalling results in a defect in thymic HPC homing, suggesting the feedback regulation of thymic progenitor homing by thymic products. Furthermore, we identify and characterize a special thymic portal EC population with features that guide HPC homing. LTβR is essential for the differentiation and homeostasis of these thymic portal ECs. Finally, we show that LTβR is required for T-cell regeneration on irradiation-induced thymic injury. Together, these results uncover a cellular and molecular pathway that governs thymic EC differentiation for HPC homing. Lymphoid progenitors migrate from the bone marrow into the thymus to give rise to T and NK cell lineages. Here the authors characterize a lymphotoxin receptor beta-dependent population of thymic endothelial cells that guide lymphoid progenitor homing in the thymus.
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Qian LL, Wang RX, Sun MQ, Xia DY, Tang X, Ji Y, Wu Y, Liu XY, Dang SP, Chai Q, Lu T. [Composition of potassium channels in normal rat coronary smooth muscle cells and activation effects of docosahexaenoic acid]. ZHONGHUA XIN XUE GUAN BING ZA ZHI 2016; 44:600-4. [PMID: 27530945 DOI: 10.3760/cma.j.issn.0253-3758.2016.07.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVE To investigate the composition of potassium channels in normal rat coronary smooth muscle cells (CASMCs) and the activation effects of docosahexaenoic acid (DHA). METHODS CASMCs were isolated by enzyme digestion.Effects of different types of potassium channel blockers and/or DHA on potassium channels currents were studied by whole-cell patch clamp technique. RESULTS Potassium currents were significantly increased with 5 μmol/L DHA perfusion (P<0.05). The current density was increased from (52.80±6.68) pA/pF to (110.09±13.39) pA/pF (P<0.05) after DHA perfusion when the stimulation voltage was 100 mV.Compared with baseline, potassium currents were significantly decreased by various inhibitor perfusion (tetraethylammonium: (49.63±5.75) pA/pF vs. (13.96±2.18) pA/pF; ibritoxin: (50.67±7.89) pA/pF vs. (26.53±4.68) pA/pF; TRAM-34: (52.60±7.02) pA/pF vs. (46.05±7.60) pA/pF; apamin: (51.97±3.83) pA/pF vs. (44.89±5.04) pA/pF; 4-aminopyridine: (51.19±3.44) pA/pF vs. (29.92±2.81) pA/pF; glyburide: (49.67±1.77) pA/pF vs. (49.61±1.87) pA/pF, all P<0.05). In presence of different inhibitors, potassium channel current densities were increased after DHA perfusion except tetraethylammonium (tetraethylammonium: ( 12.79±1.89) pA/pF; ibritoxin: (67.08±5.54) pA/pF; TRAM-34: (117.91±21.79) pA/pF; apamin: (108.33±7.06) pA/pF; 4-aminopyridine: (127.73±20.56) pA/pF; glyburide: (121.53±13.83) pA/pF, all P<0.05 compared with baseline). CONCLUSIONS Large-conductance calcium-activated potassium channel and voltage-gated potassium channel are the major constituents of potassium channels in CASMCs.DHA can activate potassium channels in CASMCs, mainly the large conductance calcium-activated potassium channel, thus dilate coronary arteries.
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Sun MQ, Qian LL, Dang SP, Wu Y, Tang X, Ji Y, Wang XY, Xia DY, Wang W, Chai Q, Lu T, Wang RX. [Docosahexaenoic acids activate large conductance calcium-activated potassium channels via phospholipase C- inositol triphosphate- calcium pathway in normal rat coronary smooth muscle cells]. ZHONGHUA XIN XUE GUAN BING ZA ZHI 2016; 44:530-5. [PMID: 27346268 DOI: 10.3760/cma.j.issn.0253-3758.2016.06.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVE To investigate the mechanisms of docosahexaenoic acids (DHA) on activating large conductance calcium-activated potassium channels (BK channels) in normal rat coronary smooth muscle cells. METHODS Normal coronary smooth muscle cells were isolated by enzyme digestion from Sprague-Dawley rats. BK currents were recorded by patch clamp in whole cell and single channel configurations, respectively. The effects of DHA on cytosolic calcium concentrations were examined by recording the changes of fluorescence intensity ratios. RESULTS DHA (1 μmol/L) could activate BK channels. Open probabilities (NP0) of BK channels at test potential 60 mV, and calcium concentrations in external solution at 0, 0.01, 0.1, 1, 3, 10, 50 and 100 μmol/L were 0.002 7±0.000 4, 0.006 0±0.001 4, 0.097 2±0.010 6, 0.137 9±0.032 9, 0.468 7±0.163 7, 2.097 1±0.310 4 and 3.120 4±0.242 7, respectively (P<0.05, n=4). Before DHA perfusion, the fluorescence intensity ratio was 0.51±0.01, and the ratios were 0.53±0.02 and 0.55±0.01 after 0.001 and 0.01 μmol/L DHA perfusion, respectively (P>0.05, n≥5). The ratios were 0.64±0.01, 0.65±0.01, 0.70±0.01, 0.69±0.01, 0.68±0.01 and 0.67±0.02 after 0.1, 0.3, 1, 3, 5 and 10 μmol/L DHA perfusion, respectively, and EC50 was (0.04±0.02) μmol/L(P<0.05, n≥4). They were all higher than that before DHA perfusion. After incubating with phospholipase C (PLC) blocker U73122 and inositol triphosphate (IP3) blocker 2-APB, the ratios were 0.52±0.01 and 0.49±0.02 on the setting of 0.1 μmol/L DHA, respectively. Compared with control group(0.64±0.01), the ratios decreased after incubating with blockers (P<0.05, n≥4). CONCLUSIONS Docosahexaenoic acids can activate large conductance calcium-activated potassium channels by the pathway of PLC-IP3-Ca(2+) to increase cytosolic calcium concentration in normal coronary smooth muscle cells, dilate the coronary vessels and bestow protective effects on cardiovascular system.
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Chai Q, Wang Z, Webb SR, Dutch RE, Wei Y. The ssrA-Tag Facilitated Degradation of an Integral Membrane Protein. Biochemistry 2016; 55:2301-4. [PMID: 27078234 DOI: 10.1021/acs.biochem.6b00038] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
ATP-dependent degradation plays a critical role in the quality control and recycling of proteins in cells. However, complete degradation of membrane proteins by ATP-dependent proteases in bacteria is not well-studied. We discovered that the degradation of a multidomain and multispan integral membrane protein AcrB could be facilitated by the introduction of a ssrA-tag at the C-terminus of the protein sequence and demonstrated that the cytoplasmic unfoldase-protease complex ClpXP was involved in the degradation. This is the first report to our knowledge to reveal that the ClpXP complex is capable of degrading integral membrane proteins. The chaperone SspB also played a role in the degradation. Using purified proteins, we demonstrated that the addition of the ssrA-tag did not drastically affect the structure of AcrB, and the degradation of detergent solubilized AcrB by purified ClpXP could be observed in vitro.
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Onder L, Nindl V, Scandella E, Chai Q, Cheng HW, Caviezel-Firner S, Novkovic M, Bomze D, Maier R, Mair F, Ledermann B, Becher B, Waisman A, Ludewig B. Alternative NF-κB signaling regulates mTEC differentiation from podoplanin-expressing precursors in the cortico-medullary junction. Eur J Immunol 2015; 45:2218-31. [PMID: 25973789 DOI: 10.1002/eji.201545677] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 04/23/2015] [Accepted: 05/12/2015] [Indexed: 01/08/2023]
Abstract
The thymic epithelium forms specialized niches to enable thymocyte differentiation. While the common epithelial progenitor of medullary and cortical thymic epithelial cells (mTECs and cTECs) is well defined, early stages of mTEC lineage specification have remained elusive. Here, we utilized in vivo targeting of mTECs to resolve their differentiation pathways and to determine whether mTEC progenitors participate in thymocyte education. We found that mTECs descend from a lineage committed, podoplanin (PDPN)-expressing progenitor located at the cortico-medullary junction. PDPN(+) junctional TECs (jTECs) represent a distinct TEC population that builds the thymic medulla, but only partially supports negative selection and thymocyte differentiation. Moreover, conditional gene targeting revealed that abrogation of alternative NF-κB pathway signaling in the jTEC stage completely blocked mTEC development. Taken together, this study identifies jTECs as lineage-committed mTEC progenitors and shows that NF-κB-dependent progression of jTECs to mTECs is critical to secure central tolerance.
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Wang Z, Zhong M, Lu W, Chai Q, Wei Y. Repressive mutations restore function-loss caused by the disruption of trimerization in Escherichia coli multidrug transporter AcrB. Front Microbiol 2015; 6:4. [PMID: 25657644 PMCID: PMC4303003 DOI: 10.3389/fmicb.2015.00004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Accepted: 01/03/2015] [Indexed: 11/13/2022] Open
Abstract
AcrAB-TolC and their homologs are major multidrug efflux systems in Gram-negative bacteria. The inner membrane component AcrB functions as a trimer. Replacement of Pro223 by Gly in AcrB decreases the trimer stability and drastically reduces the drug efflux activity. The goal of this study is to identify suppressor mutations that restore function to mutant AcrBP223G and explore the mechanism of function recovery. Two methods were used to introduce random mutations into the plasmid of AcrBP223G. Mutants with elevated drug efflux activity were identified, purified, and characterized to examine their expression level, trimer stability, interaction with AcrA, and substrate binding. Nine single-site repressor mutations were identified, including T199M, D256N, A209V, G257V, M662I, Q737L, D788K, P800S, and E810K. Except for M662I, all other mutations located in the docking region of the periplasmic domain. While three mutations, T199M, A209V, and D256N, significantly increased the trimer stability, none of them restored the trimer affinity to the wild type level. M662, the only site of mutation that located in the porter domain, was involved in substrate binding. Our results suggest that the function loss resulted from compromised AcrB trimerization could be restored through various mechanisms involving the compensation of trimer stability and substrate binding.
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Fasnacht N, Huang HY, Koch U, Favre S, Auderset F, Chai Q, Onder L, Kallert S, Pinschewer DD, MacDonald HR, Tacchini-Cottier F, Ludewig B, Luther SA, Radtke F. Specific fibroblastic niches in secondary lymphoid organs orchestrate distinct Notch-regulated immune responses. ACTA ACUST UNITED AC 2014; 211:2265-79. [PMID: 25311507 PMCID: PMC4203954 DOI: 10.1084/jem.20132528] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Fasnacht et al. now show that fibroblasts in secondary lymphoid organs are responsible for the production of Notch ligands regulating the differentiation of immune cells Fibroblast-like cells of secondary lymphoid organs (SLO) are important for tissue architecture. In addition, they regulate lymphocyte compartmentalization through the secretion of chemokines, and participate in the orchestration of appropriate cell–cell interactions required for adaptive immunity. Here, we provide data demonstrating the functional importance of SLO fibroblasts during Notch-mediated lineage specification and immune response. Genetic ablation of the Notch ligand Delta-like (DL)1 identified splenic fibroblasts rather than hematopoietic or endothelial cells as niche cells, allowing Notch 2–driven differentiation of marginal zone B cells and of Esam+ dendritic cells. Moreover, conditional inactivation of DL4 in lymph node fibroblasts resulted in impaired follicular helper T cell differentiation and, consequently, in reduced numbers of germinal center B cells and absence of high-affinity antibodies. Our data demonstrate previously unknown roles for DL ligand-expressing fibroblasts in SLO niches as drivers of multiple Notch-mediated immune differentiation processes.
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Ye C, Wang Z, Lu W, Zhong M, Chai Q, Wei Y. Correlation between AcrB trimer association affinity and efflux activity. Biochemistry 2014; 53:3738-46. [PMID: 24854514 PMCID: PMC4067148 DOI: 10.1021/bi5000838] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
![]()
The majority of membrane proteins
function as oligomers. However,
it remains largely unclear how the oligomer stability of protein complexes
correlates with their function. Understanding the relationship between
oligomer stability and activity is essential to protein research and
to virtually all cellular processes that depend on the function of
protein complexes. Proteins make lasting or transient interactions
as they perform their functions. Obligate oligomeric proteins exist
and function exclusively at a specific oligomeric state. Although
oligomerization is clearly critical for such proteins to function,
a direct correlation between oligomer affinity and biological activity
has not yet been reported. Here, we used an obligate trimeric membrane
transporter protein, AcrB, as a model to investigate the correlation
between its relative trimer affinity and efflux activity. AcrB is
a component of the major multidrug efflux system in Escherichia coli. We created six AcrB constructs
with mutations at the transmembrane intersubunit interface, and we
determined their activities using both a drug susceptibility assay
and an ethidium bromide accumulation assay. The relative trimer affinities
of these mutants in detergent micelles were obtained using blue native
polyacrylamide gel electrophoresis. A correlation between the relative
trimer affinity and substrate efflux activity was observed, in which
a threshold trimer stability was required to maintain efflux activity.
The trimer affinity of the wild-type protein was approximately 3 kcal/mol
more stable than the threshold value. Once the threshold was reached,
an additional increase of stability in the range observed had no observable
effect on protein activity.
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Perez-Shibayama C, Gil-Cruz C, Pastelin-Palacios R, Cervantes-Barragan L, Hisaki E, Chai Q, Onder L, Scandella E, Regen T, Waisman A, Isibasi A, Lopez-Macias C, Ludewig B. IFN-γ-producing CD4+ T cells promote generation of protective germinal center-derived IgM+ B cell memory against Salmonella Typhi. THE JOURNAL OF IMMUNOLOGY 2014; 192:5192-200. [PMID: 24778443 DOI: 10.4049/jimmunol.1302526] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Abs play a significant role in protection against the intracellular bacterium Salmonella Typhi. In this article, we investigated how long-term protective IgM responses can be elicited by a S. Typhi outer-membrane protein C- and F-based subunit vaccine (porins). We found that repeated Ag exposure promoted a CD4(+) T cell-dependent germinal center reaction that generated mutated IgM-producing B cells and was accompanied by a strong expansion of IFN-γ-secreting T follicular helper cells. Genetic ablation of individual cytokine receptors revealed that both IFN-γ and IL-17 are required for optimal germinal center reactions and production of porin-specific memory IgM(+) B cells. However, more profound reduction of porin-specific IgM B cell responses in the absence of IFN-γR signaling indicated that this cytokine plays a dominant role. Importantly, mutated IgM mAbs against porins exhibited bactericidal capacity and efficiently augmented S. Typhi clearance. In conclusion, repeated vaccination with S. Typhi porins programs type I T follicular helper cell responses that contribute to the diversification of B cell memory and promote the generation of protective IgM Abs.
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Chai Q, Singh B, Peisker K, Metzendorf N, Ge X, Dasgupta S, Sanyal S. Organization of ribosomes and nucleoids in Escherichia coli cells during growth and in quiescence. J Biol Chem 2014; 289:11342-11352. [PMID: 24599955 DOI: 10.1074/jbc.m114.557348] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have examined the distribution of ribosomes and nucleoids in live Escherichia coli cells under conditions of growth, division, and in quiescence. In exponentially growing cells translating ribosomes are interspersed among and around the nucleoid lobes, appearing as alternative bands under a fluorescence microscope. In contrast, inactive ribosomes either in stationary phase or after treatment with translation inhibitors such as chloramphenicol, tetracycline, and streptomycin gather predominantly at the cell poles and boundaries with concomitant compaction of the nucleoid. However, under all conditions, spatial segregation of the ribosomes and the nucleoids is well maintained. In dividing cells, ribosomes accumulate on both sides of the FtsZ ring at the mid cell. However, the distribution of the ribosomes among the new daughter cells is often unequal. Both the shape of the nucleoid and the pattern of ribosome distribution are also modified when the cells are exposed to rifampicin (transcription inhibitor), nalidixic acid (gyrase inhibitor), or A22 (MreB-cytoskeleton disruptor). Thus we conclude that the intracellular organization of the ribosomes and the nucleoids in bacteria are dynamic and critically dependent on cellular growth processes (replication, transcription, and translation) as well as on the integrity of the MreB cytoskeleton.
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Chai Q, Ferrell B, Zhong M, Zhang X, Ye C, Wei Y. Diverse sequences are functional at the C-terminus of the E. coli periplasmic chaperone SurA. Protein Eng Des Sel 2014; 27:111-6. [PMID: 24586054 DOI: 10.1093/protein/gzu003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
SurA is a major periplasmic molecular chaperone in Escherichia coli and has been shown to assist the biogenesis of several outer membrane proteins. The C-terminal fragment of SurA folds into a short β-strand, which forms a small three-stranded anti-parallel β-sheet module with the N-terminal β-hairpin. We found that the length of the C-terminal fragment, rather than its exact amino acid composition, had a big impact on SurA function. To investigate the determinant factor of the C-terminal sequence, we created a library of SurA constructs randomized in the last 10 residues. We screened the library and randomly analyzed 19 constructs that displayed SurA activity. The C-termini of these constructs shared little sequence similarity, except that β-strand-forming residues were preferentially enriched. Three SurA constructs were expressed and purified for structural characterization. Circular dichroism and fluorescence spectroscopy analyses revealed that their structures were similar to the structure of the wild-type SurA. Our results suggest that for scaffolding purpose proteins may tolerate various sequences provided certain general requirements such as hydrophobicity and secondary structure propensity are satisfied. Furthermore, the sequence tolerance of SurA at the C-terminus indicates that this area is not likely to be involved in substrate binding.
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Lu W, Zhong M, Chai Q, Wang Z, Yu L, Wei Y. Functional relevance of AcrB Trimerization in pump assembly and substrate binding. PLoS One 2014; 9:e89143. [PMID: 24551234 PMCID: PMC3925222 DOI: 10.1371/journal.pone.0089143] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 01/15/2014] [Indexed: 12/26/2022] Open
Abstract
AcrB is a multidrug transporter in the inner membrane of Escherichia coli. It is an obligate homotrimer and forms a tripartite efflux complex with AcrA and TolC. AcrB is the engine of the efflux machinery and determines substrate specificity. Active efflux depends on several functional features including proton translocation across the inner membrane through a proton relay pathway in the transmembrane domain of AcrB; substrate binding and migration through the substrate translocation pathway; the interaction of AcrB with AcrA and TolC; and the formation of AcrB homotrimer. Here we investigated two aspects of the inter-correlation between these functional features, the dependence of AcrA-AcrB interaction on AcrB trimerization, and the reliance of substrate binding and penetration on protein-protein interaction. Interaction between AcrA and AcrB was investigated through chemical crosslinking, and a previously established in vivo fluorescent labeling method was used to probe substrate binding. Our data suggested that dissociation of the AcrB trimer drastically decreased its interaction with AcrA. In addition, while substrate binding with AcrB seemed to be irrelevant to the presence or absence of AcrA and TolC, the capability of trimerization and conduction of proton influx did affect substrate binding at selected sites along the substrate translocation pathway in AcrB.
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Yu L, Lu W, Ye C, Wang Z, Zhong M, Chai Q, Sheetz M, Wei Y. Role of a conserved residue R780 in Escherichia coli multidrug transporter AcrB. Biochemistry 2013; 52:6790-6. [PMID: 24007302 DOI: 10.1021/bi400452v] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Multidrug efflux pumps play important roles in bacteria drug resistance. A major multidrug efflux system in Gram-negative bacteria is composed of the inner membrane transporter AcrB, outer membrane protein channel TolC, and membrane fusion protein AcrA. These three proteins form a large complex that spans both layers of cell membranes and the periplasmic space. AcrB exists and functions as a homotrimer. To identify residues at the trimer interface that play important roles in AcrB function, we conducted site directed mutagenesis and discovered a key residue, R780. Although R780K was partially functional, all other R780 mutants tested were completely nonfunctional. Replacement of R780 by other residues disrupted trimer association. However, a decrease of trimer stability was not the lone cause for the observed loss of activity, because the activity loss could not be restored by strengthening trimer interaction. Using both heat and chemical denaturation methods, we found that the mutation decreased protein stability. Finally, we identified a repressor mutation, M774K, through random mutagenesis. It restored the activity of AcrBR780A to a level close to that of the wild-type protein. To examine the mechanism of activity restoration, we monitored denaturation of AcrBR780A/M774K and found that the repressor mutation improved protein stability. These results suggest that R780 is critical for AcrB stability. When R780 was replaced by Ala, the protein retained the overall structure, still trimerized in the cell membrane, and interacted with AcrA. However, local structural rearrangement might have occurred and lead to the decrease of protein stability and loss of substrate efflux activity.
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Rosengarten JA, Scott PA, Larkin SE, Garbis S, Curzen NP, Townsend PA, Morgan JM, Lee H, Ling TY, Wang XL, Chai Q, Lau TW, Koestler CM, Park SJ, Daly RC, Greason KL, Cha YM. Main Session: Molecular mechanisms in cardiomyopathies. Europace 2013. [DOI: 10.1093/europace/eut194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Chai Q, Onder L, Scandella E, Gil-Cruz C, Perez-Shibayama C, Cupovic J, Danuser R, Sparwasser T, Luther SA, Thiel V, Rülicke T, Stein JV, Hehlgans T, Ludewig B. Maturation of lymph node fibroblastic reticular cells from myofibroblastic precursors is critical for antiviral immunity. Immunity 2013; 38:1013-24. [PMID: 23623380 PMCID: PMC7111182 DOI: 10.1016/j.immuni.2013.03.012] [Citation(s) in RCA: 180] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 03/29/2013] [Indexed: 01/11/2023]
Abstract
The stromal scaffold of the lymph node (LN) paracortex is built by fibroblastic reticular cells (FRCs). Conditional ablation of lymphotoxin-β receptor (LTβR) expression in LN FRCs and their mesenchymal progenitors in developing LNs revealed that LTβR-signaling in these cells was not essential for the formation of LNs. Although T cell zone reticular cells had lost podoplanin expression, they still formed a functional conduit system and showed enhanced expression of myofibroblastic markers. However, essential immune functions of FRCs, including homeostatic chemokine and interleukin-7 expression, were impaired. These changes in T cell zone reticular cell function were associated with increased susceptibility to viral infection. Thus, myofibroblasic FRC precursors are able to generate the basic T cell zone infrastructure, whereas LTβR-dependent maturation of FRCs guarantees full immunocompetence and hence optimal LN function during infection. Novel transgenic mouse model that targets FRCs in adult lymph nodes FRC-specific ablation of the LTβR did not abrogate LN development Myofibroblastic FRC precursors generate the basic infrastructure of the adult LN LTβR-mediated FRC maturation is critical for the maintenance of immunocompentence
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Lu W, Chai Q, Zhong M, Yu L, Fang J, Wang T, Li H, Zhu H, Wei Y. Corrigendum to “Assembling of AcrB Trimer in Cell Membrane” [J. Mol. Biol. 423(1) (2012) 123–134]. J Mol Biol 2013. [DOI: 10.1016/j.jmb.2012.12.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Onder L, Danuser R, Scandella E, Firner S, Chai Q, Hehlgans T, Stein JV, Ludewig B. Endothelial cell-specific lymphotoxin-β receptor signaling is critical for lymph node and high endothelial venule formation. ACTA ACUST UNITED AC 2013; 210:465-73. [PMID: 23420877 PMCID: PMC3600902 DOI: 10.1084/jem.20121462] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The development of lymph nodes (LNs) and formation of LN stromal cell microenvironments is dependent on lymphotoxin-β receptor (LTβR) signaling. In particular, the LTβR-dependent crosstalk between mesenchymal lymphoid tissue organizer and hematopoietic lymphoid tissue inducer cells has been regarded as critical for these processes. Here, we assessed whether endothelial cell (EC)-restricted LTβR signaling impacts on LN development and the vascular LN microenvironment. Using EC-specific ablation of LTβR in mice, we found that conditionally LTβR-deficient animals failed to develop a significant proportion of their peripheral LNs. However, remnant LNs showed impaired formation of high endothelial venules (HEVs). Venules had lost their cuboidal shape, showed reduced segment length and branching points, and reduced adhesion molecule and constitutive chemokine expression. Due to the altered EC-lymphocyte interaction, homing of lymphocytes to peripheral LNs was significantly impaired. Thus, this study identifies ECs as an important LTβR-dependent lymphoid tissue organizer cell population and indicates that continuous triggering of the LTβR on LN ECs is critical for lymphocyte homeostasis.
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Ye C, Chai Q, Zhong M, Wei Y. Effect of crowding by Ficolls on OmpA and OmpT refolding and membrane insertion. Protein Sci 2012; 22:239-45. [PMID: 23225740 DOI: 10.1002/pro.2205] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Revised: 11/26/2012] [Accepted: 11/29/2012] [Indexed: 11/07/2022]
Abstract
Folding of outer membrane proteins (OMPs) has been studied extensively in vitro. However, most of these studies have been conducted in dilute buffer solution, which is different from the crowded environment in the cell periplasm, where the folding and membrane insertion of OMPs actually occur. Using OmpA and OmpT as model proteins and Ficoll 70 as the crowding agent, here we investigated the effect of the macromolecular crowding condition on OMP membrane insertion. We found that the presence of Ficoll 70 significantly slowed down the rate of membrane insertion of OmpA while had little effect on those of OmpT. To investigate if the soluble domain of OmpA slowed down membrane insertion in the presence of the crowding agent, we created a truncated OmpA construct that contains only the transmembrane domain (OmpA171). In the absence of crowding agent, OmpA171 refolded at a similar rate as OmpA, although with decreased efficiency. However, under the crowding condition, OmpA171 refolded significantly faster than OmpA. Our results suggest that the periplasmic domain slows down the rate, while improves the efficiency, of OmpA folding and membrane insertion under the crowding condition. Such an effect was not obvious when refolding was studied in buffer solution in the absence of crowding.
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Lu W, Chai Q, Zhong M, Yu L, Fang J, Wang T, Li H, Zhu H, Wei Y. Assembling of AcrB trimer in cell membrane. J Mol Biol 2012; 423:123-34. [PMID: 22766312 PMCID: PMC5699209 DOI: 10.1016/j.jmb.2012.06.036] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 06/26/2012] [Accepted: 06/26/2012] [Indexed: 11/16/2022]
Abstract
Many membrane proteins exist and function as oligomers, but how monomers oligomerize in the cell membrane remains poorly understood. AcrB is an obligate homo-trimer. We previously found that the folding of individual subunit precedes oligomerization. Following folding, individual AcrB subunits must locate and interact with each other in order to dimerize and eventually trimerize. It has been unclear if AcrB trimerization is a spontaneous process following the "chance encounter and random assembling" mechanism. In other words, it is currently unknown whether monomeric subunits diffuse freely to "search" for each other after they are co-translationally inserted and folded into the cell membrane. Using four sets of experiments exploiting AcrB variants with different fusion tags, disulfide trapping, and activity measurement, here we showed that AcrB variants co-expressed in the same Escherichia coli cell did co-assemble into hybrid trimers in vivo. However, the level of co-assembly measured experimentally was not consistent with calculations derived from random assembling. The potential role of the polysome structure during protein translation and the resultant clustering effect were discussed as a potential explanation for the observed bias in AcrB subunit assembling in vivo. Our results provide new insights into the dynamic assembling and equilibration process of obligate homo-oligomeric membrane proteins in the cell membrane.
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Chen Z, Chai Q, Liao S, Chen X, He Y, Li Y, Wu W, Li B. Nonisothermal Kinetic Study: IV. Comparative Methods To Evaluate Ea for Thermal Decomposition of KZn2(PO4)(HPO4) Synthesized by a Simple Route. Ind Eng Chem Res 2012. [DOI: 10.1021/ie300774x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Ludewig B, Chai Q, Onder L, Scandella E, Sparwasser T, Luther S, Thiel V, Rülicke T, Hehlgans T. CCL19-Cre transgenics: targeting lymph node fibroblastic reticular cells in vivo (44.14). THE JOURNAL OF IMMUNOLOGY 2012. [DOI: 10.4049/jimmunol.188.supp.44.14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
The paracortex of lymph nodes (LNs) harbors a sponge-like scaffold of stromal cells known as fibroblastic reticular cells (FRCs). A major function of FRCs is to build and enwrap the conduit system of collagen fibers that directs interstitial fluids from the afferent lymph through the T-cell zone to HEVs. Furthermore, FRCs regulate T-cell migration and survival by producing the chemokines CCL19 and CCL21. To gain further knowledge on the biology of FRCs and possibly other stromal cell subsets, we have generated a bacterial artificial chromosome (BAC)-transgenic mouse model that utilizes the CCL19 promoter to direct the Cre-recombinase to LN stromal cells. Crossing of CCL19-Cre mice to the R26-EYFP reporter revealed that transgene expression in LNs was almost exclusively confined to podoplanin+CD31- cells. Likewise, transgene activity in spleens and Peyer’s patches of CCL19-Cre mice was largely restricted to FRC-like cells, i.e. stromal cells within the T cell zone and the T-B border. Selective ablation of the lymphotoxin-beta receptor on CCL19-Cre-positive cells resulted in profound changes in the development and organization of secondary lymphoid organs. Taken together, stromal CCL19-Cre expression is well-suited (i) to characterize the development of LN FRCs in vivo, (ii) to molecularly dissect the contribution of stromal cells to lymphoid organogenesis, and (iii) to address the function of LN FRCs in the generation of innate and adaptive immune responses.
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Stein J, Coelho F, Soriano S, Natale D, Swoger J, Mayer J, Chai Q, Hons M, Pieczyk M, Zerwes HG, Junt T, Sailer A, Ludewig B, Sharpe J, Figge MT. Analyzing the in vivo contribution of G-protein coupled receptors for naive B cell trafficking in lymph nodes (44.23). THE JOURNAL OF IMMUNOLOGY 2012. [DOI: 10.4049/jimmunol.188.supp.44.23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
B cell motility within lymphoid tissue is precisely orchestrated by G-protein-coupled receptors (GPCRs) of the chemokine receptor family and other GPCRs, including the recently described 7α,25-dihydroxycholesterol receptor Ebi2. Here, we performed an exhaustive twophoton microscopy (2PM) analysis of the contribution of the chemokine receptors CXCR4, CXCR5 and CCR7, as well as Ebi2, during the dynamic migration of naïve B cells inside peripheral lymph nodes (PLNs) and the kinetics of B cell accumulation from the T cell area in B cell follicles. Using the intravital 2PM model of murine popliteal PLNs paired with genetic and pharmacological inhibition of GPCRs and their ligands, we observed a non-redundant role for CXCR5 for dynamic B cell motility in the T cell area and B cell follicles, while the functional absence of CXCR4 and CCR7 did not influence B cell migration parameters. Although CXCR5 was central for efficient B cell accumulation in B cell follicles, we did not find evidence for directed migration of T cell area-borne B cells towards B cell follicles, supporting a chemokinetic, and not chemotactic, role for the CXCR5 ligand CXCL13 during this process. Lack of Ebi2 confined B cells to the central part of B cell follicles, resulting in higher average migration velocities as compared to wild type B cells. In summary, our data provide novel insight into the contribution of GPCRs during the dynamic migration of naïve B cells in non-inflamed and inflamed PLNs.
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Onder L, Scandella E, Chai Q, Firner S, Mayer CT, Sparwasser T, Thiel V, Rülicke T, Ludewig B. A novel bacterial artificial chromosome-transgenic podoplanin-cre mouse targets lymphoid organ stromal cells in vivo. Front Immunol 2011; 2:50. [PMID: 22566840 PMCID: PMC3342134 DOI: 10.3389/fimmu.2011.00050] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Accepted: 09/19/2011] [Indexed: 12/25/2022] Open
Abstract
Stromal cells provide the structural foundation of secondary lymphoid organs (SLOs), and regulate leukocyte access and cell migration within the different compartments of spleen and lymph nodes (LNs). Furthermore, several stromal cell subsets have been implied in shaping of T cell responses through direct presentation of antigen. Despite significant gain of knowledge on the biology of different SLO-resident stromal cell subsets, their molecular and functional characterization has remained incomplete. To address this need, we have generated a bacterial artificial chromosome-transgenic mouse model that utilizes the podoplanin (pdpn) promoter to express the Cre-recombinase exclusively in stromal cells of SLOs. The characterization of the Pdpn–Cre mouse revealed transgene expression in subsets of fibroblastic reticular cells and lymphatic endothelial cells in LNs. Furthermore, the transgene facilitated the identification of a novel splenic perivascular stromal cell subpopulation that forms web-like structures around central arterioles. Assessment of the in vivo antigen expression in the genetically tagged stromal cells in Pdpn–Cre mice revealed activation of both MHC I and II-restricted TCR transgenic T cells. Taken together, stromal pdpn–Cre expression is well-suited to characterize the phenotype and to dissect the function of lymphoid organ stromal cells.
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Chen WL, Huang ZQ, Chai Q, Zhang DM, Wang YY, Wang HJ, Wang L, Fan S. Percutaneous sclerotherapy of massive macrocystic lymphatic malformations of the face and neck using fibrin glue with OK-432 and bleomycin. Int J Oral Maxillofac Surg 2011; 40:572-6. [PMID: 21367582 DOI: 10.1016/j.ijom.2011.01.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Accepted: 01/21/2011] [Indexed: 11/26/2022]
Abstract
Picibanil (OK-432) and bleomycin have been used as alternative sclerosing agents for lymphatic malformations. This study evaluated the clinical curative effect of sclerotherapy using fibrin glue combined with OK-432 and bleomycin for the treatment of macrocystic lymphatic malformations of the face and neck. Fifteen paediatric patients (6 males; 9 females, aged 13 months to 14 years) who had received percutaneous sclerotherapy for massive macrocystic lymphatic malformations of the face and neck were retrospectively reviewed. Affected regions included the neck, parotid region and parapharynx, mouth floor, face and cheek, and orbital regions. All patients showed preoperative symptoms of space-occupying lesions between 4 cm × 5 cm and 12 cm × 16 cm in size. Fibrin glue with OK-432 and bleomycin was injected under general anaesthesia. All patients received preoperative and follow-up CT scans. Outcomes were assessed by three surgeons. All patients exhibited mid-facial swelling for 3-4 weeks after surgery, but no major complications. Follow-up periods ranged from 8 to 16 months. Eight lesions were completely involuted, five were mostly involuted, and two were partially involuted. Percutaneous sclerotherapy using fibrin glue with OK-432 and bleomycin provided a simple, safe, and reliable alternative treatment for massive macrocystic lymphatic malformations of the face and neck.
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Liu Z, Chai Q, Li YY, Shen Q, Ma LP, Zhang LN, Wang X, Sheng L, Li JY, Li J, Shen JK. Discovery of novel PTP1B inhibitors with antihyperglycemic activity. Acta Pharmacol Sin 2010; 31:1005-12. [PMID: 20686525 DOI: 10.1038/aps.2010.81] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
AIM To discover and optimize a series of novel PTP1B inhibitors containing a thiazolidinone-substituted biphenyl scaffold and to further evaluate the inhibitory effects of these compounds in vitro and in vivo. METHODS A total of 36 thiazolidinone substituted biphenyl scaffold derivatives were prepared. An in vitro biological evaluation was done by Enzyme-based assay. The in vivo efficacy of 7Fb as an antihyperglycemic agent was evaluated in a BKS db/db diabetic mouse model with a dose of 50 mg.kg(-1).d(-1) for 4 weeks. RESULTS The in vitro biological evaluation showed that compounds 7Fb and 7Fc could increase the insulin-induced tyrosine phosphorylation of IRbeta in CHO/hIR cells. In in vivo experiments, compound 7Fb significantly lowered the postprandial blood glucose, from 29.4+/-1.2 mmol/L with the vehicle to 24.7+/-0.6 mmol/L (P<0.01), and the fasting blood glucose from 27.3+/-1.5 mmol/L with the vehicle to 23.6+/-1.2 mmol/L (P<0.05). CONCLUSION A novel series of compounds were discovered to be PTP1B inhibitors. Among them, compound 7Fb significantly lowered the postprandial and fasting glucose levels, and the blood glucose level declined more rapidly than in metformin-treated mice. Thus, 7Fb may be a potential lead compound for developing new agents for the treatment of type II diabetes.
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