An Antibody-Drug Conjugate for Multiple Myeloma Prepared by Multi-Arm Linkers

First-line treatment of multiple myeloma, a prevalent blood cancer lacking a cure, using anti-CD38 daratumumab antibody and lenalidomide is often inadequate due to relapse and severe side effects. To enhance drug safety and efficacy, an antibody-drug conjugate, TE-1146, comprising six lenalidomide drug molecules site-specifically conjugated to a reconfigured daratumumab to deliver cytotoxic lenalidomide to tumor cells is developed. TE-1146 is prepared using the HighDAR platform, which employs i) a maleimide-containing "multi-arm linker" to conjugate multiple drug molecules creating a drug bundle, and ii) a designed peptide with a Zn2+ -binding cysteine at the C-termini of a reconfigured daratumumab for site-specific drug bundle conjugation. It is shown that TE-1146 remains intact and effectively enters CD38-expressing tumor cells, releasing lenalidomide, leading to enhanced cell-killing effects compared to lenalidomide/daratumumab alone or their combination. This reveals the remarkable potency of lenalidomide once internalized by myeloma cells. TE-1146 precisely delivers lenalidomide to target CD38-overexpressing tumor cells. In contrast, lenalidomide without daratumumab cannot easily enter cells, whereas daratumumab without lenalidomide relies on Fc-dependent effector functions to kill tumor cells.

[Comparison of 5-year follow-up outcomes between"one-stop"procedure and long-term oral anticoagulants after radiofrequency catheter ablation in patients with atrial fibrillation]

Objective: To compare the 5-year follow-up outcomes of radiofrequency catheter ablation (RFCA) combined with left atrial appendage closure (LAAC) and long-term oral anticoagulant (OAC) after RFCA in patients with atrial fibrillation. Methods: This retrospective cross-sectional study included patients with atrial fibrillation who underwent"one-stop"procedure in the First Affiliated Hospital of Ningbo University from September 2015 to December 2017 (RFCA+LAAC group). Baseline data of patients were collected. Propensity score matching at the ratio of 1∶1 was used to select patients with atrial fibrillation who took long-term OAC after RFCA (RFCA+OAC group). The maintenance rate of sinus rhythm and the incidence of adverse events during follow-up were compared between the two groups. Results: A total of 110 patients were enrolled in the RFCA+LAAC group and RFCA+OAC group, respectively. Age of patients was (67.4±8.8) years in RFCA+LAAC group, and there were 42 (38.2%) female patients. Age of patients was (67.3±7.9) years in RFCA+OAC group, and there were 47 (42.7%) female patients. The patients were followed up for mean of (5.3±1.1) years. There was no significant difference in the maintenance rate of sinus rhythm (log-rank: χ2=0.277, P=0.602) and incidence of ischemic stroke events (2.7% (3/110) vs. 4.5% (5/110), P=0.719) during follow-up between the two groups. The incidence of bleeding events (6.4% (7/110) vs. 18.2% (20/110), P=0.008) and major bleeding events (1.8% (2/110) vs. 8.2% (9/110), P=0.030) was significantly higher in the RFCA+OAC group than in the RFCA+LAAC group. Conclusion: There is no significant difference between RFCA+LAAC group and RFCA+OAC group in maintenance rate of sinus rhythm and incidence of ischemic stroke events. Patients in the RFCA+LAAC group have a lower risk of bleeding events compared to the RFCA+OAC group.

Site-specific Conjugation of 6 DOTA Chelators to a CA19-9-targeting scFv-Fc Antibody for Imaging and Therapy

Antibodies conjugated with diagnostic/therapeutic radionuclides are attractive options for inoperable cancers lacking accurate imaging methods and effective therapeutics, such as pancreatic cancer. Hence, we have produced an antibody radionuclide conjugate termed TE-1132 comprising a α-CA19-9 scFv-Fc that is site-specifically conjugated at each C-terminus to 3 DOTA chelators via a cysteine-containing peptide linker. The smaller scFv-Fc size facilitates diffusivity within solid tumors, whereas the chelator-to-antibody ratio of six enabled 177Lu-radiolabeled TE-1132 to exhibit high radioactivity up to 520 MBq/nmol. In mice bearing BxPC3 tumors, immuno-SPECT/CT imaging of [111In]In-TE-1132 and the biodistribution of [177Lu]Lu-TE-1132 showed selective tumor accumulation. Single and multiple doses of [177Lu]Lu-TE-1132 effectively inhibited the BxPC3 tumor growth and prolonged the survival of mice with no irreversible body weight loss or hematopoietic damage. The adequate pharmacokinetic parameters, prominent tumor accumulation, and efficacy with good safety in mice encourage the further investigation of theranostic TE-1132 for treating pancreatic cancer.

[Feasibility and safety of closing large left atrial appendage using the LAmbre device]

Objective: To evaluate the feasibility and safety of the LAmbre occluder for large-diameter left atrial appendage occlusion. Methods: This study was a retrospective cohort study. Patients with large orifice of the left atrial appendage (≥31 mm) and occlusion with the LAmbre device in the Arrhythmia Center of Ningbo First Hospital were included from June 2018 to March 2020. Baseline data were collected and major perioperative complications of left atrial appendage occlusion (including death, stroke, instrumental embolism, cardiac tamponade, and major bleeding events) were recorded. Patients were followed up 45 days, 6 months and 12 months after surgery. The shunt and device-related thrombosis were recorded by esophageal cardiac ultrasound or pulmonary vein CT, and the occurrence of postoperative thromboembolism, bleeding events, death and other serious adverse events were recorded. Results: The average age and left atrial appendage ostial dimension of 32 patients (37.5% women) included in this research were (70.4±8.4) years old and (34.4±2.9) mm. The LAmbre device was successfully implanted in 31(96.9%) patients. No major complications occurred during the perioperative period. During the 12-month follow-up, pericardial tamponade occurred in 1(3.2%) patient and was recovered after treatment. There was no occluder edge shunt>5 mm in patients followed up by esophageal echocardiography. No significant peri-device leak, device-related thrombus, thromboembolism or death event has occurred. Conclusion: The LAmbre occluder may be feasible and safe for large-diameter left atrial appendage occlusion.

Management of hyperparathyroid-induced hypercalcaemic crisis with intracardiac thrombi

A 29-year-old previously healthy patient presented with a hyperparathyroid-induced hypercalcaemic crisis refractory to conventional therapy. The patient developed ventricular fibrillation and subsequently required emergency parathyroidectomy and extracorporeal membrane oxygenation support. Extensive intracardiac and pulmonary trunk thrombi were identified soon after the commencement of extracorporeal membrane oxygenation, despite full anticoagulation. In this report we highlight the non-specific presentations of hypercalcaemia which may lead to delayed diagnosis, and discuss the incidence, risk factors and treatment of a hyperparathyroid-induced hypercalcaemic crisis. We emphasise the role of emergency parathyroidectomy as a salvage therapy in medically refractory We consider the likely factors leading to intracardiac thrombi formation in this case, including how hypercalcaemia may have been a contributing factor.

Bispecific Antibody Binding To RANKL and Osteonectin with Enhanced Localization to the Bone

Therapeutics reducing bone turnover, such as denosumab (Dmab), an anti-RANKL antibody, can provide treatments for patients with bone destruction. However, some patients with osteoporosis or localized primary bone tumors and many patients with various types of bone-metastatic cancer display unsatisfactory responses to Dmab. For achieving greater efficiency of RANKL neutralization in the bone microenvironment by enhancing the distribution of Dmab to the bone, we reengineered Dmab by fusing with single-chain variable fragments of an antibody specific for osteonectin (On), which is abundantly expressed in osseous tissues. The bispecific antibody, Dmab-FvOn, showed a similar activity as Dmab in inhibiting RANKL as examined in an osteoclast differentiation assay. When administered to mice, Dmab-FvOn was found to localize in increased proportions at the endosteum of the bone where osteonectin is abundant. Our study suggests that by linking anti-RANKL with an osteonectin-targeting moiety, a greater proportion of the therapeutic effector can be distributed in the bone. Future studies are needed to investigate whether the bispecific antibody can achieve higher therapeutic efficacy and lower toxicity.

Structural and Physical Basis for Anti-IgE Therapy

Omalizumab, an anti-IgE antibody, used to treat severe allergic asthma and chronic idiopathic urticaria, binds to IgE in blood or membrane-bound on B lymphocytes but not to IgE bound to its high (FcεRI) or low (CD23) affinity receptor. Mutagenesis studies indicate overlapping FcεRI and omalizumab-binding sites in the Cε3 domain, but crystallographic studies show FcεRI and CD23-binding sites that are far apart, so how can omalizumab block IgE from binding both receptors? We report a 2.42-Å omalizumab-Fab structure, a docked IgE-Fc/omalizumab-Fab structure consistent with available experimental data, and the free energy contributions of IgE residues to binding omalizumab, CD23, and FcεRI. These results provide a structural and physical basis as to why omalizumab cannot bind receptor-bound IgE and why omalizumab-bound IgE cannot bind to CD23/FcεRI. They reveal the key IgE residues and their roles in binding omalizumab, CD23, and FcεRI.

Antibodies binding to discrete segments of CϵmX of mIgE on B lymphocytes (P6004)

CϵmX is a discrete domain of 52 a.a. residues, located between the CH4 domain and the C-terminal membrane anchor peptide of the ϵ heavy chain of membrane-bound IgE (mIgE) on human B cells. Among the monoclonal antibodies (mAbs) prepared for their ability to bind to CϵmX fragments or CϵmX-containing recombinant proteins in ELISA, those that can bind to native mIgE on B cells can cause ADCC, apoptosis, and other cytolytic mechanisms on the B cells and are potential useful for controlling IgE production for treating allergic diseases. The CϵmX-specific mAbs prepared previously appear to recognize discrete and overlapping peptide segments of CϵmX. A linear peptide epitope of an antibody is defined by a contiguous peptide segment of minimal stretch that confers maximum binding by the antibody. In some instances, while the peptide epitopes recognized by two mAbs may be adjacent to each other and overlap, the two mAbs do not bind to the adjacent epitopes by a substantial degree. This can be illustrated by the pair of humanized mAbs, h4B12 and h47H4. The mAb h4B12 binds to peptide P1-15 (GLAGGSAQSQRAPDR) and h47H4 binds to peptide P7-18 (AQSQRAPDRVLC). Although the two epitopes share a segment AQSQRAPDR, the mAb h4B12 does not bind to P7-18, and h47H4 does not bind to P1-15. A related presentation from our group (Hsing-Mao Chu et al.) will also reveal that the shared peptide segment AQSQRAPDR has two markedly different conformations when it is associated with h4B12 or with h47H4.

Structural analysis of epitopes recognized by two anti-CϵmX mAbs reveals intrinsic disorder of the CϵmX domain (P6002)

In human membrane-bound IgE (mIgE), a CϵmX domain containing 52 aa residues is located between the CH4 domain and the C-terminal membrane-anchoring segment. Antibodies specific for CϵmX, which can cause lysis of mIgE+ B cells, are being developed to treat allergic diseases and an anti-CϵmX mAb h47H4 is in phase IIb clinical trials. Hence, structural characterization of CϵmX free and complexed with anti-CϵmX mAb is of wide interest and importance. We have solved the crystal structures of (i) free CϵmX fused to IgG1-Fc and (ii) part of CϵmX complexed with an anti-CϵmX mAb, h4B12-Fab, at 1.94 Å resolution. The crystal structure of the IgG1-Fc•CϵmX fusion protein of homodimer exhibits a lack of well-defined electron density for residues 10 to 52 of A subunit and in absence of B subunit in dimeric CϵmX domain. The first 33 residues are also predicted to be intrinsically disordered. The 3D complex structure and epitope mapping by ELISA showed that the anti-CϵmX mAb, h4B12, binds to GLAGGSAQSQRAPDR, which has been reported to bind another anti-CϵmX mAb, h47H4, except for the first 6 residues (in italics). Comparison of the 3-D complex structure of h4B12 and h47H4 revealed different conformations of AQSQRAPDR, a feature characteristic of the intrinsically disordered regions in the CϵmX domain. This is the first report showing that the drug target, CϵmX, contains an intrinsically disordered region that can switch to different conformations upon binding to different anti-CϵmX mAbs.

Manipulating mIgD-expressing B cells with anti-migis-δ monoclonal antibodies

Surface IgD and IgM doubly positive cells comprise the major population of B cells in the human immune system. The heavy chain of membrane-bound IgD (mδ) differs from that of IgD (δ) in that mδ contains a C-terminal membrane-anchor peptide. Our group previously proposed that the N-terminal extracellular segment of 27 aa residues of the membrane-anchor peptide of mδ, referred to as the mIg isotype-specific-δ (migis-δ) segment, may provide a unique antigenic site for isotype-specific targeting of mIgD(+) B cells. Here we report the preparation of mouse mAbs specific for human migis-δ. The mAbs bound to human migis-δ-containing recombinant proteins in an ELISA and to mIgD-expressing transfectants of a CHO cell line as analyzed by flow cytometry. MAb 20E6, which binds to an epitope toward the N-terminal of human migis-δ, could stain human B cell line MC116, which expressed mIgD and mIgM. MC116 cells could be induced to undergo apoptosis by treatment with 20E6 in the presence of a second crosslinking antibody. Chimeric 20E6 caused antibody-dependent cellular cytotoxicity of MC116 cells in the presence of human PBMCs as the source of effector cells. In cultures of PBMCs, 20E6 down-regulated the population of mIgD(+) B cells. The production of human IgM by transplanted MC116 cells in NOD-SCID (NOD.CB17-Prkdc(scid)/IcrCrlBltw) mice could be suppressed by 20E6. These results encourage further investigation of the potential of anti-migis-δ mAbs to control mIgD(+) B cells, when such a manipulation may alleviate a disease state.

Binding and catalysis of Humulus lupulus adenylate isopentenyltransferase for the synthesis of isopentenylated diadenosine polyphosphates

Various plant developmental processes involve phytohormones such as cytokinins. Isopentenyltransferase (IPT) reaction is the key rate-limiting step in cytokinin biosynthesis that transfers the isopentenyl (iP) group from dimethylallyl diphosphate to the N6-amino group of adenine. Here, a series of diadenosine polyphosphates (Ap(n)A) were screened as possible substrates of IPT, among which diadenosine tetraphosphate, diadenosine pentaphosphate and diadenosine hexaphosphate showed higher affinity than did the authentic substrates ADP and ATP. In addition, formation of mono-isopentenyl Ap(n)A and di-isopentenyl Ap(n)A was observed. Judging by the existing biosynthetic and hydrolytic systems for Ap(n)A in plants, Ap(n)A and isopentenyl-Ap(n)A may occur in the plant cells, with functional importance.

Crystal structure and substrate specificity of plant adenylate isopentenyltransferase from Humulus lupulus: distinctive binding affinity for purine and pyrimidine nucleotides

Cytokinins are important plant hormones, and their biosynthesis most begins with the transfer of isopentenyl group from dimethylallyl diphosphate (DMAPP) to the N6-amino group of adenine by either adenylate isopentenyltransferase (AIPT) or tRNA–IPT. Plant AIPTs use ATP/ADP as an isopentenyl acceptor and bacterial AIPTs prefer AMP, whereas tRNA–IPTs act on specific sites of tRNA. Here, we present the crystal structure of an AIPT–ATP complex from Humulus lupulus (HlAIPT), which is similar to the previous structures of Agrobacterium AIPT and yeast tRNA–IPT. The enzyme is structurally homologous to the NTP-binding kinase family of proteins but forms a solvent-accessible channel that binds to the donor substrate DMAPP, which is directed toward the acceptor substrate ATP/ADP. When measured with isothermal titration calorimetry, some nucleotides displayed different binding affinities to HlAIPT with an order of ATP > dATP ∼ ADP > GTP > CTP > UTP. Two basic residues Lys275 and Lys220 in HlAIPT interact with the β and γ-phosphate of ATP. By contrast, the interactions are absent in Agrobacterium AIPT because they are replaced by the acidic residues Asp221 and Asp171. Despite its structural similarity to the yeast tRNA–IPT, HlAIPT has evolved with a different binding strategy for adenylate.

Cysteine S-nitrosylation protects protein-tyrosine phosphatase 1B against oxidation-induced permanent inactivation

Protein S-nitrosylation mediated by cellular nitric oxide (NO) plays a primary role in executing biological functions in cGMP-independent NO signaling. Although S-nitrosylation appears similar to Cys oxidation induced by reactive oxygen species, the molecular mechanism and biological consequence remain unclear. We investigated the structural process of S-nitrosylation of protein-tyrosine phosphatase 1B (PTP1B). We treated PTP1B with various NO donors, including S-nitrosothiol reagents and compound-releasing NO radicals, to produce site-specific Cys S-nitrosylation identified using advanced mass spectrometry (MS) techniques. Quantitative MS showed that the active site Cys-215 was the primary residue susceptible to S-nitrosylation. The crystal structure of NO donor-reacted PTP1B at 2.6 A resolution revealed that the S-NO state at Cys-215 had no discernible irreversibly oxidized forms, whereas other Cys residues remained in their free thiol states. We further demonstrated that S-nitrosylation of the Cys-215 residue protected PTP1B from subsequent H(2)O(2)-induced irreversible oxidation. Increasing the level of cellular NO by pretreating cells with an NO donor or by activating ectopically expressed NO synthase inhibited reactive oxygen species-induced irreversible oxidation of endogenous PTP1B. These findings suggest that S-nitrosylation might prevent PTPs from permanent inactivation caused by oxidative stress.

Enzyme-substrate interactions revealed by the crystal structures of the archaeal Sulfolobus PTP-fold phosphatase and its phosphopeptide complexes

The P-loop-containing protein phos-phatases are important regulators in signal transduction. These enzymes have structural and functional similarity with a conserved sequence of Dx(25-41)HCxxGxxR(T/S) essential for catalysis. The singular protein tyrosine phosphatase (PTP) from archaeal Sulfolobus solfataricus is one of the smallest known PTPs with extreme thermostability. Here, we report the crystal structure of this phosphatase and its complexes with two tyrosyl phosphopeptides A-(p)Y-R and N-K-(p)Y-G-N. The structure suggests the minimal structural motif of the PTP family, having two variable sequences inserted between the beta2-beta3 and beta3-beta4 strands, respectively. The phosphate of both phosphopeptide substrates is bound to the P-loop through several hydrogen bonds. Comparison of several phosphatase-substrate complexes revealed that Gln135 on the Q-loop has different modes of recognition toward phosphopeptides. The substrate specificity of SsoPTP is primarily localized at the phosphotyrosine, suggesting that this phosphatase may be a prototypical PTP.

Structures of Selenomonas ruminantium phytase in complex with persulfated phytate: DSP phytase fold and mechanism for sequential substrate hydrolysis

Various inositide phosphatases participate in the regulation of inositol polyphosphate signaling molecules. Plant phytases are phosphatases that hydrolyze phytate to less-phosphorylated myo-inositol derivatives and phosphate. The phytase from Selenomonas ruminantium shares no sequence homology with other microbial phytases. Its crystal structure revealed a phytase fold of the dual-specificity phosphatase type. The active site is located near a conserved cysteine-containing (Cys241) P loop. We also solved two other crystal forms in which an inhibitor, myo-inositol hexasulfate, is cocrystallized with the enzyme. In the "standby" and the "inhibited" crystal forms, the inhibitor is bound, respectively, in a pocket slightly away from Cys241 and at the substrate binding site where the phosphate group to be hydrolyzed is held close to the -SH group of Cys241. Our structural and mutagenesis studies allow us to visualize the way in which the P loop-containing phytase attracts and hydrolyzes the substrate (phytate) sequentially.

Structures of the hyperthermophilic chromosomal protein Sac7d in complex with DNA decamers

The protein Sac7d belongs to a class of small chromosomal proteins from the hyperthermophilic archaeon Sulfolobus acidocaldarius. Two new crystal forms of Sac7d in complex with the DNA decamers CCTATATAGG and CCTACGTAGG were obtained and their structures were determined by molecular replacement. The refined models yielded R/Rfree values of 0.221/0.257 and 0.248/0.290 at 1.9 and 2.2 A resolution, respectively. The protein structures are similar to the previously determined structure of Sac7d-GCGATCGC (PDB code 1azp), but the DNA molecules are more bent overall, by 14-20 degrees. The relative positions of the Sac7d protein and the bound DNA also differ by rotations of 6-10 degrees and translations of 1.0-2.4 A. In addition to the water molecules in the central cavity, three additional conserved water molecules are found that mediate the protein-DNA interactions. The decamer DNA fragments form virtual double helices in the crystal, with a unit length of eight base pairs. The molecular packing of the new crystal forms differs from that of 1azp. The terminal nucleotides are opened up and form triple base pairs with other DNA molecules. Through lattice contacts, the Sac7d molecule also makes additional interactions with DNA, whereas only limited protein-protein interactions are seen.

Preliminary X-ray diffraction analysis of octaprenyl pyrophosphate synthase crystals fromThermotoga maritimaandEscherichia coli

Octaprenyl pyrophosphate synthase (OPPs) catalyzes the condensation of five isopentenyl pyrophosphates with farnesyl pyrophosphate to generate C(40) octaprenyl pyrophosphate. The enzymes from the hyperthermophilic bacterium Thermotoga maritima and from the mesophilic Escherichia coli were expressed in E. coli and the recombinant proteins were purified and crystallized. The T. maritima OPPs crystals belong to space group P42(1)2, with unit-cell parameters a = b = 151.53, c = 69.72 A. The E. coli OPPs crystals belong to space group C222(1), with unit-cell parameters a = 247.66, b = 266.10, c = 157.93 A. Diffraction data were collected at 100 K using synchrotron radiation and an in-house X-ray source. Structure determination of T. maritima OPPs has been carried out using MIR data sets at 2.8 A resolution. The asymmetric unit contains one dimer. An initial model with 280 residues per subunit has been built and refined to 2.28 A resolution. It shows mostly helical structure and resembles that of avian farnesyl pyrophosphate synthase.

Acute administration of SCH23390 increases D(1) receptors on nonpyramidal neurons in rat mPFC

Atypical antipsychotic drugs (APDs) such as clozapine and olanzapine antagonize both D(1) and D(2) receptors; however, little is known regarding their pharmacologic effect on specific neuronal elements within the local circuitry of corticolimbic regions, such as medial prefrontal cortex (mPFC). To characterize the effect of short-term antagonism of the D(1) receptor a high-resolution autoradiographic technique was used to assess the density (B(max)) and affinity (K(d)) of this receptor on pyramidal cells (i.e., large neurons (LNs, >/=100 microm(2))), nonpyramidal cells (i.e., small neurons (SNs, <100 microm(2))) and in the surrounding neuropil (NPL) of layer VI in rat mPFC. Either normal saline or the selective D(1) antagonist SCH23390 (1.0 mg/kg/day) were administered for 48 h via Alzet osmotic pumps. Frozen sections were incubated in [(3)H]SCH23390 (1-8 nM) in the presence or absence of the competitive inhibitor SKF38393 (10 microM). A microscopic adaptation to Scatchard analysis revealed a significant increase (82%) in B(max) for neuronal cell bodies (P < 0.05), but not for neuropil of drug-treated animals. Further analysis indicated that the increase in B(max) was present on SNs (94%, P < 0.05), but not LNs in SCH23390-treated rats. In contrast, K(d) values for LNs, SNs, and NPL were not significantly altered by drug treatment. Since the vast majority of SNs are nonpyramidal in nature, short-term administration of a selective D(1) antagonist seems to be associated with a preferential upregulation of this receptor on interneurons. Overall, these results are consistent with the hypothesis that the mechanism of action of atypical antipsychotic medications involves changes in D(1) receptor activity associated with local circuit neurons in rat mPFC.

Polymorphisms of the dopamine D4 receptor and response to antipsychotic drugs

The dopamine D4 receptor may be a site through which the clinical effects of antipsychotic drugs are mediated. Polymorphisms of a 48 base pair repeat in the third exon of the DRD4 gene code for different length segments in the third intracytoplasmic loop of the D4 receptor. The most common long (seven repeat) form of the D4 receptor has been shown in both physiologic and pharmacologic experiments to respond differently to dopamine agonists and antagonists than do shorter forms of D4. Thus, variants of D4 may partly determine patient response to antipsychotic drugs and, in particular, response to typical neuroleptics, which have a relatively low affinity for the D4 receptor, as compared to clozapine, which has a relatively high affinity for D4. DRD4 polymorphisms in the third intron were characterized in 28 patients with chronic psychosis who responded well to typical neuroleptics, 32 patients who responded well to clozapine, and 57 healthy comparison subjects. Patients responding to typical neuroleptics carried the allele for the long (seven repeat) form of the D4 receptor (allele frequency 8.9%) less frequently than patients responding to clozapine (allele frequency 23.4%, P = 0.046) or healthy comparison subjects (allele frequency 26.3%, P = 0.004). The results of this study suggest that inherited variants of D4 may explain some of the interindividual variation seen in patient response to different classes of antipsychotic medication.

Epilepsy and obesity in serotonin 5-HT2C receptor mutant mice

Serotonin 5-HT2C receptor null mutant mice were generated to assess the contribution of this receptor to the actions of serotonin. Mutant mice displayed both an epilepsy and obesity phenotype. The epilepsy syndrome was characterized by spontaneous seizures, lowered seizure threshold, enhanced seizure propagation and sound-induced seizure susceptibility. These findings implicate 5-HT2C receptors in the regulation of neuronal network excitability. It was also observed that body weight and adipose tissue deposition were elevated in adult mutant mice relative to their wild type littermates. Paired-feeding studies suggest that the obesity syndrome is a result of increased food intake. In addition, mutants displayed reduced sensitivity to the appetite suppressant actions of non-specific serotonergic agonists. These studies establish a role for 5-HT2C receptors in the serotonergic regulation of body weight and food intake.

Elevated anxiety and antidepressant-like responses in serotonin 5-HT1A receptor mutant mice

The brain serotonin (5-hydroxytryptamine; 5-HT) system is a powerful modulator of emotional processes and a target of medications used in the treatment of psychiatric disorders. To evaluate the contribution of serotonin 5-HT1A receptors to the regulation of these processes, we have used gene-targeting technology to generate 5-HT1A receptor-mutant mice. These animals lack functional 5-HT1A receptors as indicated by receptor autoradiography and by resistance to the hypothermic effects of the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). Homozygous mutants display a consistent pattern of responses indicative of elevated anxiety levels in open-field, elevated-zero maze, and novel-object assays. Moreover, they exhibit antidepressant-like responses in a tail-suspension assay. These results indicate that the targeted disruption of the 5-HT1A receptor gene leads to heritable perturbations in the serotonergic regulation of emotional state. 5-HT1A receptor-null mutant mice have potential as a model for investigating mechanisms through which serotonergic systems modulate affective state and mediate the actions of psychiatric drugs.

Novel interactions between human T-cell leukemia virus type I Tax and activating transcription factor 3 at a cyclic AMP-responsive element

Human proenkephalin gene transcription is transactivated by human T-cell leukemia virus type I (HTLV-I) Tax in human Jurkat T lymphocytes. This transactivation was further enhanced in Jurkat cells treated with concanavalin A, cyclic AMP, or 12-O-tetradecanoylphorbol-13-acetate. Deletion and cis-element transfer analyses of the human proenkephalin promoter identified a cyclic AMP-responsive AP-1 element (-92 to -86) as both necessary and sufficient to confer Tax-dependent transactivation. Different AP-1 or cyclic AMP-responsive element-binding protein (CREB)/activating transcription factor (ATF) proteins which bind this element were expressed in murine teratocarcinoma F9 cells to identify those capable of mediating Tax-dependent transactivation of human proenkephalin gene transcription. Although CREB, c-Fos, c-Jun, and JunD did not have significant effects, JunB inhibited the Tax-dependent transactivation. In contrast, ATF3 dramatically induced Tax-dependent transactivation, which was further enhanced by protein kinase A. Electrophoretic mobility shift assays with recombinant fusion proteins expressed and purified from bacteria indicate that the DNA-binding activity of ATF3 is also dramatically enhanced by Tax. Chimeric fusion proteins consisting of the DNA-binding domain of the yeast transcription factor Gal4 and the amino-terminal domain (residues 1 to 66) of ATF3 were able to mediate Tax-dependent transactivation of a Gal4-responsive promoter, which suggests a direct involvement of this region of ATF3. Recombinant fusion proteins of glutathione S-transferase with either the amino- or carboxy-terminal (residues 139 to 181) domain of ATF3 were able to specifically interact with Tax. Furthermore, specific antisera directed against Tax coimmunoprecipitated ATF3 only in the presence of Tax.

Activating transcription factor-3 stimulates 3',5'-cyclic adenosine monophosphate-dependent gene expression

Activating transcription factor-3 (ATF-3) is one member of a large family of leucine zipper transcription factors which bind to promoters responsive to cAMP and phorbol ester at the related cAMP (CRE) and phorbol ester response elements. We report here that ATF-3 is coexpressed with the neuropeptide precursor proenkephalin in human neuroblastoma SK-N-MC cells. Cotransfection experiments indicate that activation of proenkephalin gene expression by ATF-3 is dependent upon both the catalytic subunit of the cAMP-dependent protein kinase and the CRE-2 element. The CRE-2 element is essential for second messenger-inducible expression and is known to bind AP-1-like transcription factors. ATF-3 expressed in bacteria or from rabbit reticulocyte lysates binds to the proenkephalin CRE-2 element as a homodimer and as a heterodimer with Jun-D, another activator of proenkephalin transcription. ATF-3 stimulates binding of Jun-D to the proenkephalin CRE-2 element and acts synergistically with Jun-D to induce proenkephalin gene expression. Sequential immunoprecipitations of ATF-3 from SK-N-MC cells expressing proenkephalin indicate that ATF-3 is complexed with Jun-D in vivo and that both proteins are highly phosphorylated. Together, our results suggest that ATF-3 may play an important role in the regulation of gene expression by cAMP-dependent intracellular signaling pathways.

Molecular cloning and analysis of Schizosaccharomyces pombe rad9, a gene involved in DNA repair and mutagenesis

The mutant allele rad9-192 renders Schizosaccharomyces pombe cells sensitive to ionizing radiation and UV light. We have isolated from a S. pombe genomic DNA library a unique recombinant plasmid that is capable of restoring wild-type levels of radioresistance to a rad9-192-containing cell population. Plasmid integration studies using the cloned DNA, coupled with mating and tetrad analyses, indicate that this isolated DNA contains the wild-type rad9 gene. We inactivated the repair function of the cloned fragment by a single insertion of the S. pombe ura4 gene. This nonfunctional fragment was used to create a viable disruption mutant, thus demonstrating that the rad9 gene does not encode an essential cellular function. In addition, the rad9-192 mutant population is as radiosensitive as the disruption mutant, indicating that rad9 gene function is severely if not totally inhibited by the molecular defect responsible for the rad9-192 phenotype. DNA sequence analysis of rad9 reveals an open reading frame of 1,278 bp, interrupted by three introns 53 bp, 57 bp, and 56 bp long, respectively, and ending in the termination codon TAG. This gene is capable of encoding a protein of 426 amino acids, with a corresponding calculated molecular weight of 47,464 daltons. No significant homology was detected between the rad9 gene or its deduced protein sequence and sequences previously entered into DNA and protein sequence data banks.

cAMP-dependent regulation of proenkephalin by JunD and JunB: positive and negative effects of AP-1 proteins

We demonstrate that JunD, a component of the AP-1 transcription factor complex, activates transcription of the human proenkephalin gene in a fashion that is completely dependent upon the cAMP-dependent protein kinase, protein kinase A. Activation of proenkephalin transcription by JunD is dependent upon a previously characterized cAMP-, phorbol ester-, and Ca(2+)-inducible enhancer, and JunD is shown to bind the enhancer as a homodimer. Another component of the AP-1 transcription complex, JunB, is shown to inhibit activation mediated by JunD. As a homodimer JunB is unable to bind the enhancer; however in the presence of c-Fos, high-affinity binding is observed. Furthermore, JunD is shown to activate transcription of genes linked to both cAMP and phorbol ester response elements in a protein kinase A-dependent fashion, further blurring the distinction between these response elements. These results demonstrate that the transcriptional activity of an AP-1-related protein is regulated by the cAMP-dependent second-messenger pathway and suggest that JunD and other AP-1-related proteins may play an important role in the regulation of gene expression by cAMP-dependent intracellular signaling pathways.

NF-I proteins from brain interact with the proenkephalin cAMP inducible enhancer

A short region of the human proenkephalin promoter has been shown previously to mediate transcriptional regulation in response to activation of the cAMP, TPA, and Ca+ + dependent intracellular signalling pathways. Two adjacent DNA elements, CRE-1 and CRE-2, are essential for this regulation although neither element alone is sufficient for inducible expression. The CRE-2 element consists of overlapping binding sites for the transcription factors AP-1 and AP-4. The CRE-1 element has been shown to interact with a DNA binding factor called ENKTF-1. Here we characterize proteins from bovine brain which bind the CRE-1 element of the human proenkephalin gene. Interactions between proteins binding the CRE-1 and CRE-2 elements are characterized in vitro using affinity purified DNA binding proteins. We demonstrate that CRE-1 binding proteins from bovine brain consist of three different polypeptides each belonging to the NF-I family of transcription factors. Point mutation analysis of the contacts of these proteins with the CRE-1 element indicate that NF-I proteins contact the inducible enhancer at the sequence CTGGCxxxxxxCCT which overlaps the CRE-1 element (underlined) defined by in vivo point mutation analysis. Cotransfection of one of the three NF-I proteins purified from bovine brain, NF-I/Red1, together with a proenkephalin/bacterial chloramphenicol acetyl transferase (CAT) fusion gene repressed protein kinase A or forskolin stimulated CAT expression.

Changes in ovarian ultrastructure and ecdysteroid titer during the aging process of female Xyleborus ferrugineus (Coleoptera: Scolytidae)

Striking ultrastructural and hormonal parameters of premature menopause and aging are reported in female Xyleborus ferrugineus fed cholesterol, rather than 7-dehydrocholesterol, as a sole dietary sterol. The titer of free ecdysteroids in such 63-day-old females remained abnormally elevated through the period of the ovarian cycle. A similar plateauing of such elevated titer also occurred in 147-day-old, irregularly cycling females fed only cholesterol as the dietary sterol. These hormonal changes in menopausing X. ferrugineus females seem especially analogous to the maintenance of an elevated concentration of 17-beta-estradiol through the estrous, as well as the proestrous, ovary of aged irregularly cycling rats. The highly abnormal ultrastructure of ovaries of X. ferrugineus females aged 216 days on a diet containing cholesterol as the sole sterol seems quite analogous to that of the nonovulatory follicles in older, irregularly cycling rats. Our new findings involving aging X. ferrugineus females indicate further the usefulness of an insect model to study aging processes.

Ultrastructure of the prothoracic gland of variously aged female pupae of Xyleborus ferrugineus and associated ecdysteroid titers

The prothoracic glands of female pupae of Xyleborus ferrugineus at three ages (0-h, 48-h, and 72-h-old) were examined for ultrastructural changes that correlate with high titers of ecdysteroids in the entire pupa. In all three ages, the prothoracic gland cells appear compact with a prominent nucleus. Lysosome-like structures with concentrically oriented internal membrane are observed in both 0-h and 72-h-old gland cells. Mitochondria are abundant in the glands of both ages, and rough endoplasmic reticulum is relatively sparse. Numerous microtubules are present in the prothoracic gland cells of 48-h-old female pupae that contain relatively high titers of ecdysteroids. Rough endoplasmic reticulum also is especially abundant at this age of the pupa. Ecdysone titers, estimated by the radioimmunoassay method (RIA), were 161.04 +/- 26.80 pg/mg, 704.25 +/- 69.02pg/mg and 298.72 +/- 26.80pg/mg body weight in 0-h, 48-h and 72-h-old female pupae, respectively.

Ultrastructure of the compound eye of the haploid male beetle, Xyleborus ferrugineus

The compound eye of male (haploid) Xyleborus ferrugineus beetles was examined with scanning and transmission electron microscopy. The eye externally consists of ca. 19 to 33 facets. Each ommatidium is composed of a thickly biconvex lenslet with about 50 electron dense and rare layers, but at the junction area between two lenslets there are only about 35 to 37 layers that can be distinguished. A very short (3.4-4.0 mum) acone type crystalline cone is located directly beneath the lenslet. Each ommatidium is surrounded by pigment cells, and pigment granules also appear throughout the cytoplasm of the retinular cells. Some pigment granules are even present below the basement membrane. there are 8 retinular cells. The rhabdomeres of 2 centrally situated photoreceptor cells fuse into a rhabdom which is enveloped by the rhabdomeres of 6 peripheral retinular cells. The rhabdomeres of the 6 peripheral retinular cells join laterally to form a rhabdomeric ring around the central rhabdom. No tracheation was observed among the retinular cells. Virus-like particles are evident near the nucleus in each Semper cell of the crystalline cone.