TNIP1 inhibits selective autophagy via bipartite interaction with LC3/GABARAP and TAX1BP1

Mitophagy is a form of selective autophagy that disposes of superfluous and potentially damage-inducing organelles in a tightly controlled manner. While the machinery involved in mitophagy induction is well known, the regulation of the components is less clear. Here, we demonstrate that TNIP1 knockout in HeLa cells accelerates mitophagy rates and that ectopic TNIP1 negatively regulates the rate of mitophagy. These functions of TNIP1 depend on an evolutionarily conserved LIR motif as well as an AHD3 domain, which are required for binding to the LC3/GABARAP family of proteins and the autophagy receptor TAX1BP1, respectively. We further show that phosphorylation appears to regulate its association with the ULK1 complex member FIP200, allowing TNIP1 to compete with autophagy receptors, which provides a molecular rationale for its inhibitory function during mitophagy. Taken together, our findings describe TNIP1 as a negative regulator of mitophagy that acts at the early steps of autophagosome biogenesis.

Re-Analysis of the STEADY-PD II Trial-Evidence for Slowing the Progression of Parkinson's Disease

BACKGROUND

Recent examination of the STEADY-PD III isradipine clinical trial data concluded that early-stage Parkinson's disease (PD) participants who had longer exposure to isradipine had a significant delay in their need for symptomatic medication, as well as a lower medication burden at the end of the trial. These findings suggest that greater exposure to isradipine might slow disease progression.

OBJECTIVES

To test this hypothesis, the data from the STEADY-PD II isradipine clinical trial, in which an extended-release (ER) formulation of the drug was used, was re-examined.

METHODS

The re-analysis of the STEADY-PD II data was restricted to participants assigned placebo or tolerable isradipine treatment (10 mg isradipine/day or less). The effect of isradipine treatment was assessed by Unified Parkinson's Disease Rating Scale (UPDRS) at the end of the 52-week trial, rather than by last observation carried forward at the beginning of symptomatic therapy.

RESULTS

Participant cohorts were well-matched for baseline disability, initial disease progression, and time to initiation of symptomatic therapy. Participants given 10 mg/day ER isradipine had significantly smaller total and part 3 UPDRS scores at the end of the trial than did the placebo cohort. Post hoc adjustment for symptomatic therapy diminished the statistical significance of these differences. In those participants not taking a monoamine oxidase B inhibitor, the progression in UPDRS scores also was significantly reduced.

CONCLUSIONS

These results are consistent with the recent secondary analysis of the STEADY-PD III clinical trial-suggesting that clinically attainable brain exposure to isradipine may slow early-stage PD progression. © 2021 International Parkinson and Movement Disorder Society.

Secondary osteon structural heterogeneity between the cranial and caudal cortices of the proximal humerus in white-tailed deer

Cortical bone remodeling is an ongoing process triggered by microdamage, where osteoclasts resorb existing bone and osteoblasts deposit new bone in the form of secondary osteons (Haversian systems). Previous studies revealed regional variance in Haversian systems structure and possibly material, between opposite cortices of the same bone. As bone mechanical properties depend on tissue structure and material, it is predicted that bone mechanical properties will vary in accordance with structural and material regional heterogeneity. To test this hypothesis, we analysed the structure, mineral content and compressive stiffness of secondary bone from the cranial and caudal cortices of the white-tailed deer proximal humerus. We found significantly larger Haversian systems and canals in the cranial cortex but no significant difference in mineral content between the two cortices. Accordingly, we found no difference in compressive stiffness between the two cortices and thus our working hypothesis was rejected. As the deer humerus is curved and thus likely subjected to bending during habitual locomotion, we expect that similar to other curved long bones, the cranial cortex of the deer humerus is likely subjected primarily to tensile strains and the caudal cortex is subject primarily to compressive strains. Consequently, our results suggest that strain magnitude (larger in compression) and sign (compression versus tension) affect the osteoclasts and osteoblasts differently in the basic multicellular unit. Our results further suggest that osteoclasts are inhibited in regions of high compressive strains (creating smaller Haversian systems) while the osteoid deposition and mineralization by osteoblasts is not affected by strain magnitude and sign.

Prevalence of Dyskinesia and OFF by 30-Minute Intervals Through the Day and Assessment of Daily Episodes of Dyskinesia and OFF: Novel Analyses of Diary Data from Gocovri Pivotal Trials

Background:

Parkinson’s disease (PD) patients using levodopa commonly develop dyskinesia and OFF episodes that reduce quality of life.

Objective:

Evaluate prevalence of troublesome dyskinesia and OFF through the day, assessed by 30-minute intervals, as well as the mean number and duration of troublesome dyskinesia and OFF episodes, transitions between PD states, and effects of Gocovri^® (amantadine) extended release capsules on these episodes.

Methods:

Evaluate diary data from pooled Gocovri phase 3, placebo-controlled trials—analyzed for 17 hours following wake-up—at baseline and week 12.

Results:

Diaries were evaluable for 162 patients. At baseline, 67% of patients woke up OFF, with prevalence decreasing to 13% at 2 hours and then remaining relatively steady at ∼12% (range, 6–17%) across half-hour intervals thereafter. Troublesome dyskinesia prevalence rose steadily from 5% to 24% over the first 2 hours, then fluctuated between 20% and 44% through the rest of the waking day. At baseline, patients experienced a mean of 3.0 daily episodes of troublesome dyskinesia (average duration 2.0 hours each), and 2.2 daily episodes of OFF (average duration 1.1 hour each). At week 12, Gocovri-treated patients showed greater reductions than placebo in troublesome dyskinesia and OFF episodes per day (treatment difference: –1.0 episodes and –0.4 episodes, respectively) and average episode duration (treatment difference: –0.6 hours and –0.3 hours, respectively). Mean duration of individual episodes of ON without troublesome dyskinesia (Good ON) increased by 5.0 hours for Gocovri, compared with 2.0 hours for placebo. Patients taking Gocovri experienced 2.2 fewer transitions between states than patients taking placebo.

Conclusions:

Troublesome dyskinesia and OFF occurred in the morning and throughout the waking day. Gocovri-treated patients experienced fewer, shorter episodes of both troublesome dyskinesia and OFF, thereby increasing the duration of continuous Good ON episodes and reducing the frequency of transitions between motor states.

Pharmacokinetics of ADS-5102 (Amantadine) Extended Release Capsules Administered Once Daily at Bedtime for the Treatment of Dyskinesia

BACKGROUND

Preclinical and clinical studies suggest amantadine immediate-release (IR) may reduce dyskinesia in Parkinson's disease (PD), although higher doses are associated with increased CNS adverse events (AEs). ADS-5102 is an extended release amantadine capsule formulation, designed for once-daily dosing at bedtime (qhs) to provide high concentrations upon waking and throughout the day, with lower concentrations in the evening. The pharmacokinetics (PK) of ADS-5102 were assessed in two phase I studies in healthy subjects, and a blinded, randomized phase II/III dose-finding study in PD patients.

METHODS

The first phase I study assessed single ADS-5102 doses (68.5, 137, and 274 mg) in a crossover design, whereas the second phase I study evaluated ADS-5102 137 mg for 7 days followed by amantadine IR 81 mg twice daily (or reverse order). In the phase II/III double-blind study, PD patients with dyskinesia were randomized to ADS-5102 (210, 274, or 338 mg) or placebo for 8 weeks.

RESULTS

Single ADS-5102 doses resulted in a slow initial rise in amantadine plasma concentration, with delayed time to maximum concentration (12-16 h). Amantadine plasma concentrations were higher in PD patients versus healthy volunteers. The steady-state profile of once-daily ADS-5102 was significantly different from that of twice-daily amantadine IR, such that the two formulations are not bioequivalent. PK modeling suggested the recommended daily ADS-5102 dosage (274 mg qhs) resulted in 1.4- to 2.0-fold higher amantadine plasma concentrations during the day versus amantadine IR.

CONCLUSIONS

ADS-5102 can be administered once-daily qhs to achieve high amantadine plasma concentrations in the morning and throughout the day, when symptoms of dyskinesia occur.

Are we crying Wolff? 3D printed replicas of trabecular bone structure demonstrate higher stiffness and strength during off-axis loading

Roux's principle of bone functional adaptation postulates that bone tissue, and particularly trabecular bone tissue, responds to mechanical stimuli by adjusting (modeling) its architecture accordingly. Hence, it predicts that the new modeled trabecular structure is mechanically improved (stiffer and stronger) in line with the habitual in vivo loading direction. While previous studies found indirect evidence to support this theory, direct support was so far unattainable. This is attributed to the fact that each trabecular bone is unique, and that trabecular bone tissue tends to be damaged during mechanical testing. Consequently, a unique modeled trabecular structure can be mechanically tested only along one direction and a comparison to other directions for that specific structure is impossible. To address this issue, we have 3D printed 10 replicas of a trabecular structure from a sheep talus cropped along the 3 principal axes of the bone and in line with the principal direction of loading (denoted on-axis model). Next, we have rotated the same cropped trabecular structure in increments of 10° up to 90° to the bone principal direction of loading (denoted off-axis models) and printed 10 replicas of each off-axis model. Finally, all on-axis and off-axis 3D printed replicas were loaded in compression until failure and trabecular structure stiffness and strength were calculated. Contrary to our prediction, and conflicting with Roux's principle of bone functional adaptation, we found that a trabecular structure loaded off-axis tended to have higher stiffness and strength values when compared to the same trabecular structure loaded on-axis. These unexpected results may not disprove Roux's principle of bone functional adaptation, but they do imply that trabecular bone adaptation may serve additional purposes than simply optimizing bone structure to one principal loading scenario and this suggests that we still don't fully understand bone modeling in its entirety.

Amantadine improves cognitive outcome and increases neuronal survival after fluid percussion traumatic brain injury in rats

This study evaluated the effects of clinically relevant concentrations of amantadine (AMT) on cognitive outcome and hippocampal cell survival in adult rats after lateral fluid percussion traumatic brain injury (TBI). AMT is an antagonist of the N-methyl-D-aspartate-type glutamate receptor, increases dopamine release, blocks dopamine reuptake, and has an inhibitory effect on microglial activation and neuroinflammation. Currently, AMT is clinically used as an antiparkinsonian drug. Amantadine or saline control was administered intraperitoneally, starting at 1 h after TBI followed by dosing three times daily for 16 consecutive days at 15, 45, and 135 mg/kg/day. Terminal blood draws were obtained from TBI rats at the time of euthanasia at varying time points after the last amantadine dose. Pharmacokinetics analysis confirmed that the doses of AMT achieved serum concentrations similar to those observed in humans receiving therapeutic doses (100-400 mg/day). Acquisition of spatial learning and memory retention was assessed using the Morris water maze (MWM) on days 12-16 after TBI. Brain tissues were collected and stained with Cresyl-violet for long-term cell survival analysis. Treatment with 135mg/kg/day of AMT improved acquisition of learning and terminal cognitive performance on MWM. The 135-mg/kg/day dosing of AMT increased the numbers of surviving CA2-CA3 pyramidal neurons at day 16 post-TBI. Overall, the data showed that clinically relevant dosing schedules of AMT affords neuroprotection and significantly improves cognitive outcome after experimental TBI, suggesting that it has the potential to be developed as a novel treatment of human TBI.

Combination therapy with amantadine, oseltamivir and ribavirin for influenza A infection: safety and pharmacokinetics

BACKGROUND

Antiviral resistance among influenza A viruses is associated with high morbidity and mortality in immunocompromised hosts. However, treatment strategies for drug-resistant influenza A are not established. A triple-combination antiviral drug (TCAD) regimen consisting of amantadine (AMT), oseltamivir (OSL) and ribavirin (RBV) demonstrated good efficacy in an animal model.

METHODS

We first analysed the pharmacokinetics (PKs) of TCAD therapy in healthy volunteers. We then performed a pilot study of TCAD therapy in patients undergoing chemotherapy or haematopoietic cell transplantation. AMT (75 mg), OSL (50 mg) and RBV (200 mg) were administered three times a day for 10 days. The safety and PKs of TCAD therapy were monitored.

RESULTS

The PKs of TCAD therapy in healthy volunteers was shown to be similar to the PKs of each drug individually from a single dose. In the pilot study, six immunocompromised patients received TCAD therapy and one patient received OSL monotherapy. All but one patient completed 10 days of TCAD therapy without side effects; one patient receiving TCAD was withdrawn from the study because of respiratory failure and ultimately recovered. Viral load was decreased after TCAD therapy, despite the presence of either AMT- or OSL-resistant virus in two cases. One patient with 2009 influenza A/H1N1 receiving OSL monotherapy developed confirmed OSL resistance during treatment.

CONCLUSIONS

TCAD therapy had similar PKs to each individual antiviral during monotherapy following a single dose and can be administered safely in immunocompromised patients.

Modeling amantadine treatment of influenza A virus in vitro

We analyzed the dynamics of an influenza A/Albany/1/98 (H3N2) viral infection, using a set of mathematical models highlighting the differences between in vivo and in vitro infection. For example, we found that including virion loss due to cell entry was critical for the in vitro model but not for the in vivo model. Experiments were performed on influenza virus-infected MDCK cells in vitro inside a hollow-fiber (HF) system, which was used to continuously deliver the drug amantadine. The HF system captures the dynamics of an influenza infection, and is a controlled environment for producing experimental data which lend themselves well to mathematical modeling. The parameter estimates obtained from fitting our mathematical models to the HF experimental data are consistent with those obtained earlier for a primary infection in a human model. We found that influenza A/Albany/1/98 (H3N2) virions under normal experimental conditions at 37 degrees C rapidly lose infectivity with a half-life of approximately 6.6+/-0.2 h, and that the lifespan of productively infected MDCK cells is approximately 13 h. Finally, using our models we estimated that the maximum efficacy of amantadine in blocking viral infection is approximately 74%, and showed that this low maximum efficacy is likely due to the rapid development of drug resistance.

Discovery of an allosteric site in the caspases

Allosteric regulation of proteins by conformational change is a primary means of biological control. Traditionally it has been difficult to identify and characterize novel allosteric sites and ligands that freeze these conformational states. We present a site-directed approach using Tethering for trapping inhibitory small molecules at sites away from the active site by reversible disulfide bond formation. We screened a library of 10,000 thiol-containing compounds against accessible cysteines of two members of the caspase family of proteases, caspase-3 and -7. We discovered a previously unreported and conserved allosteric site in a deep cavity at the dimer interface 14 A from the active site. This site contains a natural cysteine that, when disulfide-bonded with either of two specific compounds, inactivates these proteases. The allosteric site is functionally coupled to the active site, such that binding of the compounds at the allosteric site prevents peptide binding at the active site. The x-ray crystal structures of caspase-7 bound by either compound demonstrates that they inhibit caspase-7 by trapping a zymogen-like conformation. This approach may be useful to identify new allosteric sites from natural or engineered cysteines, to study allosteric transitions in proteins, and to nucleate drug discovery efforts.

Direct activation of the apoptosis machinery as a mechanism to target cancer cells

Apoptosis plays a pivotal role in the cytotoxic activity of most chemotherapeutic drugs, and defects in this pathway provide a basis for drug resistance in many cancers. Thus the ability to restore apoptosis by using small molecules could have important therapeutic implications. Using a cell-free assay to simultaneously target multiple components of the apoptosis pathway, we identified a class of compounds that activate caspases in a cytochrome c-dependent manner and induce apoptosis in whole cells. By reconstituting the apoptosis pathway with purified proteins, we determined that these compounds promote the protein-protein association of Apaf-1 into the functional apoptosome. These compounds exert cytostatic and cytotoxic effects on a variety of cancer cell lines while having little or no activity against the normal cell lines tested. These findings suggest that direct activation of the basic apoptosis machinery may be a viable mechanism to selectively target cancer.

CD45 modulates galectin-1-induced T cell death: regulation by expression of core 2 O-glycans

Galectin-1 induces death of immature thymocytes and activated T cells. Galectin-1 binds to T cell-surface glycoproteins CD45, CD43, and CD7, although the precise roles of each receptor in cell death are unknown. We have determined that CD45 can positively and negatively regulate galectin-1-induced T cell death, depending on the glycosylation status of the cells. CD45(+) BW5147 T cells lacking the core 2 beta-1,6-N-acetylglucosaminyltransferase (C2GnT) were resistant to galectin-1 death. The inhibitory effect of CD45 in C2GnT(-) cells appeared to require the CD45 cytoplasmic domain, because Rev1.1 cells expressing only CD45 transmembrane and extracellular domains were susceptible to galectin-1 death. Moreover, treatment with the phosphotyrosine-phosphatase inhibitor potassium bisperoxo(1,10-phenanthroline)oxovanadate(V) enhanced galectin-1 susceptibility of CD45(+) T cell lines, but had no effect on the death of CD45(-) T cells, indicating that the CD45 inhibitory effect involved the phosphatase domain. Expression of the C2GnT in CD45(+) T cell lines rendered the cells susceptible to galectin-1, while expression of the C2GnT in CD45(-) cells had no effect on galectin-1 susceptibility. When CD45(+) T cells bound to galectin-1 on murine thymic stromal cells, only C2GnT(+) T cells underwent death. On C2GnT(+) cells, CD45 and galectin-1 co-localized in patches on membrane blebs while no segregation of CD45 was seen on C2GnT(-) T cells, suggesting that oligosaccharide-mediated clustering of CD45 facilitated galectin-1-induced cell death.

Structural basis of the recognition of the dishevelled DEP domain in the Wnt signaling pathway

The DEP domain of Dishevelled (Dvl) proteins transduces signals to effector proteins downstream of Dvl in the Wnt pathway. Here we report that DEP-containing mutants inhibit Wnt-induced, but not Dvl-induced, activation of the transcription factor Lef-1. This inhibitory effect is weakened by a K434M mutation. Nuclear magnetic resonance spectroscopy revealed that the DEP domain of mouse Dvl1 comprises a three-helix bundle, a beta-hairpin 'arm' and two short beta-strands at the C-terminal region. Lys 434 is located at the tip of the beta-hairpin 'arm'. Based on our findings, we conclude that DEP interacts with regulators upstream of Dvl via a strong electric dipole on the molecule's surface created by Lys 434, Asp 445 and Asp 448; the electric dipole and the putative membrane binding site are at two different locations.

CD7 delivers a pro-apoptotic signal during galectin-1-induced T cell death

Galectin-1, an endogenous lectin expressed in lymphoid organs and immune-privileged sites, induces death of human and murine thymocytes and T cells. Galectin-1 binds to several glycoproteins on the T cell surface, including CD7. However, the T cell surface glycoprotein receptors responsible for delivering the galectin-1 death signal have not been identified. We show that CD7 is required for galectin-1-mediated death. This demonstrates a novel function for CD7 as a death trigger and identifies galectin-1/CD7 as a new biologic death signaling pair.

Histidine residues underlie Congo red binding to A beta analogs

The binding mechanism of Congo red (CR) to Alzheimer's disease (AD) amyloid fibrils (A beta) in terms of binding affinity and number of sites was quantitated from absorption spectroscopy (at 200-700 nm) by measuring the concentration of CR bound (CR-B) to AD A beta assemblies as a function of CR concentration and pH in 80% ethanol. The rationale for the use of this high concentration of ethanol derives from its use in histological screens for amyloid in tissue sections. Moreover, free CR can be separated from bound CR by filtration in ethanolic but not aqueous medium. The A beta analogs studied here included: (1) peptides having different lengths: A beta1-40, A beta11-28, A beta13-28, A beta19-28, A beta11-25; (2) wildtype, control sequences of A beta1-40 and sequences having different natural amino acid substitutions: primate Pr1-40, rodent Ro1-40, hereditary cerebral haemorrhage with amyloidosis, Dutch type (HCHWA-D) Du1-40, primate reverse sequence Pr40-1; and (3) A beta11-25 sequences having different substitutions: H13D, H14D, and D23K. Negative-staining showed that A beta1-40 fibrils in buffer were indistinguishable from those in buffered ethanolic medium. For all amyloid analogs except A beta19-28, which has no histidine residues and showed no CR binding over the entire pH range 4.0-9.5, CR-B decreased as a function of increasing pH. The decrease was steepest at about pH 5 and became zero above pH 7. For analogs having the same number of histidines, CR-B fell on the same binding curve, indicating that histidine residues are the likely binding sites for CR in this medium. The pH titration of the binding was parameterized by the stoichiometry of dye to the sites, the number of histidines per molecule, the binding dissociation constant Kd, and the apparent proton dissociation constant pK of the histidine; and the calculated pH-titration curves were found to fit the observed ones. For the peptides having 1-3 histidines the average pK was 5.0-5.5, which was similar to the expected pK of histidine in low dielectric medium (80% ethanol), and the Kd's were 2.8-5.9 microM. That histidine residues underlie CR binding in A beta amyloid is consistent with previous findings that A beta peptides sediment as fibrillar assemblies at pH-3-7 and bind Congo red over the same pH range in aqueous medium. Further, the conformation near the binding motif His13-His14-Gln15-Lys16 in A beta assemblies is not greatly altered in 80% ethanol.

Improving SH3 domain ligand selectivity using a non-natural scaffold

BACKGROUND

Src homology 3 (SH3) domains bind sequences bearing the consensus motif PxxP (where P is proline and x is any amino acid), wherein domain specificity is mediated largely by sequences flanking the PxxP core. This specificity is limited, however, as most SH3 domains show high ligand cross-reactivity. We have recently shown that diverse N-substituted residues (peptoids) can replace the prolines in the PxxP motif, yielding a new source of ligand specificity.

RESULTS

We have tested the effects of combining multiple peptoid substitutions with specific flanking sequences on ligand affinity and specificity. We show that by varying these different elements, a ligand can be selectively tuned to target a single SH3 domain in a test set. In addition, we show that by making multiple peptoid substitutions, high-affinity ligands can be generated that completely lack the canonical PxxP motif. The resulting ligands can potently disrupt natural SH3-mediated interactions.

CONCLUSIONS

Peptide-peptoid hybrid scaffolds yield SH3 ligands with markedly improved domain selectivity, overcoming one of the principal challenges in designing inhibitors against these domains. These compounds represent important leads in the search for orthogonal inhibitors of SH3 domains, and can serve as tools for the dissection of complex signaling pathways.

Activation tagging in Arabidopsis

Activation tagging using T-DNA vectors that contain multimerized transcriptional enhancers from the cauliflower mosaic virus (CaMV) 35S gene has been applied to Arabidopsis plants. New activation-tagging vectors that confer resistance to the antibiotic kanamycin or the herbicide glufosinate have been used to generate several tens of thousands of transformed plants. From these, over 30 dominant mutants with various phenotypes have been isolated. Analysis of a subset of mutants has shown that overexpressed genes are almost always found immediately adjacent to the inserted CaMV 35S enhancers, at distances ranging from 380 bp to 3.6 kb. In at least one case, the CaMV 35S enhancers led primarily to an enhancement of the endogenous expression pattern rather than to constitutive ectopic expression, suggesting that the CaMV 35S enhancers used here act differently than the complete CaMV 35S promoter. This has important implications for the spectrum of genes that will be discovered by this method.

Activation tagging of the floral inducer FT

FLOWERING LOCUS T (FT), which acts in parallel with the meristem-identity gene LEAFY (LFY) to induce flowering of Arabidopsis, was isolated by activation tagging. Like LFY, FT acts partially downstream of CONSTANS (CO), which promotes flowering in response to long days. Unlike many other floral regulators, the deduced sequence of the FT protein does not suggest that it directly controls transcription or transcript processing. Instead, it is similar to the sequence of TERMINAL FLOWER 1 (TFL1), an inhibitor of flowering that also shares sequence similarity with membrane-associated mammalian proteins.

Activation tagging of the floral inducer FT

FLOWERING LOCUS T (FT), which acts in parallel with the meristem-identity gene LEAFY (LFY) to induce flowering of Arabidopsis, was isolated by activation tagging. Like LFY, FT acts partially downstream of CONSTANS (CO), which promotes flowering in response to long days. Unlike many other floral regulators, the deduced sequence of the FT protein does not suggest that it directly controls transcription or transcript processing. Instead, it is similar to the sequence of TERMINAL FLOWER 1 (TFL1), an inhibitor of flowering that also shares sequence similarity with membrane-associated mammalian proteins.

Galectin-1 specifically modulates TCR signals to enhance TCR apoptosis but inhibit IL-2 production and proliferation

Galectin-1 is an endogenous lectin expressed by thymic and lymph node stromal cells at sites of Ag presentation and T cell death during normal development. It is known to have immunomodulatory activity in vivo and can induce apoptosis in thymocytes and activated T cells (1-3). Here we demonstrate that galectin-1 stimulation cooperates with TCR engagement to induce apoptosis, but antagonizes TCR-induced IL-2 production and proliferation in a murine T cell hybridoma and freshly isolated mouse thymocytes, respectively. Although CD4+ CD8+ double positive cells are the primary thymic subpopulation susceptible to galectin-1 treatment alone, concomitant CD3 engagement and galectin-1 stimulation broaden susceptible thymocyte subpopulations to include a subset of each CD4- CD8-, CD4+ CD8+, CD4- CD8+, and CD4+ CD8- subpopulations. Furthermore, CD3 engagement cooperates with suboptimal galectin-1 stimulation to enhance cell death in the CD4+ CD8+ subpopulation. Galectin-1 stimulation is shown to synergize with TCR engagement to dramatically and specifically enhance extracellular signal-regulated kinase-2 (ERK-2) activation, though it does not uniformly enhance TCR-induced tyrosine phosphorylation. Unlike TCR-induced IL-2 production, TCR/galectin-1-induced apoptosis is not modulated by the expression of kinase inactive or constitutively activated Lck. These data support a role for galectin-1 as a potent modulator of TCR signals and functions and indicate that individual TCR-induced signals can be independently modulated to specifically affect distinct TCR functions.

Adeno-associated virus-mediated delivery of antiangiogenic factors as an antitumor strategy

Antiangiogenic tumor therapies have recently attracted intense interest for their broad-spectrum action, low toxicity, and, in the case of direct endothelial targeting, an absence of drug resistance. To promote tumor regression and to maintain dormancy, antiangiogenic agents need to be chronically administered. Gene therapy offers a potential way to achieve sustained therapeutic release of potent antiangiogenic substances. As a step toward this goal, we have generated recombinant adeno-associated virus (rAAV) vectors that carry genes coding for angiostatin, endostatin, and an antisense mRNA species against vascular endothelial growth factor (VEGF). These rAAVs efficiently transduced three human tumor cell lines tested. Transduction with an rAAV-encoding antisense VEGF mRNA inhibited the production of endogenous tumor cell VEGF. Conditioned media from cells transduced with this rAAV or with rAAV-expressing endostatin or angiostatin inhibited capillary endothelial cell proliferation in vitro. Antiangiogenic rAAVs may offer a novel gene therapy approach to undermining tumor neovascularization and cancer progression.

Exploiting the basis of proline recognition by SH3 and WW domains: design of N-substituted inhibitors

Src homology 3 (SH3) and WW protein interaction domains bind specific proline-rich sequences. However, instead of recognizing critical prolines on the basis of side chain shape or rigidity, these domains broadly accepted amide N-substituted residues. Proline is apparently specifically selected in vivo, despite low complementarity, because it is the only endogenous N-substituted amino acid. This discriminatory mechanism explains how these domains achieve specific but low-affinity recognition, a property that is necessary for transient signaling interactions. The mechanism can be exploited: screening a series of ligands in which key prolines were replaced by nonnatural N-substituted residues yielded a ligand that selectively bound the Grb2 SH3 domain with 100 times greater affinity.

Galectin-1, an endogenous lectin produced by thymic epithelial cells, induces apoptosis of human thymocytes

Galectin-1, a beta-galactoside binding protein, is produced by thymic epithelial cells and binds to human thymocytes. We have previously reported that galectin-1 induces the apoptosis of activated T lymphocytes. Because the majority of thymocytes die via apoptosis while still within the thymus, we tested whether galectin-1 could induce the apoptosis of these cells. We now report that in vitro exposure to galectin-1 induced apoptosis of two subsets of CD4(lo) CD8(lo) thymocytes. The phenotypes of susceptible thymocytes were consistent with that of both negatively selected and nonselected cells. Galectin-1-induced apoptosis was enhanced by preexposure of thymocytes to antibody to CD3, suggesting that galectin-1 may be a participant in T-cell- receptor mediated apoptosis. In contrast, pretreatment of thymocytes with dexamethasone had no effect on galectin-1 susceptibility. We noted that 71% of the cells undergoing apoptosis after galectin-1 treatment had a DNA content greater than 2N, indicating that proliferating thymocytes were most sensitive to galectin-1. We propose that galectin-1 plays a role in the apoptosis of both negatively selected and nonselected thymocytes, and that the susceptibility of thymocytes to galectin-1 is regulated, in part, by entry or exit from the cell cycle.

X-ray diffraction of scrapie prion rods and PrP peptides

Certain neurodegenerative diseases in humans and animals are caused by small proteinaceous infectious particles called prions. Limited proteolysis and detergent extraction of the prions containing PrPSc generate prion rods that are composed of a polypeptide having an apparent molecular mass of 27 to 30 kDa. This polypeptide, termed prion protein PrP 27-30, has a ragged N terminus that begins at about residue 90, but retains scrapie infectivity. Moreover, the findings in a patient having an inherited prion disease of a truncated PrP with its C terminus at residue 145 suggest that the residues 90 to 145 may be of particular importance in the pathogenesis of prion diseases. To determine the three-dimensional organization of prion rods and to identify the core region involved in amyloid formation, we recorded X-ray diffraction patterns from rods purified from scrapie-infected Syrian hamster (SHa) brains which contain PrP 27-30, and from synthetic SHaPrP peptides. Three peptides were studied corresponding to residues 113 to 120 (peptide A8A, an octamer composed of glycines and alanines), 109 to 122 (H1, the first predicted alpha-helical region of PrPC), and 90 to 145 (a 56 residue peptide containing both H1 and the second predicted alpha-helical region of PrPC, H2). Electron microscopy, carried out in parallel with the X-ray measurements, revealed that all the samples formed linear polymers which were approximately 60 to approximately 200 A wide, with fibrillar or ribbon-like morphology. Gels and dried preparations of prion rods gave X-ray patterns that indicated a beta-sheet conformation, in which the hydrogen bond distance was 4.72 A and the intersheet distance was 8.82 A. For the three PrP peptides, the intersheet spacings varied widely, owing to the side-chains of the residues involved in the formation of the beta-sheet interactions, i.e., 5.13 A for A8A, 5.91 A for lyophilized H1, 7.99 A from solubilized and dried H1 and 9.15 A for the peptide SHa 90-145. The intersheet distance of PrP 27-30 was thus within the observed range for the peptides, and suggests that the amyloidogenic core of PrP is closely modeled by the peptide SHa 90-145.

Conformational transitions in peptides containing two putative alpha-helices of the prion protein

Prions are composed largely, if not entirely, of the scrapie isoform of the prion protein (PrPSc). Conversion of the cellular isoform (PrPC) to PrPSc is accompanied by a diminution in the alpha-helical content and an increase in the beta-sheet structure. To investigate the structural basis of this transition, peptide fragments corresponding to Syrian hamster PrP residues 90 to 145 and 109 to 141, which contain the most conserved residues of the prion protein and the first two putative alpha-helical regions in a PrPC model, were studied using infrared spectroscopy and circular dichroism. The peptides could be induced to form alpha-helical structures in aqueous solutions in the presence of organic solvents, such as trifluoroethanol and hexafluoroisopropanol, or detergents, such as sodium dodecyl sulfate and dodecyl phosphocholine. NaCl at physiological concentration or acetonitrile induced the peptides to acquire substantial beta-sheet. The intermolecular nature of the beta-sheet was evident in the formation of rod-shaped polymers as detected by electron microscopy. Resistance to hydrolysis by proteinase K and epitope mapping argue that the beta-sheet structures were formed by the interaction of residues lying between 109 and 141. A similar range of residues was shown by nuclear magnetic resonance spectroscopy to be capable of forming alpha-helices. The alpha-helical structures seem to require a hydrophobic support from either intermolecular interactions or the hydrophobic environment provided by micelles, in agreement with the predicted hydrophobic nature of the packing surface among the four putative helices of PrPC and the outer surfaces of the first two helices. Our results suggest that perturbation of the packing environment of the highly conserved residues is a possible mechanism for triggering the conversion of PrPC to PrPSc where alpha-helices appear to be converted into beta-sheets.

Conformation and fibrillogenesis of Alzheimer A beta peptides with selected substitution of charged residues

A key pathological feature of Alzheimer's disease (AD) is the formation and accumulation of amyloid fibers within the neurophil as senile plaques and in the walls of cerebral and meningeal blood vessels. The major component is the 39 to 42 residue amyloid beta protein (A beta), which is an internal proteolytic fragment of the membrane-associated amyloid precursor protein. Aggregation of A beta into amyloid fibers that could be cytotoxic may be a factor in the AD-related neuronal loss. To understand the steps and molecular interactions involved in the transition from a soluble to fibrous form of A beta, and to test molecular models that postulate ion pairing between beta-strands, we have synthetized four peptides having substitutions in specific, charged residues. These included an A beta fragment, residues 11 to 25, and having histidine-to-aspartate replacements at positions 13 (H13D) and 14 (H14D), an aspartate-to-lysine at position 23 (D23K) and a 28-mer full-length extracellular domain where the positive charge cluster at His13-His14-Gln15-Lys16 was replaced by an uncharged Gly13-Gly14-Gln15-Gly16 (GGQG). Fourier-transform infrared spectroscopy and fiber X-ray diffraction determined that the H13D and H14D substitutions had negligible effect on beta-sheet formation, suggesting that these residues are not critical for the intramolecular interactions necessary for folding in the beta-conformation. However, negative-stain electron microscopy revealed that the loss of the His13 or His14 resulted in only protofilament formation, suggesting that these residues are involved in amyloid fibril assembly. By contrast, the D23K substitution virtually eliminated folding into a beta-sheet conformation, with appreciable secondary structure being detected only following extended incubation times. The complete absence of the centrally charged region GGQG arrested amyloid assembly at the protofilament stage and also reduced the stability of the beta-conformation, suggesting a contribution of Lys16 in maintaining secondary structure. While it has been conclusively demonstrated by previous investigations that amyloid formation is dependent to a large extent on hydrophobically driven interactions, our results indicate that charge-charge interactions function in concert with non-ionic interactions to stabilize the beta-sheet conformation and assembly of AD amyloid fibers.

Effects of calcium channel antagonists on the release of prostaglandin E2 from metabolically stressed muscle

Calcium influx plays a critical role in the activation of the arachidonic cascade in muscle damage. We examined the effects of L-type calcium channel antagonists on the release of prostaglandin E2 (PGE2), a bioactive metabolite of arachidonic acid metabolism, from skeletal muscle. The basal release of PGE2 was not affected by calcium channel inhibitors, such as nifedipine and verapamil. The release of PGE2 induced by dinitrophenol, an uncoupler of oxidative phosphorylation, was abolished by nifedipine and verapamil at 50 and 150 microM, respectively. It was not necessary to include the calcium channel blockers in the medium before or at the time of dinitrophenol stimulation to produce the effect on PGE2 release. The release of PGE2 was prevented for as long as calcium channel blockers were present in the medium after the dinitrophenol stress.

Alpha 1-antichymotrypsin binding to Alzheimer A beta peptides is sequence specific and induces fibril disaggregation in vitro

The serine protease inhibitor alpha 1-antichymotrypsin (ACT) consistently colocalizes with amyloid deposits of Alzheimer's disease (AD) and may contribute to the generation of amyloid proteins and/or physically affect fibril assembly. AD amyloid fibrils are composed primarily of A beta, which is a proteolytic fragment of the larger beta-amyloid precursor protein. Using negative-stain and immunochemical electron microscopy, we have investigated the binding of ACT to the fibrils formed by four synthetic A beta analogues corresponding to the wild-type human 1-40 sequence [Hwt(1-40)], a 1-40 peptide [HDu(1-40)] containing the Glu22-->Gln mutation found in hereditary cerebral hemorrhage with amyloidosis of the Dutch type, the N-terminal 1-28 residues [beta(1-28)], and an internal fragment of A beta containing residues 11-28 [beta(11-28)]. Each of these peptide analogues assembled into 70-90-A-diameter fibrils resembling native amyloid and, except for beta(11-28), bound ACT, as indicated by the appearance of 80-100-A globular particles that adhered to preformed fibrils and that could be decorated with anti-ACT antibodies. Under the conditions used, ACT binding destabilized the in vitro fibrils and produced a gradual dissolution of the macromolecular assemblies into constituent filaments and shorter fragments. The internal fragment (11-28) did not exhibit ACT binding or any structural changes. These results suggest that a specific sequence likely contained within the N-terminal 10 residues of A beta is responsible for the formation of the ACT-amyloid complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Fibril formation by primate, rodent, and Dutch-hemorrhagic analogues of Alzheimer amyloid beta-protein

Deposition of extraneuronal fibrils that assemble from the 39-43 residue beta/A4 amyloid protein is one of the earliest histopathological features of Alzheimer's disease. We have used negative-stain electron microscopy, Fourier-transform infrared (FT-IR) spectroscopy, and fiber X-ray diffraction to examine the structure and properties of synthetic peptides corresponding to residues 1-40 of the beta/A4 protein of primate [Pm(1-40); human and monkey], rodent [Ro(1-40); with Arg5-->Gly, Tyr10-->Phe, and His13-->Arg], and hereditary cerebral hemorrhage with amyloidosis of the Dutch type (HCHWA-D) [Du(1-40); with Glu22-->Gln]. As controls, we examined a reverse primate sequence [Pm*(40-1)] and an extensively substituted primate peptide [C(1-40); with Glu3-->Arg, Arg5-->Glu, Asp7-->Val, His13-->Lys, Lys16-->His, Val18-->Asp, Phe19-->Ser, Phe20-->Tyr, Ser26-->Pro, Ala30-->Val, Ile31-->Ala, Met35-->norLeu, Gly38-->Ile, Val39-->Ala, and Val40-->Gly]. The assembly of these peptides was studied to understand the relationship between species-dependent amyloid formation and beta/A4 sequence and the effect of a naturally occurring point mutation of fibrillogenesis. The three N-terminal amino acid differences between Pm(1-40) and Ro(1-40) had virtually no effect on the morphology or organization of the fibrils formed by these peptides, indicating that the lack of amyloid deposits in rodent brain is not due directly to specific changes in its beta/A4 sequence. beta-Sheet and fibril formation, judged by FT-IR, was maximal within the pH range 5-8 for Pm(1-40), pH 5-10.5 for Du(1-40), and pH 2.5-8 for Ro(1-40).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of sulfate ions on Alzheimer beta/A4 peptide assemblies: implications for amyloid fibril-proteoglycan interactions

To model the possible involvement of sulfated proteoglycans in amyloidogenesis, we examined the influence of sulfate ions, heparan, and Congo red on the conformation and morphology of peptides derived from the Alzheimer beta/A4 amyloid protein. The peptides included residues 11-28, 13-28, 15-28, and 11-25 of beta/A4. Negative-stain electron microscopy revealed a sulfate-specific tendency of the preformed peptide fibrillar assemblies of beta(11-28), beta(13-28), and beta(11-25), but not beta(15-28), to undergo extensive lateral aggregation and axial growth into "macrofibers" that were approximately 0.1-0.2 micron wide by approximately 20-30 microns long. Such effects were observed at low sulfate concentrations (e.g., 5-50 mM) and could not be reproduced under comparable conditions with Na2HPO4, Na2SeO4, or NaCl. Macrofibers in NaCl were only observed at 1,000 mM. At physiological ionic strength of NaCl, fibril aggregation was observed only with addition of sulfate ions at 5-50 mM. Selenate ions, by contrast with sulfate ions, induced only axial and not substantial lateral aggregation of fibrils. X-ray diffraction indicated that the original cross-beta peptide conformation remained unchanged; however, sulfate binding did produce an intense approximately 65 A meridional reflection not recorded with control peptides. This new reflection probably arises from the periodic deposition of the electron-dense sulfate along the (long) axis of the fibril. The sulfate binding could provide sites for the binding of additional fibrils that generate the observed lateral and axial aggregation. The binding of heparan to beta(11-28) also produced extensive aggregation, suggesting that in vivo sulfated compounds can promote macrofibers. The amyloid-specific, sulfonated dye Congo red, even in the presence of sulfate ions, produced limited aggregation and reduced axial growth of the fibrils. Therefore, electrostatic interactions are important in the binding of exogenous compounds to amyloid fibrils. Our findings suggest that the sulfate moieties of certain molecules, such as glycosaminoglycans, may affect the aggregation and deposition of amyloid fibrils that are observed as extensive deposits in senile plaques and cerebrovascular amyloid.

pH-dependent structural transitions of Alzheimer amyloid peptides

To understand the molecular interactions leading to the assembly of beta/44 protein into the hallmark fibrils of Alzheimer's disease (AD), we have examined the ability of synthetic peptides that correspond to the beta/A4 extracellular sequence to form fibrils over the range of pH 3-10. Peptides included the sequences 1-28, 19-28, 17-28, 15-28, 13-28, 11-28, and 9-28 of beta/A4. The model fibrils were compared with isolated amyloid with respect to morphology, conformation, tinctorial properties, and stability under denaturing conditions. Electron microscopy, Fourier-transform infrared (FT-IR) spectroscopy, and x-ray diffraction revealed that the ionization states of the amino acid sidechains appeared to be a crucial feature in fibril formation. This was reflected by the ability of several peptides to undergo fibril assembly and disassembly as a function of pH. Comparisons between different beta/A4 sequences demonstrated that the fibrillar structure representative of AD amyloid was dependent upon electrostatic interactions, likely involving His-13 and Asp-23, and hydrophobic interactions between uncharged sidechains contained within residues 17-21. The results also indicated an exclusively beta-sheet conformation for the synthetic (and possibly AD fibrils) in contrast to certain other (e.g., systemic) amyloids.

The cytokine CSF-1 (M-CSF) expressed by endometrial carcinomas in vivo and in vitro, may also be a circulating tumor marker of neoplastic disease activity in endometrial carcinoma patients

Endometrial epithelial cell expression of CSF-1 and FMS antigens was studied in vivo and in vitro in 24 human endometrial carcinoma and 11 benign endometrial biopsy specimens. Twenty-one of 24 adenocarcinomas and 4 of 11 benign lesions stained positively (by IHC) with rabbit anti-human CSF-1 antibodies, while all 24 carcinomas and 3 out of 11 benign lesions (all secretory endometrial specimens) showed significant IHC staining (1+ or greater) of epithelial elements and tissue macrophages with a mouse anti-FMS (CSF-1 receptor) monoclonal antibody. CSF-1 levels in plasma from endometrial carcinoma patients (85 samples, 24 patients) were also found to be markedly elevated (some greater than 100 ng/ml) in patients with active or recurrent disease. In vitro, several endometrial carcinoma cell lines were shown to express FMS complementary transcripts and FMS antigen which were very similar if not identical to those expressed in choriocarcinoma cell line positive controls. Autocrine and paracrine effects mediated by tumor or stromally produced CSF-1 and a tumor epithelial cell CSF-1 receptor may therefore contribute to the biological behavior of endometrial neoplasms in vivo and in vitro.