The α2,3-selective potentiator of GABAA receptors, KRM-II-81, reduces nociceptive-associated behaviors induced by formalin and spinal nerve ligation in rats

Clinical evidence indicates that positive allosteric modulators (PAMs) of GABAA receptors have analgesic benefit in addition to efficacy in anxiety disorders. However, the utility of GABAA receptor PAMs as analgesics is compromised by the central nervous system side effects of non-selective potentiators. A selective potentiator of GABAA receptors associated with α2/3 subunits, KRM-II-81(5-(8-ethynyl-6-(pyridin-2-yl)-4H-benzo[f]imidazo[1,5-a][1,4]diazepin-3-yl)oxazole), has demonstrated anxiolytic, anticonvulsant, and antinociceptive effects in rodents with reduced motoric side effects. The present study evaluated the potential of KRM-II-81 as a novel analgesic. Oral administration of KRM-II-81 attenuated formalin-induced flinching; in contrast, diazepam was not active. KRM-II-81 attenuated nociceptive-associated behaviors engendered by chronic spinal nerve ligation (L5/L6). Diazepam decreased locomotion of rats at the dose tested in the formalin assay (10 mg/kg) whereas KRM-II-81 produced small decreases that were not dose-dependent (10-100 mg/kg). Plasma and brain levels of KRM-II-81 were used to demonstrate selectivity for α2/3- over α1-associated GABAA receptors and to define the degree of engagement of these receptors. Plasma and brain concentrations of KRM-II-81 were positively-associated with analgesic efficacy. GABA currents from isolated rat dorsal-root ganglion cultures were potentiated by KRM-II-81 with an ED50 of 32 nM. Measures of respiratory depression were reduced by alprazolam whereas KRM-II-81 was either inactive or produced effects with lower potency and efficacy. These findings add to the growing body of data supporting the idea that α2/3-selective GABAA receptor PAMs will have efficacy and tolerability as pain medications including those for neuropathic pain. Given their predicted anxiolytic effects, α2/3-selective GABAA receptor PAMs offer an additional inroad into the management of pain.

Search for Tensor, Vector, and Scalar Polarizations in the Stochastic Gravitational-Wave Background

The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy densities of tensor, vector, and scalar modes at 95% credibility to Ω_{0}^{T}<5.58×10^{-8}, Ω_{0}^{V}<6.35×10^{-8}, and Ω_{0}^{S}<1.08×10^{-7} at a reference frequency f_{0}=25  Hz.

GW170817: Implications for the Stochastic Gravitational-Wave Background from Compact Binary Coalescences

The LIGO Scientific and Virgo Collaborations have announced the event GW170817, the first detection of gravitational waves from the coalescence of two neutron stars. The merger rate of binary neutron stars estimated from this event suggests that distant, unresolvable binary neutron stars create a significant astrophysical stochastic gravitational-wave background. The binary neutron star component will add to the contribution from binary black holes, increasing the amplitude of the total astrophysical background relative to previous expectations. In the Advanced LIGO-Virgo frequency band most sensitive to stochastic backgrounds (near 25 Hz), we predict a total astrophysical background with amplitude Ω_{GW}(f=25  Hz)=1.8_{-1.3}^{+2.7}×10^{-9} with 90% confidence, compared with Ω_{GW}(f=25  Hz)=1.1_{-0.7}^{+1.2}×10^{-9} from binary black holes alone. Assuming the most probable rate for compact binary mergers, we find that the total background may be detectable with a signal-to-noise-ratio of 3 after 40 months of total observation time, based on the expected timeline for Advanced LIGO and Virgo to reach their design sensitivity.

Prospects for observing and localizing gravitational-wave transients with Advanced LIGO, Advanced Virgo and KAGRA

We present possible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron star systems, which are the most promising targets for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and [Formula: see text] credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5-[Formula: see text] requires at least three detectors of sensitivity within a factor of [Formula: see text] of each other and with a broad frequency bandwidth. When all detectors, including KAGRA and the third LIGO detector in India, reach design sensitivity, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.

GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral

On August 17, 2017 at 12∶41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave detectors made their first observation of a binary neutron star inspiral. The signal, GW170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per 8.0×10^{4}  years. We infer the component masses of the binary to be between 0.86 and 2.26  M_{⊙}, in agreement with masses of known neutron stars. Restricting the component spins to the range inferred in binary neutron stars, we find the component masses to be in the range 1.17-1.60  M_{⊙}, with the total mass of the system 2.74_{-0.01}^{+0.04}M_{⊙}. The source was localized within a sky region of 28  deg^{2} (90% probability) and had a luminosity distance of 40_{-14}^{+8}  Mpc, the closest and most precisely localized gravitational-wave signal yet. The association with the γ-ray burst GRB 170817A, detected by Fermi-GBM 1.7 s after the coalescence, corroborates the hypothesis of a neutron star merger and provides the first direct evidence of a link between these mergers and short γ-ray bursts. Subsequent identification of transient counterparts across the electromagnetic spectrum in the same location further supports the interpretation of this event as a neutron star merger. This unprecedented joint gravitational and electromagnetic observation provides insight into astrophysics, dense matter, gravitation, and cosmology.

GW170814: A Three-Detector Observation of Gravitational Waves from a Binary Black Hole Coalescence

On August 14, 2017 at 10∶30:43 UTC, the Advanced Virgo detector and the two Advanced LIGO detectors coherently observed a transient gravitational-wave signal produced by the coalescence of two stellar mass black holes, with a false-alarm rate of ≲1 in 27 000 years. The signal was observed with a three-detector network matched-filter signal-to-noise ratio of 18. The inferred masses of the initial black holes are 30.5_{-3.0}^{+5.7}M_{⊙} and 25.3_{-4.2}^{+2.8}M_{⊙} (at the 90% credible level). The luminosity distance of the source is 540_{-210}^{+130}  Mpc, corresponding to a redshift of z=0.11_{-0.04}^{+0.03}. A network of three detectors improves the sky localization of the source, reducing the area of the 90% credible region from 1160   deg^{2} using only the two LIGO detectors to 60  deg^{2} using all three detectors. For the first time, we can test the nature of gravitational-wave polarizations from the antenna response of the LIGO-Virgo network, thus enabling a new class of phenomenological tests of gravity.

Upper Limits on the Stochastic Gravitational-Wave Background from Advanced LIGO's First Observing Run

A wide variety of astrophysical and cosmological sources are expected to contribute to a stochastic gravitational-wave background. Following the observations of GW150914 and GW151226, the rate and mass of coalescing binary black holes appear to be greater than many previous expectations. As a result, the stochastic background from unresolved compact binary coalescences is expected to be particularly loud. We perform a search for the isotropic stochastic gravitational-wave background using data from Advanced Laser Interferometer Gravitational Wave Observatory's (aLIGO) first observing run. The data display no evidence of a stochastic gravitational-wave signal. We constrain the dimensionless energy density of gravitational waves to be Ω_{0}<1.7×10^{-7} with 95% confidence, assuming a flat energy density spectrum in the most sensitive part of the LIGO band (20-86 Hz). This is a factor of ∼33 times more sensitive than previous measurements. We also constrain arbitrary power-law spectra. Finally, we investigate the implications of this search for the background of binary black holes using an astrophysical model for the background.

Directional Limits on Persistent Gravitational Waves from Advanced LIGO's First Observing Run

We employ gravitational-wave radiometry to map the stochastic gravitational wave background expected from a variety of contributing mechanisms and test the assumption of isotropy using data from the Advanced Laser Interferometer Gravitational Wave Observatory's (aLIGO) first observing run. We also search for persistent gravitational waves from point sources with only minimal assumptions over the 20-1726 Hz frequency band. Finding no evidence of gravitational waves from either point sources or a stochastic background, we set limits at 90% confidence. For broadband point sources, we report upper limits on the gravitational wave energy flux per unit frequency in the range F_{α,Θ}(f)<(0.1-56)×10^{-8}    erg cm^{-2} s^{-1} Hz^{-1}(f/25  Hz)^{α-1} depending on the sky location Θ and the spectral power index α. For extended sources, we report upper limits on the fractional gravitational wave energy density required to close the Universe of Ω(f,Θ)<(0.39-7.6)×10^{-8}  sr^{-1}(f/25  Hz)^{α} depending on Θ and α. Directed searches for narrowband gravitational waves from astrophysically interesting objects (Scorpius X-1, Supernova 1987 A, and the Galactic Center) yield median frequency-dependent limits on strain amplitude of h_{0}<(6.7,5.5,  and  7.0)×10^{-25}, respectively, at the most sensitive detector frequencies between 130-175 Hz. This represents a mean improvement of a factor of 2 across the band compared to previous searches of this kind for these sky locations, considering the different quantities of strain constrained in each case.

GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence

We report the observation of a gravitational-wave signal produced by the coalescence of two stellar-mass black holes. The signal, GW151226, was observed by the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) on December 26, 2015 at 03:38:53 UTC. The signal was initially identified within 70 s by an online matched-filter search targeting binary coalescences. Subsequent off-line analyses recovered GW151226 with a network signal-to-noise ratio of 13 and a significance greater than 5σ. The signal persisted in the LIGO frequency band for approximately 1 s, increasing in frequency and amplitude over about 55 cycles from 35 to 450 Hz, and reached a peak gravitational strain of 3.4_{-0.9}^{+0.7}×10^{-22}. The inferred source-frame initial black hole masses are 14.2_{-3.7}^{+8.3}M_{⊙} and 7.5_{-2.3}^{+2.3}M_{⊙}, and the final black hole mass is 20.8_{-1.7}^{+6.1}M_{⊙}. We find that at least one of the component black holes has spin greater than 0.2. This source is located at a luminosity distance of 440_{-190}^{+180}  Mpc corresponding to a redshift of 0.09_{-0.04}^{+0.03}. All uncertainties define a 90% credible interval. This second gravitational-wave observation provides improved constraints on stellar populations and on deviations from general relativity.

Correlation of automated volumetric analysis of brain MR imaging with cognitive impairment in a natural history study of mucopolysaccharidosis II

BACKGROUND AND PURPOSE

Reliable markers for predicting neurologic outcome in patients with MPS II are lacking. The purpose of this study is to explore whether quantitative volumetric measurements of brain MR imaging can be used to differentiate between MPS II patients with and without cognitive impairment. This MR imaging study is the first in MPS II patients to use automated/semi-automated methods to quantify brain volumes in a longitudinal design.

MATERIALS AND METHODS

Sixteen male patients with MPS II in a natural history study had annual brain MR imaging and detailed neurodevelopmental assessment over 2 years. Automated and semi-automated methods were used to determine brain volumes. Linear mixed regression models adjusting for age were used to assess the correlation between the volumetric parameters and cognition.

RESULTS

Among the 16 MPS II patients, 10 (22 MR imaging studies) had cognitive impairment whereas the other 6 (11 MR imaging studies) had normal cognition. A decreased brain tissue/ICV ratio (-5%; P < .001) and an increased lateral ventricle/ICV ratio (+4%; P = .029) were found in patients with cognitive impairment compared with patients with normal cognition. These changes were apparent in patients as young as 7 years of age in addition to older patients.

CONCLUSIONS

Quantitative volumetric measurements of brain MR imaging in MPS II patients can be obtained by using automated and semi-automated segmentation methods. MPS II patients with cognitive impairment have decreased brain tissue volumes, but longer studies with more subjects are required to confirm these results.

DairyBeef: Maximizing Quality and Profits—A Consistent Food Safety Message

To respond to meat safety and quality issues in dairy market cattle, a collaborative project team for 7 western states was established to develop educational resources providing a consistent meat safety and quality message to dairy producers, farm advisors, and veterinarians. The team produced an educational website and CD-ROM course that included videos, narrated slide sets, and on-farm tools. The objectives of this course were: 1) to help producers and their advisors understand market cattle food safety and quality issues, 2) help maintain markets for these cows, and 3) help producers identify ways to improve the quality of dairy cattle going to slaughter. DairyBeef. Maximizing Quality & Profits consists of 6 sections, including 4 core segments. Successful completion of quizzes following each core segment is required for participants to receive a certificate of completion. A formative evaluation of the program revealed the necessity for minor content and technological changes with the web-based course. All evaluators considered the materials relevant to dairy producers. After editing, course availability was enabled in February, 2003. Between February and May, 2003, 21 individuals received certificates of completion.

Association of serine protease with the rise of intracellular calcium in cytotoxic T lymphocytes

The precise role of the granular enzyme A (granzyme A), a serine protease, in the lytic process of cytotoxic T lymphocytes (CTL) is not clear. We have recently constructed a CTL line transfected with the antisense gene of granzyme A (a-GrA). These a-GrA CTL had lower GrA activity as well as decreased lytic activities, as measured by 51Cr and by DNA degradation assays. Furthermore, at low effector:target ratio (1:8) in prolonged lytic assays, they could not lyse targets as rapidly as the control CTL. When we examined their ability to exocytose BLT (CBZ-L-lys-thiobenzyl)-esterase in the presence of anti-CD3 antibody, the a-GrA CTL exocytosed poorly compared to the parental CTL or control transfectant with a CAT gene. Most strikingly, a-GrA cells could not release intracellular stores of Ca2+ in response to anti-CD3 induction, although the Ca2+ flux was normal when they were stimulated with ionomycin. When the parental CTL was treated with a specific benzyllactam inhibitor of BLT-esterase or N-tosyl-L-phenylalanylchloromethyl ketone, the Ca2+ flux induced by anti-CD3 was also suppressed. We propose that granzyme A is involved in the signal transduction pathway that causes the rise of the intracellular calcium.

CTL lysis: there is a hyperbolic relation of killing rate to exocytosable granzyme A for highly cytotoxic murine cytotoxic T lymphocytes

The lysis of susceptible targets by efficient cytotoxic T lymphocytes (CTL) increases both with time and with the ratio of CTL to target. Simple methods for calculating a killing rate constant from the time dependence of killing and for calculating the relation of the killing rate constant to the concentration of exocytosable granzyme A are given. Application of these methods to the killing of target cells by the highly efficient mouse CTL AR1 is presented. AR1 needed granzyme A for efficient killing. AR1 contained sufficient exocytosable granzyme A to kill at about 80% of the rate possible at infinite exocytosable granzyme A.

Intron-exon organization and chromosomal localization of the human TIA-1 gene

TIA-1 is a 40-kDa cytotoxic granule-associated RNA-binding protein (p40-TIA-1), the expression of which is restricted to cytolytic lymphocytes. The major granule-associated species is a 15-kDa protein (p15-TIA-1) that seems to be derived from the carboxyl terminus of p40-TIA-1. Although some evidence suggests that p15-TIA-1 is derived from p40-TIA-1 by proteolytic processing, it is also possible that each isoform is derived from discrete mRNA initiated from alternative promoters within the TIA-1 gene. To learn more about the relationship between p15-TIA-1 and p40-TIA-1, we have determined the complete intron-exon organization of the TIA-1 gene. The gene consists of 13 exons separated by 12 intervening sequences and spans greater than 46 kb of DNA located on chromosome 2, band p13. The transcription start site of the mRNA transcript encoding p40-TIA-1 was identified by primer extension and S1 mapping analysis. The putative promoter region preceding this transcription start site stimulated the expression of a reporter gene in transfected Jurkat and YT cells. Attempts to identify a second promoter capable of initiating an mRNA encoding p15-TIA-1 were unsuccessful, supporting the possibility that p15-TIA-1 can be derived from p40-TIA-1 proteolytically. Granule-associated serine proteases that have been implicated in cytolytic lymphocyte killing (granzyme A and granzyme B) were unable to cleave TIA-1, suggesting that processing may occur before TIA-1 enters the cytotoxic granule.

Intron-exon organization and chromosomal localization of the human TIA-1 gene

TIA-1 is a 40-kDa cytotoxic granule-associated RNA-binding protein (p40-TIA-1), the expression of which is restricted to cytolytic lymphocytes. The major granule-associated species is a 15-kDa protein (p15-TIA-1) that seems to be derived from the carboxyl terminus of p40-TIA-1. Although some evidence suggests that p15-TIA-1 is derived from p40-TIA-1 by proteolytic processing, it is also possible that each isoform is derived from discrete mRNA initiated from alternative promoters within the TIA-1 gene. To learn more about the relationship between p15-TIA-1 and p40-TIA-1, we have determined the complete intron-exon organization of the TIA-1 gene. The gene consists of 13 exons separated by 12 intervening sequences and spans greater than 46 kb of DNA located on chromosome 2, band p13. The transcription start site of the mRNA transcript encoding p40-TIA-1 was identified by primer extension and S1 mapping analysis. The putative promoter region preceding this transcription start site stimulated the expression of a reporter gene in transfected Jurkat and YT cells. Attempts to identify a second promoter capable of initiating an mRNA encoding p15-TIA-1 were unsuccessful, supporting the possibility that p15-TIA-1 can be derived from p40-TIA-1 proteolytically. Granule-associated serine proteases that have been implicated in cytolytic lymphocyte killing (granzyme A and granzyme B) were unable to cleave TIA-1, suggesting that processing may occur before TIA-1 enters the cytotoxic granule.

Comparison of the proteoglycanolytic activities of human leukocyte elastase and human cathepsin G in vitro and in vivo

In this study, we evaluated the in vitro and in vivo potency of human leukocyte elastase (HLE) and human cathepsin G (HCG) as proteoglycanases. In vitro evaluation was done using bovine nasal septum aggrecan and aggrecan/hyaluronan aggregate as substrates. Enzyme activity was assessed by the ability of the proteinases to abrogate the ability of aggrecan to aggregate with hyaluronan. In vivo activity of the proteinases was tested by injecting purified HLE and HCG intra-articularly into rabbit stifle joints and quantifying the levels of proteoglycan released into synovial fluids. On a molar basis, HCG was at least tenfold more potent than HLE as a proteoglycanase in vitro. Moreover, HCG was twofold more potent as a proteoglycanase in vivo. In contrast, HLE hydrolyzed elastin approximately 22-fold faster than HCG, but was only slightly more rapid than HCG when [3H]-transferrin was used as substrate. These data indicate that HCG is more potent than HLE as a proteoglycanase both in vitro and in vivo. Thus, HCG could be more important in the pathogenesis of rheumatoid arthritis than previously suspected.

Transfection of mouse cytotoxic T lymphocyte with an antisense granzyme A vector reduces lytic activity

Murine CTL have seven serine proteases, known as granzymes, in their lytic granules. Despite considerable effort, convincing evidence that these enzymes play an obligatory role in the lytic process has not been presented. To investigate the function of one of these proteases, granzyme A (GA), we utilized an antisense expression vector to lower the level of the enzyme in the cells. An expression vector containing antisense cDNA for GA and the gene for hygromycin B resistance was constructed and electroporated into the murine CTL line, AR1. Transfectants were selected based on resistance to hygromycin B, and a number of stable lines were developed. One of the antisense lines had greatly reduced levels of GA mRNA, when compared to the parental cells or to control lines transfected with the vector lacking the antisense DNA. The message levels for two other CTL granule proteins, granzyme B and perforin, were unaffected by the antisense vector. The amount of GA, as measured by enzymatic activity, was 3- to 10-fold lower in the transfectant. Most significantly, this line also consistently showed 50 to 70% lower ability to lyse nucleated target cells and to degrade their DNA. Furthermore, it exhibited 90 to 95% lower lytic activity to anti-CD3-coated SRBC. Conjugate formation with target cells, however, was normal. These data provide strong evidence that GA plays an important role in the cytolytic cycle, and that the quantity of enzyme is a limiting factor in these cytolytic cells.

Transfection of mouse cytotoxic T lymphocyte with an antisense granzyme A vector reduces lytic activity

Murine CTL have seven serine proteases, known as granzymes, in their lytic granules. Despite considerable effort, convincing evidence that these enzymes play an obligatory role in the lytic process has not been presented. To investigate the function of one of these proteases, granzyme A (GA), we utilized an antisense expression vector to lower the level of the enzyme in the cells. An expression vector containing antisense cDNA for GA and the gene for hygromycin B resistance was constructed and electroporated into the murine CTL line, AR1. Transfectants were selected based on resistance to hygromycin B, and a number of stable lines were developed. One of the antisense lines had greatly reduced levels of GA mRNA, when compared to the parental cells or to control lines transfected with the vector lacking the antisense DNA. The message levels for two other CTL granule proteins, granzyme B and perforin, were unaffected by the antisense vector. The amount of GA, as measured by enzymatic activity, was 3- to 10-fold lower in the transfectant. Most significantly, this line also consistently showed 50 to 70% lower ability to lyse nucleated target cells and to degrade their DNA. Furthermore, it exhibited 90 to 95% lower lytic activity to anti-CD3-coated SRBC. Conjugate formation with target cells, however, was normal. These data provide strong evidence that GA plays an important role in the cytolytic cycle, and that the quantity of enzyme is a limiting factor in these cytolytic cells.

High pressure gel-permeation assay for the proteolysis of human aggrecan by human stromelysin-1: kinetic constants for aggrecan hydrolysis

The adaptation of an analytical procedure for aggrecan based upon gel-permeation chromatography to an FPLC-based protocol has significantly sped up the analysis. The faster assay has permitted determination of the kinetic constants for digestion of human aggrecan by human stromelysin-1. Monomeric aggrecan appeared to be hydrolyzed by stromelysin-1 to multiple forms with lower molecular weight. The disappearance of high-molecular-weight aggrecan was first-order, showing Km much larger than 2 microM and kc/Km = 4000 M-1 s-1 at pH 7.5. The disappearance of high-molecular-weight aggrecan upon hydrolysis by stromelysin-1 at pH 5.5 was also first-order, with kc/Km = 10,700 M-1 s-1. The disappearance of high-molecular-weight aggrecan at pH 7.5 was first-order for digestion by human leukocyte elastase with kc/Km = 230,000 M-1 s-1, by human cathepsin G with kc/Km = 4200 M-1 S-1, and by human plasma plasmin with kc/Km = 2800 M-1 s-1, all with Km much larger than 2 microM.

Electron paramagnetic resonance studies of a ras p21-MnIIGDP complex in solution

The number of water molecules bound to Mn2+ in the complex with a variant of Ha ras p21 and GDP has been determined by electron paramagnetic resonance (EPR) measurements in 17O-enriched water. A resolution enhancement method has been used to improve quantitation of the spectral data. These spectroscopic measurements show that Mn2+ has four water ligands in this complex, a result in agreement with the conclusions of a previous paper [Smithers, G. W., Poe, M., Latwesen, D. G., & Reed, G. H. (1990) Arch. Biochem. Biophys. 280, 416-420]. The resolution enhancement method has also been applied in a measurement of the 17O-Mn2+ superhyperfine coupling constant of 17O in the beta-phosphate of the GDP in the ras p21 complex. The intrinsically narrow EPR signals of Mn2+ in the complex with ras p21 and GDP in 2H2O respond to resolution enhancement such that the superhyperfine splitting from the 17O nuclear spin (I = 5/2) becomes visible in the EPR signals. An 17O-Mn2+ superhyperfine coupling constant is obtained from simulation of the resolution-enhanced EPR spectrum.

Human and murine cytotoxic T lymphocyte serine proteases: subsite mapping with peptide thioester substrates and inhibition of enzyme activity and cytolysis by isocoumarins

The active site structures of human Q31 granzyme A, murine granzymes (A, B, C, D, E, and F), and human granzymes (A, B, and 3) isolated from cytotoxic T lymphocytes (CTL) were studied with peptide thioester substrates, peptide chloromethyl ketone, and isocoumarin inhibitors. Human Q31, murine, and human granzyme A hydrolyzed Arg- or Lys-containing thioesters very efficiently with kcat/KM of 10(4)-10(5) M-1 s-1. Murine granzyme B was found to have Asp-ase activity and hydrolyzed Boc-Ala-Ala-Asp-SBzl with a kcat/KM value of 2.3 X 10(5) M-1 s-1. The rate was accelerated 1.4-fold when the 0.05 M NaCl in the assay was replaced with CaCl2. The preparation of granzyme B also had significant activity toward Boc-Ala-Ala-AA-SBzl substrates, where AA was Asn, Met, or Ser [kcat/KM = (4-5) X 10(4) M-1 s-1]. Murine granzymes C, D, and E did not hydrolyze any thioester substrate but contained minor contaminating activity toward Arg- or Lys-containing thioesters. Murine granzyme F had small activity toward Suc-Phe-Leu-Phe-SBzl, along with some contaminating trypsin-like activity. Human Q31 granzyme A, murine, and human granzyme A were inhibited quite efficiently by mechanism-based isocoumarin inhibitors substituted with basic groups (guanidino or isothiureidopropoxy). Although the general serine protease inhibitor 3,4-dichloroisocoumarin (DCI) inactivated these tryptases poorly, it was the best isocoumarin inhibitor for murine granzyme B (kobs/[I] = 3700-4200 M-1 s-1). Murine and human granzyme B were also inhibited by Boc-Ala-Ala-Asp-CH2Cl; however, the inhibition was less potent than that with DCI. DCI, 3-(3-amino-propoxy)-4-chloroisocoumarin, 4-chloro-3-(3-isothiureidopropoxy)isocoumarin, and 7-amino-4-chloro-3-(3-isothiureidopropoxy)isocoumarin inhibited Q31 cytotoxic T lymphocyte mediated lysis of human JY lymphoblasts (ED50 = 0.5-5.0 microM).

Human cytotoxic lymphocyte granzyme B. Its purification from granules and the characterization of substrate and inhibitor specificity

Granzyme B has been purified to homogeneity from the granules of a human cytolytic lymphocyte line, Q31, in an enzymatically active form by a three-step procedure. Q31 granzyme B hydrolyzed Na-t-butyloxycarbonyl-L-alanyl-L-alanyl-L-aspartyl (Boc-Ala-Ala-Asp) thiobenzyl ester with a kcat of 11 +/- 5 mol/s/mol enzyme and catalytic efficiency kcat/Km of 76,000 +/- 44,000 M-1 s-1. The hydrolysis of Boc-Ala-Ala-Asp thiobenzyl ester by crude Q31 Percoll fractions paralleled the tryptase activity for granule-containing fractions, which showed that granzyme B was associated with granules. When chromatographed on Sephacryl S-300, Q31 granzyme B eluted in two broad bands corresponding to dimer and monomer, both of which electrophoresed at 35 kDa in reducing NaDodSo4 polyacrylamide, and both of which showed a lag phase in assays. The lag phase in assays could be extended with 0.03 mM pepstatin. Upon elution from ion-exchange chromatography Q31 granzyme B electrophoresed at 32 kDa in reducing NaDodSO4 polyacrylamide and did not have a lag phase in assays. The amino-terminal sequence of the 32-kDa Q31 granzyme B was identical to four other human cytotoxic T-lymphocyte granzymes B in 18 of 18 positions sequenced. Purified Q31 granzyme B had a preference for substrates with Glu or Asp as the residue amino-terminal to the scissile bond; little or no activity was noted with oligopeptide substrates for trypsin-like, chymotrypsin-like, and elastase-like proteases. Human plasma alpha 1-protease inhibitor, human plasma alpha 2-protease macroglobulin, soybean and lima-bean trypsin inhibitors, bovine aprotinin, phosphoramidon, and chymostatin inhibited Q31 granzyme B. The inhibition by alpha 1-protease inhibitor was rapid enough to be of physiological significance.

On the optimization of hydrophobic and hydrophilic substituent interactions of 2,4-diamino-5-(substituted-benzyl)pyrimidines with dihydrofolate reductase

The inhibition constants (Kiapp) were obtained from the action of 68 2,4-diamino-5-(substituted-benzyl)pyrimidines on dihydrofolate reductase from an Escherichia coli strain MB 1428. Subsequently, these results were used to formulate appropriate quantitative structure-activity relationships (QSAR). Once again these equations emphasize the paramount importance of steric/dispersion factors in enhancing antibacterial potency. Hydrophobicity also plays a role, albeit a minor one. Comparisons with the QSAR obtained versus prokaryotic dihydrofolate reductase (DHFR) demonstrate subtle differences in binding behavior between meta and para substituents which may be effectively maximized in the design of more efficacious and selective antibacterial agents. The bacterial and avian QSAR equations can be used to calculate selectivity indices for trimethoprim, tetroxoprim, and two other specially designed 2,4-diamino-5-(substituted-benzyl)pyrimidines.

The enzymatic activity of human cytotoxic T-lymphocyte granzyme A and cytolysis mediated by cytotoxic T-lymphocytes are potently inhibited by a synthetic antiprotease, FUT-175

The synthetic antiprotease, FUT-175 (6-amidino-2-naphthyl-4-guanidinobenzoate), was found to be an extraordinarily potent and rapid inhibitor of human Q31 cytotoxic T-lymphocyte granzyme A. The granzyme A was inhibited in a time-dependent manner with kobs/i = 430,000 +/- 80,000 M-1 s-1. Four other FUT-175 analogs were also found to be potent, rapid Q31 granzyme A inhibitors. All five compounds inhibited Q31 cytotoxic T-lymphocyte-mediated cytolysis of human JY lymphoma cells, but at concentrations far in excess of those needed for granzyme A inhibition. The data presented suggest that postmarketing surveillance of FUT-175 should include a review of possible immunosuppressive side-effects, such as increased susceptibility to viral infections and to neoplastic transformations.

Electron paramagnetic resonance measurements of the hydration of Mn(II) in ternary complexes with GDP and ras p21 proteins

Electron paramagnetic resonance (EPR) spectroscopy has been used to determine the hydration numbers of Mn(II) in complexes with GDP and three forms of ras p21. EPR signals of Mn(II) in the GDP complex with viral-Harvey p21pRAS1 (Arg 12, Thr 59), p21EC (Gly 12, Thr 59), and p21EJ (Val 12, Thr 59) have narrow line-widths that permit ready observation of inhomogeneous broadening from unresolved superhyperfine coupling with the nuclear spin of 17O of directly coordinated oxygen ligands. Quantitative analysis of the lineshapes for the samples in H2 17O-enriched water indicates that four water ligands coordinate to the metal ion in the GDP complexes with all three proteins. The four solvent ligands, together with an oxygen from the beta-phosphate group of GDP, leave space for only one ligand from the protein. An X-ray diffraction-derived model for the MgII beta-gamma-imidoguanosine-5'-triphosphate complex with p21 shows coordination of Mg(II) to the beta- and gamma-phosphate groups of the nucleotide as well as to the hydroxyl groups of Thr 35 and Ser 17 (Pai, E.F., Kabusch, W., Krengel, U., Holmes, K. H., John, J., and Wittinghofer, A., 1989, Nature (London) 341, 209-214). Thus, upon conversion of the nucleotide from a triphosphate to a diphosphate, solvent replaces both the gamma-phosphate of the nucleotide and one of the protein ligands. The EPR results are consistent with a recent X-ray crystallographic model for the p21-MgIIGDP complex (Milburn, M. V., Tong, L., DeVos, A. M., Brunger, A., Yamaizumi, Z., Nishimura, S., and Kim, S.-H., 1990, Science 247, 939-945). EPR spectra of complexes with the three forms of ras p21 differ with respect to the intrinsic linewidths of the EPR signals. These subtle differences in linewidth appear to originate from slight differences in local disorder near the metal-nucleotide binding site.

A cytosolic binding protein for the immunosuppressant FK506 has peptidyl-prolyl isomerase activity but is distinct from cyclophilin

CYCLOSPORIN A and the newly discovered immunosuppressant, FK-506, are potent inhibitors of T cell activation. In addition to their clinical importance in the prevention of allograft rejection, cyclosporin A and FK-506 represent important reagents for the study of the molecular mechanisms of lymphocyte activation. Cyclosporin A, a cyclic undecapeptide and FK-506, a macrolide, although chemically distinct, inhibit similar lymphocyte activation responses. The earliest responses inhibited in the T cell seem to be the expression of early phase T cell-activation genes for interleukins 2, 3 and 4, granulocyte-macrophage colony stimulating factor and gamma interferon. Although FK-506 and cyclosporin A seem to inhibit similar signal transduction processes, they do so be interacting with distinct cytosolic proteins. We report here the purification to homogeneity of a specific FK-506 binding protein that is distinct from the cyclosporin A-binding protein, cyclophilin. In addition, we show that this FK-506 binding protein, like cyclophilin, has peptidyl-prolyl isomerase activity.

Human cytotoxic lymphocyte tryptase. Its purification from granules and the characterization of inhibitor and substrate specificity

A trypsin-like enzyme (tryptase) has been purified to homogeneity from the granules of a human cytolytic lymphocyte (CTL) line, Q31, by a three-step procedure. By including 0.3% (v/v) Triton X-100 and 1 mg/ml heparin in purification buffers, near total yields of tryptase activity were obtained during the purification. The enzyme, referred to as Q31 tryptase, migrated in polyacrylamide gels with sodium dodecyl sulfate at a position corresponding to 28 kDa with and to 45 kDa without 2-mercaptoethanol. It had an amino-terminal sequence identical to a previously reported human CTL tryptase at 20 of 22 positions identified. It hydrolyzed N alpha-carbobenzyloxy-L-lysyl-thiobenzyl ester (BLT), and this BLT esterase activity was most efficient at slightly alkaline pH and was relatively more active near neutral pH than mouse CTL tryptase. Human alpha 1-protease inhibitor, human antithrombin III, phenylmethanesulfonyl fluoride, and p-aminobenzamidine inhibited the Q31 tryptase. The inhibition by human antithrombin III was rapid enough to be of physiological significance. A survey of oligopeptide p-nitroanilides found that the best substrate for human Q31 tryptase is H-D-(epsilon-carbobenzyloxy)Lys-L-Pro-L-Arg-p-nitroanilide. The Q31 tryptase appears to have broad specificity for amino acid residues at P2 and P3, i.e. at 2 and 3 residues amino-terminal to the scissile bond.

Quantitative structure-activity relationships for the inhibition of Escherichia coli dihydrofolate reductase by 5-(substituted benzyl)-2,4-diaminopyrimidines

Quantitative structure-activity relationships for the inhibition of Escherichia coli (MB 1428) dihydrofolate reductase (DHFR) by 61 5-(substituted benzyl)-2,4-diaminopyrimidines are reported and analyzed. The 61 compounds include 17 congeners whose activities have not been previously reported, five of which have a 5'-substituent larger than a methoxy group. The correlation equations indicated that the molar refractivity (MR) values of the 5'-substituent, just as with the 3'- and 4'-substituents, contributed maximally at the value of 0.79 with no increment of binding for compounds with MR larger than 0.79 (which corresponds to a 5'-methoxy substitution). This experimental result is in agreement with the crystal structure of the Escherichia coli DHFR-trimethoprim complex, which shows a reasonably large trimethoprim-binding site. The inhibition of E. coli (MB 1428) DHFR by nine of the 17 new benzylpyrimidines is at lower concentrations than for trimethoprim. However, all 17 are much less potent than trimethoprim in inhibition of growth of E. coli (1515).

Renin inhibitors. Statine-containing tetrapeptides with varied hydrophobic carboxy termini

A series of statine-containing tetrapeptides, systematically modified at the carboxy terminus with various hydrophobic aromatic groups, is described. These compounds were tested in vitro for their ability to inhibit porcine, human plasma, and purified human kidney renins. These analogues help to define optimal binding aspects in a region of the enzyme that appears to be specific for spatial arrangement of aromatic groups. Replacement of the metabolically labile Phe amide with nonpeptidal groups proved possible while achieving inhibitory potency in the nanomolar range vs. porcine kidney renin. For the compounds 6i, 6m, and 6o, a large discrepancy in potency between the human plasma and the purified human kidney renin assays was observed. This disparity does not appear to be a consequence of a previously proposed plasma binding component.

Synthesis and structure determination of [8(-13)C]guanosine 5'-diphosphate

A combined chemical and enzymatic synthesis of [8(-13)C]guanosine 5'-diphosphate (GDP) from H13COOH is described. About 35 mg nucleotide was obtained from 500 mg H13COOH. Analysis of the [8(-13)C]GDP by negative ion fast atom bombardment mass spectrometry and by 13C NMR confirmed that one atom of 13C was incorporated at the 8-position of the guanine ring at 90 +/- 10% enrichment. The chemical shift of the C(8) was 140.2 ppm downfield from internal trimethylsilylpropionate at neutral pH and room temperature, with a spin-spin coupling 1J(13C(8)-H(8] of 217 Hz and a 3J(13C(8)-H(1'] of 3.9 Hz.

Renin inhibitors. Syntheses of subnanomolar, competitive, transition-state analogue inhibitors containing a novel analogue of statine

Analogues of the renin octapeptide substrate were synthesized in which replacement of the scissile dipeptide with (3S,4S)-4-amino-3-hydroxy-6-methylheptanoic acid (statine, Sta) transformed the substrate sequence into potent, transition-state analogue, competitive inhibitors of renin. Synthesis and incorporation of the cyclohexylalanyl analogue of Sta, (3S,4S)-4-amino-5-cyclohexyl-3-hydroxypentanoic acid (ACHPA), gave the most potent inhibitors of renin yet reported, including N-isovaleryl-L-histidyl-L-prolyl-L-phenylalanyl-L-histidyl-ACHPA-L -leucyl-L- phenylalanyl amide [Iva-His-Pro-Phe-His-ACHPA-Leu-Phe-NH2,3], with renin inhibitions of Ki = 1.6 X 10(-10) M (human kidney renin), IC50 = 1.7 X 10(-10)M (human plasma renin), IC50 = 1.9 X 10(-9)M (dog plasma renin), and IC50 = 2.1 X 10(-8) M (rat plasma renin). This inhibitor 3, containing ACHPA, was 55-76 times more potent vs. human renin than the comparable Sta-containing inhibitor 1 and 17 times more potent vs. dog renin than 1. Inhibitor 3 lowered blood pressure in sodium-deficient dogs, with in vivo potency 19 times that shown by 1, in close agreement with the relative in vitro potencies. Structure-activity results are presented that show the minimal N-terminus for these inhibitors. An ACHPA-containing pentapeptide, N-[(ethyloxy)carbonyl]-L-phenylalanyl-L- histidyl-ACHPA-L-leucyl-L-phenylalanyl amide [Etoc-Phe-His-ACHPA-Leu-Phe-NH2,8], retained subnanomolar inhibitory potency. Molecular modelling studies are described that suggested the design of ACHPA.

Viral Harvey ras p21 expressed in Escherichia coli purifies as a binary one-to-one complex with GDP

The ras oncogene of Harvey murine sarcoma virus encodes a 21,000-dalton protein, p21, which mediates transformation. Viral Harvey ras p21, cloned into Escherichia coli HB101 lambda/pRAS1, has been purified to homogeneity by a three-step procedure. The purified E. coli p21 can be bound by a monoclonal antibody to viral Harvey ras p21 and has an amino acid composition consistent with that predicted from its DNA sequence. Purified E. coli p21 has been shown by HPLC analysis on an ion-exchange column to contain near stoichiometric amounts of GDP. This noncovalently associated GDP is seen in the UV absorption spectrum of the purified protein. The noncovalently associated GDP acts as a competitive inhibitor of the interaction of added guanine nucleotides with p21.

Interaction of mouse submaxillary gland renin with a statine-containing, subnanomolar, competitive inhibitor

The interaction between mouse submaxillary gland renin and a statine-containing, iodinated substrate analog inhibitor was studied. The compound, 1 (Boc-His-Pro-Phe-(4-iodo)-Phe-Sta-Leu-Phe-NH2, Sta = (3S,4S)-4-amino-3-hydroxy-6-methyl-heptanoic acid), a statine-containing analog of the renin substrate octapeptide, was a competitive inhibitor of cleavage of synthetic tetradecapeptide renin substrate by mouse submaxillary gland renin, with a Ki of 6.2 x 10(-10) M (pH 7.2, 37 degrees C). Titration of the partial quenching of the tryptophan fluorescence of the enzyme by 1 revealed tight binding with a dissociation constant less than 3 nM and a binding stoichiometry of one mole 1 per mole enzyme. The time course of tight binding of 1 to mouse renin appeared to be fast, with kON greater than or equal to 1.3 x 10(6) s-1 M-1. The UV difference spectrum generated upon binding of 1 to mouse renin had two prominent features: a strong, broad band that had a minimum at 242 nm with delta epsilon (242) = -19,500 cm-1 M-1, and a triplet of enhanced bands centered at 286 nm with delta epsilon (286) about +1100 cm-1 M-1. The strong, broad, negative band was similar to the difference between the UV absorbance of 1 in methanol and in 0.1 M citrate phosphate pH 7.2. A structure-activity correlation for analogs of 1 showed some moieties of 1 that are important for potent inhibition of mouse renin. The inhibition data for these compounds versus human kidney renin suggested that the solution of the crystal structure of 1 bound to mouse renin will provide useful information for the design of inhibitors of human kidney renin.

Preliminary X-ray crystallographic data on mouse submaxillary gland renin and renin-inhibitor complexes

We have crystallized renin from the submaxillary gland of male mice, both in its native state, and in binary complex with transition-state analog inhibitors. The best of the many crystal forms examined consisted of tetragonal bipyramids with space group symmetry P41 21 2 (or its enantiomorph) and unit cell dimensions a = b = 91.4 A, c = 211.6 A; alpha = beta = gamma = 90 degrees. This tetragonal form was compatible with both inhibited and uninhibited renin. Two of the inhibitors used were synthesized as iodinated analogs; their binary complexes with renin may serve as single-site rational heavy atom derivatives. X-ray data beyond 2.8-A resolution have been collected by oscillation photography using the Cornell High Energy Synchrotron Source in Ithaca, NY.

Intrinsic GTPase activity distinguishes normal and oncogenic ras p21 molecules

The 21-kilodalton protein (p21) encoded by normal cellular Harvey-ras has been expressed in Escherichia coli as a fusion protein by using the pUC8 vector and has been purified to greater than 95% homogeneity by ion-exchange chromatography and gel filtration. The purified protein molecules possess intrinsic GTPase activity on the basis of the following criteria: (i) elution of the GTPase activity with p21 GDP-binding activity in two different chromatography systems, (ii) parallel thermal inactivation of GTPase activity and p21 GTP-binding activity, and (iii) immunoprecipitation of the GTPase activity with monoclonal antibodies to p21. At 37 degrees C, the rate of GTP hydrolysis by the purified normal p21 assayed in solution was 5.3-6.6 mmol/min per mol of p21. The rate of GTP hydrolysis by a form of p21 [Val12] encoded by a human oncogene was significantly lower (1.4-1.9 mmol/min per mol of p21). The presence of a threonine phosphate acceptor site at residue 59 also decreased p21 GTPase activity. For regulatory proteins that use GTP as part of their biochemical mechanism, the hydrolysis of GTP to GDP reverses the biological activity of the respective proteins. The observation that oncogenic forms of p21 lose GTPase activity suggests that GTP hydrolysis may be a biochemical event that inactivates the growth-promoting effects of a p21 X GTP complex.

Renin cleavage of a human kidney renin substrate analogous to human angiotensinogen, H-Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Val-Ile-His-Ser-OH, that is human renin specific and is resistant to cathepsin D

A synthetic tetradecapeptide, H-Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Val-Ile-His-Ser-OH, which corresponds to the 13 amino terminal residues of human angiotensinogen plus a carboxy terminal serine to replace a suggested site of carbohydrate attachment, has been shown to be a good substrate for human kidney renin. At pH 7.2 and 37 degrees C the KM or Michaelis constant was 8.4 +/- 2.9 microM, and the VM or velocity at infinite tetradecapeptide concentration was 11.3 +/- 2.4 mumol angiotensin I made per hour per milligram renin. The tetradecapeptide was highly resistant to cleavage by mouse submaxillary renin. The tetradecapeptide was also slowly cleaved by human liver cathepsin D, by rabbit lung angiotensin-converting enzyme, and by reconstituted human serum, but did not yield angiotensin I. Thus, this synthetic renin substrate should permit more specific measurement of human kidney renin activity.

Mouse submaxillary gland renin. Purification and properties of minor forms, which include several differently processed forms of the major gene product and a second gene product

Three minor forms of renin from the submaxillary glands of male mice called D1, D2, and E have been purified to homogeneity. Their amino acid compositions are identical to the principal form of mouse submaxillary gland renin (renin A), except for 1, 1, and 2 extra arginine residues, respectively. The electrophoretic mobility of renin D2 does not change upon reduction, indicating that its heavy and light chains are linked by more than a disulfide bond. The light chain of renin D1 has an electrophoretic mobility different from the light chain of renin A. Renin D2 is proposed to be renin A with an arginine-arginine dipeptide connecting the carboxyl terminus of the heavy chain to the NH2 terminus of the light chain, with the light chain missing the carboxyl-terminal arginine of renin A. Renin D1 is suggested to be renin D2 with the peptide bond between an arginine and the NH2 terminus of the light chain cleaved. Renin E is proposed to be renin D1 plus the carboxyl-terminal arginine of the light chain. A fourth minor form of male mouse submaxillary renin, called renin B/A, has been purified to homogeneity in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and in isoelectric focusing. Renin B/A seems to be a second renin gene product which is difficult to separate from renin A. Renin B/A has an amino acid composition significantly different from renin A, and all three preparations of B/A had compositions significantly different from one another. For renin B/A, the light chain sequence and the first 53 NH2-terminal residues of its heavy chain sequence were identical to renin A.

Mouse submaxillary gland renin contains a noncovalently attached fatty acid

Renin A from the submaxillary gland of male mice has been shown by a gas chromatography/mass spectrometry method to contain near stoichiometric amounts of a fatty acid mixture. The fatty acids on mouse renin were partially exchangeable with free tridecanoic acid in solution, with the tridecanoic acid truly exchanged and not just adsorbed in addition to the fatty acids already present. A gas chromatography/mass spectrometry analysis of the composition of the free fatty acids of the submaxillary gland of male mice showed that the mixture of fatty acids extracted from the gland was significantly different from the mixture of free fatty acids extracted from renin A. The renin-extracted fatty acids were relatively richer in saturated fatty acids, like myristic and palmitic acids, and poorer in polyunsaturated fatty acids, like linoleic and arachidonic acid, than the free fatty acids of the gland. The enzymatic activity of mouse renin was markedly stimulated by saturated fatty acids in 50 mM sodium acetate, pH 5.38, in a concentration-dependent, saturable manner. Palmitic acid stimulated renin activity versus synthetic tetradecapeptide renin substrate about 7-fold in this buffer, with half-maximal stimulation at 14 microM. Stearic and myristic acids also showed good stimulation but linoleic acid and ethyl myristate were much less effective at the stimulation. A possible physiological role for the loss of renin activity at acid pH due to loss of bound fatty acids would be to protect the mouse against internalized renin.

Novel renin inhibitors containing the amino acid statine

The proteolytic enzyme renin (EC3.4.99.19) cleaves the protein substrate angiotensinogen to yield angiotensin I, the decapeptide substrate transformed by converting enzyme into the pressor substance angiotensin II. Although the contribution of this pathway to the maintenance of normal blood pressure is unclear, it seems to be a major factor in various hypertensive states. Important progress in the control of hypertension has been achieved by development of the potent inhibitors SQ-14,225 (captopril) and MK-421 (enalapril maleate), which block the generation of angiotensin II by the inhibition of angiotensin converting enzyme. An attractive alternative to the inhibition of converting enzyme would be the blockade of the preceding step in the cascade, the renin reaction. We report here new highly potent (IC50 = 10(-9)-10(-8) M) competitive inhibitors of renin in which statine, (3S,4S)-4-amino-3-hydroxy-6-methylheptanoic acid, is incorporated into analogues of the pig renin substrate (Fig. 1).