 |
||||
|
||||
|
||||
|
||||
Previous Article | Next Article
Volume 17, Number 15, Issue of August 1, 1997 pp. 5760-5771
Copyright ©1997 Society for NeuroscienceA Novel Allosteric Potentiator of AMPA Receptors: 4-[2-(Phenylsulfonylamino)ethylthio]-2,6-Difluoro-Phenoxyacetamide
Masayuki Sekiguchi1, Mark W. Fleck2, Mark L. Mayer2, Jiro Takeo3, Yoshiyuki Chiba3, Shinya Yamashita3, and Keiji Wada1 1 Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo 187, Japan, 2 Laboratory of Cellular and Molecular Neurophysiology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4495, and 3 Central Research Laboratory, Nippon Suisan Kaisha Limited, Hachioji, Tokyo 192, Japan
ABSTRACT
We report that a novel sulfonylamino compound, 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluoro-phenoxyacetamide (PEPA), selectively potentiates glutamate receptors of the AMPA subtype. PEPA (1-200 µM) dose dependently potentiated glutamate-evoked currents in Xenopus oocytes expressing AMPA (GluRA-GluRD), but not kainate (GluR6 and GluR6+KA2) or NMDA (
Key words: glutamate receptors; AMPA; desensitization; alternative splicing; flip and flop; allosteric modulation1 +
1-
GluRD > GluRA) and splice-variant (flop > flip) selectivity similar to that observed in oocytes. Our results show that PEPA is a novel, flop-preferring allosteric modulator of AMPA receptor desensitization at least 100 times more potent than aniracetam.
INTRODUCTION
Allosteric modulation of the three subtypes of ionotropic glutamate receptors
AMPA, kainate, and NMDA receptors
; Isaacson and Nicoll, 1991
AMPA receptors are hetero-oligomeric complexes, most likely pentamers (Wenthold et al., 1992
Although the physiological significance of the cell-specific expression of AMPA receptor subunits and splice variants is not yet fully understood, it is likely that the regulation of receptor composition determines the kinetics and strength of transmission at glutamatergic synapses. As such, drugs that modulate AMPA receptors are both useful pharmacological tools as well as potential therapeutic agents. The modulation of AMPA receptors by aniracetam and cyclothiazide, the most thoroughly examined agents, reveals profound differences in potency, pharmacological selectivity, and mechanism of action. Aniracetam is effective at millimolar concentrations and preferentially modulates flop splice variants (Johansen et al., 1995
Here we report that a novel sulfonylamino compound, PEPA, which is structurally distinct from the previously characterized pyrrolidinone or benzothiadiazine compounds typified by aniracetam and cyclothiazide (see Fig. 1), potentiates currents of recombinant AMPA receptors expressed in Xenopus oocytes. PEPA is effective at micromolar concentrations, is selective for the AMPA subtype of glutamate receptors, and preferentially modulates flop splice variants. Rapid perfusion experiments in transfected human embryonic kidney 293 (HEK 293) cells show that potentiation by PEPA results primarily from attenuation of desensitization.
Fig. 1. Chemical structures of PEPA, cyclothiazide, and aniracetam.
[View Larger Version of this Image (13K GIF file)]
MATERIALS AND METHODS
Xenopus oocyte expression system. Glutamate receptor expression in Xenopus oocytes was performed as described previously (Sekiguchi et al., 1994
The concentration of the cRNA solution injected into oocytes was 1 mg/ml, and 50 nl of the solution was injected into an oocyte. The ratio of GluRA, GluRC, or GluRD to GluRB was 1:1, unless specified otherwise. Electrophysiological responses were recorded 4-6 d after injection with a two-electrode voltage clamp at a holding potential of 100 mV, unless otherwise specified. Oocytes were perfused with frog Ringer's solution consisting of (in mM): 115 NaCl, 2 KCl, 1.8 CaCl2, and 10 HEPES, pH 7.2 with NaOH. PEPA was dissolved in dimethylsulfoxide (DMSO), usually at 100 mM, and added to frog Ringer's solution to yield final concentrations of 0.2-200 µM; the final concentration of DMSO was no more than 0.2%. The pH of the frog Ringer's solution was not changed by adding 200 µM PEPA. At room temperature no precipitation was observed in the PEPA-DMSO-frog Ringer's solution up to 200 µM PEPA. Concanavalin A (Sigma, St. Louis, MO) was dissolved in frog Ringer's solution (1 mg/ml), and the oocytes were incubated in this solution for ~3 min at room temperature before recording.
Rapid perfusion experiments in HEK 293 cells. Plasmids encoding cDNA clones of rat GluRA, GluRB, GluRC, and GluRD flip (i) and flop (o) in CMV expression vectors (gifts from Dr. Peter Seeburg) were prepared by alkaline lysis, followed by 2× cesium chloride gradient purification. HEK 293 cells (ATCC CRL 1573) were plated at low density on 35 mm Petri dishes and transfected 24 hr later, using the calcium phosphate precipitation technique of Chen and Okayama (1987) when filled with (in mM): 135 CsCl, 10 CsF, 0.5 CaCl2, 1 MgCl2, 10 HEPES, and 5 Cs4-BAPTA, pH 7.2, osmolarity 295 mOsm. Solutions were applied at a flow rate of 0.67 ml/min controlled by a syringe pump (WPI sp220i) with a stepper motor-based fast perfusion system as described previously (Vyklicky et al., 1991
des) in the presence and absence of PEPA was fit by a single exponential function for all subunits except GluRAi, for which responses in the presence of PEPA were better fit by the sum of two exponentials (see Fig. 9A). The onset (
Fig. 9. Block of desensitization by PEPA shows subunit and splice-variant selectivity. A, Whole-cell responses to fast application of 3 mM glutamate applied in the presence of 100 µM PEPA and recorded from transiently transfected HEK 293 cells expressing GluRAi, GluRAo, GluRAiBi, or GluRAoBo, as indicated. Lines drawn through the data points show the onset of desensitization fit with exponential functions, as described in Materials and Methods. For GluRAi and GluRAoBo, arrows indicate transitions between fast and slow components of the response to glutamate; the slow component of activation seen for GluRAoBo was typical of responses for subunit combinations strongly modulated by PEPA. Values for
[View Larger Version of this Image (19K GIF file)]
Fig. 8. Potentiation by PEPA is correlated with desensitization of control responses to glutamate. A, Whole-cell responses to fast application of 3 mM glutamate in the absence (left) and presence (right) of 100 µM PEPA recorded from HEK 293 cells transiently transfected with GluRBiDi; B, Similar responses for GluRBoDo. Control responses for GluRBoDo display faster desensitization, smaller equilibrium currents, and greater equilibrium potentiation by PEPA than responses for GluRBiDi. A similar correlation between the extent of control desensitization and potentiation by PEPA was observed for all flip and flop subunit combinations examined, although the extent of the block of desensitization by 100 µM PEPA varied among subunits. C, Concentration jump responses to PEPA reveal rapid onset and recovery from potentiation. D, Scatterplot correlating equilibrium potentiation by 100 µM PEPA versus the steady-state amplitude of control responses to 3 mM glutamate; data for flip () and flop (
) splice variants are fit separately with logarithmic functions (dashed lines; points are mean ± SEM). Control responses to glutamate are smaller and potentiation by PEPA is greater for flop versus flip subunits. Heteromeric combinations of GluRA, GluRC, or GluRD with GluRB were transfected at a ratio of 1:2.
[View Larger Version of this Image (31K GIF file)]
Table 1. AMPA receptor kinetics in transfected HEK 293 cells
Subunit(s) Desensitization at 2 sec (%) (Glu+PEPA) Slowing of desensitization Equilibrium potentiation I(Glu+P)/I(Glu) PEPA PEPA Ai 7.98 ± 0.48 89 ± 6 84 ± 3 11.2 5 ± 1 122 ± 14 87 ± 7 87 AiBi 10.43 ± 0.70 244 ± 19 28 ± 3 23.4 20 ± 2 306 ± 17 140 ± 8 84 AO 8.04 ± 0.69 252 ± 13 74 ± 6 31.3 18 ± 3 338 ± 28 176 ± 15 88 AOBO 6.43 ± 0.45 N.D. 1 ± 1 >300** 124 ± 20 521 ± 39 222 ± 15 79 Ci 9.92 ± 1.20 300 ± 25 45 ± 4 30.2 41 ± 4 253 ± 12 156 ± 20 85 BiCi 14.40 ± 0.76 N.D. 6 ± 2 >140** 28 ± 3 257 ± 24 153 ± 8 93 CO 3.28 ± 0.34 314 ± 18 47 ± 4 95.7 131 ± 26 308 ± 21 193 ± 16 87 BOCO 4.39 ± 0.38 564 ± 45* 15 ± 2* >300** 138 ± 30 475 ± 25 226 ± 10 89 Di 9.15 ± 0.56 365 ± 22 28 ± 5 39.9 11 ± 1 372 ± 27 201 ± 9 65 BiDi 14.15 ± 1.09 N.D. 4 ± 3 >140** 10 ± 1 335 ± 47 192 ± 11 73 DO 3.11 ± (n = 2 of 9)# N.D. 7 ± 1 >600** 75 ± 6 417 ± 29 237 ± 9 85 BODO 6.46 ± 0.65 N.D. 5 ± 1 >300** 74 ± 11 571 ± 50 267 ± 11 70 Values are mean ± SEM, in msec, for 3-20 cells per subunit. Examples illustrating analysis of
RESULTS
The action of PEPA (Fig. 1) on glutamate receptors was discovered via electrophysiological screening of compounds containing sulfonylamino groups, using the Xenopus oocyte expression system and poly(A+) mRNA prepared from rat brain. PEPA was synthesized originally in the process of developing thromboxane A2 receptor antagonists (Sato et al., 1994PEPA potentiates AMPA receptor responses with opposite splice-variant selectivity to cyclothiazide
Figure 2A shows the effects of various concentrations of PEPA on currents evoked by 100 µM glutamate in an oocyte expressing GluRCo. Glutamate-evoked currents were strongly potentiated by PEPA in a concentration-dependent manner. In contrast, Figure 2B shows the much weaker potentiation by 200 µM PEPA of glutamate-evoked currents in an oocyte expressing GluRCi. The amount of potentiation by PEPA (200 µM) was consistently much greater for GluRCo (50.2 ± 10.7-fold, n = 7) than for GluRCi (2.7 ± 0.3-fold, n = 10). Figure 2C compares the splice-variant selective action of 25 µM PEPA with the action of 1 mM aniracetam and 25 µM cyclothiazide, two well characterized allosteric modulators of AMPA receptors. PEPA caused much greater potentiation of glutamate responses in oocytes expressing GluRCo than either aniracetam or cyclothiazide. In contrast, cyclothiazide caused the greatest potentiation in oocytes expressing GluRCi. The flop-selective action of PEPA resembles that of aniracetam, but clearly PEPA is considerably more potent; in fact, potentiation by 25 µM PEPA for GluRCo responses (21.5 ± 3.9-fold, n = 7) was even larger than that produced by 25 µM cyclothiazide for GluRCi responses (13.4 ± 2.4-fold, n = 6).
Fig. 2. PEPA strongly potentiates glutamate-evoked currents in oocytes expressing GluRCo. A, B, Potentiation by PEPA of glutamate-evoked currents in Xenopus oocytes expressing GluRCo and/or GluRCi. Glutamate, 100 µM, was applied during the periods indicated by filled bars (G100). PEPA was applied at the indicated concentrations (in µM) during the periods indicated by open bars (P 1-P 200). Holding potential,
[View Larger Version of this Image (16K GIF file)]
In an attempt to define accurately the differences in the potency for modulation of AMPA receptors by PEPA and aniracetam, we performed dose-response analyses in oocytes expressing GluRCo or GluRCi. Figure 3 shows potentiation by PEPA and aniracetam expressed as the fold increase in responses to 100 µM glutamate when coapplied with modulator. Both aniracetam and PEPA were flop-preferring and produced much greater potentiation for GluRCo than for GluRCi at their limit of solubility in frog Ringer's solution. The EC50 for potentiation of GluRCo by PEPA was 50 µM (Hill coefficient = 1.03). Aniracetam did not produce any detectable potentiation at 100 µM, and at 1-2 mM it produced almost comparable potentiation to only 10 µM PEPA. Although complete dose-response curves could not be constructed for aniracetam because of its limited solubility and low potency, our data indicate that PEPA was at least 100 times more potent for potentiation of GluRCo than aniracetam (Fig. 3). Dose-response analysis of PEPA modulation for GluRCi suffered from similar limitations to those for analysis of the effects of aniracetam, and within the concentration range that it was possible to analyze we were unable to determine whether the maximum potentiation by PEPA for GluRCi was less than for GluRCo or whether, in addition, the EC50 of PEPA for GluRCi was greater than the EC50 for GluRCo. 
Fig. 3. PEPA is much more potent than aniracetam. Shown are dose-response curves for potentiation of glutamate responses by PEPA and aniracetam (Ani) in oocytes expressing GluRCo and GluRCi. Glutamate (100 µM) was applied first to oocytes to obtain control responses, and then solutions containing both glutamate and various concentrations of PEPA or aniracetam were applied. Ordinate, Fold potentiation is given as the amplitude of the response evoked by coapplication of glutamate plus modulator/amplitude of the response to glutamate alone. In the case of GluRCo, the dose-response curve for PEPA indicates the best fit to the data according to the logistic function P = 1 + Pmax/[1 + (EC50/[D])n], in which P is the fold potentiation, Pmax is the maximal potentiation, EC50 is the concentration causing 50% of maximal potentiation, [D] is the concentration of PEPA, and n is the Hill coefficient. The other data were connected simply by lines. The apparent EC50 for potentiation of GluRCo by PEPA was 50.4 µM (Hill coefficient = 1.03). Values are mean ± SEM (n = 6-8). SEM is smaller than the symbol for data points in which the error bars are not visible.
[View Larger Version of this Image (18K GIF file)]
The flop-preferring action of aniracetam has been reported previously for studies comparing GluRAoBo with GluRAiBi and GluRBoDo with GluRBiDi expressed in oocytes (Johansen et al., 1995 
Fig. 4. Subunit and splice-variant selectivity of the action of PEPA. Oocytes were injected with the AMPA receptor subunit cRNAs denoted. Glutamate (100 µM) was applied first to oocytes, and then a solution containing both glutamate (100 µM) and PEPA (200 µM) was applied. Ordinate, Fold potentiation is given as the amplitude of the response evoked by coapplication of glutamate plus PEPA/amplitude of the response to glutamate alone. Values are mean ± SEM (n = 5-22).
[View Larger Version of this Image (22K GIF file)]
PEPA is selective for AMPA subclass ionotropic glutamate receptors
Next, we tested effects of PEPA on other glutamate receptor subtypes. Figure 5A shows traces obtained from two oocytes expressing GluR6, a kainate receptor subunit. The oocyte shown in the top traces was untreated, and that in the bottom traces was treated with concanavalin A to block desensitization, as described in Materials and Methods. For the untreated oocyte, responses to 100 µM glutamate were separated by 10 min intervals to allow recovery from desensitization; then PEPA (100 µM) and glutamate were applied simultaneously, and the oocyte was washed with Ringer's solution again for 10 min to confirm recovery. After treatment with concanavalin A, solutions were applied by using the same order but with applications of glutamate separated by 1 min intervals. In contrast to its effects on AMPA receptors, PEPA did not potentiate the glutamate-evoked currents for GluR6 (n = 10) either before or after reduction of desensitization by concanavalin A; instead, PEPA caused a modest but reproducible inhibition, which was not observed with the 0.1% DMSO present in 100 µM PEPA solutions. Similar experiments performed in oocytes expressing the kainate receptor subunits GluR6 plus KA2 (n = 10) confirmed that there was also no potentiation by PEPA of these receptors (Fig. 5B). Currents evoked by simultaneous application of glutamate and glycine (10 µM each) in oocytes expressing the NMDA receptor subunits
Fig. 5. PEPA is selective for AMPA subtype glutamate receptors. A, Action of PEPA (100 µM) on glutamate responses (100 µM) of oocytes expressing GluR6, which were untreated (
[View Larger Version of this Image (15K GIF file)]
PEPA increases GluRCo apparent affinity for glutamate
Cyclothiazide has been shown previously to cause a leftward shift in the agonist dose-response relationship for native AMPA receptors in hippocampal neurons and for GluRAi expressed in oocytes (Patneau et al., 1993
Fig. 6. PEPA increases apparent affinity of GluRCo for glutamate. A, Responses to 1, 10, 100, and 500 µM glutamate in the absence (Cont) or presence (+PEPA) of 100 µM PEPA in oocytes expressing GluRCo. Calibration: 20 sec for all traces, and 20 nA for Cont and 250 nA for +PEPA. B, Dose-response curves for glutamate in oocytes expressing GluRCo without PEPA (Control) and with PEPA (10 or 100 µM). Glutamate responses are normalized to the response by 500 µM glutamate in each oocyte. The theoretical curves indicate the best fit to the data according to the logistic function I = 100/[1 + (EC50/[G])n], in which I is the relative response, and [G] is the concentration of glutamate. Values are mean ± SEM (n = 4-7).
[View Larger Version of this Image (15K GIF file)]
Weak potentiation by PEPA of kainate-evoked currents at AMPA receptors
Figure 7 compares the actions of PEPA (10 µM) on glutamate-evoked (100 µM) and kainate-evoked (100 µM) currents in oocytes expressing the flip or flop splice variants of GluRC. In oocytes expressing GluRCo, glutamate responses were much smaller than kainate responses (Fig. 7A,C), such that the ratio of their amplitudes (Iglu/Ikai) was 0.19 ± 0.02 (n = 10). This low value is attributable in part to stronger desensitization of responses to glutamate versus kainate at AMPA receptors (Patneau and Mayer, 1991
Fig. 7. Activation of AMPA receptors by kainate shows weak potentiation by PEPA. Oocytes from a single preparation were injected with cRNA specific for GluRCo or GluRCi in parallel. A, B, Glutamate-evoked (100 µM) and kainate-evoked (100 µM) responses with or without PEPA (10 µM) in oocytes expressing GluRCo (A) or GluRCi (B). Calibration, 20 sec and 100 nA. C, Comparison of the current amplitude (nA) for glutamate and kainate responses in oocytes expressing GluRCo (n = 10) or GluRCi (n = 8). D, Potentiation by 10 µM PEPA of glutamate or kainate response in oocytes expressing GluRCo (n = 10) or GluRCi (n = 7). Values in C and D are mean ± SEM.
[View Larger Version of this Image (20K GIF file)]
The difference in Iglu/Ikai ratios for GluRCi versus GluRCo is of interest because PEPA potentiated glutamate responses for GluRCo to a much greater extent than kainate responses (Fig. 7A,D), whereas for GluRCi, although potentiation by PEPA was weaker than for GluRCo, the extent of potentiation was similar for both agonists (Fig. 7B,D). A similar agonist dependence for potentiation of AMPA receptor responses by aniracetam and cyclothiazide has been observed previously (Tsuzuki et al., 1992 PEPA suppresses AMPA receptor desensitization in HEK 293 cells
A widely recognized limitation of the use of two-electrode voltage-clamp recording from oocytes is that it is impossible to apply solutions rapidly enough to resolve the very rapid desensitization exhibited by AMPA receptors. Analysis of the effects of drugs on AMPA receptor responses is confounded further by subunit and splice variant-specific differences in the amount of desensitization of control responses to glutamate, such that the amplitudes of equilibrium currents expressed by AMPA receptors vary with subunit composition (Lomeli et al., 1994
To address this issue, we used whole-cell recording with rapid perfusion to study recombinant AMPA receptor responses in transiently transfected HEK 293 cells. The kinetics of AMPA receptor desensitization was measured in response to concentration jump application of 3 mM glutamate in the absence or presence of 100 µM PEPA (Fig. 8A,B). We also measured potentiation of equilibrium responses to glutamate in response to concentration jump application of PEPA (Fig. 8C). The combined results of such analysis reveal that, for subunit combinations for which PEPA fully blocks desensitization, differences in the extent of desensitization of control responses to glutamate indeed do appear to contribute to the extent of potentiation by PEPA. For example, although PEPA produced nearly complete block of desensitization for both GluRBoDo and GluRBiDi (Fig. 8A,B), potentiation of equilibrium responses to glutamate for these subunits suggested strong flop selectivity (GluRBoDo, 74 ± 10.8-fold potentiation; GluRBiDi, 9.7 ± 1.2-fold potentiation). Experiments with additional subunits provided further support for the hypothesis that the degree of potentiation by PEPA is determined in part by the extent of desensitization of control responses to glutamate; thus, as shown in Figure 8D, the magnitude of potentiation by PEPA was related inversely to the amplitude of equilibrium responses to glutamate in the absence of PEPA. Subunit combinations for which the onset of desensitization has been shown to occur extremely rapidly
The results shown in Figure 8 suggest that PEPA directly affects the process of desensitization and that subunit-specific differences in the magnitude of PEPA potentiation are likely to reflect both the intrinsic desensitization properties of individual subunits as well as possible differences in affinity for PEPA. Although for some subunits (e.g., GluRCo and GluRDo) the rate of desensitization of control responses to glutamate was too rapid to be measured accurately by whole-cell recording, for all subunit combinations tested both the rate of onset and amount of desensitization were strongly attenuated by PEPA, making it relatively easy to compare differences in desensitization kinetics among subunits in the presence of PEPA (Table 1).
The results of such an analysis are shown in Figure 9 and emphasize both the selective modulation by PEPA of AMPA receptor flop splice variants as well as subunit-selective effects of PEPA. Thus, even for GluRA, the least sensitive subunit examined for which desensitization remained pronounced in the presence of PEPA for both flip and flop splice variants (Fig. 9A), the time constant of onset of desensitization for GluRAo ( GluRA (Fig. 9).
The effects of PEPA were enhanced further by heteromerization with the corresponding flip or flop isoforms of GluRB, and the current observed after a 2 sec application of GLU+PEPA approached 100% of peak in cells expressing GluRAoBo, GluRBiCi, GluRBiDi, and GluRBoDo; these subunit combinations, together with GluRDo, therefore were classified as effectively "nondesensitizing" within the limits of the current protocol (Fig. 9B). In an attempt to differentiate among subunits that effectively were nondesensitizing during 2 sec applications of PEPA+GLU, we also measured the kinetics of onset of (
DISCUSSION
Our results show that PEPA is a selective and potent modulator of AMPA subtype glutamate receptors, with preferential activity at flop splice variants. PEPA potentiates glutamate-evoked currents by slowing the rate of onset of desensitization and by increasing the apparent affinity of AMPA receptors for agonist. It is possible that PEPA also slows deactivation, but this was not tested in the present experiments. The effects of PEPA were much stronger for GluRC and GluRD versus GluRA, most likely reflecting either subunit-dependent differences in affinity and/or stronger desensitization of control responses to glutamate for GluRC and GluRD versus GluRA.PEPA versus aniracetam
Comparison with previous work (Johansen et al., 1995PEPA versus cyclothiazide
In the present study PEPA (25 µM) was found to potentiate glutamate responses for GluRCo to a much greater extent than the same concentration of cyclothiazide, whereas the reverse was true for GluRCi (see Fig. 2C). PEPA and cyclothiazide appear to have similar potency but opposite splice-variant selectivity; whereas PEPA preferentially modulates flop receptors, cyclothiazide has been shown to prefer flip isoforms (Partin et al., 1994Mechanism of action of PEPA
A characteristic feature of allosteric modulation by PEPA, which is common also to aniracetam and cyclothiazide, is that each drug potentiates AMPA receptor currents by suppressing desensitization. However, it has been proposed recently that aniracetam and cyclothiazide suppress desensitization by different mechanisms (Partin et al., 1996Drug design and receptor structure-function analysis
When the chemical structures are compared among aniracetam, cyclothiazide, and PEPA (see Fig. 1), no obvious features common to all three drugs are seen. There is, however, a sulfonylamino group (-SO2NH-) common to PEPA, cyclothiazide, and other benzothiadiazines that has been shown to suppress AMPA receptor desensitization (Bertolino et al., 1993
Although the actions of aniracetam and cyclothiazide are different, it has been shown previously that modulation by both drugs is sensitive to a single amino acid residue in the flip/flop domain (Partin et al., 1995
Recently, a three-dimensional model for non-NMDA glutamate receptors has been proposed (Sutcliffe et al., 1996 Pharmacological and physiological significance of allosteric modulation
Because of its strong preference for flip isoforms, cyclothiazide has been used to infer the splice-variant composition of native AMPA receptors in subpopulations of hippocampal neurons (Fleck et al., 1996
Other studies have suggested that the memory- and cognition-enhancing properties of the pyrrolidinone- and benzothiadiazine-containing drugs are related to their ability to enhance synaptic transmission via modulation of AMPA receptor gating (Arai et al., 1994
FOOTNOTES
Received March 14, 1997; revised May 19, 1997; accepted May 20, 1997.
This investigation was supported in part by research grants from the Ministry of Education, Science, Sports, and Culture, the Ministry of Health and Welfare, the Science and Technology Agency of Japan, and the Japan Foundation for Neuroscience and Mental Health. We thank Drs. S. Heinemann, M. Mishina, and P. Seeburg for cDNAs; Drs. M. Hollmann and R. Wenthold for their critical comments; and Drs. T. Nishikawa and K. Takahashi for comments and amino acid analysis via HPLC.
Correspondence should be addressed to Dr. Masayuki Sekiguchi, Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187, Japan.
REFERENCES
- Arai A, Kessler M, Xiao P, Ambros-Ingerson J, Rogers G, Lynch G (1994) A centrally active drug that modulates AMPA receptor gated currents. Brain Res 638:343-346[ISI][Medline].
- Bennett JA, Dingledine R (1995) Topology profile for a glutamate receptor: three transmembrane domains and a channel-lining re-entrant membrane loop. Neuron 14:373-384[ISI][Medline].
- Bertolino M, Baraldi M, Parenti C, Braghiroli D, DiBella M, Vicini S, Costa E (1993) Modulation of AMPA/kainate receptors by analogues of diazoxide and cyclothiazide in thin slices of rat hippocampus. Receptors Channels 1:267-278[ISI][Medline].
- Boulter J, Hollmann M, O'Shea-Greenfield A, Hartley M, Deneris E, Maron C, Heinemann S (1990) Molecular cloning and functional expression of glutamate receptor subunit genes. Science 249:1033-1037
[Abstract/Free Full Text] .- Bowie D, Mayer ML (1995) Inward rectification of both AMPA and kainate subtype glutamate receptors generated by polyamine-mediated ion channel block. Neuron 15:453-462[ISI][Medline].
- Chen C, Okayama H (1987) High-efficiency transformation of mammalian cells by plasmid DNA. Mol Cell Biol 7:2745-2752
[Abstract/Free Full Text] .- Diamond JS, Jahr CE (1995) Asynchronous release of synaptic vesicles determines the time course of the AMPA receptor-mediated EPSC. Neuron 15:1097-1107[ISI][Medline].
- Ferrer-Montiel AV, Montal M (1996) Pentameric subunit stoichiometry of a neuronal glutamate receptor. Proc Natl Acad Sci USA 93:2741-2744
[Abstract/Free Full Text] .- Fleck MW, Bähring R, Patneau DK, Mayer ML (1996) AMPA receptor heterogeneity in rat hippocampal neurons revealed by differential sensitivity to cyclothiazide. J Neurophysiol 75:2322-2333
[Abstract/Free Full Text] .- Hestrin S (1992) Activation and desensitization of glutamate-activated channels mediating fast excitatory synaptic currents in the visual cortex. Neuron 9:991-999[ISI][Medline].
- Hollmann M, O'Shea-Greenfield A, Rogers SW, Heinemann S (1989) Cloning by functional expression of a member of the glutamate receptor family. Nature 342:643-648[Medline].
- Hollmann M, Hartley M, Heinemann S (1991) Ca2+ permeability of KA-AMPA-gated glutamate receptor channels depends on subunit composition. Science 252:851-853
[Abstract/Free Full Text] .- Hollmann M, Maron C, Heinemann S (1994) N-glycosylation site tagging suggests a three transmembrane domain topology for the glutamate receptor GluR1. Neuron 13:1331-1343[ISI][Medline].
- Hume RI, Dingledine R, Heinemann SF (1991) Identification of a site in glutamate receptor subunits that controls calcium permeability. Science 253:1028-1031
[Abstract/Free Full Text] .- Isaacson JS, Nicoll RA (1991) Aniracetam reduces glutamate receptor desensitization and slows the decay of fast excitatory synaptic currents in the hippocampus. Proc Natl Acad Sci USA 88:10936-10940
[Abstract/Free Full Text] .- Ito I, Tanabe S, Kohda A, Sugiyama H (1990) Allosteric potentiation of quisqualate receptors by a nootropic drug aniracetam. J Physiol (Lond) 424:533-543
[Abstract/Free Full Text] .- Johansen TH, Chaudhary A, Verdoorn TA (1995) Interactions among GYKI-52466, cyclothiazide, and aniracetam at recombinant AMPA and kainate receptors. Mol Pharmacol 48:946-955[Abstract].
- Keinänen K, Wisden W, Sommer B, Werner P, Herb A, Verdoorn TA, Sakmann B, Seeburg PH (1990) A family of AMPA-selective glutamate receptors. Science 249:556-560
[Abstract/Free Full Text] .- Lomeli H, Mosbacher J, Melcher T, Höger T, Geiger JRP, Kuner T, Monyer H, Higuchi M, Bach A, Seeburg PH (1994) Control of kinetic properties of AMPA receptor channels by nuclear RNA editing. Science 266:1709-1713
[Abstract/Free Full Text] .- Matsui T, Sekiguchi M, Hashimoto A, Tomita U, Nishikawa T, Wada K (1995) Functional comparison of D-serine and glycine in rodents: the effect on cloned NMDA receptors and the extracellular concentration. J Neurochem 65:454-458[ISI][Medline].
- Monyer H, Seeburg PH, Wisden W (1991) Glutamate-operated channels: developmentally early and mature forms arise by alternative splicing. Neuron 6:799-810[ISI][Medline].
- Mosbacher J, Schoepfer R, Monyer H, Burnashev N, Seeburg P, Ruppersberg JP (1994) A molecular determinant for submillisecond desensitization in glutamate receptors. Science 266:1059-1062
[Abstract/Free Full Text] .- Otis T, Zhang S, Trussell LO (1996) Direct measurement of AMPA receptor desensitization induced by glutamatergic synaptic transmission. J Neurosci 16:7496-7504
[Abstract/Free Full Text] .- Partin KM, Patneau DK, Mayer ML (1994) Cyclothiazide differentially modulates desensitization of AMPA receptor splice variants. Mol Pharmacol 46:129-138[Abstract].
- Partin KM, Bowie D, Mayer ML (1995) Structural determinants of allosteric regulation in alternatively spliced AMPA receptors. Neuron 14:833-843[ISI][Medline].
- Partin KM, Fleck MW, Mayer ML (1996) AMPA receptor flip/flop mutants affecting deactivation, desensitization, and modulation by cyclothiazide, aniracetam, and thiocyanate. J Neurosci 16:6634-6647
[Abstract/Free Full Text] .- Patneau DK, Mayer ML (1991) Kinetic analysis of interactions between kainate and AMPA: evidence for activation of a single receptor in mouse hippocampal neurons. Neuron 6:785-798[ISI][Medline].
- Patneau DK, Vyklicky L, Mayer ML (1993) Hippocampal neurons exhibit cyclothiazide-sensitive rapidly desensitizing responses to kainate. J Neurosci 13:3496-3509[Abstract].
- Raman IM, Zhang S, Trussell LO (1994) Pathway-specific variants of AMPA receptors and their contribution to neuronal signaling. J Neurosci 14:4998-5010[Abstract].
- Sato M, Kawashima Y, Goto J, Yamane Y, Chiba Y, Jinno S, Satake M, Iwata C (1994) Synthesis and evaluation of novel sulfonamide derivatives as thromboxane A2 receptor antagonists. Eur J Med Chem 29:185-190.
- Sato M, Kawashima Y, Goto J, Yamane Y, Chiba Y, Jinno S, Satake M, Iwata C (1995) Synthesis and evaluation of novel fluorinated sulotroban-related sulfonamide derivatives as thromboxane A2 receptor antagonists. Eur J Med Chem 30:403-414.
- Sekiguchi M, Doi K, Zhu WS, Watase K, Yokotani N, Wada K, Wenthold RJ (1994) A deletion in the second cytoplasmic loop of GluR3 produces a dominant negative mutant of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor. J Biol Chem 269:14559-14565
[Abstract/Free Full Text] .
ABSTRACT