Papers by Michel Lazdunski
Biochemical Society Transactions, 2000
Journal of Biological Chemistry, 1992
American Journal of Medical Genetics, 2001
Ion channels provide the basis for the regulation of excitability in the central nervous system a... more Ion channels provide the basis for the regulation of excitability in the central nervous system and in other excitable tissues such as skeletal and heart muscle. Consequently, mutations in ion channel encoding genes are found in a variety of inherited diseases associated with hyper‐ or hypoexcitability of the affected tissue, the so‐called ‘channelopathies.’ An increasing number of epileptic syndromes belongs to this group of rare disorders: Autosomal dominant nocturnal frontal lobe epilepsy is caused by mutations in a neuronal nicotinic acetylcholine receptor (affected genes: CHRNA4, CHRNB2), benign familial neonatal convulsions by mutations in potassium channels constituting the M‐current (KCNQ2, KCNQ3), generalized epilepsy with febrile seizures plus by mutations in subunits of the voltage‐gated sodium channel or the GABAA receptor (SCN1B, SCN1A, GABRG2), and episodic ataxia type 1—which is associated with epilepsy in a few patients—by mutations within another voltage‐gated potas...
Annual Review of Physiology, 2000
▪ Amiloride-sensitive Na+ channels constitute a new class of proteins known as the ENaC-Deg fam... more ▪ Amiloride-sensitive Na+ channels constitute a new class of proteins known as the ENaC-Deg family of ion channels. All members in this family share a common protein structure but differ in their ion selectivity, their affinity for the blocker amiloride, and in their gating mechanisms. These channels are expressed in many tissues of invertebrate and vertebrate organisms where they serve diverse functions varying from Na+ absorption across epithelia to being the receptors for neurotransmitters in the nervous system. Here, we review progress made during the last years in the characterization, regulation, and cloning of new amiloride-sensitive Na+ channels.
European Journal of Pharmacology, 1990
The intrahippocampal injection of the mast cell degranulating (MCD) peptide, a bee venom componen... more The intrahippocampal injection of the mast cell degranulating (MCD) peptide, a bee venom component acting on the K+ channel, results in the appearance of the proto-oncogene c-fos mRNA in the ipsi- and contralateral hippocampus of the treated animals without generating convulsions. This MCD-induced transcriptional event is discussed in terms of cellular plasticity since MCD peptide is known to induce long-term potentiation.
Journal of Biological Chemistry, 1982
ABSTRACT
Journal of Biological Chemistry, 1985
Properties of the Na+/H+ exchange system in synaptosomes have been studied primarily by using acr... more Properties of the Na+/H+ exchange system in synaptosomes have been studied primarily by using acridine orange fluorescence to follow H+ efflux. Results obtained from "Na+ uptake experiments and ['Hlethylpropylamiloride binding experiments are also presented for comparison. The basal properties of the Na+/ H+ antiport in synaptosomes are similar to those found in other systems; (i) the stoichiometry of Na+/H+ exchange is 1:l; (ii) Li+ can be successfully substituted for Na+; its affinity for the exchanger (&+ = 3 mM) is higher than that of Na+ = 12 mM), but the maximal rate of H+ efflux in the presence of Li+ is about 3 times lower than the maximal rate of H+ efflux in the presence of Na+; and (iii) the Na+/H+ antiport is inhibited by amiloride derivatives with the rank order:ethylisopropylamiloride > ethylpropylamiloride > amiloride > benzamil. The most important finding of this paper is that the external pH dependence of the synaptosomal Na+/H+ antiport is controlled by the value of internal pH and vice versa. For example apparent pH0 values for halfmaximum activation of the Na+/H+ exchanger are pH, = 7.12 when pHi = 6.4 and pH, = 7.95 when pHi = 7.3. Therefore, a 0.9 pH unit increase in internal pH produces a shift of at least a 0.83 pH unit in the external pH dependence. In addition, changing pH, from 7.75 to 8.50 also shifts the half-maximum pHi value for activation of the Na+/H+ antiport from 6.67 to 7.54. A membrane mechanism that catalyzes the exchange of Na+ for H+ has recently been characterized in a variety of cell types such as skeletal muscle cells (1, 2), fibroblasts (3-7), cardiac cells (8,9), kidney cells (10-E), and lymphocytes (16). Moolenaar et al. (17) described the existence of a Na+/H+ exchange system in neuroblastoma cells, and a similar system seems also to be present in glial cells (18-20). In a preliminary communication we previously reported the presence of a highly active Na+/H+ exchange system in rat brain synaptosomes (21). In this paper, we extend the analysis of the properties of this Na+/H+ exchange system using a combination of three complementary approaches including "Na+ uptake studies, pH measurements using the fluorescence of * This work was supported by grants from the Centre National de la Recherche Scientifique, the Fondation sur les Maladies Vasculaires,
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Journal of Biological Chemistry, 1985
[3H]Ethylpropylamiloride is a useful radioactive label to identify the Na+/H+ exchange system (Vi... more [3H]Ethylpropylamiloride is a useful radioactive label to identify the Na+/H+ exchange system (Vigne, P., Frelin, C., Audinot, M., Borsotto, M., Cragoe, E. J., and Lazdunski, M. (1984) EMBO J. 3, 2647-2651). This paper extends the analysis of the properties of interaction of [3H]ethylpropylamiloride with the exchanger and describes its use with hypertrophied kidneys. [3H]Ethylpropylamiloride-binding sites copurify with the luminal membrane marker alkaline phosphatase but not with the basolateral membrane marker (Na+,K+)ATPase, thus indicating an asymmetric distribution of the Na+/H+ exchanger. Specific [3H]ethylpropylamiloride binding is dependent on pH. The pH dependency indicates that an ionizable function with a pKapp of 7.0 is essential in the association of the amiloride derivative. H+ acts competitively on [3H]ethylpropylamiloride binding; Na+, Li+, or cholinium ions have no effect on the association. Compensatory adaptation of the kidney to chronic reduction of renal mass is accompanied by a 1.7-fold increase in the activity of the Na+/H+ exchange system. Properties of interaction of internal and external pH with the Na+/H+ exchanger of normal and hypertrophied kidneys are identical. Titration of [3H]ethylpropylamiloride-binding sites in normal and hypertrophied kidneys suggests that the increased activity of the Na+/H+ exchange system is not accompanied by an increased concentration of exchangers.
Journal of Biological Chemistry, 1989
Four new monochain phospholipases were purified from the Oxyuranus scutellatus (taipan) venom. Th... more Four new monochain phospholipases were purified from the Oxyuranus scutellatus (taipan) venom. Three of them were highly toxic when injected into mice brain. One of these neurotoxic phospholipases, OSZ, was iodinated and used in binding experiments to demonstrate the presence of two families of specific binding sites in rat brain synaptic membranes. The affinities were exceptionally high, Kd1 = 1.5 f 0.5 p~ and Ka = 45 f 10 PM, and the maximal binding capacities were BmaX = 1 f 0.4 and Bmx2 = 3 f 0.5 pmol/mg of protein. Both binding sites were sensitive to proteolysis and demonstrated to be located on proteins of M, 85,000-88,000 and 36,000-51,000 by cross-linking and photoaffinity labeling techniques. The binding of "'1-OSz to synaptic membranes was dependent on Ca2+ ions and enhanced by Zn2+ ions which inhibit phospholipase activity. Competition experiments have shown that, except for B-bungarotoxin, a number of known toxic snake or bee phospholipases have very high affinities for the newly identified binding sites. A good correlation (r = 0.80) was observed between toxicity and affinity but not between phospholipase activity and affinity.
Journal of Biological Chemistry, 1983
This work was supported by the Centre National de la Recherche Scientifique, the Commissariat a 1... more This work was supported by the Centre National de la Recherche Scientifique, the Commissariat a 1'Energie Atomique, and the Foundation pour la Recherche Mkdicale. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "aduertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. ~-fibroblasts and which permit analyzation of some of the mechanistic properties of serum action on the Na'/H+ exchanger.
Journal of Biological Chemistry, 1994
The abbreviations used are: TOPA, 2,4,5-trihydroxyphenylalanine; PAGE, polyacrylamide gel electro... more The abbreviations used are: TOPA, 2,4,5-trihydroxyphenylalanine; PAGE, polyacrylamide gel electrophoresis; Chaps, 3-1(3-cholamidopro-py1)dimethylammoniol-1-propanesulfonic acid.
Journal of Biological Chemistry, 1989
Journal of Biological Chemistry, 1988
This work was supported by the Centre National de la Recherche Scientifique (LP 7300 and Action d... more This work was supported by the Centre National de la Recherche Scientifique (LP 7300 and Action de Recherche Intbgrei! "Chimie Biologie"), the "Fondation Searle pour la Recherche contre 1'Hypertension," and the Fondation sur les Maladies Vasculaires. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "aduertisernent" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. ll To whom correspondence should be addressed.
Journal of Biological Chemistry, 1994
The protein binds amiloride and some of its derivatives, such as phenamil, benzamil, and ethylpro... more The protein binds amiloride and some of its derivatives, such as phenamil, benzamil, and ethylpropylamiloride. These properties have previously suggested that ABP might be associated with an amiloride-sensitive Na' channel. It corresponds in fact to an amiloride-sensitive diamine oxidase (DAO) that catalyzes the degradation of compounds such as putrescine or histamine. The analysis of the organization of the sequence of the human ABP/DAO gene reveals that the 2.4-kilobase messenger RNA is transcribed from two close origins identifying the proximal promoter. After sequencing, some corrections within the initial cDNA sequence have been made. Human ABP/DAO corresponds to a 751-residue polypeptide. The promoter activity of 1800 base pairs upstream of the transcription start sites of the long form has been analyzed. T w o bulks of cis-activating sequences have been identified. One of them constitutes the proximal promoter. It contains a palindromic sequence previously described as E-PAL. This motif is essential for the full activity of the promoter and behaves like a composite element. This first molecular cloning of a human gene coding for a diamine oxidase will allow us to further understand its regulation during cell growth andor embryonic development. Amiloride acts as a diuretic via the closure of epithelial Na' channels (1). Amiloride and its derivatives such as phenamil, benzamil, bromobenzamil, and methyl bromoamiloride have been extensively used in recent years to try to biochemically identify the epithelial Na' channel (2-5). An amiloride binding protein (AEiP)' has been cloned from human kidney and rat colon and shown to be present in many epithelial tissues (6, 7). This protein is able to bind amiloride and its derivatives with pharmacological properties very similar to those of the Na' channel. However, its expression does not induce any channel Lutte contre la Mucoviscidose (AFLM), and INSERM Grant CRE * This work was supported by CNRS, the Association Franqaise de 910204. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "aduertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. to the GenBankTM/EMBL Data Bank with accession numbedsl X78212.
Journal of Biological Chemistry, 1994
Toxins, 2019
Phlotoxin-1 (PhlTx1) is a peptide previously identified in tarantula venom (Phlogius species) tha... more Phlotoxin-1 (PhlTx1) is a peptide previously identified in tarantula venom (Phlogius species) that belongs to the inhibitory cysteine-knot (ICK) toxin family. Like many ICK-based spider toxins, the synthesis of PhlTx1 appears particularly challenging, mostly for obtaining appropriate folding and concomitant suitable disulfide bridge formation. Herein, we describe a procedure for the chemical synthesis and the directed sequential disulfide bridge formation of PhlTx1 that allows for a straightforward production of this challenging peptide. We also performed extensive functional testing of PhlTx1 on 31 ion channel types and identified the voltage-gated sodium (Nav) channel Nav1.7 as the main target of this toxin. Moreover, we compared PhlTx1 activity to 10 other spider toxin activities on an automated patch-clamp system with Chinese Hamster Ovary (CHO) cells expressing human Nav1.7. Performing these analyses in reproducible conditions allowed for classification according to the potency...
The EMBO Journal, 1995
The effects of the mild cystic fibrosis (CF) mutation P574H were analysed and compared with those... more The effects of the mild cystic fibrosis (CF) mutation P574H were analysed and compared with those of three severe ones (AI507, AF508 and R560T). Immunochemical and functional analyses indicate that the rank order of CFTR expression at the cell surface is: wild type CFTR > P574H > > AF508 > > R560T-0. Patchclamp analysis indicates that the open probability of P574H Clchannels is almost twice as high as that of the wild type CFTR-CIchannel. This increased intrinsic activity of individual P574H CFTR-Clchannels compensates for the lower number of P574H CFTR-Clchannels reaching the cell surface, and probably explains the milder form of CF associated with the P574H mutation. NS004, a recently described activator, restores near normal CFTR activity in cells expressing the P574H-CFTR channel. The P574H mutation modifies the gating mode of the channel with a large increase (.X7) in the mean channel open time. Proline 574 might play an important role in the process connecting ATP hydrolysis at the nucleotide binding domain and opening and closing events of the CFTR-Clchannel.
The Journal of Neuroscience, 2001
The EMBO Journal, 1994
Molecular cloning of the amiloride-sensitive Na+ channel has permitted analysis of the mechanisms... more Molecular cloning of the amiloride-sensitive Na+ channel has permitted analysis of the mechanisms of its stimulation by steroids. In rat lung cells in primary culture, where its mRNA has been detected, the activity of an amiloride-sensitive channel, highly selective for Na+, is controlled by corticosteroids. Dexamethasone (0.1 ltM) or aldosterone (1 IM) induced, after a minimum 10 h treatment, a large increase of the amiloride-induced hyperpolarization and of the amiloride-sensitive current. A parallel increase in the amount of the mRNA was observed. The corresponding gene is thus a target for steroid action. Using synthetic specific agonists and antagonists for mineralo-and glucocorticoid receptors, it has been shown that the steroid action on Na+ channel expression is mediated via glucocorticoid receptors. Triiodothyronine, known to modulate steroid action in several tissues, had no effect on both the amiloridesensitive Na+ current and the level of the mRNA for the Na+ channel protein, but potentiates the stimulatory effect of dexamethasone. The increase in Na+ channel activity observed in the lung around birth can thus be explained by a direct increase in transcription of the Na+ channel gene.
The EMBO Journal, 1996
Outward rectifier K+ channels have a characteristic structure with six transmembrane segments and... more Outward rectifier K+ channels have a characteristic structure with six transmembrane segments and one pore region. A new member of this family of transmembrane proteins has been cloned and called Kv8.1. Kv8.1 is essentially present in the brain where it is located mainly in layers II, IV and VI of the cerebral cortex, in hippocampus, in CA1-CA4 pyramidal cell layer as well in granule cells of the dentate gyrus, in the granule cell layer and in the Purkinje cell layer of the cerebellum. The Kv8.1 gene is in the 8q22.3-8q24.1 region of the human genome. Although Kv8.1 has the hallmarks of functional subunits of outward rectifier K+ channels, injection of its cRNA in Xenopus oocytes does not produce K+ currents. However Kv8.1 abolishes the functional expression of members of the Kv2 and Kv3 subfamilies, suggesting that the functional role of Kv8.1 might be to inhibit the function of a particular class of outward rectifier K+ channel types. Immunoprecipitation studies have demonstrated that inhibition occurs by formation of heteropolymeric channels, and results obtained with Kv8.1 chimeras have indicated that association of Kv8.1 with other types of subunits is via its N-terminal domain.
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Papers by Michel Lazdunski