Biophysical and structural characterization of the putative nickel chaperone CooT from Carboxydothermus hydrogenoformans.

Carboxydothermus hydrogenoformans is a model microorganism for the study of [NiFe]-CODH, a key enzyme of carbon cycle in anaerobic microorganisms. The enzyme possesses a unique active site (C-cluster), constituted of a distorted [NiFe3S4] cubane linked to a mononuclear Fe(II) center. Both the biogenesis of the C-cluster and the activation of CODH by nickel insertion remain unclear. Among the three accessory proteins thought to play a role in this latter step (CooC, CooJ, and CooT), CooT is identified as a nickel chaperone involved in CODH maturation in Rhodospirillum rubrum. Here, we structurally and biophysically characterized a putative CooT protein present in C. hydrogenoformans (pChCooT). Despite the low sequence homologies between CooT from R. rubrum (RrCooT) and pChCooT (19% sequence identity), the two proteins share several similarities, such as their overall structure and a solvent-exposed Ni(II)-binding site at the dimer interface. Moreover, the X-ray structure of pChCooT reveals the proximity between the histidine 55, a potential nickel-coordinating residue, and the cysteine 2, a highly conserved key residue in Ni(II)-binding.

[Metabotropic glutamate receptors: new molecular targets in the treatment of neurological and psychiatric diseases]. / Receptores metabotrópicos de glutamato: nuevas dianas moleculares en la terapia de enfermedades neurológicas y psiquiátricas.

AIM: To describe the current state of knowledge about the processes of neuronal signalling mediated by the metabotropic glutamate (mGlu) receptors and their potential role in the treatment of neurological and psychiatric disorders. DEVELOPMENT: The mGlu receptors are a large family of G-protein coupled receptors that modulate excitatory synaptic transmission through several transduction mechanisms. Recent advances in the molecular biology, physiology and pharmacology of these receptors revealed their potential role in a variety of central nervous system disorders such as epilepsy, pain, ischemia, and neurodegenerative diseases. These findings have shown that modulating glutamatergic transmission with drugs interacting selectively on mGlu receptors might have important beneficial effects. A number of results in this direction are very promising and are used to develop new drugs that overcome the multiple side-effects produced by the drugs acting on ionotropic glutamate receptors. Thus, several evidence have provided clear indications of the potential use of selective agonists and antagonists of the different mGlu receptor subtypes as neuroprotective agents. CONCLUSIONS: Determining the role of mGlu receptors in physiological as well as in pathophysiological states will be relevant to develop new treatments for diseases in which glutamatergic neurotransmission is altered. In this sense, the current progress indicates that mGlu receptors are novel and promising therapeutic targets for neurological and psychiatric disorders.

Receptores metabotrópicos de glutamato: nuevas dianas moleculares en la terapia de enfermedades neurológicas y psiquiátricas / Metabotropic glutamate receptors: new molecular targets in the treatment of neurological and psychiatric diseases

Objetivo. Describir el estado actual de conocimientos sobre los procesos de señalización neuronal mediados por los receptores metabotrópicos de glutamato (mGlu) y su potencial papel en el tratamiento de enfermedades neurológicas y psiquiátricas. Desarrollo. Los receptores mGlu son una gran familia de receptores acoplados a proteínas G que modulan la transmisión sináptica excitadora a través de varias vías de transducción. Las investigaciones centradas en conocer la biología molecular, fisiología y farmacología de los receptores mGlu han puesto de manifiesto su implicación en varios trastornos del sistema nervioso central, entre los que destacan la epilepsia, el dolor, la isquemia y las enfermedades neurodegenerativas. Estos descubrimientos han permitido demostrar que la modulación de la transmisión glutamatérgica con fármacos que actúan selectivamente sobre los receptores mGlu puede tener importantes efectos beneficiosos. Los resultados obtenidos son muy prometedores y están siendo aprovechados para el desarrollo de nuevos medicamentos que han permitido solucionar los múltiples efectos secundarios producidos por los fármacos que actúan sobre los receptores ionotrópicos de glutamato. En esta dirección, existen claras evidencias del uso potencial de agonistas y antagonistas selectivos de los distintos tipos de receptores mGlu como agentes neuroprotectores. Conclusiones. Determinar el papel de los receptores mGlu en condiciones fisiológicas y patológicas es de especial relevancia para el desarrollo de nuevos tratamientos de enfermedades producidas por alteraciones en la neurotransmisión glutamatérgica. En este sentido, los progresos actuales indican que los receptores mGlu constituyen nuevas y prometedoras dianas para la terapia de enfermedades neurológicas y psiquiátricas

Aim. To describe the current state of knowledge about the processes of neuronal signalling mediated by the metabotropic glutamate (mGlu) receptors and their potential role in the treatment of neurological and psychiatric disorders. Development. The mGlu receptors are a large family of G-protein coupled receptors that modulate excitatory synaptic transmission through several transduction mechanisms. Recent advances in the molecular biology, physiology and pharmacology of these receptors revealed their potential role in a variety of central nervous system disorders such as epilepsy, pain, ischemia, and neurodegenerative diseases. These findings have shown that modulating glutamatergic transmission with drugs interacting selectively on mGlu receptors might have important beneficial effects. A number of results in this direction are very promising and are used to develop new drugs that overcome the multiple side-effects produced by the drugs acting on ionotropic glutamate receptors. Thus, several evidence have provided clear indications of the potential use of selective agonists and antagonists of the different mGlu receptor subtypes as neuroprotective agents. Conclusions. Determining the role of mGlu receptors in physiological as well as in pathophysiological states will be relevant to develop new treatments for diseases in which glutamatergic neurotransmission is altered. In this sense, the current progress indicates that mGlu receptors are novel and promising therapeutic targets for neurological and psychiatric disorders

Purification of heterologous sarcoplasmic reticulum Ca2+-ATPase Serca1a allowing phosphoenzyme and Ca2+-affinity measurements.

We describe here a protocol to prepare milligrams of active and stable heterologous sarcoplasmic reticulum Ca(2+)-ATPase (Serca1a). Serca1a was tagged with 6 histidines at its C-terminal end and overexpressed using the baculovirus-Sf9 system. In a first trial, Serca1a accounted for 24% of membrane proteins, 95% of which were inactive. Glucose in the culture medium reduced the production of Serca1a to 3 to 5% of membrane proteins and all Serca1a was active. Seventy-five percent of active Serca1a was solubilized by C(12)E(8) in the presence of phosphatidylcholine under conditions avoiding denaturation. Purification by Ni(2+)-nitrilo-triacetic acid affinity chromatography was tried, but only 3% of active Serca1a remained bound to the column, as if the His-tag were not accessible. Yields of 43% were reached by purification on reactive red 120 columns when eluting with 2 M NaCl. The purity was about 25% and Serca1a was stable for at least 1 week at 0 degrees C. Typically, 500 ml of culture medium produced 3 mg of active Serca1a and 1 mg of purified active Serca1a allowing measurements of phosphoenzyme (2 nmol/mg) or Ca(2+) affinity (2 microM at pH 7).

Autonomous folding of the recombinant large cytoplasmic loop of sarcoplasmic reticulum Ca2+-ATPase probed by affinity labeling and trypsin digestion.

Recombinant large cytoplasmic loop (LCL, residues 329-740) of sarcoplasmic reticulum Ca2+-ATPase, expressed in and purified from Escherichia coli, comprises most of the active site and binds ATP [Moutin, M.-J., Cuillel, M., Rapin, C., Miras, R., Anger, M., Lompré, A.-M. & Dupont, Y. (1994) J. Biol. Chem. 269, 11147-11154]. In this study, we show that fluorescein-5' isothiocyanate (FITC) specifically labels the same lysine residue as in the native Ca2+-ATPase (Lys515), with similar kinetics and pH dependence. ATP blocks the reaction with the lysine residue, but at higher concentrations compared with those for the native pump, in agreement with the lower ATP-binding affinity found previously. Graded tryptic digestion of LCL shows that favored cleavage is at the T1 site and that the N-terminal 75% of LCL are resistant to trypsin, as is native Ca2+-ATPase. Other experiments reveal differences to the native pump. (a) FITC derivatizes some -SH groups of LCL. (b) The C-terminal 25% of the polypeptide is susceptible to end-clipping by trypsin. (c) 2',3'-O-(2,4,6-trinitrophenyl)-ATP fails to specifically label the LCL (on the equivalent of Lys492), although it binds tightly (KD = 1.3 microM) and (d) Glutaraldehyde does not specifically cross-link LCL (between the equivalent of Lys492 and Arg678). These results could be explained by a flexible and loose structure of the hinge region of LCL (C-terminal 25%). Anchoring this region in the membrane and/or interaction with the missing beta-strand domain may be required for its compact folding and proper interaction with the rest of LCL. The results suggest that the N-terminal 75% of LCL expressed in E. coli folds autonomously to a fairly stable unit and native-like structure, encompassing the phosphorylation and central ATP binding sections. The hinge region does not appear to be part of the FITC-binding site but constitutes portions of the 2',3'-O-(2,4,6-trinitrophenyl)-ATP and, probably, ATP-binding site.

Neurons expressing 5-HT2 receptors in the rat brain: neurochemical identification of cell types by immunocytochemistry.

The serotonin2 (5-HT2) receptor has been implicated in a number of behavioral and physiological processes. It may also play a role in cellular development and differentiation, and represents a site of action of hallucinogens and certain psychotherapeutic drugs. To better understand the functions and regulation of the 5-HT2 receptor, we have undertaken a series of studies in which we attempted to identify the specific cell types that express the receptor. This was accomplished using a variety of double-labeling strategies with an antibody we raised against the rat 5-HT2 receptor protein. In this review, we recount of some of our previously published findings and present some new data in which we identify subpopulations of cholinergic neurons in the brainstem and gamma-aminobutynic acid (GABA)ergic interneurons in the cortex that express 5-HT2 receptor immunoreactivity. Developmentally, the appearance of 5-HT2 receptor immunoreactivity occurs relatively late in teh ontogeny of the cells in which it is expressed, mostly in the early postnatal period. This argues against a significant role for this receptor in early development, though it may participate in some aspect of terminal differentiation. We discuss the significance of the cell-type-specific and temporal expression of the 5-HT2 receptor in the context of current hypotheses of neuropsychiatric disorders such as schizophrenia.

Measurements of ATP binding on the large cytoplasmic loop of the sarcoplasmic reticulum Ca(2+)-ATPase overexpressed in Escherichia coli.

The large cytoplasmic loop of the sarcoplasmic reticulum Ca(2+)-ATPase (LCL), situated between Lys329 and Phe740, is believed to contain both its phosphorylation and ATP binding domains. A cDNA fragment coding for this amino acid sequence was generated in vitro and cloned in vector pQE8 which allowed the overexpression in Escherichia coli of this Ca(2+)-ATPase domain fused with a cluster of 6 histidines at its NH2 terminus. The fusion protein produced in an insoluble form within bacteria was solubilized in 4 M urea, purified on immobilized Ni2+, and then renatured by elimination of urea. More than 4 mg of purified renatured fusion protein was obtained from 500 ml of culture. ATP binding on the refolded protein was demonstrated by two methods: 1) detection of ATP-induced intrinsic fluorescence change and 2) binding of the fluorescent ATP analogue 2',3'-O-(2,4,6-trinitrophenyl)-adenosine-5'-triphosphate (TNP-ATP) and its chase by ATP. It is shown that the LCL protein has one single TNP-ATP binding site having a dissociation constant (Kd) of 1.6-1.9 microM. Both methods yielded a Kd for ATP around 200 microM. Binding of other nucleotides was detected with a sequence of Kd identical to that found for native Ca(2+)-ATPase: ATP < ADP < GTP < AMP < ITP. A Mg2+ binding site was also found on the LCL protein (Kd = 100 microM at pH 7.2). The fluorescence of bound TNP-ATP was found to be highly dependent on Mg2+ binding on this site.

Diversity of animal models of aggression: their impact on the putative alcohol/aggression link.

Many attempts have been made to "model" the putative link between alcohol and "aggression" using a variety of situations employing a wide range of animal species. In general, these attempts have proved somewhat disappointing. One reason for this appears to be the fact that the different "aggression" tests tap varied mixtures of offensive, defensive and predatory motivations (i.e., they are not homogenous). Indeed, one can make the claim that the majority of examples of "aggression" associated with alcohol-ingesting humans are inappropriate (nonadaptive) responses whereas many animal models tap adaptive territorial or socially competitive actions. A further problem is that alcohol has very wide-ranging effects on neurophysiology and endocrine functioning. Recent evidence from studies on infra-human animals and clinical situations suggests that some of alcohol's effects on social conflict are expressed by actions in signaling and perception rather than motivation. This aspect is briefly examined in some studies with laboratory mice.

Stereological study of the synaptic profiles belonging to interneurons in the dorsal lateral geniculate nucleus of the rabbit.

This study is concerned with some characteristics of the interneurons belonging to the dLGN (dorsal Lateral Geniculate Nucleus) of the rabbit. The work deals with the distribution of such cells in the alpha E sector of the nucleus and their F1 and F2 presynaptic contacts. The F1 and the F2 profiles are present in all three of the alpha E zones studied. The F1 profiles are significantly more numerous in the upper zone (57 +/- 2 profiles per 10(4) microns2 of section) and the middle zone (59 +/- 3 profiles per 10(4) microns2 of section) than in the lower one (41 +/- 2 profiles per 10(4) microns2 of section). The F2 profiles are more abundant in the alpha E sector than the F1 ones are, particularly in the lower zone, where F2 profiles (104 +/- 4 profiles per 10(4) microns2 of section) are not only significantly more numerous than F1 profiles but also more abundant than the F2 profiles in the middle zone (84 +/- 3 profiles per 10(4) microns2 of section) and upper zone (88 +/- 2 profiles per 10(4) microns2 of section). These results and their comments reveal diverse density of the element distribution from the dorsal to the ventral part of the alpha E sector as well as the possible relationship or independence from the extranuclear afferent inputs.