RESUMEN
BACKGROUND: This article aims to demonstrate the importance of the TMJ (Temporomandibular Joint) decompression in the treatment of degenerative processes and disc displacements, reporting two clinical cases treated with orthopedic and decompressive correction of TMJ. MATERIAL AND METHODS: The studies reported in this article show patients with muscle and joint pain who were evaluated pre and post-treatment through MRI (Magnetic Resonance Irradiation) to follow-up bone marrow regeneration and TMJ disc placement. Transcutaneous electrical stimulation (TENS), measurement equipment and IO (Intraoral Orthotic) were used to evaluate and treat the patients. A critical review of literature has also been conducted to confront clinical outcomes. RESULTS: Marrow bone regeneration and disc placement were observed in both patients. CONCLUSIONS: The use of measurement equipment associated with TENS to find the correct rest position of the Jaw an the use of IO to decompress the TMJ was an effective way to promote bone marrow regeneration and disc placement, consequently improving function and quality of life.
Asunto(s)
Médula Ósea/fisiología , Descompresión Quirúrgica , Regeneración , Trastornos de la Articulación Temporomandibular/cirugía , Adulto , Anciano , Femenino , Humanos , Aparatos Ortopédicos , Disco de la Articulación TemporomandibularRESUMEN
Essential oils from the stems and leaves of Croton doctoris were analyzed by gas chromatography and mass spectrometry, resulting in 22 identified compounds. The effects of these essential oils on the germination, root and shoot growth, total chlorophyll content, potential root respiration, peroxidase activity, catalase, superoxide dismutase, and mitotic index in lettuce and onion were determined. Antioxidant, antimicrobial, and cytotoxic activity were also investigated. The results revealed that the stem oil consisted of 15 compounds, of which caryophyllene oxide (24.5%) and E-caryophyllene (13.3%) were the major constituents. The leaf oil contained E-caryophyllene (39.6%) and α-humulene (13.2%) as major compounds. The oils inhibited the germination and growth of lettuce and onion seedlings and reduced chlorophyll content, root respiration, and cell division. They also caused oxidative stress, indicated by the increased activity of the evaluated antioxidant enzymes. These abnormal physiological processes contributed to the inhibition of plant growth. The most pronounced phytotoxic effects were observed in the stem oil. The cytotoxicity tests indicated that leaf oil was more active than stem oil, resulting from the presence of biologically active sesquiterpenes that inhibit the growth of cancer cells.
Asunto(s)
Croton , Euphorbiaceae , Aceites Volátiles , Germinación , Lactuca , Aceites Volátiles/toxicidad , Hojas de la Planta , Aceites de PlantasRESUMEN
Abstract Essential oils from the stems and leaves of Croton doctoris were analyzed by gas chromatography and mass spectrometry, resulting in 22 identified compounds. The effects of these essential oils on the germination, root and shoot growth, total chlorophyll content, potential root respiration, peroxidase activity, catalase, superoxide dismutase, and mitotic index in lettuce and onion were determined. Antioxidant, antimicrobial, and cytotoxic activity were also investigated. The results revealed that the stem oil consisted of 15 compounds, of which caryophyllene oxide (24.5%) and E-caryophyllene (13.3%) were the major constituents. The leaf oil contained E-caryophyllene (39.6%) and -humulene (13.2%) as major compounds. The oils inhibited the germination and growth of lettuce and onion seedlings and reduced chlorophyll content, root respiration, and cell division. They also caused oxidative stress, indicated by the increased activity of the evaluated antioxidant enzymes. These abnormal physiological processes contributed to the inhibition of plant growth. The most pronounced phytotoxic effects were observed in the stem oil. The cytotoxicity tests indicated that leaf oil was more active than stem oil, resulting from the presence of biologically active sesquiterpenes that inhibit the growth of cancer cells.
Resumo Os óleos essenciais do caule e da folha de Croton doctoris foram analisados por cromatografia gasosa (GC) e espectrometria de massa (GC-MS) resultando em 22 compostos identificados. Os efeitos dos óleos essenciais na germinação, crescimento de raízes e parte aérea, teor total de clorofila, respiração radicular, atividade de peroxidase, catalase e superóxido de dimetase e índice mitótico foram determinados em alface e cebola. Atividade antioxidante, antimicrobiana e citotóxica também foram investigadas. Os resultados revelaram que o óleo do caule é constituído por 15 compostos, dos quais os principais são o óxido de cariofileno (24,5%) e E-cariofileno (13,3%). O óleo foliar apresentou E-cariofileno (39,6%) seguido de -humuleno (13,2%) como compostos majoritários. Os óleos inibiram a germinação e o crescimento das plântulas de alface e cebola e reduziram o conteúdo de clorofila, a respiração radicular e a divisão celular. Eles também causaram estresse oxidativo, indicado pelo aumento da atividade das enzimas antioxidantes avaliadas. Esses processos fisiológicos anormais contribuem para a inibição do crescimento das plantas. Os efeitos fitotóxicos mais pronunciados foram observados no óleo do caule. Nos testes de citotoxicidade observou-se que o óleo das folhas foi mais ativo, resultante da presença de sesquiterpenos biologicamente ativos que atuam inibindo o crescimento das células cancerígenas.
RESUMEN
Essential oils from the stems and leaves of Croton doctoris were analyzed by gas chromatography and mass spectrometry, resulting in 22 identified compounds. The effects of these essential oils on the germination, root and shoot growth, total chlorophyll content, potential root respiration, peroxidase activity, catalase, superoxide dismutase, and mitotic index in lettuce and onion were determined. Antioxidant, antimicrobial, and cytotoxic activity were also investigated. The results revealed that the stem oil consisted of 15 compounds, of which caryophyllene oxide (24.5%) and E-caryophyllene (13.3%) were the major constituents. The leaf oil contained E-caryophyllene (39.6%) and α-humulene (13.2%) as major compounds. The oils inhibited the germination and growth of lettuce and onion seedlings and reduced chlorophyll content, root respiration, and cell division. They also caused oxidative stress, indicated by the increased activity of the evaluated antioxidant enzymes. These abnormal physiological processes contributed to the inhibition of plant growth. The most pronounced phytotoxic effects were observed in the stem oil. The cytotoxicity tests indicated that leaf oil was more active than stem oil, resulting from the presence of biologically active sesquiterpenes that inhibit the growth of cancer cells.
Os óleos essenciais do caule e da folha de Croton doctoris foram analisados por cromatografia gasosa (GC) e espectrometria de massa (GC-MS) resultando em 22 compostos identificados. Os efeitos dos óleos essenciais na germinação, crescimento de raízes e parte aérea, teor total de clorofila, respiração radicular, atividade de peroxidase, catalase e superóxido de dimetase e índice mitótico foram determinados em alface e cebola. Atividade antioxidante, antimicrobiana e citotóxica também foram investigadas. Os resultados revelaram que o óleo do caule é constituído por 15 compostos, dos quais os principais são o óxido de cariofileno (24,5%) e E-cariofileno (13,3%). O óleo foliar apresentou E-cariofileno (39,6%) seguido de α-humuleno (13,2%) como compostos majoritários. Os óleos inibiram a germinação e o crescimento das plântulas de alface e cebola e reduziram o conteúdo de clorofila, a respiração radicular e a divisão celular. Eles também causaram estresse oxidativo, indicado pelo aumento da atividade das enzimas antioxidantes avaliadas. Esses processos fisiológicos anormais contribuem para a inibição do crescimento das plantas. Os efeitos fitotóxicos mais pronunciados foram observados no óleo do caule. Nos testes de citotoxicidade observou-se que o óleo das folhas foi mais ativo, resultante da presença de sesquiterpenos biologicamente ativos que atuam inibindo o crescimento das células cancerígenas.
Asunto(s)
Aceites Volátiles/toxicidad , Euphorbiaceae , Croton , Aceites de Plantas , Hojas de la Planta , Lactuca , GerminaciónRESUMEN
Essential oils from the stems and leaves of Croton doctoris were analyzed by gas chromatography and mass spectrometry, resulting in 22 identified compounds. The effects of these essential oils on the germination, root and shoot growth, total chlorophyll content, potential root respiration, peroxidase activity, catalase, superoxide dismutase, and mitotic index in lettuce and onion were determined. Antioxidant, antimicrobial, and cytotoxic activity were also investigated. The results revealed that the stem oil consisted of 15 compounds, of which caryophyllene oxide (24.5%) and E-caryophyllene (13.3%) were the major constituents. The leaf oil contained E-caryophyllene (39.6%) and α-humulene (13.2%) as major compounds. The oils inhibited the germination and growth of lettuce and onion seedlings and reduced chlorophyll content, root respiration, and cell division. They also caused oxidative stress, indicated by the increased activity of the evaluated antioxidant enzymes. These abnormal physiological processes contributed to the inhibition of plant growth. The most pronounced phytotoxic effects were observed in the stem oil. The cytotoxicity tests indicated that leaf oil was more active than stem oil, resulting from the presence of biologically active sesquiterpenes that inhibit the growth of cancer cells.
Os óleos essenciais do caule e da folha de Croton doctoris foram analisados por cromatografia gasosa (GC) e espectrometria de massa (GC-MS) resultando em 22 compostos identificados. Os efeitos dos óleos essenciais na germinação, crescimento de raízes e parte aérea, teor total de clorofila, respiração radicular, atividade de peroxidase, catalase e superóxido de dimetase e índice mitótico foram determinados em alface e cebola. Atividade antioxidante, antimicrobiana e citotóxica também foram investigadas. Os resultados revelaram que o óleo do caule é constituído por 15 compostos, dos quais os principais são o óxido de cariofileno (24,5%) e E-cariofileno (13,3%). O óleo foliar apresentou E-cariofileno (39,6%) seguido de α-humuleno (13,2%) como compostos majoritários. Os óleos inibiram a germinação e o crescimento das plântulas de alface e cebola e reduziram o conteúdo de clorofila, a respiração radicular e a divisão celular. Eles também causaram estresse oxidativo, indicado pelo aumento da atividade das enzimas antioxidantes avaliadas. Esses processos fisiológicos anormais contribuem para a inibição do crescimento das plantas. Os efeitos fitotóxicos mais pronunciados foram observados no óleo do caule. Nos testes de citotoxicidade observou-se que o óleo das folhas foi mais ativo, resultante da presença de sesquiterpenos biologicamente ativos que atuam inibindo o crescimento das células cancerígenas.
Asunto(s)
Croton/química , Croton/toxicidad , Aceites Volátiles/uso terapéuticoRESUMEN
The cytotoxic effects of seven constituents isolated from Duguetia glabriuscula were evaluated against Hep2 human larynx carcinoma cells. The cytotoxicity exhibited by beta-sitosterol was as strong as that of cis-platin. (+)-Alloaromadendran-10,14beta-diol caused inhibition of cellular growth with IC50 values lower than 25 microg/ml, a feature that was considered as revealing significant activity. Polycarpol showed borderline cytotoxicity, whereas the other compounds were inactive.
Asunto(s)
Annonaceae/química , Antineoplásicos Fitogénicos/toxicidad , Sitoesteroles/toxicidad , Línea Celular Tumoral , Cisplatino/toxicidad , Humanos , Concentración 50 Inhibidora , Corteza de la Planta/química , Extractos Vegetales/química , Extractos Vegetales/toxicidad , Hojas de la Planta/química , Hidrocarburos Policíclicos Aromáticos/toxicidad , Pruebas de Toxicidad/métodosRESUMEN
The Q-SNARE syntaxin 1 is a central component of the synaptic membrane fusion machinery. Syntaxin probably interacts with multiple proteins during synaptic vesicle exocytosis. In vitro, the tightest binding partners for syntaxin 1 are other SNAREs (synaptobrevin/VAMP and SNAP-25) and munc18-1 (also known as rbsec1/nsec1). Recent studies on Drosophila syntaxin led to the surprising finding that a syntaxin mutant which does not bind the munc18-homolog Rop nevertheless functionally substitutes for wild-type syntaxin in membrane fusion (Wu et al., Neuron 23, 593-605, 1999). This observation suggested that syntaxin 1 binding to munc18-1 is not essential for fusion, a puzzling conclusion in view of the tight binding of munc18 and syntaxin homologs in all organisms. To address this issue, we have now reinvestigated the interaction of syntaxin with munc18 and Rop. We find that the syntaxin sequence that was mutated in the Drosophila studies is not essential for munc18/Rop binding, and that the mutant is in fact able to bind to munc18/Rop. Thus the fact that the mutant syntaxin rescues release cannot be used as an argument that munc18 binding is not essential. In addition to munc18 and SNAREs, several other proteins have been suggested to interact with various domains of syntaxin 1, notably the calcium-sensor synaptotagmin and the vesicle protein CSP. Our results confirm that the SNARE motif in syntaxin binds to synaptotagmin, but this interaction does not require the very C-terminus of the motif. Interestingly, binding of synaptotagmin appears to be decreased in the closed conformation of syntaxin. In contrast, no interaction of CSP with syntaxin was detected even under low-stringency conditions. Our data suggest 1., that assays measuring protein/protein interactions that involve syntaxin may be more difficult to evaluate than is often assumed because of the sticky nature of the proteins involved, and 2., that it is currently not possible to draw conclusions about the importance of the various interactions with the available data from Drosophila or vertebrates.
Asunto(s)
Antígenos de Superficie/metabolismo , Proteínas de Unión al Calcio , Glicoproteínas de Membrana/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Proteínas/metabolismo , Proteínas de Transporte Vesicular , Secuencias de Aminoácidos , Animales , Antígenos de Superficie/química , Sitios de Unión , Encéfalo/metabolismo , Cromatografía de Afinidad , Drosophila , Electroforesis en Gel de Poliacrilamida , Glutatión Transferasa/metabolismo , Immunoblotting , Glicoproteínas de Membrana/química , Proteínas Munc18 , Proteínas del Tejido Nervioso/química , Péptidos/química , Unión Proteica , Estructura Terciaria de Proteína , Proteínas/química , Ratas , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/metabolismo , Sinaptotagminas , Sintaxina 1RESUMEN
Molecular characterization of mammalian voltage-sensitive K+ channel genes and their expression became possible with the cloning of the Shaker locus of Drosophila. However, analysis of the expression patterns and subunit composition of native K+ channel protein complexes requires immunological probes specific for the individual K+ channel gene products expressed in excitable tissue. Here, we describe the generation and characterization of monoclonal antibodies (mAbs) against eight distinct mammalian K+ channel polypeptides; the Kv1.1, Kv1.2, Kv1.4, Kv1.5 and Kv1.6 Shaker-related alpha-subunits, the Kv2.1 Shab-related alpha-subunit, and the Kv beta 1 and Kv beta 2 beta-subunits. We characterized the subtype-specificity of these mAbs against native K+ channels in mammalian brain and against recombinant K+ channels expressed in transfected mammalian cells. In addition, we used these mAbs to investigate the cellular and subcellular distribution of the corresponding polypeptides in rat cerebral cortex, as well as their expression levels across brain regions.
Asunto(s)
Anticuerpos Monoclonales/biosíntesis , Especificidad de Anticuerpos , Péptidos/inmunología , Canales de Potasio con Entrada de Voltaje , Canales de Potasio/inmunología , Secuencia de Aminoácidos , Animales , Química Encefálica , Células COS , Corteza Cerebral/química , Canales de Potasio de Tipo Rectificador Tardío , Técnica del Anticuerpo Fluorescente Indirecta , Immunoblotting , Canal de Potasio Kv.1.2 , Canal de Potasio Kv1.4 , Ratones , Ratones Endogámicos BALB C , Datos de Secuencia Molecular , Canales de Potasio/análisis , Ratas , Ratas Sprague-Dawley , Proteínas Recombinantes/análisis , Proteínas Recombinantes/inmunología , Canales de Potasio Shab , TransfecciónRESUMEN
To define the molecular characteristics of K+ channel beta-subunit polypeptides, we have studied their biochemical properties and subcellular distribution in transfected mammalian cells. We find that the recombinant voltage-dependent K+ (Kv) beta1.1 and Kvbeta2 polypeptides have distinct detergent solubility properties owing to a novel association of Kvbeta1.1 with the actin-based cytoskeleton. Mutational and chimeric protein analyses show that the unique aminoterminus of Kvbeta1.1 is both necessary and sufficient for mediating the association of beta-subunits with cytoskeleton. Thus, the interaction with cytoskeleton is mediated through the amino-terminal domain previously shown to be necessary for modulating alpha-subunit inactivation, but not necessary for interaction with alpha-subunit polypeptides. These data reveal that different domains of beta-subunit polypeptides mediate interactions with cytoskeleton and with alpha-subunits, and provide a structural basis for previous reports that linked the extent of beta-subunit-induced inactivation to the state of the actin cytoskeleton.
Asunto(s)
Citoesqueleto/metabolismo , Canales de Potasio/metabolismo , Actinas/metabolismo , Animales , Sitios de Unión , Células COS , Núcleo Celular/química , Citoplasma/química , Citoesqueleto/efectos de los fármacos , Detergentes/farmacología , Inmunohistoquímica , Fragmentos de Péptidos/análisis , Fragmentos de Péptidos/genética , Fragmentos de Péptidos/metabolismo , Canales de Potasio/análisis , Canales de Potasio/química , Canales de Potasio/genética , Unión Proteica/efectos de los fármacos , Isoformas de Proteínas/análisis , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Proteínas Recombinantes de Fusión/análisis , Proteínas Recombinantes de Fusión/biosíntesis , Proteínas Recombinantes de Fusión/metabolismo , Eliminación de Secuencia , Solubilidad/efectos de los fármacos , TransfecciónRESUMEN
Two serine proteinases, MSP 1 and MSP 2, were isolated from Bothrops moojeni venom by chromatographies on Sephadex G-100, DEAE-Sephacel (pH 7.5) and SP-Sephadex C-50 (pH 7.5). Both enzymes are basic glycoproteins. On sodium dodecyl sulfate-polyacrylamide electrophoresis, MSP 1 presented two close protein bands corresponding to the mol. wts of 34,000 and 32,500. MSP 2 behaved as a single-chain protein with a mol. wt of 38,000. Specific esterolytic activities of MSP 1 and MSP 2 on alpha-N-tosyl-L-arginine methyl ester (TAME) are 33 mumol min-1 mg-1 and 184 mumol min-1 mg-1, respectively. The most sensitive substrates for the amidolytic activity of both proteinases were the thrombin substrate D-Phe-pipecolyl(Pip)-Arg-4-nitroanilide(Nan) and the glandular kallikrein substrate D-Val-Leu-Arg-Nan. MSP 1, in a concentration of 10(-8) M, causes platelet aggregation in platelet-rich plasma and washed platelets. It also enhances the ADP-induced platelet aggregation. Prostaglandin E1 (PGE1), phenylmethylsulfonyl fluoride (PMSF) and ethylenediamine tetracetic acid (EDTA) abolished completely the aggregation induced by MSP 1. Torresea cearensis trypsin inhibitor (TCTI) inhibited both amidolytic (Ki = 1.96 x 10(-7) M) and platelet-aggregating (Ki = 1.66 x 10(-7) M) activities of MSP 1. The esterolytic activity of MSP 1 and MSP 2 was completely abolished by PMSF, only partially by soybean trypsin inhibitor (SBTI) and benzamidine and not affected by Trasylol. MSP 2 was also inhibited by TCTI (Ki = 0.7 x 10(-7) M).
Asunto(s)
Venenos de Crotálidos/enzimología , Agregación Plaquetaria/efectos de los fármacos , Serina Endopeptidasas/aislamiento & purificación , Adenosina Difosfato/farmacología , Amidas/metabolismo , Secuencia de Aminoácidos , Animales , Coagulación Sanguínea/efectos de los fármacos , Caseínas/metabolismo , Cobayas , Hemorragia/inducido químicamente , Hemorragia/patología , Caballos , Humanos , Técnicas In Vitro , Cininas/metabolismo , Datos de Secuencia Molecular , Peso Molecular , Serina Endopeptidasas/metabolismo , Serina Endopeptidasas/farmacología , Inhibidores de Serina Proteinasa/farmacología , Tosilarginina Metil Éster/metabolismoRESUMEN
The ethanolic extracts from the roots, the underground trunk and the leaves of Aiouea trinervis were active in the brine shrimp (Artemia salina) lethality assay (LD (50): 1.93, 0.92 and 262.1 microg/mL, respectively). Fractionation of the extracts led to the isolation of four butanolides, namely (-)-epilitsenolides C (2) and C (1) ( 1 and 2), isoobtusilactone A ( 3) and obtusilactone A ( 4), two of which ( 1 and 2) are reported for the first time as genuine natural products. The lignans (+)-sesamin ( 5) and (+)-methylpiperitol ( 6) and polyprenol-12 ( 7) were isolated as well. Their structures were determined with spectral methods (1D-, 2D-NMR and MS). Compounds 1, 2, 3, 5 and 6 were tested for their cytotoxic activities in Hep (2) human cancer cells. The butanolides 2 and 3 were the most active (IC (50): 5.96 microg/mL and 4.95 microg/mL, respectively) whereas the other compounds showed moderate IC (50) values ranging from 12.20 microg/mL to 25.64 microg/mL. The genotoxic properties of the crude ethanolic extracts and of compounds 3 and 5 were also evaluated in this study on CHO K1 and HTC mammalian cells with single-cell gel electrophoresis (comet assay). The crude extracts as well as the compounds tested induced DNA migration in this assay, which was indicative of DNA damage (genotoxic effect).
Asunto(s)
Antineoplásicos Fitogénicos/farmacología , Lauraceae , Fitoterapia , Extractos Vegetales/farmacología , Animales , Antineoplásicos Fitogénicos/administración & dosificación , Antineoplásicos Fitogénicos/uso terapéutico , Artemia/efectos de los fármacos , Línea Celular Tumoral/efectos de los fármacos , Ensayo Cometa , Daño del ADN/efectos de los fármacos , Humanos , Concentración 50 Inhibidora , Lignanos/administración & dosificación , Lignanos/farmacología , Lignanos/uso terapéutico , Mutágenos/administración & dosificación , Mutágenos/farmacología , Mutágenos/uso terapéutico , Extractos Vegetales/administración & dosificación , Extractos Vegetales/uso terapéutico , Hojas de la Planta , Raíces de PlantasRESUMEN
The differential expression and association of cytoplasmic beta-subunits with pore-forming alpha-subunits may contribute significantly to the complexity and heterogeneity of voltage-gated K+ channels in excitable cells. Here we examined the association and colocalization of two mammalian beta-subunits, Kvbeta1 and Kvbeta2, with the K+ channel alpha-subunits Kv1.1, Kv1.2, Kv1.4, Kv1.6, and Kv2.1 in adult rat brain. Reciprocal coimmunoprecipitation experiments using subunit-specific antibodies indicated that Kvbeta1 and Kvbeta2 associate with all the Kv1 alpha-subunits examined, and with each other, but not with Kv2.1. A much larger portion of the total brain pool of Kv1-containing channel complexes was found associated with Kvbeta2 than with Kvbeta1. Single- and multiple-label immunohistochemical staining indicated that Kvbeta1 codistributes extensively with Kv1.1 and Kv1.4 in cortical interneurons, in the hippocampal perforant path and mossy fiber pathways, and in the globus pallidus and substantia nigra. Kvbeta2 codistributes extensively with Kv1.1 and Kv1.2 in all brain regions examined and was strikingly colocalized with these alpha-subunits in the juxtaparanodal region of nodes of Ranvier as well as in the axons and terminals of cerebellar basket cells. Taken together, these data provide a direct demonstration that Kvbeta1 and Kvbeta2 associate and colocalize with Kv1 alpha-subunits in native tissues and provide a biochemical and neuroanatomical basis for the differential contribution of Kv1 alpha- and beta-subunits to electrophysiologically diverse neuronal K+ currents.
Asunto(s)
Química Encefálica , Proteínas del Tejido Nervioso/análisis , Canales de Potasio con Entrada de Voltaje , Canales de Potasio/análisis , Animales , Western Blotting , Cerebelo/química , Canales de Potasio de Tipo Rectificador Tardío , Técnica del Anticuerpo Fluorescente Indirecta , Globo Pálido/química , Técnicas para Inmunoenzimas , Interneuronas/química , Canal de Potasio Kv.1.1 , Canal de Potasio Kv.1.2 , Canal de Potasio Kv1.4 , Fibras Musgosas del Hipocampo/química , Proteínas del Tejido Nervioso/química , Especificidad de Órganos , Vía Perforante/química , Canales de Potasio/química , Nódulos de Ranvier/química , Ratas , Canales de Potasio Shab , Sustancia Negra/químicaRESUMEN
In all synapses, Ca2+ triggers neurotransmitter release to initiate signal transmission. Ca2+ presumably acts by activating synaptic Ca2+ sensors, but the nature of these sensors--which are the gatekeepers to neurotransmission--remains unclear. One of the candidate Ca2+ sensors in release is the synaptic Ca2+-binding protein synaptotagmin I. Here we have studied a point mutation in synaptotagmin I that causes a twofold decrease in overall Ca2+ affinity without inducing structural or conformational changes. When introduced by homologous recombination into the endogenous synaptotagmin I gene in mice, this point mutation decreases the Ca2+ sensitivity of neurotransmitter release twofold, but does not alter spontaneous release or the size of the readily releasable pool of neurotransmitters. Therefore, Ca2+ binding to synaptotagmin I participates in triggering neurotransmitter release at the synapse.
Asunto(s)
Proteínas de Unión al Calcio/fisiología , Calcio/metabolismo , Glicoproteínas de Membrana/fisiología , Proteínas del Tejido Nervioso/fisiología , Neurotransmisores/fisiología , Sinapsis/fisiología , Animales , Proteínas de Unión al Calcio/genética , Proteínas de Unión al Calcio/metabolismo , Células Cultivadas , Glicoproteínas de Membrana/química , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Ratones , Mutagénesis Sitio-Dirigida , Proteínas del Tejido Nervioso/química , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Neuronas/metabolismo , Neurotransmisores/química , Neurotransmisores/genética , Neurotransmisores/metabolismo , Mutación Puntual , Unión Proteica , Conformación Proteica , Vesículas Sinápticas/metabolismo , Sinaptotagmina I , SinaptotagminasRESUMEN
Recent cloning of K+ channel beta subunits revealed that these cytoplasmic polypeptides can dramatically alter the kinetics of current inactivation and promote efficient glycosylation and surface expression of the channel-forming alpha subunits. Here, we examined the expression, distribution, and association of two of these beta subunits, Kv beta 1 and Kv beta 2, in adult rat brain. In situ hybridization using cRNA probes revealed that these beta-subunit genes are heterogeneously expressed, with high densities of Kv beta 1 mRNA in the striatum, CA1 subfield of the hippocampus, and cerebellar Purkinje cells, and high densities of Kv beta 2 mRNA in the cerebral cortex, cerebellum, and brainstem. Immunohistochemical staining using subunit-specific monoclonal and affinity-purified polyclonal antibodies revealed that the Kv beta 1 and Kv beta 2 polypeptides frequently co-localize and are concentrated in neuronal perikarya, dendrites, and terminal fields, and in the juxtaparanodal region of myelinated axons. Immunoblot and reciprocal co-immunoprecipitation analyses indicated that Kv beta 2 is the major beta subunit present in rat brain membranes, and that most K+ channel complexes containing Kv beta 1 also contain Kv beta 2. Taken together, these data suggest that Kv beta 2 is a component of almost all K+ channel complexes containing Kv 1 alpha subunits, and that individual channels may contain two or more biochemically and functionally distinct beta-subunit polypeptides.