RESUMEN
Disturbances in the sleep-wake cycle are a debilitating, yet rather common condition not only in humans, but also in family dogs. While there is an emerging need for easy-to-use tools to document sleep alterations (in order to ultimately treat and/or prevent them), the veterinary tools which yield objective data (e.g. polysomnography, activity monitors) are both labor intensive and expensive. In this study, we developed a modified version of a previously used sleep questionnaire (SNoRE) and determined criterion validity in companion dogs against polysomnography and physical activity monitors (PAMs). Since a negative correlation between sleep time and cognitive performance in senior dogs has been demonstrated, we evaluated the correlation between the SNoRE scores and the Canine Dementia Scale (CADES, which includes a factor concerning sleep). There was a significant correlation between SNoRE 3.0 questionnaire scores and polysomnography data (latency to NREM sleep, ρ = 0.507, p < 0.001) as well as PAMs' data (activity between 1:00 and 3:00 AM, p < 0.05). There was a moderate positive correlation between the SNoRE 3.0 scores and the CADES scores (ρ = 0.625, p < 0.001). Additionally, the questionnaire structure was validated by a confirmatory factor analysis, and it also showed an adequate test-retest reliability. In conclusion the present paper describes a valid and reliable questionnaire tool, that can be used as a cost-effective way to monitor dog sleep in clinical settings.
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Juniperus , Sueño de Onda Lenta , Humanos , Animales , Perros , Mascotas , Reproducibilidad de los Resultados , Sueño , Polisomnografía , RonquidoRESUMEN
In humans, pain due to osteoarthritis has been demonstrated to be associated with insomnia and sleep disturbances that affect perception of pain, productivity, and quality of life. Dogs, which develop spontaneous osteoarthritis and represent an increasingly used model for human osteoarthritis, would be expected to show similar sleep disturbances. Further, these sleep disturbances should be mitigated by analgesic therapy. Previous efforts to quantify sleep in osteoarthritic dogs using accelerometry have not demonstrated a beneficial effect of analgesic therapy; this is despite owner-reported improvements in dogs' sleep quality. However, analytic techniques for time-series accelerometry data have advanced with the development of functional linear modeling. Our aim was to apply functional linear modeling to accelerometry data from osteoarthritic dogs participating in a cross-over non-steroidal anti-inflammatory (meloxicam) drug trial. Significant differences in activity patterns were seen dogs receiving drug (meloxicam) vs. placebo, suggestive of improved nighttime resting (sleep) and increased daytime activity. These results align with owner-reported outcome assessments of sleep quality and further support dogs as an important translational model with benefits for both veterinary and human health.
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Enfermedades de los Perros/tratamiento farmacológico , Osteoartritis/tratamiento farmacológico , Dolor/tratamiento farmacológico , Trastornos del Inicio y del Mantenimiento del Sueño/tratamiento farmacológico , Analgésicos/farmacología , Animales , Enfermedades de los Perros/etiología , Enfermedades de los Perros/fisiopatología , Perros , Femenino , Humanos , Masculino , Meloxicam/farmacología , Osteoartritis/complicaciones , Osteoartritis/fisiopatología , Dolor/etiología , Dolor/fisiopatología , Sueño/efectos de los fármacos , Sueño/fisiología , Trastornos del Inicio y del Mantenimiento del Sueño/etiología , Trastornos del Inicio y del Mantenimiento del Sueño/fisiopatologíaRESUMEN
A literature review identified six placebo-controlled studies of analgesics in client-owned cats with degenerative joint disease-associated pain. Five studies with 96 cats had available data. Caregiver responses on a clinical metrology instrument, Client-Specific Outcome Measure (CSOM), were compared to measured activity. Cats were categorised as 'successes' or 'failures' based on change in CSOM score and activity counts from baseline. Effect sizes based on CSOM score were calculated; factors that were associated with success/failure were analysed using logistic regression. Effect sizes ranged from 0.97 to 1.93. The caregiver placebo effect was high, with 54-74 per cent of placebo-treated cats classified as CSOM successes compared with 10-63 per cent of cats classified as successes based on objectively measured activity. 36 per cent of CSOM successes were also activity successes, while 19 per cent of CSOM failures were activity successes. No significant effects of cat age, weight, baseline activity, radiographic score, orthopaedic pain score or study type on CSOM success in the placebo groups were found. The caregiver placebo effect across these clinical trials was remarkably high, making demonstration of efficacy for an analgesic above a placebo difficult. Further work is needed to determine whether a potential placebo-by-proxy effect could benefit cats in clinical settings.
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Analgésicos/uso terapéutico , Cuidadores/psicología , Enfermedades de los Gatos/tratamiento farmacológico , Artropatías/veterinaria , Osteoartritis/veterinaria , Dolor/veterinaria , Efecto Placebo , Animales , Gatos , Femenino , Humanos , Artropatías/complicaciones , Masculino , Optimismo , Osteoartritis/complicaciones , Dolor/tratamiento farmacológico , Dolor/etiología , Resultado del TratamientoRESUMEN
BACKGROUND: Neutralizing antibodies against nerve growth factor (NGF) are analgesic in rodent models, naturally occurring degenerative joint disease (DJD) pain in dogs, and chronic pain in humans. OBJECTIVES: To evaluate the efficacy of a fully felinized anti-NGF antibody (NV-02) for the treatment of DJD pain and mobility impairment in cats. ANIMALS: Thirty-four client-owned cats with DJD-associated pain and mobility impairment. METHODS: In a placebo-controlled, pilot, masked clinical study, cats were randomized to a single treatment with NV-02 (0.4 mg/kg SC [n = 11] or 0.8 mg/kg SC [n = 12]) or placebo (saline, SC [n = 11]). Activity was measured objectively. Additionally, owners completed clinical metrology instruments (client-specific outcome measures [CSOM] and feline musculoskeletal pain index [FMPI]) on days 0 (screening), 14 (baseline), 35, 56, and 77. A repeated-measures model was used to evaluate the objective activity data. RESULTS: NV-02 significantly increased objectively measured activity overall (P = .017) and at 2 (P = .035), 3 (P = .007), 4 (P = .006), 5 (P = .007), and 6 (P = .017) weeks after treatment. CSOM scores (P = .035) and pain (P = .024) showed a significant effect of treatment 3 weeks after administration. In the treatment group, 83% of the owners correctly identified the treatment administered compared with 45% of owners in the placebo group (P = .013). No treatment-related adverse effects were identified. CONCLUSIONS: These pilot data demonstrate a 6-week duration positive analgesic effect of this fully felinized anti-NGF antibody in cats suffering from DJD-associated pain.
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Analgésicos no Narcóticos/uso terapéutico , Anticuerpos Monoclonales/uso terapéutico , Enfermedades de los Gatos/terapia , Factor de Crecimiento Nervioso/inmunología , Osteoporosis/veterinaria , Dolor Intratable/veterinaria , Animales , Gatos , Método Doble Ciego , Femenino , Inyecciones Subcutáneas/veterinaria , Cojera Animal/terapia , Masculino , Osteoporosis/terapia , Dolor Intratable/terapia , Proyectos Piloto , Especificidad de la Especie , Resultado del TratamientoRESUMEN
BACKGROUND: In veterinary clinical pain studies, there is a paucity of data on test-retest variability in Clinical Metrology Instruments (CMIs), and it is unknown whether CMIs should be administered using independent (respondents not permitted to see previous answers) or dependent (respondents shown previous answers) interviewing. OBJECTIVES: To compare baseline variability in CMIs designed to assess pain in dogs with osteoarthritis, and compare CMI scores using independent (InD) and dependent interviewing (DI) for the Canine Brief Pain Inventory (CBPI) and the Client-Specific Outcome Measures (CSOM). ANIMALS: Fifty-one client-owned dogs with radiographic evidence of osteoarthritis and associated pain. METHODS: Clinical Metrology Instruments data were collected during 2 randomized, double-masked, placebo-controlled, proof of principle pilot studies with parallel treatment groups. Enrolled dogs received either placebo or antinerve growth factor antibody (NV-01). RESULTS: Agreement between baseline CMI scores was good (CBPI Pain P = .29, CBPI Interference P = .32, CSOM P = .036, LOAD P = .67, HCPI P = .27), being best for the LOAD (ICC = 0.89). CMI responses collected during independent and dependent interviewing were not statistically different (CBPI Pain P = .33, CBPI Interference P = .28, CSOM P = .42) and showed good agreement. Additionally, dependent interviewing resulted in increased treatment effect sizes. CONCLUSIONS AND CLINICAL IMPORTANCE: There is little difference between independent and dependent interviewing, however, dependent interviewing resulted in increased treatment effect sizes. By using dependent interviewing, investigators could increase clinical trial power through minimal change to study design. Further research is warranted to investigate the use of dependent interviewing.
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Enfermedades de los Perros/terapia , Osteoartritis/veterinaria , Dimensión del Dolor/veterinaria , Dolor/veterinaria , Animales , Anticuerpos/inmunología , Anticuerpos/uso terapéutico , Enfermedades de los Perros/inmunología , Enfermedades de los Perros/fisiopatología , Perros , Método Doble Ciego , Inmunoterapia/veterinaria , Factor de Crecimiento Nervioso/inmunología , Osteoartritis/fisiopatología , Osteoartritis/terapia , Dolor/tratamiento farmacológico , Proyectos Piloto , Prueba de Estudio ConceptualRESUMEN
BACKGROUND: Recently, a potential association was identified between Bartonella exposure and arthritides in mammalian species other than cats. HYPOTHESIS/OBJECTIVES: We hypothesized that Bartonella exposure is associated with more severe degenerative joint disease (DJD) and a greater burden of DJD-associated pain in client-owned cats. ANIMALS: Ninety-four client-owned cats (6 months to 20 years old), ranging from clinically unaffected to severely lame because of DJD. METHODS: Using physical examination and radiography, pain and radiographic scores were assigned to each part of the bony skeleton. Sera were tested for Bartonella henselae, B. koehlerae, and B. vinsonii subsp. berkhoffii (genotypes I, II, and III) antibodies using immunofluorescence antibody assays. Variables were categorized and logistic regression used to explore associations. RESULTS: Seropositivity to Bartonella was identified in 33 (35.1%) cats. After multivariate analysis controlling for age, total DJD score (OR, 0.51; 95% CI, 0.26-0.97; P = .042), appendicular pain score (OR, 0.33; 95% CI, 0.17-0.65; P = .0011), and total pain score (OR, 0.35; 95% CI, 0.17-0.72; P = .0045) were significantly inversely associated with Bartonella seroreactivity status, indicating that cats with higher DJD and pain scores were less likely to be Bartonella seropositive. CONCLUSIONS AND CLINICAL IMPORTANCE: Based upon this preliminary study, Bartonella spp. seropositivity was associated with decreased severity of DJD and decreased DJD-associated pain in cats. Additional studies are needed to verify these findings, and if verified, to explore potential mechanisms.
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Infecciones por Bartonella/veterinaria , Bartonella/aislamiento & purificación , Enfermedades de los Gatos/sangre , Osteoartritis/veterinaria , Dolor/veterinaria , Animales , Anticuerpos Antibacterianos/sangre , Infecciones por Bartonella/inmunología , Enfermedades de los Gatos/etiología , Enfermedades de los Gatos/inmunología , Gatos , Femenino , Técnica del Anticuerpo Fluorescente/veterinaria , Masculino , Oportunidad Relativa , Osteoartritis/complicaciones , Dolor/etiología , Factores de RiesgoRESUMEN
BACKGROUND: Detection of clinically relevant pain relief in cats with degenerative joint disease (DJD) is complicated by a lack of validated outcome measures and a placebo effect. HYPOTHESIS/OBJECTIVES: To evaluate a novel approach for detection of pain relief in cats with DJD. ANIMALS: Fifty-eight client-owned cats. METHODS: Prospective, double-masked, placebo-controlled, stratified, randomized, clinical study. Enrolled cats were 6-21 years of age, with owner-observed mobility impairment, evidence of pain in at least 2 joints during orthopedic examination, and overlapping radiographic evidence of DJD, and underwent a 2-week baseline period, 3-week treatment period with placebo or meloxicam, and 3-week masked washout period. Outcome measures were evaluated at days 0, 15, 36, and 57. RESULTS: Both groups significantly improved after the treatment period (day 36) on client-specific outcome measures (CSOM) and feline musculoskeletal pain index (FMPI) (P < .0001 for both); there was no difference between the groups on CSOM or FMPI score improvement. After the masked washout period, more cats that received meloxicam during the treatment period had a clinically relevant decrease in CSOM score (P = .048) and FMPI score (P = .021) than cats that received placebo. CONCLUSIONS AND CLINICAL IMPORTANCE: Using both a client-specific and a general clinical metrology instrument, owners of cats with DJD were able to detect evident recurrence of clinical signs after withdrawal of active medication than after withdrawal of placebo, and that this study design might be a novel and useful way to circumvent the placebo effect and detect the efficacy of pain-relieving medications.
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Enfermedades de los Gatos/diagnóstico , Osteoartritis/veterinaria , Dimensión del Dolor/veterinaria , Animales , Antiinflamatorios no Esteroideos/uso terapéutico , Enfermedades de los Gatos/tratamiento farmacológico , Gatos , Método Doble Ciego , Femenino , Masculino , Meloxicam , Osteoartritis/complicaciones , Osteoartritis/diagnóstico , Osteoartritis/tratamiento farmacológico , Tiazinas/uso terapéutico , Tiazoles/uso terapéuticoRESUMEN
AIMS/HYPOTHESIS: Toll-like receptor 4 (TLR4) is a receptor for saturated fatty acids (SFAs), global deficiency of which has been shown to protect against inflammation, insulin resistance and atherosclerotic lesion formation. Because macrophages express Tlr4 and are important in insulin resistance and atherosclerotic lesion formation due to their infiltration of white adipose tissue (WAT) and the artery wall, respectively, we hypothesised that deficiency of macrophage TLR4 could protect against these disorders. METHODS: Bone marrow transplantation of agouti, LDL-receptor deficient (A(y)/a; Ldlr (-/-)) mice with marrow from either C57BL/6 or Tlr4 (-/-) mice was performed. Recipient mice with Tlr4 (+/+) marrow (MthetaTLR4(+/+)) or with Tlr4 (-/-) marrow (MthetaTLR4(-/-)) were then placed on one of four diets: (1) low fat; (2) high fat; (3) high fat rich in SFAs (HF(SFA)); and (4) HF(SFA) supplemented with fish oil. RESULTS: There were no differences in body composition or plasma lipids between MthetaTLR4(+/+) and MthetaTLR4(-/-) mice on any of the diets. However, we observed a decrease in some macrophage and inflammatory markers in WAT of female low fat-fed MthetaTLR4(-/-) mice compared with MthetaTLR4(+/+) mice. MthetaTLR4(-/-) mice fed low-fat diet also displayed decreased atherosclerotic lesion area. There were no differences in macrophage accrual in WAT or atherosclerosis between MthetaTLR4(+/+) and MthetaTLR4(-/-) mice fed any of the high-fat diets. Finally, no difference was seen in insulin sensitivity between MthetaTLR4(+/+) and MthetaTLR4(-/-) mice fed the HF(SFA) diet. CONCLUSIONS/INTERPRETATION: These data suggest that under certain dietary conditions, macrophage expression of Tlr4 can be an important mediator of macrophage accumulation in WAT and the artery wall.
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Tejido Adiposo/fisiología , Arterias/fisiología , Macrófagos/fisiología , Músculo Liso Vascular/fisiología , Receptor Toll-Like 4/deficiencia , Animales , Aterosclerosis/sangre , Aterosclerosis/genética , Aterosclerosis/patología , Aterosclerosis/fisiopatología , Peso Corporal , Colesterol/sangre , Colesterol en la Dieta , Cruzamientos Genéticos , Cartilla de ADN , Sacarosa en la Dieta , Femenino , Regulación de la Expresión Génica , Masculino , Ratones , Ratones Endogámicos C57BL , Receptor Toll-Like 4/genéticaRESUMEN
Recently, we have shown that a novel recombinant bispecific single-chain antibody construct (bscCD19 x CD3), induces highly efficacious lymphoma-directed cytotoxicity mediated by unstimulated peripheral T lymphocytes. Functional analysis of bscCD19 x CD3 has so far been exclusively performed with human B lymphoma cell lines and T cells from healthy donors. Here we analysed the properties of bscCD19 x CD3 using primary B cells and autologous T cells from healthy volunteers or patients with B-cell chronic lymphocytic leukaemia (B-CLL). We show that bscCD19 x CD3 induces T-cell-mediated depletion of nonmalignant B cells in all four cases and depletion of primary lymphoma cells in 22 out of 25 cases. This effect could be observed at low effector-to-target (E:T) ratios and in the majority of cases without additional activation of autologous T cells by IL-2. Even in samples derived from patients heavily pretreated with different chemotherapy regimens, strong cytotoxic effects of bscCD19 x CD3 could be observed. The addition of bscCD19 x CD3 to patients' cells resulted in an upregulation of activation-specific cell surface antigens on autologous T cells and elevated levels of CD95 on lymphoma B cells. Although anti-CD95 antibody CH-11 failed to induce apoptosis in lymphoma cells, we provide evidence that B-CLL cell depletion by bscCD3 x CD3 is mediated at least in part by apoptosis via the caspase pathway.
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Anticuerpos Biespecíficos/uso terapéutico , Antígenos CD19/inmunología , Complejo CD3/inmunología , Citotoxicidad Inmunológica , Leucemia Linfocítica Crónica de Células B/terapia , Depleción Linfocítica , Linfocitos T/inmunología , Anciano , Anciano de 80 o más Años , Anexina A5/metabolismo , Especificidad de Anticuerpos , Linfocitos B/inmunología , Inhibidores de Caspasas , Caspasas/metabolismo , Muerte Celular/efectos de los fármacos , División Celular/efectos de los fármacos , Activación Enzimática/efectos de los fármacos , Femenino , Citometría de Flujo , Humanos , Inmunoterapia/métodos , Interleucina-2/metabolismo , Leucemia Linfocítica Crónica de Células B/inmunología , Leucocitos Mononucleares/metabolismo , Masculino , Persona de Mediana Edad , Células Tumorales CultivadasRESUMEN
The osteochondrodysplasias are a heterogeneous group of disorders characterized by abnormal growth and remodeling of cartilage and bone, affecting from 2 to 4.7 per 10,000 individuals. Most osteochondrodysplasias are heritable and many have elaborate patterns of genetic transmission. Affected individuals generally require management by multidisciplinary teams of specialists. In this review, we divide the osteochondrodysplasias into groups based on their genetic relationships, including mutations in various types of collagen, fibroblast growth factor, cartilage oligomeric matrix protein, parathyroid hormone receptor, the diastrophic dysplasia sulfate transporter, enzymes such as steroid sulfatases, transcription factor SOX9, and a cysteine proteinase, cathepsin K. We describe the major osteochondrodysplasias, define their causes and clinical manifestations, and provide the orthopaedic surgeon with an understanding of the underlying molecular defects as well as the anatomical aspects of these disorders.
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Osteocondrodisplasias/genética , Acondroplasia/genética , Adolescente , Arilsulfatasas/genética , Catepsina K , Catepsinas/genética , Niño , Colágeno/genética , Femenino , Ligamiento Genético , Humanos , Recién Nacido , Mutación , Osteocondrodisplasias/diagnóstico por imagen , Osteogénesis Imperfecta/genética , Fenotipo , Estudios Prospectivos , Radiografía , Receptores de Factores de Crecimiento de Fibroblastos/genética , Receptores de Hormona Paratiroidea/genética , Displasia Tanatofórica/genética , Factores de Transcripción/genética , Cromosoma XRESUMEN
Myosin binding protein C (MyBP-C) is one of the major sarcomeric proteins involved in the pathophysiology of familial hypertrophic cardiomyopathy (FHC). The cardiac isoform is tris-phosphorylated by cAMP-dependent protein kinase (cAPK) on beta-adrenergic stimulation at a conserved N-terminal domain (MyBP-C motif), suggesting a role in regulating positive inotropy mediated by cAPK. Recent data show that the MyBP-C motif binds to a conserved segment of sarcomeric myosin S2 in a phosphorylation-regulated way. Given that most MyBP-C mutations that cause FHC are predicted to result in N-terminal fragments of the protein, we investigated the specific effects of the MyBP-C motif on contractility and its modulation by cAPK phosphorylation. The diffusion of proteins into skinned fibers allows the investigation of effects of defined molecular regions of MyBP-C, because the endogenous MyBP-C is associated with few myosin heads. Furthermore, the effect of phosphorylation of cardiac MyBP-C can be studied in a defined unphosphorylated background in skeletal muscle fibers only. Triton skinned fibers were tested for maximal isometric force, Ca(2+)/force relation, rigor force, and stiffness in the absence and presence of the recombinant cardiac MyBP-C motif. The presence of unphosphorylated MyBP-C motif resulted in a significant (1) depression of Ca(2+)-activated maximal force with no effect on dynamic stiffness, (2) increase of the Ca(2+) sensitivity of active force (leftward shift of the Ca(2+)/force relation), (3) increase of maximal rigor force, and (4) an acceleration of rigor force and rigor stiffness development. Tris-phosphorylation of the MyBP-C motif by cAPK abolished these effects. This is the first demonstration that the S2 binding domain of MyBP-C is a modulator of contractility. The anchorage of the MyBP-C motif to the myosin filament is not needed for the observed effects, arguing that the mechanism of MyBP-C regulation is at least partly independent of a "tether," in agreement with a modulation of the head-tail mobility. Soluble fragments occurring in FHC, lacking the spatial specificity, might therefore lead to altered contraction regulation without affecting sarcomere structure directly.
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Proteínas Portadoras/fisiología , Músculo Esquelético/metabolismo , Contracción Miocárdica/fisiología , Miosinas/fisiología , Fragmentos de Péptidos/fisiología , Sarcómeros/metabolismo , Calcio/fisiología , Proteínas Portadoras/metabolismo , Elasticidad , Técnicas Histológicas , Contracción Isométrica/fisiología , Cinética , Fibras Musculares Esqueléticas/fisiología , Fosforilación , Proteínas Recombinantes/metabolismo , SolubilidadRESUMEN
The solution of the crystallographic macromolecular phase problem requires incorporation of heavy atoms into protein crystals. Several 2'-halogenated nucleotides have been reported as potential universal phasing tools for nucleotide binding proteins. However, only limited data are available dealing with the effect of 2'-substitution on recognition by the protein. We have determined equilibrium dissociation constants of 2'-halogenated ATP analogues for the ATP binding proteins UMP/CMP kinase and the molecular chaperone DnaK. Whereas the affinities to UMP/CMP kinase are of the same order of magnitude as for unsubstituted ATP, the affinities to DnaK are drastically decreased to undetectable levels. For 2'-halogenated GTP analogues, the kinetics of interaction were determined for the small GTPases p21ras(Y32W) (fluorescent mutant) and RabS. The rates of association were found to be within about one order of magnitude of those for the nonsubstituted nucleotides, whereas the rates of dissociation were accelerated by factors of approximately 100 (p21ras) or approximately 10(5) (Rab5), and the resulting equilibrium dissociation constants are in the nm or microM range, respectively. The data demonstrate that 2'halo-ATP and -GTP are substrates or ligands for all proteins tested except the chaperone DnaK. Due to the very high affinities of a large number of GTP binding proteins to guanine nucleotides, even a 10(5)-fold decrease in affinity as observed for Rab5 places the equilibrium dissociation constant in the microM range, so that they are still well suited for crystallization of the G-protein:nucleotide complex.
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Adenosina Trifosfato/análogos & derivados , Cristalografía por Rayos X/métodos , Proteínas de Escherichia coli , Guanosina Trifosfato/análogos & derivados , Proteínas/química , Adenosina Trifosfato/síntesis química , Guanosina Trifosfato/síntesis química , Proteínas HSP70 de Choque Térmico/química , Proteínas HSP70 de Choque Térmico/metabolismo , Halógenos , Indicadores y Reactivos , Cinética , Nucleósido-Fosfato Quinasa , Proteínas Proto-Oncogénicas p21(ras)/química , Proteínas Proto-Oncogénicas p21(ras)/metabolismo , Proteínas de Unión al GTP rab5/química , Proteínas de Unión al GTP rab5/metabolismoRESUMEN
Myosin binding protein C is a protein of the myosin filaments of striated muscle which is expressed in isoforms specific for cardiac and skeletal muscle. The cardiac isoform is phosphorylated rapidly upon adrenergic stimulation of myocardium by cAMP-dependent protein kinase, and together with the phosphorylation of troponin-I and phospholamban contributes to the positive inotropy that results from adrenergic stimulation of the heart. Cardiac myosin binding protein C is phosphorylated by cAMP-dependent protein kinase on three sites in a myosin binding protein C specific N-terminal domain which binds to myosin-S2. This interaction with myosin close to the motor domain is likely to mediate the regulatory function of the protein. Cardiac myosin binding protein C is a common target gene of familial hypertrophic cardiomyopathy and most mutations encode N-terminal subfragments of myosin binding protein C. The understanding of the signalling interactions of the N-terminal region is therefore important for understanding the pathophysiology of myosin binding protein C associated cardiomyopathy. We demonstrate here by cosedimentation assays and isothermal titration calorimetry that the myosin-S2 binding properties of the myosin binding protein C motif are abolished by cAMP-dependent protein kinase-mediated tris-phosphorylation, decreasing the S2 affinity from a Kd of approximately 5 microM to undetectable levels. We show that the slow and fast skeletal muscle isoforms are no cAMP-dependent protein kinase substrates and that the S2 interaction of these myosin binding protein C isoforms is therefore constitutively on. The regulation of cardiac contractility by myosin binding protein C therefore appears to be a 'brake-off' mechanism that will free a specific subset of myosin heads from sterical constraints imposed by the binding to the myosin binding protein C motif.
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Proteínas Portadoras/metabolismo , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Miocardio/metabolismo , Subfragmentos de Miosina/metabolismo , Calorimetría , Centrifugación , Fosforilación , Unión Proteica , Isoformas de ProteínasAsunto(s)
Traumatismos Craneocerebrales , Heridas por Arma de Fuego , Traumatismos Craneocerebrales/diagnóstico por imagen , Traumatismos Craneocerebrales/patología , Traumatismos Craneocerebrales/cirugía , Armas de Fuego , Humanos , Masculino , Persona de Mediana Edad , Radiografía , Heridas por Arma de Fuego/diagnóstico por imagen , Heridas por Arma de Fuego/patología , Heridas por Arma de Fuego/cirugíaRESUMEN
The myosin filaments of striated muscle contain a family of enigmatic myosin-binding proteins (MyBP), MyBP-C and MyBP-H. These modular proteins of the intracellular immunoglobulin superfamily contain unique domains near their N termini. The N-terminal domain of cardiac MyBP-C, the MyBP-C motif, contains additional phosphorylation sites and may regulate contraction in a phosphorylation dependent way. In contrast to the C terminus, which binds to the light meromyosin portion of the myosin rod, the interactions of this domain are unknown. We demonstrate that fragments of MyBP-C containing the MyBP-C motif localise to the sarcomeric A-band in cardiomyocytes and isolated myofibrils, without affecting sarcomere structure. The binding site for the MyBP-C motif resides in the N-terminal 126 residues of the S2 segment of the myosin rod. In this region, several mutations in beta-myosin are associated with FHC; however, their molecular implications remained unclear. We show that two representative FHC mutations in beta-myosin S2, R870H and E924K, drastically reduce MyBP-C binding (Kd approximately 60 microM for R870H compared with a Kd of approximately 5 microM for the wild-type) down to undetectable levels (E924K). These mutations do not affect the coiled-coil structure of myosin. We suggest that the regulatory function of MyBP-C is mediated by the interaction with S2, and that mutations in beta-myosin S2 may act by altering the interactions with MyBP-C.