RESUMEN
Objective: To investigate the demographic characteristics and clinical influencing factors which associates with the occurrence probability of persistent or intermittent hypoviremia (LLV) in patients with chronic hepatitis B (CHB) treated with nucleos(t)ide analogues (NAs). Methods: A single-center retrospective analysis was performed on patients with CHB who received outpatient NAs therapy for≥48 ± 2 weeks. According to the serum hepatitis B virus (HBV) DNA load at 48±2 weeks treatment, the study groups were divided into LLV (HBV DNA < 20 IU/ml and < 2 000 IU/ml) and MVR group (sustained virological response, HBV DNA < 20 IU/ml). Demographic characteristics and clinical data at the start of NAs treatment (considered as baseline) were retrospectively collected for both patient groups. The differences in the reduction of HBV DNA load during treatment was compared between the two groups. Correlation and multivariate analysis were further conducted to analyze the associated factors influencing the LLV occurrence. Statistical analysis was performed using the independent samples t-test, c2 test, Spearman analysis, multivariate logistic regression analysis, or area under the receiver operating characteristic curve. Results: A total of 509 cases were enrolled, with 189 and 320 in the LLV and MVR groups, respectively. Compared to patients with MVR group at baseline: (1) the demographics characteristics of patients showed that LLV group was younger in age (39.1 years, P = 0.027), had a stronger family history (60.3%, P = 0.001), 61.9% received ETV treatment, and higher proportion of compensated cirrhosis (20.6%, P = 0.025) at baseline; (2) the serum virological characteristics of patients showed that LLV group had higher HBV DNA load, qHBsAg level, qHBeAg level, HBeAg positive rate, and the proportion of genotype C HBV infection but decreased HBV DNA during treatment (P < 0.001) at baseline; (3) the biochemical characteristics of patients showed that LLV group had lower serum ALT levels (P = 0.007) at baseline; (4) the noninvasive fibrosis markers of patients showed that LLV group were characterized by high aspartate aminotransferase platelet ratio index (APRI) (P = 0.02) and FIB-4 (P = 0.027) at baseline. HBV DNA, qHBsAg and qHBeAg were positively correlated with LLV occurrence (r = 0.559, 0.344, 0.435, respectively), while age and HBV DNA reduction were negatively correlated (r = -0.098, -0.876, respectively). Logistic regression analysis showed that ETV treatment history, high HBV DNA load at baseline, high qHBsAg level, high qHBeAg level, HBeAg positive, low ALT and HBV DNA level were independent risk factors for patients with CHB who developed LLV with NAs treatment. Multivariate prediction model had a good predictive value for LLV occurrence [AUC 0.922 (95%CI: 0.897 ~ 0.946)]. Conclusion: In this study, 37.1% of CHB patients treated with first-line NAs has LLV. The formation of LLV is influenced by various factors. HBeAg positivity, genotype C HBV infection, high baseline HBV DNA load, high qHBsAg level, high qHBeAg level, high APRI or FIB-4 value, low baseline ALT level, reduced HBV DNA during treatment, concomitant family history, metabolic liver disease history, and age < 40 years old are potential risk factors for developing LLV in patients with CHB during the therapeutic process.
Asunto(s)
Hepatitis B Crónica , Humanos , Adulto , Hepatitis B Crónica/complicaciones , Estudios Retrospectivos , Estudios Transversales , Antígenos e de la Hepatitis B , ADN Viral , Antivirales/uso terapéutico , Virus de la Hepatitis B/genética , DemografíaRESUMEN
Objective: To analyze the correlation between indocyanine green retention rate at 15 minutes (ICG-R15) and modified Scheuer score in liver tissues of patients with hepatitis B e antigen-positive/negative chronic hepatitis B (CHB), and further explore the indocyanine green clearance test (ICGCT) applied value in judging the progress of CHB-related liver disease. Methods: 407 HBeAg (+) / HBeAg (-) CHB inpatients with normal or slightly elevated serum alanine aminotransferase (ALT) [< 2 times the upper limit of normal (ULN)] and modified Scheuer score were collected, and divided into mild liver disease group (M group, 131 cases, modified Scheuer score < G2S2) and progressive liver disease group (A group, 276 cases, modified Scheuer score≥G2 and / or S2). Furthermore, the groups were sub-divided into HBeAg (+) - M group, HBeAg (-) - M group, HBeAg (+) - A group and HBeAg (-) - A group. The correlation between ICG-R15 and modified Scheuer score was analyzed retrospectively. The data were analyzed by SPSS 24.0 software. Results: Basic clinical characteristics: Among the 407 CHB cases with normal or mildly elevated serum ALT, 171 were HBeAg(+) CHB and 236 were HBeAg(-) CHB. The baseline mean serum HBV DNA was higher in HBeAg(+) CHB patients [(6.06 ± 1.95) log10IU/ml] than HBeAg(-) CHB patients [(3.60±1.37)log10IU/ml (P = 0.000)]. Included patients ICG-R15 detection characteristics: (1) The baseline mean value of ICG-R15 was not statistically significant between the two groups of HBeAg(+) CHB and HBeAg(-) CHB, and was basically within the normal range (< 10%); (2) Comparison of ICG-R15 baseline mean value among the subgroups showed that the patients in the HBeAg(+)-A group/HBeAg(-)-A group were higher than the HBeAg(+)-M group/HBeAg(-)-M group patients, and the difference was statistically significant (P = 0.013/P = 0.000). Included patients' correlation analysis between ICG-R15 and modified Scheuer score: (1) ICG-R15 and modified Scheuer score had shown weak positive correlation with inflammatory activity grade (g) in HBeAg (+) / HBeAg (-) CHB (r = 0.237, P = 0.002); r = 0.244, P = 0.000); (2) There was a weak positive correlation between ICG-R15 and fibrosis stage (s) in HBeAg (+) / HBeAg (-) CHB (r = 0. 254, P = 0; r = 0.225, P = 0.001). Included patients ICG-R15 predictive value for the severity of liver histological progression: when the cut-off value of ICG-R15 was 5.1%, the area under the receiver operating characteristic curve from M group to A group was 0.601 (P = 0.001) for predicting HBeAg (+) / HBeAg (-) CHB patients. Conclusion: ICG-R15 is positively correlated with the modified Scheuer score of liver tissue in HBeAg (+)/HBeAg (-) CHB patients with normal or slightly elevated ALT. In addition, when the cut-off value of ICG-R15 was 10%, it could not accurately reflect the effective hepatocyte reserve function of HBeAg (+) / HBeAg (-) CHB patients with normal or slightly elevated ALT. Importantly, when the cut-off value of ICG-R15 is 4.0% ~ 5.0%, it may have predictive value for liver disease progression to modified Scheuer score ≥ G2 and / or ≥S2 in HBeAg (+) / HBeAg (-) CHB patients with normal or slightly elevated ALT.
Asunto(s)
Antígenos e de la Hepatitis B , Hepatitis B Crónica , Alanina Transaminasa , ADN Viral , Virus de la Hepatitis B/genética , Humanos , Verde de Indocianina , Estudios RetrospectivosRESUMEN
ABSTRACT: Methamphetamine ï¼MAMPï¼ is a kind of amphetamine-type stimulants ï¼ATSï¼ which contains one chiral carbon atom in its structure. Therefore a pair of enantiomers, S-ï¼+ï¼-MAMP and R-ï¼-ï¼-MAMP exist. R type and S type methamphetamines possess similar physicochemical properties, but has largely different pharmacological and toxic effects. S-ï¼+ï¼-MAMP is the main component of addictive drug "Ice" at present, seriously affecting human health and public safety. The separation analysis and mechanism of toxic effects discussions on MAMP are the current research focuses. This paper reviews the research progress of separation analysis methods and toxic effects of methamphetamine enantiomers to provide reference for forensic study and forensic practice.
Asunto(s)
Metanfetamina/química , Estimulantes del Sistema Nervioso Central , Humanos , Estereoisomerismo , Detección de Abuso de SustanciasAsunto(s)
Factor VIII/administración & dosificación , Hemofilia A/tratamiento farmacológico , Hemostáticos/uso terapéutico , Anciano , Animales , Femenino , Hemofilia A/sangre , Hemostasis , Humanos , Masculino , Persona de Mediana Edad , Proteínas Recombinantes/administración & dosificación , PorcinosRESUMEN
This study explores the correlation between molybdenum target (mo-target) mammography signs and pathological prognostic factors of breast cancer. We selected 320 breast cancer patients who were treated between January 2014 and January 2016; using single-factor and multiple-factor logistic regression method, we made correlation analysis on their clinical features, pathological features and mo-target mammography signs. Among mo-target mammography signs, lumps accompanied with calcification and blurry edge were associated with high histologic grades; lumps accompanied with calcification and clear edge were associated with Ki-67 positive; compared with the patients who had lumps with non-stellate edges, positive rates of estrogen receptor (ER) and progesterone receptor (PR) were significantly higher for the patients who had lumps with stellate edges (p < 0.01), while positive rate of human epidermal growth factor receptor-2 (HER-2) and tumor proliferative activity were significantly lower (p < 0.05, p < 0.01). According to the study, we can conclude that mo-target mammography signs mainly include lumps and calcification. Mo-target mammography can improve the accuracy of diagnosis and reduce misdiagnosis or missed diagnosis. Part of mo-target mammography signs are associated with clinical pathology prognostic factors; by grasping the relation, breast cancer patient conditions are expected to be relieved.
Asunto(s)
Neoplasias de la Mama/diagnóstico por imagen , Neoplasias de la Mama/patología , Mamografía , Molibdeno , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Persona de Mediana Edad , PronósticoRESUMEN
INTRODUCTION: Acquired haemophilia (AH) is a rare disorder caused by autoantibodies against factor VIII. AIM: The Hemostasis & Thrombosis Research Society (HTRS) Registry was used to monitor the safety of recombinant FVII (rFVIIa). This study aims to report data from the HTRS Registry regarding safety and efficacy of rFVIIa for haemostatic management of surgeries and other invasive procedures in patients with AH. METHODS: For each rFVIIa-treated procedure, the initial dose, total dose, average infused dose, number of doses and treatment duration were calculated. Efficacy was assessed on a 4-point scale. RESULTS: Of 166 registered patients with AH, 37 patients underwent 58 procedures [30 (51%) rFVIIa-treated]. The median (range) age of all patients undergoing procedures was 70 (13-93) years; for rFVIIa-treated patients, 74 (28-89) years. Approximately 67% (39/58) of all procedures were elective. Overall, the most common procedures were endoscopy (12) and central venous access device (10); rFVIIa was used preoperatively (11), postoperatively (13) and during six follow-up procedures during ongoing postoperative rFVIIa treatment. The median (range) initial dose was 90.0 (44-187) µg kg(-1) preoperatively and 106.0 (56-270) µg kg(-1) postoperatively. For rFVIIa-treated episodes with a reported outcome, 20 (91%) were rated excellent/good or no additional agents used and 2 (9%) were rated as poor/ineffective requiring a switch to another bypassing agent. No thromboembolic events were reported. CONCLUSIONS: Adequate haemostasis was provided for 91% of rFVIIa-treated procedures at doses largely conforming to the package insert. No safety concerns were reported.
Asunto(s)
Bases de Datos Factuales , Factor VIIa/uso terapéutico , Hemofilia A/tratamiento farmacológico , Hemofilia A/cirugía , Sistema de Registros , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Factor VIIa/efectos adversos , Femenino , Hemofilia A/epidemiología , Humanos , Masculino , Persona de Mediana Edad , Proteínas Recombinantes/efectos adversos , Proteínas Recombinantes/uso terapéutico , Seguridad , Estados Unidos , Adulto JovenRESUMEN
This study explores the value of 64-layer spinal computed tomography (CT) in diagnosing hepatocellular carcinoma (HCC) through performing dynamic contrast-enhanced scans. The study includes analysis of enhancement presentation of HCC in dynamic contrast-enhanced scan performed by multislice spinal CT (MSCT), comparison of detection rate and positive predictive value of neoplastic foci in subdivided arterial phases and portal venous phases, optimization of optimal scanning scheme for diagnosing HCC and discussion of the value of quantitative indexes such as T-D curve, maximum enhancement rate and clearance rate in diagnosing and identifying HCC. A total of 61 lesions were detected in 40 patients with HCC who were selected from the First Peoples Hospital, Jining, Shandong, China. Density difference was observed with statistical significance between the solid part of tumor and normal liver in different periods after CT scan and enhanced scan (H = 45.208, P less than 0.01), and difference in the late arterial phase was the most obvious; enhanced peak value mostly appeared in the late arterial phase. In terms of lesion detection rate, the difference of HCC detection rate was statistically significant in early, middle and late arterial phase and early and late portal vein phases (χ² = 32.910, P = 0.001) and the rate was the highest in the late arterial phase (78.689%). Lesions were divided into 3 cm or less group (small HCC) and over 3 cm group based on the maximum parameter. Detection rate of the late arterial phase was the highest, 85% (3 cm or less) and 75.61% (over 3 cm), respectively. When lesions with high density in arterial phase and/or low density in portal venous phase were considered as positive, and moreover, those confirmed clinically or pathologically were as true positive, we found positive predictive value of the over 3 cm group reached 100% in all phases, but that of 3 cm or less group was the highest (100%) in early and late portal venous phases. Among four scanning schemes involving early, middle and late arterial phases, detection rate of the early and late arterial phases and three arterial phases were consistent, reaching the highest value (3 cm or less group: 90%; the 3 cm over group: 78.049%). This study confirmed that the late arterial phase was the best time to detect abundant blood supplied HCC. The scanning scheme involving double arterial phases (early and late), late portal venous phase and stable phase which can help improve detection rate and correct diagnosis rate of HCC, was thought to be the most effective. Using dynamic enhanced CT examination in the diagnosis of HCC is meaningful both in qualitative and quantitative diagnosis. T-D curve, in particular, can intuitively and objectively reflect enhanced characteristics of HCC, and can be used to make a preliminary diagnosis of some atypical liver cancers.
Asunto(s)
Carcinoma Hepatocelular/irrigación sanguínea , Neoplasias Hepáticas/irrigación sanguínea , Tomografía Computarizada Multidetector , Neovascularización Patológica/diagnóstico por imagen , Intensificación de Imagen Radiográfica , Adulto , Anciano , Anciano de 80 o más Años , Carcinoma Hepatocelular/diagnóstico por imagen , Femenino , Humanos , Neoplasias Hepáticas/diagnóstico por imagen , Masculino , Persona de Mediana EdadRESUMEN
BACKGROUND: The role of immunosuppression in the management of patients with congenital hemophilia and inhibitors is uncertain. The use of rituximab has been limited to case reports and case series. In most reports, rituximab was used as second-line or third-line treatment following failure of conventional immune tolerance induction therapy, and more commonly in pediatric patients. OBJECTIVES: The objective of this study was to describe our experience with rituximab for the eradication of factor VIII inhibitors in adult patients with non-severe hemophilia A. PATIENTS: We retrospectively reviewed the medical records of adult patients with non-severe hemophilia A and a diagnosis of FVIII inhibitor treated with rituximab (four weekly doses of 375 mg m(-2) ) as first-line treatment at our hemophilia center. RESULTS: We identified nine consecutive adult patients with hemophilia A (moderate, n = 5; mild, n = 4) at our institution between 2000 and 2013, with a median age of 54 years (range, 24-77 years) at the time of inhibitor diagnosis. No patient received concomitant immune tolerance induction therapy. All nine patients had successful eradication of FVIII inhibitors. The median time from the first dose of rituximab to a clinical response was 95 days (range, 12-278 days). The median follow-up was 56 months (range, 13-139 months). Following inhibitor eradication, eight patients were rechallenged with FVIII concentrates. Two patients developed inhibitor recurrence associated with surgery. CONCLUSION: This case series demonstrates that rituximab is a useful first-line treatment to achieve sustained inhibitor eradication in adult patients with non-severe hemophilia A.
Asunto(s)
Anticuerpos Monoclonales de Origen Murino/uso terapéutico , Anticuerpos/sangre , Coagulantes/uso terapéutico , Factor VIII/uso terapéutico , Hemofilia A/tratamiento farmacológico , Inmunosupresores/uso terapéutico , Adulto , Anciano , Anticuerpos Monoclonales de Origen Murino/efectos adversos , Coagulantes/inmunología , Factor VIII/inmunología , Femenino , Hemofilia A/sangre , Hemofilia A/diagnóstico , Hemofilia A/inmunología , Humanos , Inmunosupresores/efectos adversos , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Rituximab , Índice de Severidad de la Enfermedad , Factores de Tiempo , Resultado del Tratamiento , Adulto JovenRESUMEN
BACKGROUND AND OBJECTIVES: The adverse reactions in combination of angiotensin-converting enzyme inhibitors (ACEIs) and Ang II receptor blockers (ARBs) were severer than that in monotherapy for patients with nephropathy. The effect of candesartan on pharmacokinetics of enalaprilat in nephrotic rats was investigated to make references for the clinical therapy in patients with nephropathy to avoid related adverse effects. MATERIALS AND METHODS: Nephrotic rats were prepared by adriamycin injection. Control group and one nephrotic group received enalapril alone, another nephrotic group received enalapril and candesartan simultaneously. Blood samples were drawn at time points after a single oral administration. The concentration of enalaprilat was determined using LC-MS/MS. RESULTS: Compared with control group and nephrotic group received enalapril alone respectively, Tmax of enalaprilat in nephrotic group received both enalapril and candesartan cilexetil prolonged about 21.43% and 6.224%, respectively; AUC(0-t) increased by 185.3% and 60.63%, respectively; Cmax increased by 219.4% and 56.64%, respectively; t1/2 increased by 163.7% and 30.05%, respectively; CL/F reduced by 65.12% and 40.78%, respectively. There were no significant differences of the V1/F of enalaprilat between three groups. The CL/F and t1/2 of enalaprilat showed significant correlations with serum creatinine (Scr) respectively (r = -0.7502; r = 0.5626). DISCUSSION: The combination with candesartan in nephrotic rats significantly changed the pharmacokinetics of enalaprilat, showing increased accumulation and decreased elimination. In view of these findings, we should lower dosage and prolong dosing interval for nephrotic patients in the combination of enalapril and candesartan.
Asunto(s)
Bloqueadores del Receptor Tipo 1 de Angiotensina II/farmacología , Inhibidores de la Enzima Convertidora de Angiotensina/farmacocinética , Bencimidazoles/farmacología , Enalaprilato/farmacocinética , Nefrosis/tratamiento farmacológico , Tetrazoles/farmacología , Animales , Compuestos de Bifenilo , Interacciones Farmacológicas , Femenino , Masculino , Nefrosis/metabolismo , Ratas , Ratas Sprague-DawleyAsunto(s)
Anticuerpos Monoclonales de Origen Murino/uso terapéutico , Hemofilia A/tratamiento farmacológico , Terapia de Inmunosupresión/métodos , Anciano , Anciano de 80 o más Años , Autoanticuerpos , Femenino , Hemofilia A/inmunología , Humanos , Masculino , Persona de Mediana Edad , Rituximab , Resultado del Tratamiento , Adulto JovenRESUMEN
At the moment of hemostasis, the platelet must be able to reorganize its cytoskeleton through a complexly orchestrated signaling cascade that is regulated, in part, by polyphosphoinositides. In the past 6 years, evidence has accumulated that PH domains bind these polyphosphoinositides and play a role in cytoskeletal changes. Work to date implies that the amino-terminal PH domain of pleckstrin induces a shift of F-actin towards the cell cortex and participates in the production of lamellipodia. The effect of pleckstrin on actin is, in turn, regulated by the phosphorylation of pleckstrin by PKC. Evidence also suggests that PH domains of Dbl family exchange factors play a role in the PI3K-stimulated activation of Rac. It is likely that the PH domains of pleckstrin, as well as the PH domains of the Dbl family of exchange factors, are only a few examples of PH domains that are able to influence the organization of the cytoskeleton.
Asunto(s)
Proteínas Sanguíneas/fisiología , Proteínas de Caenorhabditis elegans , Citoesqueleto/fisiología , Fosfoproteínas , Activación Plaquetaria/fisiología , Transducción de Señal , Actinas/fisiología , Secuencias de Aminoácidos , Animales , Proteínas Sanguíneas/química , Proteínas de Unión al GTP , Humanos , Fosfolípidos/fisiología , Fosforilación , Estructura Terciaria de Proteína , Proteínas RGSRESUMEN
In hematopoietic cells, the signals initiated by activation of the phosphoinositide 3-kinase (PI3K) family have been implicated in cell proliferation and survival, membrane and cytoskeletal reorganization, chemotaxis, and the neutrophil respiratory burst. Of the four isoforms of human PI3K that phosphorylate phosphatidylinositol 4, 5-bisphosphate, only p110gamma (or PI3Kgamma) is associated with the regulatory subunit, p101, and is stimulated by G protein betagamma heterodimers. We performed immunolocalization of transfected p110gamma in HepG2 cells and found that, under resting conditions, p110gamma was present in a diffuse cytoplasmic pattern, but translocated to the cell nucleus after serum stimulation. Serum-stimulated p110gamma translocation was inhibited by pertussis toxin and could also be induced by overexpression of Gbetagamma in the absence of serum. In addition, we found that deletion of the amino-terminal 33 residues of p110gamma had no effect on association with p101 or on its agonist-regulated translocation, but truncation of the amino-terminal 82 residues yielded a p110gamma variant that did not associate with p101 and was constitutively localized in the nucleus. This finding implies that the intracellular localization of p110gamma is regulated by p101 as well as Gbetagamma. The effect of PI3Kgamma in the nucleus is an area of active investigation.
Asunto(s)
Núcleo Celular/enzimología , Proteínas de Unión al GTP/metabolismo , Toxina del Pertussis , Fosfatidilinositol 3-Quinasas/química , Fosfatidilinositol 3-Quinasas/metabolismo , Factores de Virulencia de Bordetella/farmacología , Secuencia de Aminoácidos , Animales , Células COS , Carcinoma Hepatocelular , Clonación Molecular , Medio de Cultivo Libre de Suero , Epítopos/química , Humanos , Neoplasias Hepáticas , Fosfatidilinositol 3-Quinasas/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Transducción de Señal , Transfección , Células Tumorales CultivadasRESUMEN
Pleckstrin homology (PH) domains are present in over one hundred signaling molecules, where they are thought to mediate membrane targeting by binding to phosphoinositides. They were initially defined at the NH(2) and COOH termini of the molecule, pleckstrin, a major substrate for protein kinase C in platelets. We have previously reported that pleckstrin associates with the plasma membrane, where it induces the formation of villous and ruffled structures from the surface of transfected cells (1). We now show that overexpression of pleckstrin results in reorganization of the actin cytoskeleton. This pleckstrin effect is regulated by its phosphorylation and requires the NH(2)-terminal, but not the COOH-terminal, PH domain. Overexpression of the NH(2)-terminal PH domain alone of pleckstrin is sufficient to induce the cytoskeletal effects. Pleckstrin-induced actin rearrangements are not inhibited by pharmacologic inhibition of phosphatidylinositol 3-kinase, nor are they blocked by co-expression of a dominant negative phosphatidylinositol 3-kinase. The cytoskeletal effects of pleckstrin can be blocked by co-expression of a dominant negative Rac1 variant, but not wild-type Rac and not a dominant negative Cdc42 variant. These data indicate that the NH(2)-terminal PH domain of pleckstrin induces reorganization of the actin cytoskeleton via a pathway dependent on Rac but independent of Cdc42 and phosphatidylinositol 3-kinase.
Asunto(s)
Proteínas Sanguíneas/metabolismo , Citoesqueleto/metabolismo , Fosfoproteínas , Proteínas de Unión al GTP rac/metabolismo , Actinas/metabolismo , Animales , Células COS , Fosfatidilinositol 3-Quinasas/metabolismo , Fosforilación , Proteína de Unión al GTP cdc42/metabolismoAsunto(s)
Resistencia a la Proteína C Activada/genética , Resistencia a la Proteína C Activada/metabolismo , Factor V/genética , Mutación Puntual , Oclusión de la Arteria Retiniana/genética , Oclusión de la Vena Retiniana/metabolismo , Factor V/metabolismo , Humanos , Proteína C/metabolismo , Oclusión de la Arteria Retiniana/metabolismoRESUMEN
Reorganization of the actin cytoskeleton is an early cellular response to a variety of extracellular signals. Dissection of pathways leading to actin rearrangement has focused largely on those initiated by growth factor receptors or integrins, although stimulation of G protein-coupled receptors also leads to cytoskeletal changes. In transfected Cos-7SH cells, activation of the chemoattractant formyl peptide receptor induces cortical actin polymerization and a decrease in the number of central actin bundles. In this report, we show that cytoskeletal reorganization can be transduced by G protein betagamma heterodimers (Gbetagamma), phosphoinositide 3-kinase gamma (PI3-Kgamma), a guanosine exchange factor (GEF) for Rac, and Rac. Expression of inactive variants of either PI3-Kgamma, the Rac GEF Vav, or Rac blocked the actin rearrangement. Neither wortmannin nor LY294002, pharmacologic inhibitors of PI3-K, could inhibit the actin rearrangement induced by a constitutively active Rac. The inhibition of cytoskeletal reorganization by the dominant negative Vav variants could be rescued by coexpression of a constitutively active form of Rac. In contrast, a Vav variant with its pleckstrin homology (PH) domain missing constitutively induced JNK activation and led to cytoskeletal reorganization, even without stimulation by PI3-Kgamma. This suggests that the PH domain of Vav controls the guanosine exchange activity of Vav, perhaps by a mechanism regulated by D3 phosphoinositides generated by PI3-K. Taken together, these findings delineate a pathway leading from activation of a G protein-coupled receptor to actin reorganization which sequentially involves Gbetagamma, PI3-Kgamma, a Rac GEF, and Rac.
Asunto(s)
Actinas/fisiología , Proteínas Bacterianas , Proteínas de Unión al GTP/metabolismo , Fosfatidilinositol 3-Quinasas/metabolismo , Receptores de Superficie Celular/metabolismo , Animales , Células COS , Proteínas Portadoras/metabolismo , Proteínas de Ciclo Celular/metabolismo , Factores Quimiotácticos , Citoesqueleto/fisiología , Guanosina , Células HL-60 , Humanos , Péptidos y Proteínas de Señalización Intracelular , Proteína de Unión al GTP cdc42 , Proteínas de Unión al GTP racRESUMEN
Pleckstrin homology (PH) domains are sequences of approximately 100 amino acids that form "modules" that have been proposed to facilitate protein/protein or protein/lipid interactions. Pleckstrin, first described as a substrate for protein kinase C in platelets and leukocytes, is composed of two PH domains, one at each end of the molecule, flanking an intervening sequence of 147 residues. Evidence is accumulating to support the hypothesis that PH domains are structural motifs that target molecules to membranes, perhaps through interactions with G betagamma or phosphatidylinositol 4,5-bisphosphate (PIP2), two putative PH domain ligands. In the present studies, we show that pleckstrin associates with membranes in human platelets. We further demonstrate that, in transfected Cos-1 cells, pleckstrin associates with peripheral membrane ruffles and dorsal membrane projections. This association depends on phosphorylation of pleckstrin and requires the presence of its NH2-terminal, but not its COOH-terminal, PH domain. Moreover, PH domains from other molecules cannot effectively substitute for pleckstrin's NH2-terminal PH domain in directing membrane localization. Lastly, we show that wild-type pleckstrin actually promotes the formation of membrane projections from the dorsal surface of transfected cells, and that this morphologic change is similarly PH domain dependent. Since we have shown previously that pleckstrin-mediated inhibition of PIP2 metabolism by phospholipase C or phosphatidylinositol 3-kinase also requires pleckstrin phosphorylation and an intact NH2-terminal PH domain, these results suggest that: (a) pleckstrin's NH2-terminal PH domain may regulate pleckstrin's activity by targeting it to specific areas within the cell membrane; and (b) pleckstrin may affect membrane structure, perhaps via interactions with PIP2 and/or other membrane-bound ligands.