Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 49
Filtrar
Más filtros

Banco de datos
Tipo del documento
Intervalo de año de publicación
1.
Cell ; 184(3): 675-688.e19, 2021 02 04.
Artículo en Inglés | MEDLINE | ID: mdl-33421369

RESUMEN

CRISPR-Cas systems provide prokaryotes with acquired immunity against viruses and plasmids, but how these systems are regulated to prevent autoimmunity is poorly understood. Here, we show that in the S. pyogenes CRISPR-Cas system, a long-form transactivating CRISPR RNA (tracr-L) folds into a natural single guide that directs Cas9 to transcriptionally repress its own promoter (Pcas). Further, we demonstrate that Pcas serves as a critical regulatory node. De-repression causes a dramatic 3,000-fold increase in immunization rates against viruses; however, heightened immunity comes at the cost of increased autoimmune toxicity. Using bioinformatic analyses, we provide evidence that tracrRNA-mediated autoregulation is widespread in type II-A CRISPR-Cas systems. Collectively, we unveil a new paradigm for the intrinsic regulation of CRISPR-Cas systems by natural single guides, which may facilitate the frequent horizontal transfer of these systems into new hosts that have not yet evolved their own regulatory strategies.


Asunto(s)
Proteína 9 Asociada a CRISPR/metabolismo , Sistemas CRISPR-Cas/genética , Expresión Génica , Homeostasis/genética , ARN Guía de Kinetoplastida/genética , Autoinmunidad/genética , Secuencia de Bases , Secuencia Conservada , Regulación hacia Abajo/genética , Modelos Genéticos , Mutación/genética , Operón/genética , Regiones Promotoras Genéticas/genética , Streptococcus pyogenes/genética , Estrés Fisiológico/genética , Transcripción Genética , Activación Transcripcional/genética
2.
Mol Microbiol ; 2024 Apr 25.
Artículo en Inglés | MEDLINE | ID: mdl-38664995

RESUMEN

Regulation of bacterial transcription is a complex and multi-faceted phenomenon that is critical for growth and adaptation. Proteins in the CarD_CdnL_TRCF family are widespread, often essential, regulators of transcription of genes required for growth and metabolic homeostasis. Research in the last decade has described the mechanistic and structural bases of CarD-CdnL-mediated regulation of transcription initiation. More recently, studies in a range of bacteria have begun to elucidate the physiological roles of CarD-CdnL proteins as well as mechanisms by which these proteins, themselves, are regulated. A theme has emerged wherein regulation of CarD-CdnL proteins is central to bacterial adaptation to stress and/or changing environmental conditions.

3.
J Gen Intern Med ; 38(4): 1038-1045, 2023 03.
Artículo en Inglés | MEDLINE | ID: mdl-36441366

RESUMEN

The problem of unaffordable prescription medications in the United States is complex and can result in poor patient adherence to therapy, worse clinical outcomes, and high costs to the healthcare system. While providers are aware of the financial burden of healthcare for patients, there is a lack of actionable price transparency at the point of prescribing. Real-time prescription benefit (RTPB) tools are new electronic clinical decision support tools that retrieve patient- and medication-specific out-of-pocket cost information and display it to clinicians at the point of prescribing. The rise in US healthcare costs has been a major driver for efforts to increase medication price transparency, and mandates from the Centers for Medicare & Medicaid Services for Medicare Part D sponsors to adopt RTPB tools may spur integration of such tools into electronic health records. Although multiple factors affect the implementation of RTPB tools, there is limited evidence on outcomes. Further research will be needed to understand the impact of RTPB tools on end results such as prescribing behavior, out-of-pocket medication costs for patients, and adherence to pharmacologic treatment. We review the terminology and concepts essential in understanding the landscape of RTPB tools, implementation considerations, barriers to adoption, and directions for future research that will be important to patients, prescribers, health systems, and insurers.


Asunto(s)
Medicare Part D , Medicamentos bajo Prescripción , Anciano , Humanos , Estados Unidos , Prescripciones , Gastos en Salud
4.
PLoS Genet ; 16(1): e1008591, 2020 01.
Artículo en Inglés | MEDLINE | ID: mdl-31961855

RESUMEN

Bacterial growth and division require regulated synthesis of the macromolecules used to expand and replicate components of the cell. Transcription of housekeeping genes required for metabolic homeostasis and cell proliferation is guided by the sigma factor σ70. The conserved CarD-like transcriptional regulator, CdnL, associates with promoter regions where σ70 localizes and stabilizes the open promoter complex. However, the contributions of CdnL to metabolic homeostasis and bacterial physiology are not well understood. Here, we show that Caulobacter crescentus cells lacking CdnL have severe morphological and growth defects. Specifically, ΔcdnL cells grow slowly in both rich and defined media, and are wider, more curved, and have shorter stalks than WT cells. These defects arise from transcriptional downregulation of most major classes of biosynthetic genes, leading to significant decreases in the levels of critical metabolites, including pyruvate, α-ketoglutarate, ATP, NAD+, UDP-N-acetyl-glucosamine, lipid II, and purine and pyrimidine precursors. Notably, we find that ΔcdnL cells are glutamate auxotrophs, and ΔcdnL is synthetic lethal with other genetic perturbations that limit glutamate synthesis and lipid II production. Our findings implicate CdnL as a direct and indirect regulator of genes required for metabolic homeostasis that impacts morphogenesis through availability of lipid II and other metabolites.


Asunto(s)
Proteínas Bacterianas/metabolismo , Caulobacter crescentus/genética , Homeostasis , Factores de Transcripción/metabolismo , Proteínas Bacterianas/genética , Caulobacter crescentus/metabolismo , Caulobacter crescentus/fisiología , División Celular , Secuencia Conservada , Metaboloma , Factores de Transcripción/genética
5.
J Infect Dis ; 221(2): 267-275, 2020 01 02.
Artículo en Inglés | MEDLINE | ID: mdl-31504652

RESUMEN

Staphylococcus aureus is a common pathogen causing infections in humans with various degrees of severity, with pneumonia being one of the most severe infections. In as much as staphylococcal pneumonia is a disease driven in large part by α-hemolysin (Hla) and Panton-Valentine leukocidin (PVL), we evaluated whether active immunization with attenuated forms of Hla (HlaH35L/H48L) alone, PVL components (LukS-PVT28F/K97A/S209A and LukF-PVK102A) alone, or combination of all 3 toxoids could prevent lethal challenge in a rabbit model of necrotizing pneumonia caused by the USA300 community-associated methicillin-resistant S. aureus (MRSA). Rabbits vaccinated with Hla toxoid alone or PVL components alone were only partially protected against lethal pneumonia, whereas those vaccinated with all 3 toxoids had 100% protection against lethality. Vaccine-mediated protection correlated with induction of polyclonal antibody response that neutralized not only α-hemolysin and PVL, but also other related toxins, produced by USA300 and other epidemic MRSA clones.


Asunto(s)
Toxinas Bacterianas/inmunología , Exotoxinas/inmunología , Proteínas Hemolisinas/inmunología , Leucocidinas/inmunología , Neumonía Necrotizante/prevención & control , Neumonía Estafilocócica/prevención & control , Animales , Toxinas Bacterianas/administración & dosificación , Modelos Animales de Enfermedad , Exotoxinas/administración & dosificación , Proteínas Hemolisinas/administración & dosificación , Humanos , Leucocidinas/administración & dosificación , Staphylococcus aureus Resistente a Meticilina , Neumonía Necrotizante/inmunología , Neumonía Estafilocócica/inmunología , Conejos , Vacunación
6.
Artículo en Inglés | MEDLINE | ID: mdl-31160288

RESUMEN

Pseudomonas aeruginosa is a challenge for clinicians due to increasing drug resistance and dwindling treatment options. We report on the activity of MEDI3902, an antibody targeting type 3 secretion protein PcrV and Psl exopolysaccharide, in rabbit bloodstream and lung infection models. MEDI3902 prophylaxis or treatment was protective in both acute models and exhibited enhanced activity when combined with a subtherapeutic dose of meropenem. These findings further support MEDI3902 for the prevention or treatment of serious P. aeruginosa infections.


Asunto(s)
Anticuerpos Biespecíficos/uso terapéutico , Neumonía/tratamiento farmacológico , Infecciones por Pseudomonas/tratamiento farmacológico , Pseudomonas aeruginosa/patogenicidad , Animales , Bacteriemia/tratamiento farmacológico , Bacteriemia/microbiología , Bacteriemia/terapia , Inmunoterapia , Meropenem/uso terapéutico , Neumonía/microbiología , Neumonía/terapia , Infecciones por Pseudomonas/microbiología , Infecciones por Pseudomonas/terapia , Pseudomonas aeruginosa/efectos de los fármacos , Conejos , Resultado del Tratamiento
7.
Biochem Cell Biol ; 95(1): 76-81, 2017 02.
Artículo en Inglés | MEDLINE | ID: mdl-28165291

RESUMEN

Lactoferrin (LF) is a protein with antimicrobial activity, which is conferred in part by 2 regions contained in its N-terminal lobe. These regions have been used to develop the following synthetic peptides: lactoferricin17-30, lactoferrampin265-284, and LF chimera (a fusion of lactoferricin17-30 and lactoferrampin265-284). We have reported that these LF peptides have antibacterial activity against several pathogenic bacteria; however, the exact mechanism of action has not been established. Here, we report the effects of LF peptides on the viability of enteroaggregative Escherichia coli (EAEC) and the ability of these peptides to penetrate into the bacteria cytoplasm. The viability of EAEC treated with LF peptides was determined via enumeration of colony-forming units, and the binding and internalization of the LF peptides was followed via immunogold labeling and electron microscopy. Treatment of EAEC with 20 and 40 µmol/L LF peptides reduced bacterial growth compared with untreated bacteria. Initially the peptides associated with the plasma membrane, but after 5 to 30 min of incubation, the peptides were found in the cytoplasm. Remarkably, bacteria treated with LF chimera developed cytosolic electron-dense structures that contained the antimicrobial peptide. Our results suggest that the antibacterial mechanism of LF peptides on EAEC involves their interaction with and penetration into the bacteria.


Asunto(s)
Antibacterianos/farmacología , Péptidos de Penetración Celular/farmacología , Infecciones por Escherichia coli/tratamiento farmacológico , Escherichia coli/efectos de los fármacos , Lactoferrina/farmacología , Escherichia coli/aislamiento & purificación , Infecciones por Escherichia coli/microbiología , Humanos
8.
Am J Physiol Heart Circ Physiol ; 308(11): H1323-35, 2015 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-25840830

RESUMEN

Coronary collateral growth (CCG) is impaired in metabolic syndrome. microRNA-21 (miR-21) is a proproliferative and antiapoptotic miR, which we showed to be elevated in metabolic syndrome. Here we investigate whether impaired CCG in metabolic syndrome involved miR-21-mediated aberrant apoptosis. Normal Sprague-Dawley (SD) and metabolic syndrome [J. C. Russel (JCR)] rats underwent transient, repetitive coronary artery occlusion [repetitive ischemia (RI)]. Antiapoptotic Bcl-2, phospho-Bad, and Bcl-2/Bax dimers were increased on days 6 and 9 RI, and proapoptotic Bax and Bax/Bax dimers and cytochrome-c release concurrently decreased in JCR versus SD rats. Active caspases were decreased in JCR versus SD rats (~50%). Neutrophils increased transiently on day 3 RI in the collateral-dependent zone of SD rats but remained elevated in JCR rats, paralleling miR-21 expression. miR-21 downregulation by anti-miR-21 induced neutrophil apoptosis and decreased Bcl-2 and Bcl-2/Bax dimers (~75%) while increasing Bax/Bax dimers, cytochrome-c release, and caspase activation (~70, 400, and 400%). Anti-miR-21 also improved CCG in JCR rats (~60%). Preventing neutrophil infiltration with blocking antibodies resulted in equivalent CCG recovery, confirming a major role for deregulated neutrophil apoptosis in CCG impairment. Neutrophil and miR-21-dependent CCG inhibition was in significant part mediated by increased oxidative stress. We conclude that neutrophil apoptosis is integral to normal CCG and that inappropriate prolonged miR-21-mediated survival of neutrophils plays a major role in impaired CCG, in part via oxidative stress generation.


Asunto(s)
Apoptosis , Oclusión Coronaria/metabolismo , Vasos Coronarios/metabolismo , Síndrome Metabólico/metabolismo , MicroARNs/metabolismo , Neutrófilos/metabolismo , Animales , Células Cultivadas , Vasos Coronarios/patología , Vasos Coronarios/fisiopatología , Citocromos c/metabolismo , Masculino , MicroARNs/genética , Estrés Oxidativo , Proteínas Proto-Oncogénicas c-bcl-2/genética , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Ratas , Ratas Sprague-Dawley , Ratas Zucker , Regulación hacia Arriba , Proteína X Asociada a bcl-2/genética , Proteína X Asociada a bcl-2/metabolismo
9.
FASEB J ; 28(9): 4088-99, 2014 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-24903275

RESUMEN

Inadequate cell proliferation is considered a major causative factor for impaired coronary collateral growth (CCG). Proangiogenic growth factors (GFs) stimulate cell proliferation, but their administration does not promote CCG in patients. These GFs are increased in patients with metabolic syndrome and in animal models, where CCG is impaired. Here, we investigated whether excessive cell proliferation underlies impaired CCG in metabolic syndrome. Normal [Sprague-Dawley (SD)] and metabolic syndrome [James C. Russell (JCR)] rats underwent repetitive ischemia (RI; transient, repetitive coronary artery occlusion and myocardial ischemia). We have shown that CCG was maximal at d 9 of RI in SD rats but did not occur in JCR rats. The increase in cell proliferation (PCNA, Ki-67, cyclin A, phospho- cdc2, p21Waf, p27Kip) was transient (∼4-fold, d 3 RI) in SD rats but greater and sustained in JCR rats (∼8- to 6-fold, d 3-9 RI). In JCR rats, this was associated with increased and sustained miR-21 expression and accumulation of proliferating synthetic vascular smooth muscle cells in the lumen of small arterioles, which failed to undergo outward expansion. Administration of anti-miR-21 blocked RI-induced cell proliferation and significantly improved CCG in JCR rats (∼60%). miR-21-dependent excessive cell proliferation in the later stages of collateral remodeling correlates with impaired CCG in metabolic syndrome.


Asunto(s)
Proliferación Celular/genética , Circulación Colateral/fisiología , Enfermedad de la Arteria Coronaria/prevención & control , Circulación Coronaria/fisiología , Síndrome Metabólico/fisiopatología , MicroARNs/metabolismo , Músculo Liso Vascular/citología , Isquemia Miocárdica/prevención & control , Animales , Apoptosis , Western Blotting , Células Cultivadas , Enfermedad de la Arteria Coronaria/metabolismo , Enfermedad de la Arteria Coronaria/patología , Modelos Animales de Enfermedad , Técnicas para Inmunoenzimas , Masculino , MicroARNs/genética , Músculo Liso Vascular/metabolismo , Isquemia Miocárdica/metabolismo , Isquemia Miocárdica/patología , Neovascularización Patológica/prevención & control , ARN Mensajero/genética , Ratas , Ratas Sprague-Dawley , Reacción en Cadena en Tiempo Real de la Polimerasa , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa
10.
Arterioscler Thromb Vasc Biol ; 33(4): 727-36, 2013 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-23393394

RESUMEN

OBJECTIVE: Transient, repetitive occlusion stimulates coronary collateral growth (CCG) in normal animals. Vascular smooth muscle cells (VSMCs) switch to synthetic phenotype early in CCG, then return to contractile phenotype. CCG is impaired in the metabolic syndrome. We determined whether impaired CCG was attributable to aberrant VSMC phenotypic modulation by miR-145-mediated mechanisms, and whether restoration of physiological miR-145 levels in metabolic syndrome (JCR rat) improved CCG. APPROACH AND RESULTS: CCG was stimulated by transient, repetitive left anterior descending artery occlusion and evaluated after 9 days by coronary blood flow measurements (microspheres). miR-145 was delivered to JCR VSMCs via adenoviral vector (miR-145-Adv). In JCR rats, miR-145 was decreased late in CCG (≈ 2-fold day 6; ≈ 4-fold day 9 versus SD), which correlated with decreased expression of smooth muscle-specific contractile proteins (≈ 5-fold day 6; ≈ 10-fold day 9 versus SD), indicative of VSMCs' failure to return to the contractile phenotype late in CCG. miR-145 expression in JCR rats (miR-145-Adv) on days 6 to 9 of CCG completely restored VSMCs contractile phenotype and CCG (collateral/normal zone flow ratio was 0.93 ± 0.09 JCR+miR-145-Adv versus 0.12 ± 0.02 JCR versus 0.87 ± 0.02 SD). CONCLUSIONS: Restoration of VSMC contractile phenotype through miR-145 delivery is a highly promising intervention for restoration of CCG in the metabolic syndrome.


Asunto(s)
Circulación Colateral , Circulación Coronaria , Terapia Genética , Síndrome Metabólico/terapia , MicroARNs/metabolismo , Músculo Liso Vascular/metabolismo , Miocitos del Músculo Liso/metabolismo , Vasoconstricción , Adenoviridae/genética , Animales , Vasos Coronarios/metabolismo , Vasos Coronarios/fisiopatología , Modelos Animales de Enfermedad , Técnicas de Transferencia de Gen , Vectores Genéticos , Masculino , Síndrome Metabólico/genética , Síndrome Metabólico/metabolismo , Síndrome Metabólico/patología , Síndrome Metabólico/fisiopatología , Proteínas Musculares/biosíntesis , Músculo Liso Vascular/patología , Músculo Liso Vascular/fisiopatología , Miocitos del Músculo Liso/patología , Fenotipo , Ratas , Ratas Endogámicas SHR , Ratas Sprague-Dawley , Ratas Zucker , Factores de Tiempo
11.
Arterioscler Thromb Vasc Biol ; 33(6): 1339-49, 2013 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-23599440

RESUMEN

OBJECTIVE: We have previously shown that transient coronary artery occlusion stimulated coronary collateral growth (CCG) in healthy (Sprague Dawley) but not in metabolic syndrome (JCR:LA-cp [JCR] ) rats. Here, we sought to determine whether matrix metalloproteinases (MMPs) negatively regulate CCG in the metabolic syndrome via release of endostatin and angiostatin. APPROACH AND RESULTS: Rats underwent transient, repetitive left anterior descending occlusion and resultant myocardial ischemia (RI) for 0 to 10 days. CCG was measured in the collateral-dependent and normal zones using microspheres, MMP activation by Western blot, and endostatin and angiostatin by ELISA on days 0, 3, 6, 9, or 10 of RI. Endostatin and angiostatin were increased in JCR but not in Sprague Dawley rats on days 6 and 9 of RI. Increased endostatin and angiostatin correlated with increased MMP12 (≈ 4-fold) activation in JCR but not in Sprague Dawley rats on days 6 and 9 of RI. Inhibition of MMP12 in JCR rats nearly completely blocked endostatin (≈ 85%) and angiostatin (≈ 90%) generation and significantly improved CCG (collateral-dependent zone flow was ≈ 66% of normal zone flow versus ≈ 12% for JCR RI). CONCLUSIONS: Compromised CCG in the metabolic syndrome is, in large part, because of increased MMP12 activation and consequent increased generation of endostatin and angiostatin, which inhibits late-stage collateral remodeling.


Asunto(s)
Angiostatinas/metabolismo , Circulación Colateral/fisiología , Oclusión Coronaria/metabolismo , Endostatinas/metabolismo , Metaloproteinasa 12 de la Matriz/metabolismo , Síndrome Metabólico/metabolismo , Angiostatinas/análisis , Animales , Western Blotting , Circulación Coronaria/fisiología , Oclusión Coronaria/fisiopatología , Modelos Animales de Enfermedad , Endostatinas/análisis , Ensayo de Inmunoadsorción Enzimática , Síndrome Metabólico/fisiopatología , Distribución Aleatoria , Ratas , Ratas Sprague-Dawley , Valores de Referencia
12.
J Pediatr Gastroenterol Nutr ; 58(3): 387-90, 2014 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-24553473

RESUMEN

OBJECTIVE: Chronic blood transfusion therapy reduces clinical events in children with sickle cell anemia but increases risk for an iron-related liver injury. Liver biopsy is the gold standard technique for quantifying liver iron content (LIC) and evaluating liver pathology. Ferritin, liver enzymes, and R2* magnetic resonance imaging of the liver are obtained as surrogate markers. In this study we compared surrogate markers with the gold standard, liver biopsy, in assessing liver histology. METHODS: We conducted a retrospective review of 259 liver biopsies in 109 children with sickle cell anemia on chronic transfusion therapy and chelation therapy during a 9-year period at a single center. Liver pathology was compared with LIC, ferritin, and alanine aminotransferase. RESULTS: Ferritin correlates with LIC (r = 0.74, P < 0.001), although there is a broad range of ferritin values for a given LIC. Furthermore, patients with a high LIC (≥7 mg Fe/g dry weight) demonstrated significantly higher ferritin as compared to the patients with lower LIC <7 (P < 0.001). Periportal/portal inflammation also showed a significant relation. There was no significance when comparing ferritin and lobular inflammation or ferritin and alanine aminotransferase. When evaluating LIC in relation to fibrosis, the present study revealed that there was only a significant correlation with severe fibrosis (F = 36, P < 0.001). CONCLUSIONS: The results suggest that although correlations exist among ferritin and LIC and severe fibrosis and LIC, caution should be taken when they are used in isolation. Liver biopsy provides important pathologic information that cannot be obtained through surrogate markers.


Asunto(s)
Anemia de Células Falciformes/terapia , Ferritinas/metabolismo , Hierro/metabolismo , Cirrosis Hepática/etiología , Hígado/patología , Reacción a la Transfusión , Adolescente , Adulto , Alanina Transaminasa/sangre , Anemia de Células Falciformes/sangre , Anemia de Células Falciformes/metabolismo , Anemia de Células Falciformes/patología , Biomarcadores/sangre , Biomarcadores/metabolismo , Biopsia , Terapia por Quelación , Niño , Preescolar , Humanos , Inflamación/metabolismo , Hígado/metabolismo , Cirrosis Hepática/sangre , Cirrosis Hepática/metabolismo , Estudios Retrospectivos , Índice de Severidad de la Enfermedad , Adulto Joven
13.
Hered Cancer Clin Pract ; 12(1): 19, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-25225577

RESUMEN

BACKGROUND: PALB2 has emerged as a breast cancer susceptibility gene. Mutations in PALB2 have been identified in almost all breast cancer populations studied to date, but the rarity of these mutations and lack of information regarding their penetrance makes genetic counseling for these families challenging. We studied BRCA1/2 -negative breast and/or ovarian cancer families to a) assess the contribution of PALB2 mutations in this series and b) identify clinical, pathological and family history characteristics that might make PALB2 screening more efficient. METHODS: The coding region of the PALB2 gene was analyzed in 175 probands with family histories of breast and/or ovarian cancer ascertained from a single Canadian institution in Eastern Ontario. RESULTS: We identified 2 probands with PALB2 mutations that are known or strongly considered to be pathogenic and 3 probands with missense mutations that are possibly pathogenic. One of the identified truncating mutations [c.3113G > A (p.Gly1000_Trp1038del - major product)], has been previously described while the other four mutations [c.3507_3508delTC (p.H1170Ffs*19), c.1846G > C (p.D616H), c.3418 T > G (p.W1140G), c.3287A > G (p.N1096S)] have not been previously reported. Loss of heterozygosity was detected in two breast tumors from one c.3507_3508delTC mutation carrier but not in other available tumors from that family or in tumors from carriers of other mutations. CONCLUSIONS: PALB2 mutation screening identifies a small, but significant number of mutations in BRCA1/2 -negative breast and/or ovarian cancer families. We show that mutations are more likely to be found in families with three or more breast cancers as well as other BRCA2-related cancers. In our cohort, both clearly pathogenic mutations were identified in premenopausal breast cancer cases (2/77, 2.6%). Testing should be preferentially offered to affected women from such families.

14.
Mol Biol Cell ; 35(7): ar97, 2024 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-38758654

RESUMEN

Bacterial cell division is crucial for replication and requires careful coordination via proteins collectively called the divisome. The tubulin-like GTPase FtsZ is the master regulator of this process and serves to recruit downstream divisome proteins and regulate their activities. Upon assembling at mid-cell, FtsZ exhibits treadmilling motion driven by GTP binding and hydrolysis. Treadmilling is proposed to play roles in Z-ring condensation and in distribution and regulation of peptidoglycan (PG) cell wall enzymes. FtsZ polymer superstructure and dynamics are central to its function, yet their regulation is incompletely understood. We addressed these gaps in knowledge by evaluating the contribution of GTPase activity to FtsZ's function in vitro and in Caulobacter crescentus cells. We observed that a lethal mutation that abrogates FtsZ GTP hydrolysis impacts FtsZ dynamics and Z-ring positioning, but not constriction. Aberrant Z-ring positioning was due to insensitivity to the FtsZ regulator MipZ when GTPase activity is reduced. Z-ring mislocalization resulted in DNA damage, likely due to constriction over the nucleoid. Collectively, our results indicate that GTP hydrolysis serves primarily to position the Z-ring at mid-cell in Caulobacter. Proper Z-ring localization is required for effective coordination with chromosome segregation to prevent DNA damage and ensure successful cell division.


Asunto(s)
Proteínas Bacterianas , Caulobacter crescentus , División Celular , Proteínas del Citoesqueleto , GTP Fosfohidrolasas , Guanosina Trifosfato , Caulobacter crescentus/metabolismo , Caulobacter crescentus/genética , Proteínas Bacterianas/metabolismo , Proteínas del Citoesqueleto/metabolismo , Guanosina Trifosfato/metabolismo , GTP Fosfohidrolasas/metabolismo , División Celular/fisiología , Hidrólisis , Mutación
15.
PNAS Nexus ; 3(4): pgae154, 2024 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-38650860

RESUMEN

In response to nutrient deprivation, bacteria activate a conserved stress response pathway called the stringent response (SR). During SR activation in Caulobacter crescentus, SpoT synthesizes the secondary messengers guanosine 5'-diphosphate 3'-diphosphate and guanosine 5'-triphosphate 3'-diphosphate (collectively known as (p)ppGpp), which affect transcription by binding RNA polymerase (RNAP) to down-regulate anabolic genes. (p)ppGpp also impacts the expression of anabolic genes by controlling the levels and activities of their transcriptional regulators. In Caulobacter, a major regulator of anabolic genes is the transcription factor CdnL. If and how CdnL is controlled during the SR and why that might be functionally important are unclear. In this study, we show that CdnL is down-regulated posttranslationally during starvation in a manner dependent on SpoT and the ClpXP protease. Artificial stabilization of CdnL during starvation causes misregulation of ribosomal and metabolic genes. Functionally, we demonstrate that the combined action of SR transcriptional regulators and CdnL clearance allows for rapid adaptation to nutrient repletion. Moreover, cells that are unable to clear CdnL during starvation are outcompeted by wild-type cells when subjected to nutrient fluctuations. We hypothesize that clearance of CdnL during the SR, in conjunction with direct binding of (p)ppGpp and DksA to RNAP, is critical for altering the transcriptome in order to permit cell survival during nutrient stress.

16.
Am J Manag Care ; 30(2): e32-e38, 2024 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-38381546

RESUMEN

OBJECTIVES: Transitions of care are pivotal, vulnerable times as patients are discharged from the hospital. Telephonic care coordination is standard care, but labor intensive. We implemented a patient postdischarge digital engagement (PDDE) program to scale coordination. We hypothesized that PDDE could reduce readmissions for low-risk patients and supplement care coordination for medium- and high-risk patients. STUDY DESIGN: Pragmatic, stepped-wedge cluster randomization trial with 5 implementation waves based upon primary care clinic region. METHODS: All inpatient hospital discharges between March 2020 and November 2020 were stratified by readmission risk. Low-risk patients were offered access to PDDE, and moderate-risk and high-risk patients were offered access to PDDE and care coordination. Readmission was defined as an unplanned inpatient admission within 30 days from discharge. An intention-to-treat primary analysis was conducted using mixed-effects logistic regression clustering for wave; a treatment-on-the-treated analysis was also conducted to assess the impact among program users. RESULTS: A total of 5490 patient discharges were examined (2735 control; 2755 intervention); 1949 patients were high risk, 2032 were medium risk, and 1509 were low risk. PDDE intervention did not significantly affect readmission among low-risk (95% CI, -0.23 to 0.90; P = .23), medium-risk (95% CI, -0.14 to 0.60; P = .21), and high-risk (95% CI, -0.32 to 0.64; P = .48) groups after adjustment for time and patient factors. In a treatment-on-the-treated analysis, among patients who activated the PDDE program, readmission was also similar among the low-, medium-, and high-risk cohorts. CONCLUSIONS: Our study expanded resource-limited care coordination by offering low-risk patients a service they were unable to receive previously while having no impact on readmission. PDDE efficiently provided additional touch points between patients and providers.


Asunto(s)
Alta del Paciente , Readmisión del Paciente , Humanos , Cuidados Posteriores , Hospitalización , Pacientes Internos
17.
Am J Med Genet A ; 161A(6): 1425-31, 2013 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-23613284

RESUMEN

Mutations in the cyclin-dependent kinase inhibitor-2A (CDKN2A) gene have been associated with a number of malignancies, most notably cutaneous malignant melanoma (CMM). Mutations in this gene have also been associated with pancreatic cancer and breast cancer, as well as astrocytomas and other nervous system tumors (NST). Among NST, rare solitary internal neurofibromas have been reported, but multiple cutaneous neurofibromas have only been described in two families. In the first family, the affected individuals all carried a heterozygous G>C mutation at the splice acceptor site of intron 1 resulting in skipping of CDKN2A exon 2, while the affected individuals in the second family had a deletion that encompassed the whole CDKN2A/CDKN2B/ANRIL locus. We now report on a proposita presenting with multiple biopsy-proven cutaneous neurofibromas and a solitary spinal neurofibroma found to have a deletion of 14 nucleotides in exon 2 of CDKN2A, providing further evidence that p14, p16, and/or ANRIL are specifically involved in the pathogenesis of neurofibromas as a feature of the familial atypical multiple malignant melanoma spectrum.


Asunto(s)
Inhibidor p16 de la Quinasa Dependiente de Ciclina/genética , Melanoma/genética , Neurofibromatosis/genética , Neoplasias Cutáneas/genética , Neoplasias de la Columna Vertebral/genética , Adulto , Secuencia de Bases , Diagnóstico Diferencial , Femenino , Humanos , Melanoma/diagnóstico , Neurofibromatosis/diagnóstico , Linaje , Eliminación de Secuencia , Neoplasias Cutáneas/diagnóstico , Neoplasias de la Columna Vertebral/diagnóstico , Melanoma Cutáneo Maligno
18.
J Med Genet ; 49(7): 473-9, 2012 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-22791840

RESUMEN

BACKGROUND: Holoprosencephaly (HPE), the most common malformation of the human forebrain, may result from mutations in over 12 genes. Sonic Hedgehog (SHH) was the first such gene discovered; mutations in SHH remain the most common cause of non-chromosomal HPE. The severity spectrum is wide, ranging from incompatibility with extrauterine life to isolated midline facial differences. OBJECTIVE: To characterise genetic and clinical findings in individuals with SHH mutations. METHODS: Through the National Institutes of Health and collaborating centres, DNA from approximately 2000 individuals with HPE spectrum disorders were analysed for SHH variations. Clinical details were examined and combined with published cases. RESULTS: This study describes 396 individuals, representing 157 unrelated kindreds, with SHH mutations; 141 (36%) have not been previously reported. SHH mutations more commonly resulted in non-HPE (64%) than frank HPE (36%), and non-HPE was significantly more common in patients with SHH than in those with mutations in the other common HPE related genes (p<0.0001 compared to ZIC2 or SIX3). Individuals with truncating mutations were significantly more likely to have frank HPE than those with non-truncating mutations (49% vs 35%, respectively; p=0.012). While mutations were significantly more common in the N-terminus than in the C-terminus (including accounting for the relative size of the coding regions, p=0.00010), no specific genotype-phenotype correlations could be established regarding mutation location. CONCLUSIONS: SHH mutations overall result in milder disease than mutations in other common HPE related genes. HPE is more frequent in individuals with truncating mutations, but clinical predictions at the individual level remain elusive.


Asunto(s)
Estudios de Asociación Genética/métodos , Proteínas Hedgehog/genética , Holoprosencefalia/genética , Mutación , Femenino , Genotipo , Proteínas Hedgehog/metabolismo , Humanos , Masculino , Prosencéfalo/patología
19.
Artículo en Inglés | MEDLINE | ID: mdl-37220550

RESUMEN

This research addresses an identified need to further understand digital literacies (DL) and whether undergraduate students view DL as being important in their lives and in their learning. Using a cross-sectional survey sent to a stratified random sample of 2500 undergraduates representative of the overall student population at a medium-sized Canadian undergraduate university (survey response rate of 19.8%, N = 496), we explored the relationships between social media and digital literacies, particularly in different disciplinary contexts. We also explored the ways in which students report using social media in their university learning, showing that students value social media for collaboration, discussion, information finding and sharing, and practise activities related to their learning. Additionally, we examined the importance students place on DL, and how they perceive and rate their own abilities with digital literacies across three domains: procedural and technical, cognitive, and sociocultural. Findings illustrate an observable gap between the high importance that students place on digital literacies (including DL for social media) in their learning and their lives and the lack of coverage students reported receiving about these topics in their undergraduate education. Based on the study's findings, we discuss the specific ways that those in the higher education community can address this gap by engaging with and fostering development of digital literacies within specific disciplinary and professional contexts, and in interdisciplinary or transdisciplinary learning settings across the curriculum.

20.
PLoS One ; 18(11): e0291306, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-38015905

RESUMEN

OBJECTIVE: To conduct a scoping review that systematically examines the body of research on social media in undergraduate teaching and learning in order to identify key issues, trends, gaps, and needs. Our objectives include determining what methods have been commonly used to study social media in undergraduate teaching and learning, and to synthesise insights from published research findings within the fields of higher education, educational technology, and the scholarship of teaching and learning. INTRODUCTION: The use of social media technologies in post-secondary environments has been increasing over time, and especially following the shift to remote teaching and learning during the COVID-19 pandemic, this growth has continued. This review addresses a need to analyse and understand the body of research on the use of social media across undergraduate contexts for teaching and learning. INCLUSION CRITERIA: This scoping review includes peer-reviewed journal articles on social media in an undergraduate teaching or learning context published at any time, in English. In addition to including concepts and terms related to social media broadly, based on global social media usage, we include within our search the most commonly used social media platforms. We excluded items from the grey literature (such as reports, dissertations, and theses), and studies that focus on groups outside of the undergraduate population of interest (e.g., in elementary, secondary, or graduate settings, etc.). METHODS: Systematic searching will be conducted in relevant subject and multidisciplinary databases: Education Database, Education Research Complete, ERIC, British Education Index, Australian Education Index, Academic Search Complete, and Scopus. Records will be deduplicated and screened using Covidence software, with each record independently reviewed by two researchers in both rounds, screening titles and abstracts in the first round, and full-text of articles in the second. Researchers will meet to discuss discrepancies and make decisions using a consensus model, and a third researcher will be independently tasked with resolving any conflicts. Data extraction will also use two independent researchers to review each article.


Asunto(s)
Medios de Comunicación Sociales , Humanos , Pandemias , Australia , Aprendizaje , Estudiantes , Literatura de Revisión como Asunto
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA