Common Regulatory Pathways Mediate Activity of MicroRNAs Inducing Cardiomyocyte Proliferation.

Loss of functional cardiomyocytes is a major determinant of heart failure after myocardial infarction. Previous high throughput screening studies have identified a few microRNAs (miRNAs) that can induce cardiomyocyte proliferation and stimulate cardiac regeneration in mice. Here, we show that all of the most effective of these miRNAs activate nuclear localization of the master transcriptional cofactor Yes-associated protein (YAP) and induce expression of YAP-responsive genes. In particular, miR-199a-3p directly targets two mRNAs coding for proteins impinging on the Hippo pathway, the upstream YAP inhibitory kinase TAOK1, and the E3 ubiquitin ligase ß-TrCP, which leads to YAP degradation. Several of the pro-proliferative miRNAs (including miR-199a-3p) also inhibit filamentous actin depolymerization by targeting Cofilin2, a process that by itself activates YAP nuclear translocation. Thus, activation of YAP and modulation of the actin cytoskeleton are major components of the pro-proliferative action of miR-199a-3p and other miRNAs that induce cardiomyocyte proliferation.

Paracrine effect of regulatory T cells promotes cardiomyocyte proliferation during pregnancy and after myocardial infarction.

Cardiomyocyte proliferation stops at birth when the heart is no longer exposed to maternal blood and, likewise, to regulatory T cells (Tregs) that are expanded to promote maternal tolerance towards the fetus. Here, we report a role of Tregs in promoting cardiomyocyte proliferation. Treg-conditioned medium promotes cardiomyocyte proliferation, similar to the serum from pregnant animals. Proliferative cardiomyocytes are detected in the heart of pregnant mothers, and Treg depletion during pregnancy decreases both maternal and fetal cardiomyocyte proliferation. Treg depletion after myocardial infarction results in depressed cardiac function, massive inflammation, and scarce collagen deposition. In contrast, Treg injection reduces infarct size, preserves contractility, and increases the number of proliferating cardiomyocytes. The overexpression of six factors secreted by Tregs (Cst7, Tnfsf11, Il33, Fgl2, Matn2, and Igf2) reproduces the therapeutic effect. In conclusion, Tregs promote fetal and maternal cardiomyocyte proliferation in a paracrine manner and improve the outcome of myocardial infarction.

Reversible Notch1 acetylation tunes proliferative signalling in cardiomyocytes.

Aims: The Notch signalling pathway regulates the balance between proliferation and differentiation in several tissues, including the heart. Our previous work has demonstrated that the proliferative potential of neonatal cardiomyocytes relies on Notch1 activity. A deep investigation on the biochemical regulation of the Notch signalling in cardiomyocytes is the focus of the current research. Methods and results: We show that the Notch1 intracellular domain is acetylated in proliferating neonatal rat cardiomyocytes and that acetylation tightly controls the amplitude and duration of Notch signalling. We found that acetylation extends the half-life of the protein, and enhanced its transcriptional activity, therefore counteracting apoptosis and sustaining cardiomyocyte proliferation. Sirt1 acted as a negative modulator of Notch1 signalling; its overexpression in cardiomyocytes reverted Notch acetylation and dampened its stability. A constitutively acetylated fusion protein between Notch1 and the acetyltransferase domain of p300 promoted cardiomyocyte proliferation, which was remarkably sustained over time. Viral vector-mediated expression of this protein enhanced heart regeneration after apical resection in neonatal mice. Conclusion: These results identify the reversible acetylation of Notch1 as a novel mechanism to modulate its signalling in the heart and tune the proliferative potential of cardiomyocytes.

Reversible acetylation regulates vascular endothelial growth factor receptor-2 activity.

The tyrosine kinase receptor vascular endothelial growth factor receptor 2 (VEGFR2) is a key regulator of angiogenesis. Here we show that VEGFR2 is acetylated in endothelial cells both at four lysine residues forming a dense cluster in the kinase insert domain and at a single lysine located in the receptor activation loop. These modifications are under dynamic control of the acetyltransferase p300 and two deacetylases HDAC5 and HDAC6. We demonstrate that VEGFR2 acetylation essentially regulates receptor phosphorylation. In particular, VEGFR2 acetylation significantly alters the kinetics of receptor phosphorylation after ligand binding, allowing receptor phosphorylation and intracellular signaling upon prolonged stimulation with VEGF. Molecular dynamics simulations indicate that acetylation of the lysine in the activation loop contributes to the transition to an open active state, in which tyrosine phosphorylation is favored by better exposure of the kinase target residues. These findings indicate that post-translational modification by acetylation is a critical mechanism that directly affects VEGFR2 function.

Vasculitis paraneoplásica: presentación de 2 casos clínicos / Paraneoplastic vasculitis: presentation of two clinical case

Las vasculitis constituyen un grupo heterogéneo de enfermedades que se definen por un proceso inflamatorio de la pared vascular, con obstrucción y necrosis distal. Son poco frecuentes y pueden ser primarias o asociadas a infecciones, enfermedades sistémicas o excepcionalmente a neoplasias. La asociación de vasculitis y neoplasia es infrecuente; la vasculitis se presentaantes, de forma concomitante o posteriormente al diagnóstico de la neoplasia. Las más frecuentemente asociadas son las de origen hematooncológico y luego, en menor medida, los tumores sólidos. Las manifestaciones cutáneas por afectación de “pequeño vaso” son las más habituales, y dentro de ellas las leucocitoclásticas. Se presentan 2 casos clínicos excepcionales de vasculitis paraneoplásicas, el primer caso se trata de una paciente de 57 años con lesiones vasculíticas de pequeño vaso asociadas a cáncer broncopulmonar y el segundo caso se trata de una paciente de 79 años con diagnóstico previo de glioblastoma encefálico de alto grado y lesiones en miembros inferiores con características de vasculitis de pequeño vaso.

Vasculitis constitutes a heterogeneous group of diseases that are defined by an inflammatory process of the vascular wall, with occlusion and distal necrosis. They are rare and may be primary or secondary infections, systemic disease or exceptionally to neoplasic disease. The association of vasculitis and neoplasia is uncommon; vasculitis occurs before, concomitantly or subsequently to the diagnosis of neoplasia. The most frequently associated are the hemato-oncology and then to a lesser extent the solid tumors. Cutaneous manifestations by affectation of “small vessel” are the most common. We present 2 exceptional clinical cases of vasculitis associated with cancer, the first case is about a 57 years old patient with lesions of small vessel associated with bronchopulmonary cancer and the second case is a 79 years old patient diagnosed with brain glioblastoma of high-grade and injuries in lower limbs with characteristics of small vessel vasculitis.

Síndrome de Kearns-Sayre, presentación de un caso clínico / Kearns-Sayre Syndrome

El síndrome de Kearns Sayre es una mitocondriopatía caracterizada por disfunciones multiorgánicas que clásicamente se desarrolla antes de los veinte años de edad. Esta rara enfermedad fue descrita en 1958 por Thomas P. Kearns y George P. Sayre a través del reporte de un caso que representaba la triada clínica de oftalmoplejia externa, retinopatía pigmentaria y bloqueos de la conducción cardíaca; siendo esta última alteración la que determina el pronóstico. Aún no se cuenta con un tratamiento curativo para esta enfermedad. En este artículo presentamos el caso clínico de una paciente de 39 años a la que se realizó el diagnóstico de Kearns-Sayre.

Frecuencia de lactancia materna exclusiva, factores asociados y relación con el desarrollo antropométricoy patologías en una población delactantes atendida en ASSBASALUD ESE, Manizales (Colombia) 2010-2011 / Exclusive breastfeeding frequency, associated factors and relationship with an-thropometric development and pathologies in a population of infants treated at Assbasalud ESE, Manizales (Colombia) 2010-2011

Objetivo: Describir la frecuencia, factores asociados, y efectos de la lactancia materna sobre variables antropométricas, y patologías de los lactantes nacidos en ASSBASALUD E.S.E Manizales (Colombia). Materiales y métodos: Estudio de corte transversal, con una población objeto de 1261 niños que nacieron en ASSBASALUD E.S.E. sede Clínica San Cayetano entre 2010 y 2011. Resultados: El 30,9% de las madres practicaron lactancia materna exclusiva, destete precoz en el 64,7% de los casos, el 99,8% de las madres iniciaron lactancia materna con un promedio de duración de 3,81 meses; el inicio de la alimentación complementaria se dio en promedio a los 3,72 meses, el 99,6% de las gestantes recibieron educación en lactancia materna, con promedio de controles de crecimiento y desarrollo durante los 6 primeros meses de 1,86. Se observó que los niños que recibieron lactancia materna exclusiva tenían una ganancia de peso (8,9% más 1° control) y talla (3% más 1° control) mayor que aquellos que no la recibían. No se encontró relación significativa entre la lactancia materna exclusiva y protección frente a enfermedades respiratorias, diarrea, alergias o malnutrición. Conclusiones: La lactancia materna exclusiva favorece un crecimiento pondoestatural adecuado en aquellos lactantes a quienes se les brinda en formaadecuada. La pobre adherencia a la lactancia materna exclusiva puede relacionarse con métodos inapropiados de educación sobre el tema o a fallas en el seguimiento y apoyo permanente que complemente la información...

GCN5-dependent acetylation of HIV-1 integrase enhances viral integration.

BACKGROUND: An essential event during the replication cycle of HIV-1 is the integration of the reverse transcribed viral DNA into the host cellular genome. Our former report revealed that HIV-1 integrase (IN), the enzyme that catalyzes the integration reaction, is positively regulated by acetylation mediated by the histone acetyltransferase (HAT) p300. RESULTS: In this study we demonstrate that another cellular HAT, GCN5, acetylates IN leading to enhanced 3'-end processing and strand transfer activities. GCN5 participates in the integration step of HIV-1 replication cycle as demonstrated by the reduced infectivity, due to inefficient provirus formation, in GCN5 knockdown cells. Within the C-terminal domain of IN, four lysines (K258, K264, K266, and K273) are targeted by GCN5 acetylation, three of which (K264, K266, and K273) are also modified by p300. Replication analysis of HIV-1 clones carrying substitutions at the IN lysines acetylated by both GCN5 and p300, or exclusively by GCN5, demonstrated that these residues are required for efficient viral integration. In addition, a comparative analysis of the replication efficiencies of the IN triple- and quadruple-mutant viruses revealed that even though the lysines targeted by both GCN5 and p300 are required for efficient virus integration, the residue exclusively modified by GCN5 (K258) does not affect this process. CONCLUSIONS: The results presented here further demonstrate the relevance of IN post-translational modification by acetylation, which results from the catalytic activities of multiple HATs during the viral replication cycle. Finally, this study contributes to clarifying the recent debate raised on the role of IN acetylated lysines during HIV-1 infection.

Concerted action of cellular JNK and Pin1 restricts HIV-1 genome integration to activated CD4+ T lymphocytes.

Long-standing evidence indicates that quiescent human peripheral blood T lymphocytes (PBLs) do not support efficient HIV infection. In resting PBLs, reverse transcription of viral RNA takes longer than in activated cells, partially because formation of the late products of reverse transcription is decreased by RNA binding by apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G (APOBEC3G). In a subsequent step, integration of the viral complementary DNA that is eventually formed is markedly impaired. Here we show that cellular c-Jun N-terminal kinase (JNK), an enzyme that is not expressed in resting CD4+ T cells, regulates permissiveness to HIV-1 infection, and we unravel a new, sequential post-translational pathway of protein modification that regulates viral DNA integration. We found that, in activated T lymphocytes, viral integrase, which mediates HIV-1 cDNA integration into the host cell genome, is phosphorylated by JNK on a highly conserved serine residue in its core domain. Phosphorylated integrase, in turn, becomes a substrate for the cellular peptidyl prolyl-isomerase enzyme Pin1, which catalyzes a conformational modification of integrase. These concerted activities increase integrase stability and are required for efficient HIV-1 integration and infection. Lack of these modifications restricts viral infection in nonactivated, primary CD4+ T lymphocytes.

Acetylation of HIV-1 integrase by p300 regulates viral integration.

Integration of HIV-1 into the human genome, which is catalyzed by the viral protein integrase (IN), preferentially occurs near transcriptionally active genes. Here we show that p300, a cellular acetyltransferase that regulates chromatin conformation through the acetylation of histones, also acetylates IN and controls its activity. We have found that p300 directly binds IN both in vitro and in the cells, as also specifically demonstrated by fluorescence resonance energy transfer technique analysis. This interaction results in the acetylation of three specific lysines (K264, K266, K273) in the carboxy-terminus of IN, a region that is required for DNA binding. Acetylation increases IN affinity to DNA, and promotes the DNA strand transfer activity of the protein. In the context of the viral replication cycle, point mutations in the IN acetylation sites abolish virus replication by specifically impairing its integration capacity. This is the first demonstration that HIV-1 IN activity is specifically regulated by post-translational modification.

Regulation of E2F-1 after DNA damage by p300-mediated acetylation and ubiquitination.

Here we report a novel, noncompetitive mechanism that links acetylation and ubiquitination, in which the association of transcription factor E2F-1 with the cellular coactivator and acetyltransferase p300 determines its acetylation and subsequent ubiquitination. By using an antibody specifically recognizing the acetylated form of E2F-1 (AcE2F-1), we found that, after DNA damage, AcE2F-1 accumulates in the cells in a time-dependent manner, and that acetylation is increased by the expression of p300. Remarkably, the same DNA damaging conditions also induce the accumulation of ubiquitinated E2F-1, an event that is again markedly stimulated by p300 overexpression. The effects of p300 on E2F-1 ubiquitination require the integrity of the HAT domain of p300 and of the three acetylated lysines in E2F-1. Of note, p300-induced E2F-1 ubiquitination does not depend on the p45Skp2 E3 ligase, since it does not extend to other p45Skp2 targets and also occurs with an E2F-1 mutant devoid of the p45Skp2-binding domain but still retaining the acetylated region. Finally, p300-induced E2F-1 ubiquitination is not influenced by RB.