The genus Burkholderia includes over 60 species isolated from a wide range of environmental niches and can be tentatively divided into two major species clusters. The first cluster includes pathogens such as Burkholderia glumae, B. pseudomallei, and B. mallei and 17 well-studied species of the Burkholderia cepacia complex. The other recently established cluster comprises at least 29 nonpathogenic species, which in most cases have been found to be associated with plants. It was previously established that Burkholderia kururiensis, a member of the latter cluster, possesses an N-acyl homoserine lactone (AHL) quorum-sensing (QS) system designated "BraI/R," which is found in all species of the plant-associated cluster. In the present study, two other BraI/R-like systems were characterized in B. xenovorans and B. unamae and were designated the BraI/R XEN and BraI/R UNA systems, respectively. Several phenotypes were analyzed, and it was determined that exopolysaccharide was positively regulated by the BraIR-like system in the species B. kururiensis, B. unamae, and B. xenovorans, highlighting commonality in targets. However, the three BraIR-like systems also revealed differences in targets since biofilm formation and plant colonization were differentially regulated. In addition, a second AHL QS system designated XenI2/R2 and an unpaired LuxR solo protein designated BxeR solo were also identified and characterized in B. xenovorans LB400 T . The two AHL QS systems of B. xenovorans are not transcriptionally regulating each other, whereas BxeR solo negatively regulated xenI2. The XenI2/R2 and BxeR solo proteins are not widespread in the Burkholderia species cluster. In conclusion, the present study represents an extensive analysis of AHL QS in the Burkholderia plant-associated cluster demonstrating both commonalities and differences, probably reflecting environmental adaptations of the various species.From its establishment in 1992, the genus Burkholderia has been extensively studied since its members are catabolically versatile and are found in many different environments and some are of medical importance (87). Validly described species have been isolated from a wide range of niches, including soil, water, wastes, plants, fungi, animals, and humans. Importantly, several species have been reported to have either a beneficial or a pathogenic interaction with plants, animals, or humans (62, 81). Currently available Burkholderia genome sequences suggest that this genus owes its niche versatility to its large genomes comprised of several large replicons, as well as to lateral gene transfer events and plasmid acquisition (13,44).Taxonomic analysis of more than 60 species described to date shows an internal division of the genus that can be viewed in two major clusters (11, 49). The first cluster includes pathogens such as Burkholderia glumae, B. pseudomallei, and B. mallei, as well as the 17 well-studied species of the Burkholderia cepacia complex (BCC) (83). The second and more recently established cluster comprises more than ...

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.

Hereditary hearing loss (HHL) is an extremely heterogeneous disorder with autosomal dominant, recessive, and X-linked forms. Here, we described an Italian pedigree affected by HHL but also prostate hyperplasia and increased ratio of the free/ total PSA levels, with the unusual and extremely rare Y-linked pattern of inheritance. Using exome sequencing we found a missense variant (r.206A>T leading to p.Asp69Val) in the TBL1Y gene. TBL1Y is homologous of TBL1X, whose partial deletion has described to be involved in X-linked hearing loss. Here, we demonstrate that it has a restricted expression in adult human cochlea and prostate and the variant identified induces a lower protein stability caused by misfolded mutated protein that impairs its cellular function. These findings indicate that TBL1Y could be considered a novel candidate for HHL.

Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): AIRC Introduction Adult mammals fail to regenerate the myocardium after ischemic injury (1). Different strategies to achieve myocardial regeneration have been considered including reactivation of progenitor cell populations, cell replacement therapies, cell reprograming and molecules able to stimulate cardiomyocyte proliferation (2). None of these approaches has been so far successful. The supply of nutrients and oxygen to the myocardium after the occlusion of a coronary artery depends on pre-existing and newly formed collateral vessels (3). The relevance of revascularization in the context of cardiac regeneration is suggested by the evidence that angiogenesis precedes cardiomyocyte proliferation in a model of neonatal heart injury (4). Our laboratory has recently demonstrated that the heart has a low angiogenetic potential (5). To what extent this is responsible for the poor regenerative capacity of the heart remains to be determined. Thus, understanding the mechanisms blocking angiogenesis in the adult heart could lead to the development of efficient strategies to promote cardiac revascularization and regeneration. Purpose Our purpose is to understand the mechanisms responsible for the low angiogenic potential of the adult mammalian heart. In particular, we designed a proteomic approach to detect differences in the composition of the perivascular extracellular matrix between the neonatal (angiogenic) with and the adult (not angiogenic) heart. Methods and Results We adopted an in vivo biotinylation strategy to label vascular extracellular proteins in vivo, followed by protein identification by mass spectrometry. A reactive derivative of biotin was systemically injected in both neonatal and adult mice (n=4) to label vascular and peri-vascular extracellular proteins. Biotinylated proteins were purified from total hearts by streptavidin-conjugated beads, eluted, and digested with trypsin. The resulting peptides were analyzed by LC-MS/MS. Among the differentially expressed proteins, we identified lumican and its receptor, integrin beta-1. This ligand-receptor pair is known to impair tube formation by endothelial cells and to interfere with both expression and activity of matrix metalloproteinases (MMPs) in vitro (6). Western blot and gene expression analysis confirmed up-regulation of lumican in the adult compared to neonatal heart, as well as a different glycosylation pattern. Lumican knock-out both ex vivo and in vivo resulted in increased vessel density. On the other hand, overexpression of lumican impaired the proliferative capacity of cardiac endothelial cells. Finally, MMP-14 activity was inhibited by adult, but not neonatal cardiac extract. Conclusions In vivo proteomic analysis identified lumican as a major contributor of the low angiogenic potential of the adult mammalian heart. These results point to lumican silencing as a promising strategy to achieve cardiac revascularization.