Redundant Roles of Tead1 and Tead2 in Notochord Development and the Regulation of Cell Proliferation and Survival▿

Four members of the TEAD/TEF family of transcription factors are expressed widely in mouse embryos and adult tissues. Although in vitro studies have suggested various roles for TEAD proteins, their in vivo functions remain poorly understood. Here we examined the role of Tead genes by generating mouse mutants for Tead1 and Tead2. Tead2−/− mice appeared normal, but Tead1−/−; Tead2−/− embryos died at embryonic day 9.5 (E9.5) with severe growth defects and morphological abnormalities. At E8.5, Tead1−/−; Tead2−/− embryos were already small and lacked characteristic structures such as a closed neural tube, a notochord, and somites. Despite these overt abnormalities, differentiation and patterning of the neural plate and endoderm were relatively normal. In contrast, the paraxial mesoderm and lateral plate mesoderm were displaced laterally, and a differentiated notochord was not maintained. These abnormalities and defects in yolk sac vasculature organization resemble those of mutants for Yap, which encodes a coactivator of TEAD proteins. Moreover, we demonstrated genetic interactions between Tead1 and Tead2 and Yap. Finally, Tead1−/−; Tead2−/− embryos showed reduced cell proliferation and increased apoptosis. These results suggest that Tead1 and Tead2 are functionally redundant, use YAP as a major coactivator, and support notochord maintenance as well as cell proliferation and survival in mouse development

Astroglial NF-κB mediates oxidative stress by regulation of NADPH oxidase in a model of retinal ischemia reperfusion injury

Astrocytes undergo rapid activation after injury, which is mediated in part by the transcription factor NF-κB. Consequently, activated astrocytes have been shown to induce the NF-κB regulated phagocyte NADPH oxidase (PHOX), resulting in elevated production of reactive oxygen species (ROS). We investigated the regulatory mechanisms of PHOX-induced oxidative stress in astrocytes and its non cell-autonomous effects on retinal ganglion cell (RGC) loss following retinal ischemia-reperfusion (IR) injury. To study PHOX activity and neurotoxicity mediated by glial NF-κB, we employed GFAP-IκBα-dn transgenic mice (TG), where the NF-κB canonical pathway is suppressed specifically in astrocytes. Our analysis showed that NF-κB activation in astrocytes correlated with an increased expression of PHOX and ROS production in primary cells and whole retinas subjected to oxygen-glucose deprivation (OGD) or IR injury. Selective blockade of NF-κB in astrocytes or application of NADPH oxidase inhibitors suppressed RGC loss in co-cultures with astroglia challenged by OGD. Furthermore, genetic suppression of astroglial NF-κB reduced oxidative stress in ganglion layer neurons in vivo in retinal IR. Collectively, our results suggest that astroglial NF-κB-regulated PHOX activity is a crucial toxicity pathway in the pathogenesis of retinal IR injury

Heme Oxygenase-1 Influences Apoptosis via CO-mediated Inhibition of K+ Channels

Hypoxic/ischemic episodes can trigger oxidative stress-mediated loss of central neurons via apoptosis, and low pO2 is also a feature of the tumor microenvironment, where cancer cells are particularly resistant to apoptosis. In the CNS, ischemic insult increases expression of the CO-generating enzyme heme oxygenase-1 (HO-1), which is commonly constitutively active in cancer cells. It has been proposed that apoptosis can be regulated by the trafficking and activity of K+ channels, particularly Kv2.1. We have explored the idea that HO-1 may influence apoptosis via regulation of Kv2.1. Overexpression of Kv2.1 in HEK293 cells increased their vulnerability to oxidant-induced apoptosis. CO (applied as the donor CORM-2) protected cells against apoptosis and inhibited Kv2.1 channels. Similarly in hippocampal neurones, CO selectively inhibited Kv2.1 and protected neurones against oxidant-induced apoptosis. In medulloblastoma sections we identified constitutive expression of HO-1 and Kv2.1, and in the medulloblastoma-derived cell line DAOY, hypoxic HO-1 induction or exposure to CO protected cells against apoptosis, and also selectively inhibited Kv2.1 channels expressed in these cells. These studies are consistent with a central role for Kv2.1 in apoptosis in both central neurones and cancer cells. They also suggest that HO-1 expression can strongly influence apoptosis via CO-mediated regulation of Kv2.1 activity

The versatile TolC-like Slr1270 in the cyanobacterium S

Here we report on the functional characterization of the hypothetical protein Slr1270, a TolC homologue in Synechocystis sp. PCC 6803. Analysis of a slr1270 insertion deletion mutant and respective wild-type revealed that the mutant presents increased susceptibility to antibiotics. In addition, a detailed study of the exoproteome showed that Slr1270 mediates protein secretion. Among the protein substrates dependent on Slr1270 function, we found the S-layer structural component. Electron microscopy studies of the slr1270 mutant showed that the S-layer is indeed absent. The requirement of functional Slr1270 for protein secretion and drug resistance mechanisms suggests that Slr1270 plays a role similar to that described for TolC in other bacteria. Additional phenotypic traits could also be observed, including slower growth rates at low temperature, impairment in biofilm formation and increased activity of enzymes detoxifying reactive oxygen species. Furthermore, an increased capacity of outer membrane vesicles (OMVs) formation and release was also found in the slr1270 mutant, a feature that has not yet been observed in bacteria lacking TolC. This work highlights the marked physiological fitness that the TolC-like Slr1270 bestows to the photosynthetic model Synechocystis sp. PCC 6803 and presents a valuable model for studying OMVs formation and release.SCOPUS: ar.jFLWINinfo:eu-repo/semantics/publishe