Suchergebnisse

Angiogenesis is a dynamic process relying on endothelial cell rearrangements within vascular tubes, yet the underlying mechanisms and functional relevance are poorly understood. Here we show that PI3Kα regulates endothelial cell rearrangements using a combination of a PI3Kα-selective inhibitor and endothelial-specific genetic deletion to abrogate PI3Kα activity during vessel development. Quantitative phosphoproteomics together with detailed cell biology analyses in vivo and in vitro reveal that PI3K signalling prevents NUAK1-dependent phosphorylation of the myosin phosphatase targeting-1 (MYPT1) protein, thereby allowing myosin light chain phosphatase (MLCP) activity and ultimately downregulating actomyosin contractility. Decreased PI3K activity enhances actomyosin contractility and impairs junctional remodelling and stabilization. This leads to overstretched endothelial cells that fail to anastomose properly and form aberrant superimposed layers within the vasculature. Our findings define the PI3K/NUAK1/MYPT1/MLCP axis as a critical pathway to regulate actomyosin contractility in endothelial cells, supporting vascular patterning and expansion through the control of cell rearrangement. ; CERCA Programme/Generalitat de Catalunya for institutional support. This work was funded by Ministerio de Ciencia, Innovación y Universidades, which is part of Agencia Estatal de Investigación (AEI, Spain) through the projects SAF2014-59950-P, SAF2017-82072-ERC, and SAF2017-89116-R co-funded by European Regional Developmental Fund (ERDF), a way to build Europe; by the Catalan Government through the projects 2014-SGR and 2017-SGR; and by la Fundació Bancària "La Caixa ; Peer Reviewed

On August 14, 2003, in a matter of minutes, the lights went out, affecting around fifty million people in the northeastern United States (allegedly most powerful nation on the planet), Ontario, and Quebec. This constituted the biggest blackout in North American history. Only a couple of weeks later, commuters in London (UK) were affected by a power outage in the underground. In September in Copenhagen and southern Sweden almost four million users were left in the dark. After alternative explanations were ruled out and the expected political game of passing the blaming around receded, many began attributing these all too common problems of brownouts and blackouts on systemic, underlying conditions. The processes of liberalization and privatization of the power sectors ended up under negative public scrutiny. This is the kind of time in which von-der-Fehr and Millan's book saw the light.

31 pages, 10 figures, 1 additional file.-- Provisional PDF. ; [Background] Endothelial cell-cell junctions maintain endothelial integrity and regulate vascular morphogenesis and homeostasis. Cell-cell junctions are usually depicted with a linear morphology along the boundaries between adjacent cells and in contact with cortical F-actin. However, in the endothelium, cell-cell junctions are highly dynamic and morphologically heterogeneous. ; [Results] We report that endothelial cell-cell junctions can attach to the ends of stress fibres instead of to cortical F-actin, forming structures that we name discontinuous adherens junctions (AJ). Discontinuous AJ are highly dynamic and are increased in response to tumour necrosis factor (TNF)-α, correlating with the appearance of stress fibres. We show that vascular endothelial (VE)-cadherin/β-catenin/α-catenin complexes in discontinuous AJ are linked to stress fibres. Moreover, discontinuous AJ connect stress fibres from adjacent cells independently of focal adhesions, of which there are very few in confluent endothelial cells, even in TNF- α−stimulated cells. RNAi-mediated knockdown of VE-cadherin, but not zonula occludens-1, reduces the linkage of stress fibres to cell-cell junctions, increases focal adhesions, and dramatically alters the distribution of these actin cables in confluent endothelial cells. ; [Conclusions] Our results indicate that stress fibres from neighbouring cells are physically connected through discontinuous AJ, and that stress fibres can be stabilized by AJ-associated multiprotein complexes distinct from focal adhesions. ; This work was supported by the Ludwig Institute for Cancer Research, Association for International Cancer Research (AICR) and the European Commission contract LSHG-CT- 2003-502935 (MAIN). JM was supported by a Marie Curie fellowship (No. HPMF-CT-2000- 01061) and a British Heart Foundation intermediate fellowship (No. FS/04/006), a grant from the Spanish Ministerio de Ciencia e Innovación (SAF2008-01936) and a Ramón y Cajal contract from the Spanish Government. NR is supported by a JAE predoctoral fellowship from CSIC (Spain). BM was supported by a FPI fellowship (SAF-2008-01936). ; Peer reviewed