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International audience; Inflammation is a well-known pathophysiological factor of atherosclerosis but its therapeutic targeting has long been ignored. However, recent advances in the understanding of the immune mechanisms implicated in atherosclerosis have unveiled several therapeutic targets currently undergoing clinical trials. These studies have also shed light on a dialogue between the immune compartment and vascular smooth muscle cells (VSMCs) that plays a critical role in atherosclerotic disease initiation, progression, and stabilization. Our review focuses on the link between cellular and soluble immune effectors and VSMC behavior at different phases of the pathology. Furthermore, we discuss the potential targeting of these interactions to efficiently prevent cardiovascular diseases. MOLECULAR AND CELLULAR DETERMINANTS OF ATHEROSCLEROSIS Cardiovascular diseases (CVDs) remain the leading cause of death worldwide and are in constant increase in western as well as low and middle-income countries [https://www.who.int/news-room/ fact-sheets/detail/cardiovascular-diseases-(cvds)], underpinning the importance of finding novel therapeutic approaches. The major cause of CVD is atherosclerosis. This pathology involves inflammatory and fibroproliferative mechanisms engaging communication between vascular cells [endothelial cells and vascular smooth muscle cells (VSMCs)] and immune cells. Atherosclerotic plaque progression leads to intimal thickening and culminates in late stages with plaque rupture which can cause myocardial infarctions and strokes. The first initiating event of atherosclerosis involves shear stress perturbations responsible for endothelial cell dysfunction and inflammation leading to accumulation of low density lipoprotein (LDL) in the subendothelial space. Novel recent data has demonstrated that contrary to what was expected, this mechanism is not a passive movement of LDL across the endothelial barrier. Indeed, it involves the binding of LDL to the SRB-I receptor and subsequent transcytosis involving the guanine nucleotide exchange factor (DOCK4)/Rac pathway (Huang et al., 2019) and specific lipidic compartments (caveolae) found in great quantity in atheroprone regions. This mechanism is responsible for the initiation of the flow-dependent inflammatory priming of cells in atheroprone locations (Ramirez et al., 2019). LDL accumulation and oxidation in the medial area of arteries further amplifies inflammation by inducing chemokine secretion and expression of adhesion molecules at the surface of endothelial cells, such as intercellular adhesion molecule (ICAM)

et al., Guided cell migration is a key mechanism for cell positioning in morphogenesis. The current model suggests that the spatially controlled activation of receptor tyrosine kinases (RTKs) by guidance cues limits Rac activity at the leading edge, which is crucial fo establishing and maintaining polarized cell protrusions at the front. However, little is known about the mechanisms by which RTKs control the local activation of Rac. Here, usinga multidisciplinary approach, we identify the GTP exchange factor (GEF) Vav as a key regulator of Rac activity downstream of RTKs in a developmentally regulated cell migration event, that of the Drosophila border cells (BCs). We show that elimination of the vav gene impairs BC migration. Live imaging analysis reveals that vav is required for the stabilization and maintenance of protrusions at the front of the BC cluster. In addition, activation of the PDGF/VEGF-related receptor (PVR) by its ligand the PDGF/PVF1 factor brings about activation of Vav protein by direct interaction with the intracellular domain of PVR. Finally, FRET analyses demonstrate that Vav is required in BCs for the asymmetric distribution of Rac activity at the front. Our results unravel an important role for the Vav proteins as signal transducers that couple signalling downstream of RTKs with local Rac activation during morphogenetic movements., Research in M.D.M.-B. laboratory is funded by the Spanish Ministerio de Ciencia y Tecnología (MCYT) [grant numbers BFU2004-02840/BMC, BFU2010-16669 and CSD-2007-00008 to M.D.M.-B.], by the EMBO Young Investigator Programme and by the Junta de Andalucía [grant numbers P06-CVI-01592 and P09-CVI-5058]. C.H.F.-E. is supported by a fellowship funded by the Consolider Project Grant [grant number CSD-2007-00008] and M.M. was supported by a Juan de la Cierva contract. The institutional support from the Junta de Andalucía to the CABD is acknowledged. S.K. is supported by the German-Israeli-Foundation (GIF). G.E. is funded by the Canadian Institutes for Health Research [grant number MOP-114899] by the Natural Sciences and Engineering Research Council of Canada and holds a Canada Research Chair (Tier II) in Vesicular Trafficking and Cell Signaling.

International audience; NPM-ALK is a chimeric tyrosine kinase detected in most anaplastic large cell lymphomas which results from the reciprocal translocation t(2,5)(p23;q35) that fuses the N-terminal domain of nucleophosmin (NPM) to the catalytic domain of the ALK receptor. The constitutive activity of the kinase is responsible for its oncogenicity through the stimulation of several downstream signaling pathways leading to cell proliferation, migration and survival. We previously demonstrated that the high level of phosphatidylinositol 5-phosphate (PtdIns5P) measured in NPM-ALK expressing cells is controlled by the phosphoinositide kinase PIKfyve, a lipid kinase known for its role in vesicular trafficking. Here, we show that PIKfyve associates with NPM-ALK and that the interaction involves the 181-300 region of the oncogene. Moreover, we demonstrate that the tyrosine kinase activity of the oncogene controls PIKfyve lipid kinase activity, but is dispensable for the formation of the complex. Silencing or inhibition of PIKfyve, by using siRNA or the PIKfyve inhibitor YM201636, have no effect on NPM-ALK-mediated proliferation and migration, but strongly reduce invasive capacities of NPM-ALK expressing cells and their capacity to degrade the extracellular matrix. Accordingly, immunofluorescence studies confirm a perturbation of MMP-9 localization at the cell surface and defect in maturation. Altogether, these results suggest a role for PIKfyve in NPM-ALK mediated invasion.

International audience; Arterial remodeling in hypertension and intimal hyperplasia involves inflammation and disrupted flow, both of which contribute to smooth muscle cell dedifferentiation and proliferation. In this context, our previous results identified phosphoinositide 3-kinase gamma (PI3Kγ) as an essential factor in inflammatory processes of the arterial wall. Here, we identified for the first time a kinase-independent role of nonhematopoietic PI3Kγ in the vascular wall during intimal hyperplasia using PI3Kγ deleted mice and mice expressing a kinase-dead version of the enzyme. Moreover, we found that the absence of PI3Kγ in VSMCs leads to the modulation of cell proliferation associated with an increase in intracellular cAMP levels. Real-time analysis of cAMP dynamics revealed that PI3Kγ modulates the degradation of cAMP in primary vascular smooth muscle cells (VSMC) independent of its kinase activity through the regulation of the phosphodiesterase (PDE) 4 enzyme. Importantly, the use of an N-terminal competing peptide of PI3Kγ blocked primary VSMC proliferation. These data provide evidence for a kinase-independent role of PI3Kγ in arterial remodeling and reveal novel strategies targeting the docking function of PI3Kγ for the treatment of cardiovascular diseases.