Biology subjects

Loirand, G.

Publications and source records attributed to Loirand, G..

3 recordsLinked to original sources

bioRxiv2025

NET1/ARHGEF8 is a mechanosensitive Guanine Exchange Factor controlling vascular smooth muscle cells' contractility

Cyclic stretch, generated by pulsatile blood pressure, has been identified as a pivotal regulator of vascular smooth muscle cell (VSMC) behavior and arterial wall homeostasis. Research has demonstrated that RhoA activation is a fundamental component of VSMC responses to mechanical stress through its action on cytoskeletal remodeling. However, the upstream mechanosensitive regulators of RhoA activation remain insufficiently defined. In this study, we identify the guanine nucleotide exchange factor (RhoGEF) NET1/ARHGEF8 as a stretch-responsive protein. NET1 appears to be highly expressed in arteries and VSMCs. Under physiological levels of cyclic stretch, NET1 localizes to the cytosol and interacts with RhoA. In contractile cells, loss of NET1 blunted stretch-induced MYPT1 phosphorylation and impaired cell adhesion and spreading, without exerting any effect on cell proliferation. As we demonstrated, NET1s contribution to the stretch-induced response of VSMC was due to its localization in the cytosol. The expression of a cytosolic NET1 mutant promoted contractile gene expression and increased cell contractile capacity. Collectively, these findings identify NET1 as a stretch-sensitive RhoGEF in VSMCs that contributes to their adhesion and contractile behavior.

cell biology↗

bioRxiv2025

ANGPTL6 variant induces cerebral vascular dysfunction and predisposes to intracranial aneurysm in mice

BackgroundIntracranial aneurysm (IA) is a common cerebrovascular abnormality characterized by localized dilation and wall thinning in intracranial arteries, that frequently leads to fatal sub-arachnoid hemorrhage. Pathophysiological mechanisms responsible for AI remains largely unknown, but increasing evidence suggest that genetic susceptibility plays a predominant role. We recently identified a rare nonsense variant in ANGPTL6 gene that prevented angiopoietin-like 6 (ANGPTL6) secretion and predisposed to IA. The aim of this study is now to understand why the ANGPTL6 variant predisposes to IA. MethodsAngptl6-knock in mice were generated by homologous recombination. Cerebral arteries of the circle of Willis have been analyzed under basal and hemodynamic overload conditions. Functional properties of cerebral arteries have been analyzed by pressure arteriography. Effect of recombinant ANGPTL6 have been assessed on vascular smooth muscle cells and ANGPTL6 partners have been analyzed by surface plasmon resonance. ResultsAngptl6-knock in mice display endothelial dysfunction expressed by reduced NO production in response to flow in cerebral arteries. They present exaggerated dilatation of cerebral arteries under hypertensive stress, and aggravated wall damage and aneurysmal remodeling of the intima and media at arterial bifurcations of the circle of Willis under hemodynamic overload. Matrix bound ANGPTL6 decreased VSMC migration and increased adhesion and FAK signaling activation, without affecting VSMC phenotype. Surface plasmon resonance analyses identified v{beta}5 integrin as a new ANPTL6 receptor. ConclusionsAngptl6-knock in mice mimicked the main features of IA in humans. ANGPTL6 appears to be an extracellular matrix component regulating vascular cell function, which may be involved in mechanosensing and generating adapted vascular cell responses to hemodynamic stress. Non-secreted ANGPTL6 variants would result in the loss of this function, thus favoring IA under conditions of hemodynamic overload.

physiology↗

bioRxiv2022

ARHGEF18 participates in Endothelial Cell Mechano-sensitivity in Response to Flow

The shear stress resulting from blood flow is a major regulator of endothelial cell (EC) biology and morphology. Rho protein-mediated cytoskeleton remodeling is an early and essential step of EC responses to flow. However, how Rho protein signaling is controlled by shear stress remains unclear. Here we demonstrate that phosphorylation, activity and expression of the Rho nucleotide exchange factor (RhoGEF) ARHGEF18 in ECs are modulated by the magnitude of shear stress. ARHGEF18 interacts with tight junctions, participates in ECs elongation and alignment and allows the maintenance of the endothelial barrier under physiological flow conditions. ARHGEF18 also promotes EC adhesion and migration by controlling focal adhesion formation. In vivo, ARHGEF18 is involved in flow response of ECs and in the control of vascular permeability in mice. Together, our results identified ARHGEF18 as the first flow-sensitive RhoGEF in ECs, whose activity is essential for the maintenance of intercellular junctions and the control of vascular permeability in vivo.

cell biology↗