Our data implicate the participation

of MT in endothelial IQGAP1-dependent junction remodeling during lymphocyte diapedesis. First, following knockdown of IQGAP1, we observed a decrease in polymerized tubulin and MT density near AJ in cells lacking IQGAP1 expression. Although the effect of IQGAP1 knockdown on EC MT is modest, the effect is confirmed by both biochemical and semi-quantitative imaging techniques. Second, APC knockdown elicits similar effects. Third, direct pharmacologic induction Venetoclax molecular weight of MT depolymerization mimicking the effect of IQGAP1 knockdown inhibited lymphocyte TEM. In each case, lymphocytes were seen to accumulate over the luminal surface of the nascent migration channel in a similar position.

Taken together, these three lines of evidence are consistent with a model that IQGAP1 and the junction-associated MT network participates in remodeling of the EC at the interendothelial junction during leukocyte TEM. Previous work identified that endothelial MT are critical for development of an actin-based docking structure underneath the adherent lymphocyte, which might function to promote lymphocyte adhesion under arterial shear stress and TEM 4, 40. IQGAP1 is enriched at intercellular junctions, hence is not anticipated to participate in docking structure formation. Moreover, our data identify no defect in lymphocyte encounters with intercellular junctions. The current AUY-922 observations

indicate that functionally, endothelial MT act to enable paracellular diapedesis of the HUVEC monolayer by adherent lymphocytes. Previously, it has been reported MT loss produced by prolonged ND incubation of EC results in increased neutrophil and monocyte TEM associated with VE-cadherin loss, actin stress fiber formation, and gap formation at interendothelial junctions 32, 33. Sucrase However, under the conditions used in these experiments, our immunofluorescence microscopy and flow cytometry results did not identify a change in VE-cadherin cell surface expression or localization at junctions after brief ND treatment. Further, our data illustrate the structural and functional integrity of the monolayer under condition of IQGAP1 knockdown. The discordant results in TEM assays emphasize the importance of careful evaluation of monolayer integrity with each manipulation. Similar to our observations, other groups reported intact EC monolayer and decreased monocyte or lymphocyte diapedesis under static conditions after endothelial MT depolymerization 4, 19. In the current experiments, we report on endothelial MT function during lymphocyte diapedesis under shear stress. Our results confirm a role for endothelial MT to remodel the interendothelial cell junction under these short, physiologic timeframes.