These data indicate that, like IQGAP1, the endothelial MT cytoskeleton facilitates lymphocyte diapedesis, but does not appear to be critical for displacement of VE-cadherin from the nascent migration

channel. Each stage of leukocyte TEM is regulated by signaling pathways mediated in both leukocytes and EC that facilitate progress to the next stage. For instance, engagement of the adhesion molecule ICAM-1 during firm adhesion leads to signaling events that HDAC inhibitor mechanism result in actin remodeling, VE-cadherin phosphorylation, and subsequently, paracellular leukocyte diapedesis 13, 16, 17. Thus, molecules localized at the interendothelial cell junctions are candidate proteins to regulate paracellular transmigration

of leukocytes. In this study, we examined the involvement of endothelial IQGAP1 in this process, since this molecule Proteases inhibitor localizes at the cell–cell junctions and regulates dynamic assembly of cytoskeleton components: actin filaments and MT. The major observations of this study are that IQGAP1, and interendothelial junction-associated MT, regulate paracellular TEM of lymphocytes. IQGAP1 knockdown both impairs lymphocyte TEM and decreases cortical MT density underlying the AJ of HUVEC in vitro. Similarly, knockdown of APC, a component of the protein complex linking IQGAP1 and MT, decreases lymphocyte TEM. Brief treatment of EC with ND has similar effects on both lymphocyte TEM and cortical MT. Reverse transcriptase These interventions promote accumulation of lymphocytes on the luminal surface of the EC monolayer, above the level of VE-cadherin. Surprisingly, a

similar fraction of such lymphocytes were associated with an underlying gap in the VE-cadherin band among IQGAP1 knockdown, MT depolymerization, and control monolayers. IQGAP1 has been implicated to participate in dynamic interendothelial junction remodeling after VEGF stimulation 27. IQGAP1 couples VEGFR2 to the β-catenin/VE-cadherin complex to facilitate VEGF-stimulated events such as tyrosine phosphorylation of VE-cadherin. VEGF stimulation increases IQGAP1 association with VE-cadherin, and loss of IQGAP1 expression reduces the assembly of the VEGFR2/VE-cadherin complex, involved in disassembly of endothelial AJ. In contrast to this reported data, however, we did not observe any changes in the basal assembly of AJ components in IQGAP1 knockdown EC monolayers or barrier function of the IQGAP1 knockdown monolayer. In our experiments, the IQGAP1-deficient HUVEC were plated at confluence, then maintained in complete media with 20% FBS for 48 h to promote junction maturation. Hence, in the current experiments, effects of IQGAP1 knockdown on cell migration or repopulation at subconfluent densities were minimized.