Cytoskeletal Mechanisms For The Migration Of Vascular Endothelial Cells And Neutrophils

Cell migration is a fundamental property of many cells and plays an essential role in numerous physiological and pathological processes, including angiogenesis and immune response. Movement is controlled by internal and external signals, which acive complex signal transduction cascades resulting in highly dynamic and localised remodelling of the actin-myosin cytoskeleton and the microtubule system, cell-cell and cell-substrate interactions. Several microtubule-associated proteins are involved in cell polarization and migration, through interactions with microtuble cytoskeleton.Hsp70/Hsp90-organizing protein (HOP) is a member of the co-chaperone family, which can directly bind to Hsp70/Hsp90through TPR domains. HOP serves as a facilitator in the formation of specific multichaperone complexes, and regulate their activities. Besides, HOP can interact with other chaperones apart from Hsp70and Hsp90and involved in other important processes in the cell that may not have partnership with either the Hsp70or Hsp90chaperone machinery. The participation of HOP in cell motility and endothelial cell functions remains largely unknown. In the first part of study, we demonstrate that HOP is critically involved in endothelial cell migration and angiogenesis. Tube formation and capillary sprouting experiments reveal that depletion of HOP expression significantly inhibits vessel formation from endothelial cells. Wound healing and transwell migration assays show that HOP is important for endothelial cell migration. By examination of centrosome reorientation and membrane ruffle dynamics, we find that HOP plays a crucial role in the establishment of cell polarity in response to migratory stimulus. Furthermore, our data show that HOP interacts with tubulin and colocalizes with microtubules in endothelial cells. These findings indicate HOP as a novel regulator of angiogenesis that functions through promoting vascular endothelial cell polarization and migration.Neutrophils are the most numerous and most important cellular component of the innate immune response。When recruited by macrophages in tissue, neutrophils migrate out of blood vessels, arrive at sites of infection or inflammation, ingest and destroy many pathogens. Actin cytoskeleton dynamic highly change during neutrophils adhesion, migration, and phagocytosis. Thus the regulation of actin dynamics is crucial for neutrophils to fulfill their roles in innate immunity.Many factors have been implicated in signal-induced actin polymerization, but the essential nature of the potential negative modulators is still poorly understood. Here we report that NADPH oxidase-dependent physiologically generated reactive oxygen species (ROS) negatively regulate actin polymerization in stimulated neutrophils via driving reversible actin glutathionylation. ROS depletion leads to significantly higher amout of F-actin. Disruption of glutaredoxin1(Grxl), the main enzyme that catalyzes actin deglutathionylation in mamalian cells, increased actin glutathionylation, attenuated actin polymerization, and consequently impaired neutrophil polarization, chemotaxis, adhesion, and phagocytosis. Consistently, Grxl-deficient murine neutrophils showed impaired in vivo recruitment to sites of inflammation and reduced bactericidal capability. In contrast, overexpressing glutaredoxin1results in reduced actin glutathionylation and increased F-actin. Together, these results present a physiological role for glutaredoxin and ROS-induced reversible actin glutathionylation in regulation of actin dynamics in neutrophils.