VCAM-1 Activation of Endothelial Cell Protein Tyrosine Phosphatase 1B

Abstract

Lymphocytes migrate from the blood into tissue by binding to and migrating across endothelial cells. One of the endothelial cell adhesion molecules that mediate lymphocyte binding is VCAM-1. We have reported that binding to VCAM-1 activates endothelial cell NADPH oxidase for the generation of reactive oxygen species (ROS). The ROS oxidize and stimulate an increase in protein kinase C (PKC)α activity. Furthermore, these signals are required for VCAM-1-dependent lymphocyte migration. In this report, we identify a role for protein tyrosine phosphatase 1B (PTP1B) in the VCAM-1 signaling pathway. In primary cultures of endothelial cells and endothelial cell lines, Ab cross-linking of VCAM-1 stimulated an increase in serine phosphorylation of PTP1B, the active form of PTP1B. Ab cross-linking of VCAM-1 also increased activity of PTP1B. This activation of PTP1B was downstream of NADPH oxidase and PKCα in the VCAM-1 signaling pathway as determined with pharmacological inhibitors and antisense approaches. In addition, during VCAM-1 signaling, ROS did not oxidize endothelial cell PTP1B. Instead PTP1B was activated by serine phosphorylation. Importantly, inhibition of PTP1B activity blocked VCAM-1-dependent lymphocyte migration across endothelial cells. In summary, VCAM-1 activates endothelial cell NADPH oxidase to generate ROS, resulting in oxidative activation of PKCα and then serine phosphorylation of PTP1B. This PTP1B activity is necessary for VCAM-1-dependent transendothelial lymphocyte migration. These data show, for the first time, a function for PTP1B in VCAM-1-dependent lymphocyte migration.

Endothelial cell PTP1B regulates leukocyte recruitment during allergic inflammation

“…8C) among the groups. These data with reduced lung eosinophil recruitment and increased eosinophil binding to the luminal surface of the endothelium in the iePTP1B/Ϫdox are consistent with in vitro studies demonstrating that endothelial cell PTP1B functions in leukocyte transendothelial migration (16).…”

“…We have previously demonstrated in vitro that PTP1B plays an active role in promotion of VCAM-1-dependent lymphocyte transendothelial migration through an endothelial signal transduction cascade sequentially involving activation of endothelial cell NOX2 (36), PKC␣ (16), and PTP1B (16). This VCAM-1-activated PTP1B induces signals that lead to activation of ERK1/2 in endothelial cells (1).…”

“…In this pathway, VCAM-1-stimulated protein kinase C-␣ (PKC␣) phosphorylates and activates PTP1B, which then induces signals for activation of ERK1/2 (1). Importantly, inhibition of PTP1B blocks VCAM-1-dependent lymphocyte transendothelial migration in vitro (16). However, it is not known whether endothelial PTP1B functions in vivo during leukocyte recruitment.…”

“…We reported that ligation of VCAM-1 activates the protein tyrosine phosphatase 1B (PTP1B) (1,16). In this pathway, VCAM-1-stimulated protein kinase C-␣ (PKC␣) phosphorylates and activates PTP1B, which then induces signals for activation of ERK1/2 (1).…”

“…Given the significant function for PTP1B in promotion of VCAM-1-dependent leukocyte migration in vitro (16) and the central role for VCAM-1 in the recruitment of eosinophils in allergic inflammation (6), we determined whether nonhematopoietic PTP1B or endothelial PTP1B was required for eosinophil migration in vivo. PTP1B-deficient mice are useful for in vivo studies because they are physiologically normal under basal conditions.…”