N-Glycans of SREC-I (scavenger receptor expressed by endothelial cells): Essential role for ligand binding, trafficking and stability

Purpose: We demonstrated that IGFBP-3 stimulates hematopoietic stem cells (HSC) to differentiate into endothelial cells, form capillaries, and stabilize the vasculature (Chang, et al, PNAS 2007). Local IGFBP- 3 production is increased by hypoxia and facilitates the homing of HSC to areas of injury. In the circulation, IGFBP-3 is bound to HDL. In this study, we investigated the signaling pathways responsible for the robust migratory effects of IGFBP-3. Methods: The effects of IGFBP-3 on NO generation in human vascular precursors (CD 34 + , CD14 − ), human lung microvascular endothelial cells, and human umbilical vein endothelial cells were examined using DAF-FM fluorescence. Western analysis was use for detection of eNOS and vasodilator-stimulated phosphoprotein (VASP), which redistributes to lamellipodia forming an active motor complex that supports motility and is phosphorylated in response to NO. Localization of VASP was performed by immunohistochemistry. SK-1 was assessed following IGFBP-3 stimulation. Results: In CD34 + cells and endothelial cells, IGFBP-3 stimulated eNOS phosphorylation at Ser1177 (102 ± 1.8%, P = 0.0002) and increased NO generation (275 ± 50%, P = 0.05) by increasing SK-1 and S1P generation. IGFBP-3 was bound and internalized by the HDL receptor, scavenger receptor 1B (SR1B). NO generation following IGFBP-3 exposure was reduced by SK inhibitors or SR-1B blocking antibody pretreatment (35 ± 5%, P < 0.02). IGFBP-3 generated NO increased phosphorylation of VASP at Ser239 and promoted the redistribution of VASP to lamellipodia. Conclusions: IGFBP-3 effects on cell migration are NO dependent and mediated in part by activation of the HDL receptor SR1B suggesting that some of the beneficial effects of HDL are mediated by the association of IGFBP-3.

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Thrombospondin‐1 Plays an Essential Role in Hippo Signaling During the Early Phase of Trypanosoma cruzi Infection in Heart Endothelial Cells

The FASEB Journal ◽

10.1096/fasebj.2021.35.s1.04150 ◽

2021 ◽

Vol 35 (S1) ◽

Author(s):

Ashutosh Arun ◽

Kayla Rayford ◽

Ayorinde Cooley ◽

Girish Rachakonda ◽

Fernando Villalta ◽

...

Keyword(s):

Endothelial Cells ◽

Trypanosoma Cruzi ◽

Early Phase ◽

Essential Role ◽

Hippo Signaling ◽

Thrombospondin 1 ◽

Cruzi Infection

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Scavenger receptor expressed by endothelial cells (SREC)-I interacts with protein phosphatase 1α in L cells to induce neurite-like outgrowth

Biochemical and Biophysical Research Communications ◽

10.1016/j.bbrc.2007.06.047 ◽

2007 ◽

Vol 360 (1) ◽

pp. 269-274 ◽

Cited By ~ 9

Author(s):

Junko Ishii ◽

Hideki Adachi ◽

Norihito Shibata ◽

Hiroyuki Arai ◽

Masafumi Tsujimoto

Keyword(s):

Endothelial Cells ◽

Protein Phosphatase ◽

Scavenger Receptor ◽

L Cells

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Abstract 16: BcrKinase is a Novel Akt Kinase That Modulates Scavenger Receptor BI- and PDZK1-dependent Actions of HDL in Endothelium

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.36.suppl_1.16 ◽

2016 ◽

Vol 36 (suppl_1) ◽

Author(s):

Anastasia Sacharidou ◽

Wan-Ru Lee ◽

Philip E Shaul ◽

Chieko Mineo

Keyword(s):

Endothelial Cells ◽

Endothelial Cell ◽

Kinase Activity ◽

Scavenger Receptor ◽

Adaptor Protein ◽

Myelogenous Leukemia ◽

Endothelial Cell Migration ◽

Kinase Assay ◽

Type I ◽

Akt Kinase

High density lipoprotein cholesterol (HDL) has direct atheroprotective actions on endothelium. These are mediated by scavenger receptor class B, type I (SR-BI) and its adaptor protein PDZK1, and they entail the activation of Akt kinase, which phosphorylates and thereby stimulates endothelial nitric oxide synthase (eNOS). In the present work we sought to determine how PDZK1 couples HDL/SR-BI to Akt and eNOS to modulate endothelial function. Using tandem affinity purification (TAP) following the infection of the human endothelial cell line EAhy926 with adenovirus expressing TAP-tagged PDZK1, we identified Breakpoint Cluster Region (Bcr) kinase as a PDZK1 interacting protein in endothelium. Whereas Bcr is well-known as a component of the Bcr-Abl fusion protein that results from translocation of the Philadelphia chromosome in chronic myelogenous leukemia, little is known of its function in endothelial cells. Bcr contains several distinctive domains including a C-terminal PDZ binding motif and a serine/threonine protein kinase domain. In primary human aortic endothelial cells (HAEC), we determined that endogenous Bcr interacts with PDZK1 in an HDL-dependent manner, and that Bcr is required for HDL-induced activation of eNOS and HDL stimulation of endothelial cell migration, which underlies the ability of the lipoprotein to promote endothelial monolayer integrity. Studies of mutant forms of Bcr with disruption of PDZK1 binding or kinase activity introduced into endothelial cells further revealed that Bcr-PDZK1 interaction and its kinase function are required for HDL activation of Akt and eNOS. Using a novel kinase assay that we recently developed that employs time-resolved Forster resonance energy transfer, we found that via SR-BI and PDZK1, HDL stimulates Bcr kinase activity in endothelial cells more than 20-fold. In addition, using Akt-based peptides in studies of the two known kinases for Akt, mTOR and PDK1, we determined that HDL activates Bcr kinase to directly phosphorylate Akt-Ser473 in an mTOR independent manner, and that Akt-Thr308 is a direct substrate of PDK1. These collective findings have identified Bcr to be a novel kinase for Akt, and they have revealed that Bcr is critically involved in HDL modulation of endothelial cell phenotype.

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Abstract 624: Endothelial Scavenger Receptor Class B, Type I (SR-BI) Mediates LDL Uptake by the Artery Wall and Promotes Atherosclerosis in Hypercholesterolemic Mice

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.36.suppl_1.624 ◽

2016 ◽

Vol 36 (suppl_1) ◽

Author(s):

Linzhang Huang ◽

Ken Chambliss ◽

Mohamed Ahmed ◽

Chieko Mineo ◽

Philip W Shaul

Keyword(s):

Endothelial Cells ◽

Scavenger Receptor ◽

Plasma Lipid ◽

Density Lipoprotein ◽

Type I ◽

Artery Wall ◽

Blocking Antibody ◽

Scavenger Receptor Class ◽

Class B ◽

Ldl Uptake

In endothelial cells, high density lipoprotein cholesterol (HDL) binding to scavenger receptor class B, type I (SR-BI) promotes the production of the antiatherogenic signaling molecule nitric oxide (NO) and also endothelial repair. To study how SR-BI in endothelium impacts atherosclerosis, we bred newly-created floxed SR-BI mice, vascular endothelial cadherin promoter-driven Cre recombinase transgenic (VECad-Cre), and apoE -/- mice to generate apoE -/- with normal endothelial SR-BI expression (SR-BI ECIN ;apoE -/- ) or selective deletion of SR-BI from endothelium (SR-BI ECOUT ;apoE -/- ). At weaning all mice were placed on an atherogenic diet (20% fat, 1.25% cholesterol), and plasma lipid profiles and atherosclerosis were evaluated 8 weeks later. Endothelial deletion of SR-BI did not alter the plasma lipid profile. Surprisingly, male SR-BI ECOUT ;apoE -/- mice displayed 63% less atherosclerosis in the en face aorta than male SR-BI ECIN ;apoE -/- mice, aortic root lesions were comparably affected, and similar findings were obtained in females. Recognizing that SR-BI binds both HDL and low density lipoprotein cholesterol (LDL), to then discern how endothelial SR-BI promotes atherosclerosis we determined using Di-I-labeled oxidized LDL (oxLDL) if SR-BI influences oxLDL uptake by endothelial cells. Such uptake is the first step in the endothelial transcytosis that delivers LDL to the artery wall to initiate atherogenesis. OxLDL uptake by primary human aortic endothelial cells was blunted by 87% by SR-BI blocking antibody, and it was also decreased by SR-BI deletion via siRNA, and by the chemical inhibitor of SR-BI BLT-1. Furthermore, SR-BI blocking antibody and BLT-1 caused marked declines in endothelial oxLDL transcytosis. Moreover, 4 hours following IV administration, oxLDL uptake in aorta was decreased by 84% in SR-BI ECOUT ;apoE -/- versus SR-BI ECIN ;apoE -/- mice. These collective findings indicate that endothelial SR-BI plays an important role in atherogenesis, and that it likely does so by mediating LDL uptake into the artery wall. They further suggest that there are mechanisms that govern LDL transport across endothelium that may be targeted to provide novel means to combat atherosclerosis.

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