Distinct Tie2 tyrosine phosphorylation sites dictate phenotypic switching in endothelial progenitor cells

Abstract

Angiogenesis is a regulated process involving the proliferation, migration, and remodeling of different cell types particularly mature endothelial and their progenitor cells, nominated as endothelial progenitor cells (EPCs). Tie2/Tek is a tyrosine kinase receptor expressed by endothelial cells that induces signal transduction pathways involved in endothelial biology. To address the potential importance of the various tyrosine residues of Tie2 in EPC development, we generated a series of Tie2 tyrosine mutated (Y1106F, Y1100F, and Y1111F) EPCs and then assess the biological features of these cells. Clonogenic, tubulogenic, proliferative, migratory, and functional properties of these cells were analyzed. Next, GFP-positive EPCs containing Tie2 tyrosine mutations were systemically transplanted into sublethaly irradiated mice to analyze the potency of these cells for marrow reconstitution. We found that mutation in the Tie2 tyrosine 1106 residue directed EPCs toward a mature endothelial phenotype, which was associated with augmented tubulogenic and migratory properties, and increased phosphorylation of the active site (tyrosine 992) as well as increased vascular perfusion in the in vivo Matrigel plug assay. Moreover, transplantation of 1106 Tie2 mutant EPCs failed to reconstitute the bone marrow after myeloablation, whereas transplantation of EPCs with the 1100 or 1111 Tie2 tyrosine mutation resulted in bone marrow engraftment, leading to improved survival of recipient mice. Our findings demonstrate that the tyrosine 1106 residue in Tie2 plays a key role to maintain the stemness features of EPCs. K E Y W O R D Sbone marrow reconstitution, endothelial progenitor cell, Tie2, tyrosine phosphorylation

A Novel Approach for Development of Intraocular Biodegradable Ranibizumab Implant: A Solution for Stability of Protein Activity

“…The dissociation tests indicated the importance of these interactions in complexation; this feature can be used for dissociating the drug in vivo . 21 In the present study, the dissociation percentage of the PBS medium was about 70%, which might represent the possible presence of hydrophobic bonds between hydrophobic amino acids and hydrophobic regions of DS. 21 On the other hand, the dissociation percentage in the aqueous medium and aqueous solubility were approximately 10%, indicating stable ionic interactions of HIP complexes in the medium with a very low ionic strength.…”

“… 22 Many researchers have selected other ion pairing agents and protein drugs with significant differences in their molecular weight, resulting in a high molar mass ratio. 21 Therefore, DS was selected in the present study.…”

“…First, the cells were stained by Ki67. 21 For this purpose, they were washed with PBS, blocked with BSA, and then incubated with an anti‐Ki67 antibody for two hours at 4°C. Next, the treated cells were incubated with Texas red goat anti-rabbit IgG (diluted 1:1000 in PBS containing 1% BSA) and washed with PBS for one hour at room temperature.…”

Exposure to Fine Particulate Matter Air Pollution Alters mRNA and miRNA Expression in Bone Marrow-Derived Endothelial Progenitor Cells from Mice

“…Other gene expression changes we observed are consistent with an impairment in EPC differentiation. For instance, signaling through the angiopoietin receptor Tek (Tie2), a commonly used marker of mature EPCs, is important in controlling the differentiation of these cells [ 56 ]. Its downregulation ( Table 2 and Table 6 ) suggests inefficient EPC maturation in exposed animals.…”

Mesenchymal stem cell and endothelial progenitor cells coinjection improves LPS‐induced lung injury via Tie2 activation and downregulation of the TLR4/MyD88 pathway

“…Despite the beneficial effects of these cells, some challenges such as low proliferative rate, low ability to migrate to target tissues, and premature aging remain 30 . Subunits of hematopoietic stem cells such as endothelial progenitor cells isolated from the circulating blood, bone marrow, and cord blood are differentiated into adult endothelial cells 20,31,32 . It has been also observed that in patients with acute respiratory distress syndrome (ARDS), the number of circulating EPCs is increased, and is associated with survival in these patients 33 .…”