Different modes of endothelial–smooth muscle cell interaction elicit differential β-catenin phosphorylations and endothelial functions

Abstract

β-Catenin phosphorylation plays important roles in modulating its functions, but the effects of different phosphorylated forms of β-catenin in response to heterocellular interaction are unclear. Here we investigated whether distinct modes of phosphorylation on β-catenin could be triggered through heterocellular interactions between endothelial cells (ECs) and smooth muscle cells (SMCs), and the consequent modulation of EC functions. ECs were cocultured with SMCs to initiate direct contact and paracrine interaction. EC-SMC coculture induced EC β-catenin phosphorylations simultaneously at tyrosine 142 (Tyr142) and serine 45/threonine 41 (Ser45/Thr41) at the cytoplasm/nuclei and the membrane, respectively. Treating ECs with SMC-conditional medium induced β-catenin phosphorylation only at Ser45/Thr41. These findings indicate that different phosphorylation effects of EC-SMC coculture were induced through heterocellular direct contact and paracrine effects, respectively. Using specific blocking peptides, antagonists, and siRNAs, we found that the β-catenin Tyr142-phosphorylation was mediated by connexin 43/Fer and that the β-catenin Ser45/ Thr41-phosphorylation was mediated by SMC-released bone morphogenetic proteins through VE-cadherin and bone morphogenetic protein receptor-II/Smad5. Transfecting ECs with β-cateninTyr142 or -Ser45 mutants showed that these two phosphorylated forms of β-catenin modulate differential EC function: The Tyr142-phosphorylated β-catenin stimulates vascular cell-adhesion molecule-1 expression to increase EC-monocytic adhesion, but the Ser45/Thr41-phosphorylated β-catenin attenuates VE-cadherindependent junction structures to increase EC permeability. Our findings provide new insights into the understanding of regulatory complexities of distinct modes of β-catenin phosphorylations under EC-SMC interactions and suggest that different phosphorylated forms of β-catenin play important roles in modulating vascular pathophysiology through different heterocellular interactions.endothelial permeability | inflammation I t is known that β-catenin is a major component of cell junctions and a gene transcription factor that plays important roles in regulating cell functions (1). A well-known regulatory mechanism of β-catenin is through the N-terminal serial phosphorylations at serine 45 (Ser45) and then threonine 41 (Thr41)/ Ser33/37, which consequently initiate the self-degradation of β-catenin. However, recent evidence indicates that the effects of different phosphorylated modes of β-catenin, including tyrosine (Tyr) 142/654 and Ser-45, on its activity regulations are more complex than originally understood (1, 2). For example, β-catenin Ser45-phosphorylation does not necessarily lead to its degradation, but instead modulates cell migration in tumor cells (2); β-catenin Tyr142/654-phosphorylation by membrane receptor tyrosine kinases (RTKs) or cytosolic Fyn/Fer tyrosine kinases increases its transcription cofactor activity to regulate target gene activations in epithelial and tumor cells (1, 3). In add...

Nuclear phosphorylated Y142 β-catenin accumulates in astrocytomas and glioblastomas and regulates cell invasion

“…4,30,31,46 c-Met interacts with b-catenin 47 and PY142 b-catenin is increased in developing hippocampal neurons stimulated with HGF. 31 We report here that PY142 b-catenin levels are detected in GBM biopsies and cell cultures (under basal conditions), which increase upon treatment with HGF in U87MG cells.…”

Interleukin 2 Activates Brain Microvascular Endothelial Cells Resulting in Destabilization of Adherens Junctions

“…IL2-induced Phosphorylation of VE-cadherin-We next analyzed the mechanism by which VE-cadherin and its associated adaptor proteins (p120 and ␤-catenin) are dissociated upon IL2 stimulation. Post-translational modifications, such as phosphorylation events, contribute to destabilization of the AJ complex and loss of endothelial barrier function in various endothelial cell subsets (14,16,17,45). Indeed, IL2 evoked a significant increase in Tyr-685 phosphorylation of VE-cadherin in these cells (Fig.…”

TGFβ Triggers miR-143/145 Transfer From Smooth Muscle Cells to Endothelial Cells, Thereby Modulating Vessel Stabilization

“…Then, a coculture experiment was performed in which the 2 cell types were separately seeded on the 2 sides of a polyethylene terephthalate membrane with a porosity of 1.0 μm, which allowed SMC protrusions to be in direct contact with ECs. 23,24 Using this system, we were able to detect miR-143/145 in ECs after 24 hours of coculture ( Figure 1A). To determine whether the contact was inducing direct transfer or de novo transcription of miR-143/145 in ECs, we used a hybrid system in which primary human ECs were cultured Figure 1C).…”