ELTD1 Activation Induces an Endothelial-EMT Transition to a Myofibroblast Phenotype.

Helen Sheldon,Koon Hwee Ang,Lucia Moreira,Syed Haider,Svetlana Reilly,Alison H Banham,Dian Wang,Salwa Lin,Adrian L Harris,John Alexander,Esther Bridges

doi:10.3390/ijms222011293

Abstract

ELTD1 is expressed in endothelial and vascular smooth muscle cells and has a role in angiogenesis. It has been classified as an adhesion GPCR, but as yet, no ligand has been identified and its function remains unknown. To establish its role, ELTD1 was overexpressed in endothelial cells. Expression and consequently ligand independent activation of ELTD1 results in endothelial-mesenchymal transistion (EndMT) with a loss of cell-cell contact, formation of stress fibres and mature focal adhesions and an increased expression of smooth muscle actin. The effect was pro-angiogenic, increasing Matrigel network formation and endothelial sprouting. RNA-Seq analysis after the cells had undergone EndMT revealed large increases in chemokines and cytokines involved in regulating immune response. Gene set enrichment analysis of the data identified a number of pathways involved in myofibroblast biology suggesting that the endothelial cells had undergone a type II EMT. This type of EMT is involved in wound repair and is closely associated with inflammation implicating ELTD1 in these processes.

Highlights

epidermal growth factor (EGF), latrophilin and seven transmembrane domain-containing protein 1 (ELTD1), recently re-designated Adhesion G Protein-Coupled Receptor L4 (ADGRL4), is an orphan adhesion G Protein-Coupled Receptor (GPCR) of the Latrophilin family
JCat bioinformatics tool without altering the amino acid coding sequence. Codon optimised ELTD1 (coELTD1) expression was confirmed in the stable human microvascular endothelial cell line HMEC-1 and in human umbilical vein endothelial cells (HUVEC) by Western blotting (Figure 1A,B)
5 days after infection with a coELTD1-expressing lentivirus, both cell types underwent a form of endothelialmesenchymal transistion (EndMT), exhibiting an elongated spindle-like morphology (Figure 2A and Control Video S1 Control and Video S2 ELTD1)

Summary

Introduction

EGF, latrophilin and seven transmembrane domain-containing protein 1 (ELTD1), recently re-designated Adhesion G Protein-Coupled Receptor L4 (ADGRL4), is an orphan adhesion G Protein-Coupled Receptor (GPCR) of the Latrophilin family. It was first identified in 2001 by Nechiporuk et al and was expressed in cardiomyocytes and smooth muscles during heart development [1]. ELTD1 has a long extracellular N-terminus containing epidermal growth factor (EGF) and calcium-binding EGF domains, these domains are found in other adhesion GPCRs where they mediate cell-cell interactions and cell migration [2]. Several members of the adhesion GPCR family have been implicated in angiogenesis. ELTD1 expression was identified in normal vasculature [7]

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Conclusion