Expression of periaxin (PRX) specifically in the human cerebrovascular system: PDZ domain-mediated strengthening of endothelial barrier function

Michael M Wang,Svetlana M Stamatovic,Xiaojie Zhang,Anuska V Andjelkovic,Allison M Johnson,Soo Jung Lee,Snehaa Maripudi,Richard F Keep

doi:10.1038/s41598-018-28190-7

Michael M Wang, Svetlana M Stamatovic + Show 6 more

Open Access

https://doi.org/10.1038/s41598-018-28190-7

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Abstract

Regulation of cerebral endothelial cell function plays an essential role in changes in blood-brain barrier permeability. Proteins that are important for establishment of endothelial tight junctions have emerged as critical molecules, and PDZ domain containing-molecules are among the most important. We have discovered that the PDZ-domain containing protein periaxin (PRX) is expressed in human cerebral endothelial cells. Surprisingly, PRX protein is not detected in brain endothelium in other mammalian species, suggesting that it could confer human-specific vascular properties. In endothelial cells, PRX is predominantly localized to the nucleus and not tight junctions. Transcriptome analysis shows that PRX expression suppresses, by at least 50%, a panel of inflammatory markers, of which 70% are Type I interferon response genes; only four genes were significantly activated by PRX expression. When expressed in mouse endothelial cells, PRX strengthens barrier function, significantly increases transendothelial electrical resistance (~35%; p < 0.05), and reduces the permeability of a wide range of molecules. The PDZ domain of PRX is necessary and sufficient for its barrier enhancing properties, since a splice variant (S-PRX) that contains only the PDZ domain, also increases barrier function. PRX also attenuates the permeability enhancing effects of lipopolysaccharide. Collectively, these studies suggest that PRX could potentially regulate endothelial homeostasis in human cerebral endothelial cells by modulating inflammatory gene programs.

Highlights

We identified periaxin (PRX) as a novel human cerebral endothelial PDZ-domain protein
To test for nuclear localization signals in the C-terminus of PRX, we tested the localization of a GFP fusion to PRX sequences that are not present in small isoform of PRX (S-PRX). We found that this protein (GFP-D-PRX; Fig. 4B) had a similar distribution to S-PRX
To test if PRX has a role in barrier function, we investigated potential effects of PRX on primary mouse cerebral endothelial cell barrier function

Summary

Introduction

To identify new human brain endothelial cell proteins, we screened a public database for cerebral factors with vascular expression. Results Identification of a human specific PDZ-domain protein in cerebral endothelial cells. These studies demonstrated that the polyclonal antibodies to PRX recognized both human and mouse protein but that there is human-specific expression in the brain endothelium.

Results

Conclusion