# Phospholipase D2/SphK1 Signaling and Adherens Junction Assembly and Barrier Restoration

> **NIH NIH P01** · UNIVERSITY OF ILLINOIS AT CHICAGO · 2020 · $340,072

## Abstract

Project Summary
Disassembly of adherens junctions (AJs) of lung endothelial cell (EC) monolayers by edemagenic agents
causes microvascular hyper-permeability and protein-rich pulmonary edema formation, and if uncorrected, it
leads to deterioration of lung gas exchange. These changes reflect the failure of the lung's intrinsic
homeostatic mechanisms, and as such, they are the hallmarks of acute respiratory distress syndrome (ARDS).
Despite our current understanding of the multi-faceted pathogenic mechanisms increasing lung vascular
permeability, little is known about the molecular regulation of endothelial barrier restoration following lung
injury. The focus of Project 4 will be on defining the role of what we postulate is a key regulatory enzyme
phospholipase D2 (PLD2). We propose based on our Supporting Data that PLD2-activated signaling
pathways are crucial in the formation of adhesive contacts between ECs via activation of homotypic
interactions of VE-cadherin, and in turn restore lung endothelial barrier integrity. The underlying molecular
mechanisms regulating VE-cadherin assembly and the closure of adherens junctions (AJs) however are not
well understood. In Project 4 we will interrogate the central concept that that activation of PLD2 generates
phosphatidic acid (PA), which in turn stimulates the activation of sphingosine kinase 1 (SphK1) in a
phosphorylation-dependent manner that results in the localized generation of sphingosine-1-phosphate (S1P).
Thereafter, efflux of S1P via the S1P transporter Spinster homologue-2 (Spns2) facilitates the ligation of
S1PR1 in an autocrine/paracrine manner to induce cortactin-dependent formation of lamellipodia and re-
annealing of AJs through VE-cadherin interactions. The signaling elements of this pathway, mechanisms of
their activation, and how formation of membrane protrusions restores AJ integrity will be defined. Thus,
in Project 4 we will pursue the following Specific Aims: (i) we will determine the obligatory role of PLD2
generation of PA in mediating trafficking of VE-cadherin, and thereby the formation of AJs and
restoration of the lung endothelial barrier; and (ii) we will determine the role of the PLD2SphK1
signaling axis in activating S1P efflux via the transporter Spinster homologue-2 (Spns2), a rate limiting
step, and how the subsequent tyrosine phosphorylation of cortactin mediates the re-sealing of AJs.
Together, these studies will delineate for the first time to our knowledge the required and sufficient roles of
PLD2, Spns2, VE-cadherin and cortactin acting in concert in the formation of lamellipodia to facilitate resealing
of endothelial gaps and restoration of endothelial barrier following lung injury. We expect that our studies will
provide the framework for the deveolpment of novel therapeutic approaches to combat and treat ARDS
patients with leaky lung vessels and intractable pulmonary edema.

## Key facts

- **NIH application ID:** 9970544
- **Project number:** 5P01HL060678-20
- **Recipient organization:** UNIVERSITY OF ILLINOIS AT CHICAGO
- **Principal Investigator:** VISWANATHAN NATARAJAN
- **Activity code:** P01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $340,072
- **Award type:** 5
- **Project period:** 2000-03-08 → 2022-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9970544

## Citation

> US National Institutes of Health, RePORTER application 9970544, Phospholipase D2/SphK1 Signaling and Adherens Junction Assembly and Barrier Restoration (5P01HL060678-20). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9970544. Licensed CC0.

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