# Soluble adenylyl cyclases in pulmonary endothelial permeability

> **NIH NIH P01** · UNIVERSITY OF SOUTH ALABAMA · 2020 · $300,166

## Abstract

PROJECT SUMMARY
Soluble adenylyl cyclases generate a cAMP signal that breaks down microtubules leading to endothelial cell
barrier disruption. The P. aeruginosa type 3 secretion system effector exoenzyme Y is one such soluble
cyclase. However, we have discovered that this enzyme is a promiscuous nucleotidyl cyclase capable of
generating both purine and pyrimidine (i.e. non-canonical) cyclic nucleotide monophosphates, including cGMP,
cUMP, and cAMP. The cAMP signal, and to a lesser extent the cGMP signal, activates protein kinase A, which
phosphorylates tau leading to microtubule breakdown. Phosphorylated tau accumulates inside the
endothelium for several hours as a high molecular weight, or oligomeric, form, and is then released from the
cell into the supernatant in vitro, and bronchoalveolar lavage and blood in vivo. Preliminary data suggest
cellular release of high molecular weight tau is stimulated by cUMP. Our previously published work and recent
preliminary studies indicate high molecular weight tau retrieved from cellular supernatant fractions is heat
stable, protease resistant, insoluble in certain detergents, insensitive to RNase and DNase treatments, and can
be resolved in a 30-50% ammonium sulfate fraction by column chromatography. It can be sedimented by
centrifugation with an angular momentum of 1.14 x 1012. This high molecular weight tau is transmissible
between cells, leading to inter-endothelial cell gap formation, increased permeability and cytotoxicity;
pulmonary microvascular endothelial cells are especially sensitive to this injury. Its cytotoxicity is inactivated
by phenol extraction, by post-translational modification with diethylpyrocabonate, and with hexafluoro-2-
propanol, all characteristics of amyloid proteins. We have searched for a means to prevent the transmissible
cytotoxicity as an anti-inflammatory therapy. We have recently discovered that prion protein is expressed in
lung endothelium. Whereas prion antibody treatment initiates a pro-survival signal and prevents tau-induced
hyperpermeability and cytotoxicity, prion protein genetic deletion increases endothelial sensitivity to the high
molecular weight tau. Hence, this proposal tests the hypothesis that ExoY generates purine and pyrimidine
cyclic nucleotides in endothelium and induces release of high molecular weight tau capable of generating
transmissible hyperpermeability and cytotoxicity, an effect prevented by antibody ligation of prion protein.

## Key facts

- **NIH application ID:** 9962990
- **Project number:** 5P01HL066299-18
- **Recipient organization:** UNIVERSITY OF SOUTH ALABAMA
- **Principal Investigator:** Troy Stevens
- **Activity code:** P01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $300,166
- **Award type:** 5
- **Project period:** — → —

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9962990

## Citation

> US National Institutes of Health, RePORTER application 9962990, Soluble adenylyl cyclases in pulmonary endothelial permeability (5P01HL066299-18). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9962990. Licensed CC0.

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