# Akt-mediated phosphorylation of hsp70 regulates mitochondrial localization of SOD2 and oxidative stress in pulmonary artery endothelial cells during postnatal transition

> **NIH NIH K08** · MEDICAL COLLEGE OF WISCONSIN · 2021 · $41,256

## Abstract

Project Summary
Pulmonary circulation undergoes adaptive processes critical for survival of the newborn at birth. For a successful
postnatal transition, several events come to play, including increased pulmonary blood flow and remodeling of
muscularized small-medium size pulmonary arteries (PAs). One important mechanism regulating these
processes is the activation of adaptive processes that regulate mitochondrial oxidative stress. However, the
mechanism is unknown. For the past five years, through the mentored career development award, we have been
exploring the molecular processes that maintain the activity of mitochondrial-localized superoxide dismutase
(SOD2) appropriate for ROS levels in mitochondria during postnatal transition. Our findings demonstrate that
phosphorylation of heat shock protein-70 (hsp70), a major cytosolic molecular chaperone is a critical mechanism
regulating mitochondrial oxidative stress during exposure of the fetal lungs to high oxygen environment. We
found that elevated ROS induces the activation of protein kinase-B (AKT1), which in turn phosphorylates Hsp70
on Serine-(S631) to promote the import of SOD2 into the mitochondria in response to stress. We also found that
when phosphorylated on S631, Hsp70 recruits Obg-like ATPase-1 (OLA1) to Hsp70-SOD2 complexes and the
binding of OLA1 drives the mitochondrial SOD2 import by antagonizing CHIP-mediated ubiquitination and
proteasomal degradation of Hsp70 and its downstream target, SOD2. Disruption of AKT-mediated
phosphorylation of Hsp70S631 increases mitochondrial ROS levels. We also observed that AKT activity is
significantly decreased in persistent pulmonary hypertension of the newborn (PPHN) and contributes to impaired
vasorelaxation in the disease. However, all these studies were done in vitro, therefore it is important to verify this
critical mechanism in vivo. Our working hypothesis is that dynamic phosphorylation of Hsp70S631 by AKT is a
novel mechanism promoting postnatal adaptation of pulmonary circulation at birth through mechanisms
regulating mitochondrial import of SOD2 and redox balance. To test this hypothesis in an in vivo model, we will
test the effect of disrupting OLA1 binding to hsp70 or AKT-mediated phosphorylation of Hsp70 in vivo using
Sprague Dawley (SD) rats. We have generated a series of cell-permeable decoy peptide inhibitors of AKT and
OLA1. For this, 4 weeks old rats will be treated with GSG (Akt inhibitor), or GLGIV (OLA1 inhibitor) peptide for 4
weeks in normoxic conditions. Echocardiographic measurements of tricuspid regurgitant jets (TR jets) and
cardiac function will be performed. We will also quantify mitochondrial ROS levels using mitoSOX staining and
HPLC. Vasorelaxation responses of PA in the treated and untreated groups to physiological stimuli in an ex-vivo
preparations will be determined. It is anticipated that interruptions of hsp70 interactions with Akt or OLA1 will
induce vascular remodeling and PPHN. While CHIP inhibition would in...

## Key facts

- **NIH application ID:** 10402122
- **Project number:** 3K08HL133379-05S1
- **Recipient organization:** MEDICAL COLLEGE OF WISCONSIN
- **Principal Investigator:** Adeleye J afolayan
- **Activity code:** K08 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $41,256
- **Award type:** 3
- **Project period:** 2016-09-01 → 2022-01-09

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10402122

## Citation

> US National Institutes of Health, RePORTER application 10402122, Akt-mediated phosphorylation of hsp70 regulates mitochondrial localization of SOD2 and oxidative stress in pulmonary artery endothelial cells during postnatal transition (3K08HL133379-05S1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10402122. Licensed CC0.

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