# Phosphorylation of the podocyte cytoskeleton in diabetic nephropathy

> **NIH NIH R03** · BETH ISRAEL DEACONESS MEDICAL CENTER · 2022 · $131,250

## Abstract

Podocyte dysfunction is an early, key event in the pathogenesis of diabetic nephropathy. Podocytes rely on their
cytoskeleton to maintain their structure and function while facing constant mechanical stress inside the
glomerulus. a-Actinin 4 (ACTN4) is an essential crosslinker of the actin cytoskeleton; mutations in ACTN4 lead
to human kidney disease. Recent evidence has identified an important phosphorylation event in ACTN4 at serine
(S) 159. In phosphomimetic cellular and animal models, this phosphorylation of ACTN4 is associated with
podocyte vulnerability under mechanical stress. Moreover, phosphorylation of wild type (WT) ACTN4 at S159 is
stimulated by high glucose and associated with cytoskeletal derangements, similar to derangements associated
with disease-causing mutant ACTN4. The long-term goal that this R03 application advances is to understand
the cytoskeleton’s role in podocyte dysfunction underlying diabetic nephropathy. The overall objective of the
current proposal is to elucidate the pathway by which high glucose leads to phosphorylation of ACTN4 as a
potential mediator of podocyte vulnerability. The central hypothesis is that increased phosphorylation of ACTN4
is stimulated by high glucose and fosters podocyte vulnerability to mechanical stress. The rationale for this
project is that finding new pathways leading to podocyte vulnerability could fill critical gaps in knowledge related
to the pathogenesis of diabetic nephropathy. To attain the overall objective of this application, the following two
specific aims will be pursued. Aim 1 will define the association between phosphorylation of ACTN4 and diabetic
nephropathy in vivo. Wild type (WT) control and diabetic nephropathy kidney tissue will be obtained from mice,
rats, and humans. Targeted mass spectrometry will be used to quantify ACTN4 phosphorylation across all
samples. Aim 2 will determine the impact of high glucose-mediated ACTN4 phosphorylation in vitro. Microfluidic
glomeruli-on-chips will be seeded with either human podocytes carrying WT ACTN4 or human podocytes
carrying nonphosphorylatable S159A ACTN4. These glomeruli-on-chips will be exposed to culture media
containing high glucose while subjected to mechanical stretch and shear stress. The proposed research is
innovative since it employs the latest, state-of-the art techniques to study phosphorylation of the cytoskeleton
and podocyte vulnerability. The proposed research is significant because it will define a novel pathway by which
high glucose mediates podocyte dysfunction through phosphorylation of the podocyte cytoskeleton.
Demonstrating that (1) this pathway is upregulated in in vivo models of diabetic nephropathy and that (2) this
pathway contributes to podocyte vulnerability under mechanical stress will provide strong justification to further
study phosphorylation of ACTN4 as a mechanism underlying the onset and progression of diabetic nephropathy.
Data from this R03 will support an R01 to identify the kinases an...

## Key facts

- **NIH application ID:** 10456149
- **Project number:** 5R03DK129637-02
- **Recipient organization:** BETH ISRAEL DEACONESS MEDICAL CENTER
- **Principal Investigator:** Di Feng
- **Activity code:** R03 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $131,250
- **Award type:** 5
- **Project period:** 2021-07-23 → 2024-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10456149

## Citation

> US National Institutes of Health, RePORTER application 10456149, Phosphorylation of the podocyte cytoskeleton in diabetic nephropathy (5R03DK129637-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10456149. Licensed CC0.

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