# Structural and Molecular Mechanisms of Stress Fiber Repair

> **NIH NIH F31** · ROCKEFELLER UNIVERSITY · 2022 · $46,752

## Abstract

PROJECT SUMMARY
 For tissues to maintain a physical steady-state equilibrium with its dynamic surroundings (“mechanical
homeostasis”), individual cells must be able to perceive mechanical cues in their local environment and respond
accordingly. Mechanical homeostasis plays an essential role in morphogenesis, and its dysregulation can lead
to disease states such as hypertension, fibrosis, and asthma. While there has been significant progress in
understanding the physiological significance of mechanical homeostasis and cellular mechanosensation, the
molecular mechanisms by which proteins convert mechanical stimuli into biochemical signals
(“mechanotransduction”) are poorly understood, impeding the development of targeted therapeutics for
dysregulated mechanotransduction and its disease states.
 The actin cytoskeleton plays a prominent role in mechanotransduction, notably actin-myosin cables
known as stress fibers (SFs) which both actively generate contractile forces and transmit extracellular forces
impinging on cell-cell and cell-matrix adhesions into the cytoplasm. Dynamic regulation of SF assembly,
disassembly, and contractility are important for many physiological processes involving cellular mechanics and
dynamic cell shape changes, such as epithelial tissue homeostasis and morphogenesis. Stochastic mechanical
imbalance in SFs can result in mechanically-induced ruptures, termed stress fiber strain site (SFSS). While some
SFSS proceed towards catastrophic breakage, the majority are repaired by zyxin, a mechanosensitive LIM (LIN-
11, Isl-1, & Mec-3) protein. Zyxin first localizes to strain sites through its three C-terminal tandem LIM domains,
then recruits the cross-linking protein ɑ-actinin and polymerization factor VASP through its N-terminal domains
to mediate SF repair in a matter of minutes. While there is evidence for this sequence of events at the cellular
level, the biophysical mechanism of zyxin-mediated SF repair is not well understood. Furthermore, the
architectural features of a SFSS which are recognized by zyxin’s LIM domains are unknown.
 Here I propose to determine the molecular and structural mechanism of zyxin-mediated SF repair.
Through biophysical reconstitution and cellular assays, I will test the hypothesis that zyxin, α-actinin, and VASP
directly co-assemble to repair mechanically damaged actin filaments and determine the biophysical mechanism
of zyxin-mediated mechanical homeostasis (Aim 1). I will then apply cutting-edge correlative cryo-light electron
microscopy to test the hypothesis that zyxin binds to a force-dependent actin conformation we have observed in
vitro (Aim 2). In addition to providing specific insights into mechanical homeostasis of SFs, these studies are
also likely to reveal general mechanisms of mechanotransduction through the cytoskeleton. In the longer term,
this work will guide the development of therapeutics against dysregulated mechanotransduction pathways.

## Key facts

- **NIH application ID:** 10536382
- **Project number:** 1F31HL165906-01
- **Recipient organization:** ROCKEFELLER UNIVERSITY
- **Principal Investigator:** Donovan Yong Zhi Phua
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $46,752
- **Award type:** 1
- **Project period:** 2022-09-01 → 2024-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10536382

## Citation

> US National Institutes of Health, RePORTER application 10536382, Structural and Molecular Mechanisms of Stress Fiber Repair (1F31HL165906-01). Retrieved via AI Analytics 2026-05-28 from https://api.ai-analytics.org/grant/nih/10536382. Licensed CC0.

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