# The mechanical and biochemical mechanism of oncogenic Rac1P29S mutation in melanoma survival signaling

> **NIH NIH F30** · WASHINGTON UNIVERSITY · 2020 · $19,236

## Abstract

Project Summary
 This proposal tests if a melanoma-enriched, hyperactivating mutation in Rac1 can drive pro-survival
signaling in melanoma cells by altering intracellular forces. This would be a powerful mechanism linking the
effects of an oncogenic Rac1 mutation to alterations in physical stimuli that amplify biochemical signals and
drive malignancy.
 Next-generation tumor sequencing has led to the discovery of a reoccurring mutation in the Rac1
GTPase gene in melanoma that results in a proline-to-serine switch at residue 29 (Rac1P29S). The Rac1P29S
mutation is transforming, is associated with increased risk of metastasis, and confers resistance to
chemotherapeutics like vemurafenib in melanoma. The mechanisms by which Rac1P29S drives melanoma
progression are unknown.
 Wild type Rac1 is a key regulator of cytoskeletal organization and adhesion formation between the cell
and the extracellular matrix (ECM). Adhesion proteins sense mechanical interactions between the cell and the
ECM and activate pro-survival pathways in cancer. Expression of hyperactive Rac1P29S results in cells with
large, elongated focal adhesions and prominent stress fibers, suggesting high contractility and tension at the
cell-ECM adhesions. Additionally, Rac1P29S-mediated pro-survival signaling is abrogated upon inhibition of
these adhesions. This proposal tests if the role of Rac1P29S in driving melanoma progression is dependent on
mechanical cues resulting from the increased cell contractility and tension at cell-ECM adhesions.
 The first goal of this proposal is to test if Rac1P29S increases cell contractility and forces at cell-ECM
adhesions. Traction force microscopy (TFM) will be used to measure traction forces at cell-ECM adhesions in
Rac1P29S and Rac1WT cells. The second goal of this proposal is to test if Rac1P29S increases RhoA signaling by
competitively binding RhoGDI, an inhibitor of both Rac1 and RhoA. It is expected that RhoA activity will be
increased in Rac1P29S and Rac1WT cells, but will be abrogated upon inhibition of Rac1P29S-RhoGDI interaction.
It is also expected that inhibition of traction forces and RhoA signaling will reduce Rac1P29S's pro-survival
activity, resulting in increased melanoma sensitivity to a drug challenge. The final goal of this study is to
determine if Rac1P29S itself is responsive to force stimuli at adhesions, establishing a positive feedback loop
that would further amplify pro-survival signaling. If force stimuli at adhesions regulate Rac1P29S activity will be
tested by measuring melanoma drug sensitivity following inhibition of adhesion-activated force-sensitive Rac1
regulators. Elucidating Rac1P29S's bi-directionality in amplifying mechano-responsive signaling by both
stimulating and responding to force stimuli at adhesions would place Rac1P29S at the center of mechanically
sensitive positive-feedback loop that drives melanoma malignancy.

## Key facts

- **NIH application ID:** 10017670
- **Project number:** 5F30CA206399-05
- **Recipient organization:** WASHINGTON UNIVERSITY
- **Principal Investigator:** Ashwathi Mohan
- **Activity code:** F30 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $19,236
- **Award type:** 5
- **Project period:** 2017-03-01 → 2020-09-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10017670

## Citation

> US National Institutes of Health, RePORTER application 10017670, The mechanical and biochemical mechanism of oncogenic Rac1P29S mutation in melanoma survival signaling (5F30CA206399-05). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10017670. Licensed CC0.

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