# The Role of Mammalian Diaphanous Formin 1 in Leading Edge Cell Protrusion

> **NIH NIH F31** · ALBERT EINSTEIN COLLEGE OF MEDICINE · 2024 · $48,974

## Abstract

ABSTRACT
The actin cytoskeleton is regulated by members of the p21 Rho family of small GTPases by propagating
signals to downstream effectors including the mammalian diaphanous-related formin 1, mDia1. The formin
mDia1 directly modulates the actin cytoskeleton by nucleating actin and assembling linear actin filaments. In
addition to the enzymatic activity, mDia1 can recruit proteins containing SH3 domains such as non-receptor
tyrosine kinase, Src. There is a limited understanding of the mDia1-specific, RhoGTPase-mediated functions
that contribute to cellular protrusive structures, specifically at the leading edge. To protrude, cells require
polymerization of actin filaments to mechanically extend the leading edge. The newly extended protrusion can
become stabilized by formation of adhesion sites or retracted by disassembly of adhesions. In this proposal we
seek to delineate RhoGTPase paralogs that regulate mDia1 and its subsequent downstream functions in
leading edge cell protrusions. We hypothesize that the RhoGTPases RhoC and/or RhoA are activating mDia1
at the leading edge to recruit Src to sites of adhesion and to polymerize actin filaments, respectively. To gain
understanding into the RhoGTPase regulation of mDia1, in Aim 1 we will develop Förster Resonance Energy
Transfer (FRET) based biosensor tools capable of reporting the activity status of mDia1 in living cells. We will
focus on the development of Near-Infra red (NIR) fluorescent protein biosensor of mDia1 to allow simultaneous
detection of cyan-yellow FRET RhoGTPase biosensors or to use the blue-green optogenetic tools targeting
RhoGTPases and their upstream regulators, in single living cells. We will use this approach to determine the
RhoC and RhoA regulation of mDia1 at the leading edge. For Aim 2, we will uncover the downstream function
of mDia1 by recruitment of Src to sites of adhesion and how this impacts adhesion turnover during protrusive
events. Additionally, we will elucidate the spatiotemporal dynamics of mDia1 in mediating linear actin assembly
at the leading edge protrusions. We will discern the mDia1-specific, localized activities and functions using our
newly developed mDia1 biosensor in WT and RhoGTPase perturbed cells. Our approach will allow us to
delineate the spatiotemporal dynamics of mDia1 and the respective RhoGTPase paralogs regulating them in
cells during leading edge protrusions.

## Key facts

- **NIH application ID:** 10831833
- **Project number:** 5F31GM150215-02
- **Recipient organization:** ALBERT EINSTEIN COLLEGE OF MEDICINE
- **Principal Investigator:** Andrea Ramirez
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $48,974
- **Award type:** 5
- **Project period:** 2023-05-01 → 2025-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10831833

## Citation

> US National Institutes of Health, RePORTER application 10831833, The Role of Mammalian Diaphanous Formin 1 in Leading Edge Cell Protrusion (5F31GM150215-02). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10831833. Licensed CC0.

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