# Structural-Functional Mechanisms Controlling Actin Filament Barbed and Pointed End Dynamics

> **NIH NIH R01** · UNIVERSITY OF PENNSYLVANIA · 2024 · $325,000

## Abstract

Project Summary
Actin, which exists in filamentous (F-actin) and monomeric (G-actin) forms, is the most abundant protein in the
cytoplasm of eukaryotic cells and a key player in countless processes in health and disease, including cell
motility, muscle contraction, cancer metastasis, and cardiomyopathies. F-actin is a polar filament, with fast
polymerizing barbed (+) and depolymerizing pointed (-) ends. The control of monomer addition/dissociation
at the ends of the actin filament is a key event that affects all cellular functions of actin in health and disease.
This process is tightly regulated in cells by actin's ATPase activity and many proteins that control subunit
exchange at the ends of the filament. Among those are proteins that accelerate subunit addition at the barbed
end (formins), accelerate subunit dissociation from the pointed end (cyclase-associated protein and cofilin), or
“cap” the barbed (CapZ, gelsolin) and pointed (Tmod-Tpm) ends of F-actin. Barbed end capping by CapZ is in
turn regulated by several proteins, including CARMIL. The structural-functional mechanisms that control the
activities of these proteins and filament end dynamics are poorly understood. To address this lack of
understanding, this grant will tackle the following Aims: 1) Control of actin dynamics at the barbed end, 2)
Mechanism of barbed end uncapping by CARMIL, 3) Control of actin dynamics at the pointed end. The
rationale and likelihood of success of the Aims is substantiated by extensive preliminary work, including: a) all
the relevant proteins have been obtained, including a majority in human cells, b) determination of preliminary
cryo-electron microscopy (cryo-EM) structures of the free and CapZ-capped barbed end, c) determination of
preliminary cryo-EM structures of the free and Tmod-Tpm-capped pointed end, d) determination of preliminary
cryo-EM structures of CARMIL alone and in complex with CapZ, e) a CARMIL knockout cell line obtained by
CRISPR/Cas9 (collaboration with the Lappalainen lab, Helsinki), and f) proteomics data revealing key post-
translational modifications in CARMIL. The proposed studies should substantially advance our understanding
of F-actin barbed and pointed end dynamics, a process that impacts cellular activities of actin in health and
disease.

## Key facts

- **NIH application ID:** 10774457
- **Project number:** 1R01GM152412-01
- **Recipient organization:** UNIVERSITY OF PENNSYLVANIA
- **Principal Investigator:** ROBERTO DOMINGUEZ
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $325,000
- **Award type:** 1
- **Project period:** 2024-08-01 → 2026-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10774457

## Citation

> US National Institutes of Health, RePORTER application 10774457, Structural-Functional Mechanisms Controlling Actin Filament Barbed and Pointed End Dynamics (1R01GM152412-01). Retrieved via AI Analytics 2026-06-12 from https://api.ai-analytics.org/grant/nih/10774457. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*