# Molecular mechanisms of force production and force sensing during clathrin-mediated endocytosis

> **NIH NIH R01** · YALE UNIVERSITY · 2024 · $332,083

## Abstract

ABSTRACT
Eukaryotic cells use clathrin-mediated endocytosis (CME) to internalize nutrients, receptors and
recycle their plasma membrane. Defects in endocytosis are implicated in various diseases such
as cancer, neuropathies, and metabolic syndromes, and the CME machinery can be hijacked by
pathogens to infect cells. Deforming the membrane into ~50-nm endocytic vesicles requires the
choregraphed assembly and disassembly of 60+ proteins. Because the CME machinery
continuously exchanges and CME is diffraction-limited, the precise molecular mechanisms for
force production have remained elusive. Models based on actin polymerization have been
proposed but the amount of force they can realistically produce is 1-2 orders of magnitude too
low. In this project, we will build on the discoveries we made during last funding period to study
new mechanisms of force production at the CME site and determine mechanisms for the
regulation of membrane tension, which is a key parameter for endocytosis. In aim 1, we
hypothesize that crosslinking highly dynamic actin filaments can produce large amounts of force
in a sustained way. We will characterize the biophysical properties of fimbrin in vitro, use
mathematical modeling to uncover mechanisms of sustained force production by crosslinking of
dynamic actin filaments, and test the model’s predictions by single-molecule tracking at the
CME site. Aim 2 will focus on discovering the molecular mechanisms underlying the fast
exchange of endocytic proteins we discovered during last funding period. We will test different
hypotheses using mathematical modeling, measure the dependence of fimbrin’s detachment
rate as a function of force, and determine whether the exchange of endocytic protein depends
on the stage of endocytosis. In aim 3, we will characterize mechanisms for the regulation of
plasma membrane tension and its influence on CME. We will use optical tweezers to determine
whether membrane tension is locally and temporally regulated and use mathematical modeling
to understand how a local reduction in membrane tension modulates the forces required for
endocytosis. Altogether, our results will uncover new paradigms for dynamic force production
and membrane tension control that will impact a variety of cellular processes.

## Key facts

- **NIH application ID:** 10852011
- **Project number:** 5R01GM115636-09
- **Recipient organization:** YALE UNIVERSITY
- **Principal Investigator:** Julien Berro
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $332,083
- **Award type:** 5
- **Project period:** 2016-04-01 → 2025-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10852011

## Citation

> US National Institutes of Health, RePORTER application 10852011, Molecular mechanisms of force production and force sensing during clathrin-mediated endocytosis (5R01GM115636-09). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10852011. Licensed CC0.

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