# The impact of dynamic actin polymerization on mitochondrial dynamics and function

> **NIH NIH R35** · DARTMOUTH COLLEGE · 2024 · $794,426

## Abstract

The ‘actin cytoskeleton’ is not one structure but a number of distinct structures assembled and disassembled for
different purposes. In mammalian cells, a few abundant and easily recognizable structures dominate our view
of the actin cytoskeleton, including: stress fibers, lamellipodia and filopodia. However, a growing number of less
abundant and/or highly transient actin-based structures have been revealed, controlling important cellular
processes. Two such actin structures are the subject of this application: 1) CIA, calcium-induced actin; and 2)
ADA, acute depolarization-induced actin. Though highly transient, both structures are extensive in the cytosol
and affect important processes. In addition, both CIA and ADA impact the structure and function of mitochondria.
CIA depends on calcium activation of the formin protein INF2, which stimulates actin polymerization on the
endoplasmic reticulum and throughout the cytosol. Downstream effects of CIA include increased mitochondrial
calcium and increased mitochondrial fission. The importance of CIA is illustrated by the fact that INF2 mutations
link to two diseases, focal segmental glomerulosclerosis (FSGS) and Charcot-Marie-Tooth disease (CMTD).
ADA is triggered by mitochondrial depolarization (either pharmacologically-induced or hypoxia-induced), which
activates two parallel pathways: 1) mitochondrial calcium release activates protein kinase C-, activating in turn
Rac, WAVE complex, and Arp2/3 complex; and 2) decreased ATP activates AMP-dependent protein kinase
(AMPK) through LKB1, activating in turn Cdc42 and FMNL formins. The ADA actin network is tightly associated
with mitochondria. An exciting new result is that one immediate consequence of ADA is rapid stimulation of
glycolysis. Additionally, ADA temporarily inhibits longer-term consequences of mitochondrial depolarization such
as mitochondrial reorganization and recruitment of the mitophagy protein Parkin. The goals in this grant period
are to elucidate both the mechanisms triggering CIA and ADA, as well as their downstream effects. These goals
will be accomplished using a combination of cellular approaches (live-cell microscopy, proteomics, metabolic
analysis) and biochemical approaches (cell-free reconstitution, analysis of purified proteins on model lipid
membranes). The questions to be asked include the following. 1) How is INF2 activated by increased calcium?
2) How are INF2-polymerized filaments organized into a network by myosin II and fascin? 3) How does CIA
interface with known mitochondrial fission proteins such as Mff and Drp1 to stimulate fission? 4) How do PKC
and AMPK activate Rac and Cdc42, respectively, during ADA? 5) How do Arp2/3 complex and FMNL formins
work together during ADA? 6) How does ADA stimulate glycolysis? These questions address fundamental
mechanistic questions important to a wide range of mammalian cells, and occupy an exciting frontier between
cytoskeletal biology, mitochondrial biology, and metabolism.
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## Key facts

- **NIH application ID:** 10899666
- **Project number:** 5R35GM122545-08
- **Recipient organization:** DARTMOUTH COLLEGE
- **Principal Investigator:** HENRY N HIGGS
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $794,426
- **Award type:** 5
- **Project period:** 2017-09-01 → 2027-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10899666

## Citation

> US National Institutes of Health, RePORTER application 10899666, The impact of dynamic actin polymerization on mitochondrial dynamics and function (5R35GM122545-08). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10899666. Licensed CC0.

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