# HUWE1 in Skeletal Muscle Prevents Muscle Fatigue via Maintaining Iron and Calcium Homeostasis

## TL;DR

This study shows that HUWE1 in skeletal muscle helps prevent fatigue by managing iron and calcium levels during exercise.

## Contribution

The study reveals a novel regulatory pathway involving HUWE1 in maintaining iron and calcium balance during exercise.

## Key findings

- Loss of HUWE1 in skeletal muscle reduces exercise performance and causes iron overload.
- HUWE1 regulates SERCA activity and ferroportin expression to control calcium and iron homeostasis.
- Dietary iron restriction improves exercise performance and reduces oxidative stress in HUWE1-deficient mice.

## Abstract

Iron is critical to optimal athletic performance because of its role in energy metabolism, oxygen transport, and acid‐base balance. However, the precise mechanism how skeletal muscle maintains iron homeostasis during exercise remains enigmatic. Here, it is demonstrated that the HECT‐domain containing ubiquitin ligase E3 Huwe1 (also known as MULE or ARF‐BP1) in skeletal muscle is suppressed upon exhausted exercise. Loss of Huwe1 in skeletal muscle restrains the exercise performance of Huwe1 conditional knockout (cKO) mice, accompanied with pronounced oxidative stress. Mechanistically, Huwe1 depletion stabilizes c‐Myc protein, leading to upregulated sarcolipin (Sln) expression with inhibited SarcoEndoplasmic Reticulum Calcium ATPase (SERCA) activity, and downregulated ferroportin (Fpn, also known as Slc40a1) expression with iron overload. Silencing of c‐Myc restores SERCA activity and iron export. Consistently, SERCA activator CDN1163, Sln silencing, or dietary iron restriction ameliorates the exercise performance of Huwe1 cKO mice. Of note, improved exercise performance is accompanied with diminished oxidative stress in Huwe1 cKO mice upon iron restriction. Taken together, the results unveil a key function for HUWE1 in skeletal muscle as a fundamental coordinator of iron and calcium homeostasis by regulating SERCA activity and iron metabolism. These findings reveal a regulatory pathway on controlling iron/calcium homeostasis and exercise capacity.

This study investigates the impact of iron homeostasis on exercise. Loss of the HECT domain‐containing ubiquitin ligase E3 (HUWE1) in skeletal muscle restrains the exercise performance in mice with downregulated ferroportin expression leading to iron overload, which is ameliorated by dietary iron restriction. Therefore, it unveils a key function for HUWE1 in skeletal muscle to coordinate iron homeostasis during exercise.