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

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.