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Disease-associated TNFRSF11B variants differentially disrupt osteoprotegerin secretion and function
Reina Suzuki1, Hisayo Nishida-Fukuda2, Shinji Fukuda2
1Department of Orthodontics, School of Dentistry, Aichi Gakuin University, 2-11 Suemori-dori, Chikusa-ku, Nagoya, Aichi 464-8651, Japan.
Bone
|August 10, 2026
Summary
Osteoprotegerin (OPG) mutations impact bone health by disrupting its secretion and function. This study identifies specific mutation effects and reveals endoplasmic reticulum-associated degradation (ERAD) as a key regulator of OPG secretion.
Area of Science:
- Biochemistry
- Genetics
- Bone Biology
Background:
- Osteoprotegerin (OPG), encoded by TNFRSF11B, is crucial for inhibiting osteoclastogenesis by acting as a decoy receptor for RANKL.
- Loss-of-function mutations in TNFRSF11B lead to bone metabolic disorders like juvenile Paget's disease, but the precise mechanisms of OPG dysfunction are not fully understood.
- Understanding how specific TNFRSF11B variants affect OPG secretion and activity is essential for elucidating disease pathogenesis.
Purpose of the Study:
- To quantitatively assess the impact of disease-associated TNFRSF11B variants on OPG secretion and its osteoclastogenesis-inhibitory activity.
- To elucidate the molecular mechanisms underlying OPG dysfunction caused by specific mutations.
- To investigate the role of endoplasmic reticulum-associated degradation (ERAD) in regulating OPG secretion.
Main Methods:
- Expressed wild-type and variant OPG proteins as Gaussia luciferase fusion constructs to measure extracellular secretion.
- Evaluated functional activity using a mouse osteoclastogenesis assay to assess OPG's inhibitory capacity.
- Investigated the role of ERAD by employing proteasome inhibition and knockdown of ERAD components (HRD1, SEL1L).
Main Results:
- Cysteine substitution variants (C65F, C87Y) showed severe secretion defects.
- Variants T76P and D182del exhibited reduced secretion and inhibitory activity, while F117L had normal secretion but impaired function.
- Truncation variants (D323fs, R333Ter) had reduced secretion but retained significant anti-RANKL activity; ERAD inhibition increased OPG secretion for wild-type and these variants.
Conclusions:
- Mutation-specific mechanisms contribute to OPG dysfunction in bone metabolic disorders.
- Endoplasmic reticulum-associated degradation (ERAD) plays a significant role in regulating OPG secretion.
- These findings provide insights into the pathogenesis of TNFRSF11B-related bone diseases and potential therapeutic targets.