TRP14 inhibits osteoclast differentiation via its catalytic activity

Area of Science:

• Biochemistry
• Cell Biology
• Immunology

Background:

• Thioredoxin-related protein of 14 kDa (TRP14) is a disulfide reductase with a known inhibitory role in nuclear factor-κB (NF-κB) activation.
• The biological function of TRP14, particularly in osteoclast (OC) biology, remains largely unexplored.
• Osteoclast differentiation and function are critically dependent on NF-κB signaling and cellular redox regulation.

Purpose of the Study:

• To investigate the role of TRP14 in the differentiation and function of osteoclasts.
• To elucidate the mechanisms by which TRP14 influences osteoclastogenesis and bone resorption.
• To evaluate the therapeutic potential of modulating TRP14 activity for bone resorption diseases.

Main Methods:

• Utilized RAW 264.7 macrophage cells engineered to express wild-type TRP14, a catalytically inactive mutant, or small interfering RNA for TRP14 depletion.
• Assessed osteoclast differentiation, actin ring formation, and bone resorption.
• Measured reactive oxygen species (ROS) accumulation and activation of key signaling pathways including NF-κB, c-Jun NH2-terminal kinase, p38, c-Fos, and nuclear factor of activated T cell, cytoplasmic 1 (NFATc1).
• Employed N-acetylcysteine and diphenylene iodonium for ROS and NF-κB inhibition studies.
• Investigated the effects of ectopic TRP14 expression on receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis.

Main Results:

• TRP14 depletion significantly enhanced osteoclast differentiation, actin ring formation, bone resorption, and reactive oxygen species (ROS) accumulation.
• Loss of TRP14 promoted NF-κB, c-Jun NH2-terminal kinase, and p38 activation, alongside increased c-Fos expression and subsequent NFATc1 induction.
• Pharmacological inhibition of ROS and NF-κB attenuated the enhanced osteoclast differentiation observed in TRP14-depleted cells.
• Ectopic expression of wild-type TRP14, but not its inactive mutant, inhibited RANKL-induced ROS accumulation, NF-κB activation, and osteoclast differentiation.

Conclusions:

• TRP14 plays a crucial role in regulating osteoclast differentiation and bone resorption via its catalytic activity.
• TRP14 functions by modulating cellular redox state and NF-κB signaling pathways.
• Targeting and enhancing TRP14 activity presents a promising therapeutic avenue for managing bone resorption diseases.