Pasteurella multocida toxin- induced osteoclastogenesis requires mTOR activation

Area of Science:

• Molecular biology
• Cell biology
• Immunology

Background:

• Pasteurella multocida toxin (PMT) causes atrophic rhinitis in pigs, characterized by turbinate bone loss.
• The molecular mechanisms underlying PMT-induced bone loss are not fully understood.

Purpose of the Study:

• To investigate the role of mTOR complex 1 (mTORC1) in PMT-induced osteoclast formation and bone resorption.
• To elucidate the molecular pathway linking PMT to osteoclastogenesis.

Main Methods:

• Utilized RAW264.7 macrophages to study PMT effects.
• Assessed osteoclast differentiation and bone resorption capacity.
• Investigated the impact of the mTORC1 inhibitor rapamycin.
• Analyzed protein and gene expression of key signaling molecules including p70 S6K1, PDCD4, c-Jun, and cathepsin K.

Main Results:

• PMT induced differentiation of macrophages into functional osteoclasts that resorbed bone.
• Rapamycin significantly inhibited PMT-induced osteoclast formation and bone resorption.
• PMT upregulated c-Jun and cathepsin K in an mTOR-dependent manner.
• PMT-induced mTOR activation led to decreased PDCD4 expression, facilitating c-Jun activation.

Conclusions:

• mTOR signaling is crucial for PMT-induced osteoclast formation.
• PMT toxin activates mTOR, downregulates PDCD4, and upregulates c-Jun, promoting osteoclastogenesis and bone loss.