Inhibition of NFAM1 suppresses phospho-SAPK/JNK signaling during osteoclast differentiation and bone resorption

Area of Science:

• Cell Biology
• Molecular Biology
• Bone Biology

Background:

• NFAT activating protein with ITAM motif 1 (NFAM1) signaling is linked to increased osteoclast formation and bone resorption in Paget's disease of bone.
• The precise molecular mechanisms by which NFAM1 regulates osteoclast differentiation and bone resorption remain largely undefined.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying NFAM1's role in osteoclast differentiation and bone resorption.
• To investigate the impact of NFAM1 on key signaling pathways involved in osteoclastogenesis.

Main Methods:

• Investigated NFAM1 expression in preosteoclast cells following RANK ligand (RANKL) stimulation.
• Utilized NFAM1 knockdown (KD) stable cell lines (RAW264.7) to assess the effects on cytokine production and signaling pathway activation.
• Analyzed the expression and activity of key transcription factors and kinases, including STAT6, c-fos, p-c-Jun, and JNK.
• Evaluated osteoclast differentiation and bone resorption capacity in mouse bone marrow cell cultures with NFAM1 inhibition.

Main Results:

• RANKL stimulation increased NFAM1 expression in preosteoclast cells.
• NFAM1 knockdown significantly reduced levels of interleukin-6, tumor necrosis factor-α, and CXCL-5.
• NFAM1 knockdown suppressed RANKL-induced p-STAT6, c-fos, p-c-Jun, and JNK activity, specifically through inhibition of p-SAPK/JNK.
• NFAM1 inhibition led to decreased NFATc1 expression, suppressed osteoclast differentiation, and reduced bone resorption capacity.

Conclusions:

• NFAM1 plays a critical role in regulating osteoclast differentiation and bone resorption.
• NFAM1 modulates osteoclastogenesis by controlling the SAPK/JNK signaling pathway.
• Targeting NFAM1 may offer a therapeutic strategy for bone diseases characterized by excessive osteoclast activity.