MYSM1 attenuates osteoarthritis by recruiting PP2A to deubiquitinate and dephosphorylate RIPK2

Area of Science:

• Biochemistry
• Molecular Biology
• Pathology

Background:

• Osteoarthritis (OA) is a prevalent degenerative joint disease characterized by cartilage degradation.
• Current treatments for OA do not modify disease progression, highlighting the need for novel therapeutic targets.

Purpose of the Study:

• To investigate the roles of Myb-like, SWIRM, and MPN domains 1 (MYSM1) and Receptor-interacting protein kinase 2 (RIPK2) in OA pathogenesis.
• To elucidate the molecular mechanisms by which MYSM1 and RIPK2 influence OA progression.

Main Methods:

• Analysis of MYSM1 levels in OA patients and mouse models.
• Genetic manipulation (knockout/overexpression) of MYSM1 in mouse models of OA.
• Investigation of RIPK2 activity and its downstream signaling pathways (NF-κB, MAPK).
• Assessment of the effects of RIPK2 mutations and silencing on OA phenotypes.

Main Results:

• Reduced MYSM1 levels were observed in OA cartilage.
• MYSM1 deficiency exacerbated OA, while its overexpression ameliorated OA.
• MYSM1 inhibited NF-κB and MAPK pathways, whereas RIPK2 activation promoted OA-like phenotypes.
• MYSM1 deubiquitinates and dephosphorylates RIPK2 at serine 176 via PP2A recruitment, counteracting RIPK2's pro-inflammatory effects.

Conclusions:

• MYSM1 plays a protective role in OA pathogenesis by inhibiting pro-inflammatory signaling.
• RIPK2 acts as a downstream effector that promotes OA progression.
• Targeting the MYSM1-RIPK2 axis presents a potential therapeutic strategy for osteoarthritis.