Lactucopicrin promotes the autophagic degradation of MAP2K4/MKK4 by mediating CCDC50 palmitoylation to alleviate osteoarthritis progression.

Lactucopicrin (LCP) alleviates OA progression in a destabilization of the medial meniscus (DMM) mouse model by reducing cartilage degeneration and preserving matrix integrity.

• LCP was identified as an effective autophagy activator in the context of osteoarthritis.
• In vivo testing was conducted using a DMM-induced OA mouse model.
• LCP treatment reduced cartilage degeneration and preserved matrix integrity in this model.
• LCP was described as a 'promising agent for targeting this pathway to inhibit OA progression.'

LCP enhances ZDHHC4-catalyzed palmitoylation of the cargo receptor CCDC50, facilitating selective autophagic degradation of MAP2K4/MKK4.

• CCDC50 functions as a cargo receptor whose palmitoylation is catalyzed by ZDHHC4.
• Palmitoylation of CCDC50 by ZDHHC4 directs MAP2K4/MKK4 for selective autophagic degradation.
• This selective autophagy pathway represents a novel mechanism linking palmitoylation to cargo receptor-mediated degradation.
• The acyl-biotin exchange (ABE) method was used to assess palmitoylation.

LCP directly binds to His72 of ZDHHC4 via its p-hydroxybenzoic acid moiety, boosting enzymatic activity.

• Structural analysis identified the binding interaction between LCP and ZDHHC4.
• The p-hydroxybenzoic acid moiety of LCP mediates direct binding to His72 of ZDHHC4.
• This binding boosts ZDHHC4 enzymatic (palmitoylation) activity.
• Drug affinity responsive target stability (DARTS) assay was among the methods used to confirm direct binding.

Degradation of MAP2K4/MKK4 via the ZDHHC4-CCDC50 axis leads to suppression of MAPK/JNK signaling and attenuation of chondrocyte senescence.

• Selective autophagic degradation of MAP2K4/MKK4 resulted in reduced phosphorylated MAPK/JNK (p-MAPK/JNK) levels.
• Suppression of MAPK/JNK signaling was associated with attenuation of chondrocyte senescence.
• Markers of senescence assessed included SA-GLB1/β-gal and senescence-associated secretory phenotype (SASP) components such as IL6.
• Cartilage matrix markers COL2A1, COL10A1, MMP13, and ADAMTS5 were used to assess cartilage integrity.

A novel ZDHHC4-CCDC50-MAP2K4/MKK4-MAPK/JNK regulatory axis linking palmitoylation, autophagy, and senescence was established.

• The study identifies a previously undescribed regulatory axis connecting protein palmitoylation, selective autophagy, and cellular senescence.
• This axis operates in the context of degenerative joint disease.
• The findings provide mechanistic insights into the crosstalk between autophagy, protein palmitoylation, and cellular senescence.
• Dysregulation of autophagy contributes to OA progression by promoting chondrocyte senescence, inflammation, and cartilage degradation.

Autophagy dysregulation contributes to OA progression by promoting chondrocyte senescence, inflammation, and cartilage degradation, making autophagy enhancement a therapeutic strategy.

• Macroautophagy/autophagy plays a crucial role in maintaining cellular homeostasis and protecting against OA.
• Its dysregulation promotes chondrocyte senescence, inflammation, and cartilage degradation.
• Enhancing autophagic activity 'represents a promising therapeutic strategy for OA.'
• H2O2 was used to induce oxidative stress and cellular senescence in chondrocytes for in vitro experiments.