文摘
Mutations of the gene encoding sequestosome1 (SQSTM1/p62), clustering in or near the UBA domain, have been described in Paget's disease of bone (PDB); among these the P392L substitution is the most prevalent. Protein p62 mediates several cell functions, including the control of NF-¦ÊB signaling, and autophagy. This scaffolding protein interacts with atypical PKC¦Æ in the RANKL-induced signaling complex. We have previously shown that osteoclasts (OCs) overexpressing the p62P392L variant were in a constitutively activated state, presenting activated kinase p-PKC¦Æ/¦Ë and activated NF-¦ÊB prior to RANKL stimulation. In the present study, we investigated the relationships between PKC¦Æ and NF-¦ÊB activation in human OCs transfected with p62 variants. We showed that PKC¦Æ and p-PKC¦Æ/¦Ë co-localize with p62, and that PKC¦Æ is involved in the RANKL-induced NF-¦ÊB activation and in the RANKL-independent activation of NF-¦ÊB observed in p62P392L-transfected cells. We also observed a basal and RANKL-induced increase in I¦ÊB¦Á levels in the presence of the p62P392L mutation that contrasted with the NF-¦ÊB activation. In this study we propose that PKC¦Æ plays a role in the activation of NF-¦ÊB by acting as a p65 (RelA) kinase at Ser536, independently of I¦ÊB¦Á; this alternative pathway could be used preferentially in the presence of the p62P392L mutation, which may hinder the ubiquitin-proteasome pathway. Overall, our results highlight the importance of p62-associated PKC¦Æ in the overactive state of pagetic OCs and in the activation of NF-¦ÊB, particularly in the presence of the p62P392L mutation.