As Tks5 is known to promote the formation of podosomes/invadopodia in transformed/cancer cells, we tested if these cells also have the potential to fuse with osteoclasts. Among the cells tested, B16F0 melanoma cells formed circumferential podosomes with Tks5 AMPK inhibitors accumulation in the presence of RANKL, TGFb and TNFa. Co culture of B16F0 melanoma cells with osteoclasts in an inflammatory milieu promoted increased formation of melanoma osteoclast hybrid cells. Our results revealed a previously unknown mechanism of regulation of both circumferential podosome formation and cell cell fusion by Tks5. IL 17 producing helper T cells are a distinct T cell subset characterized by its pathological role in autoimmune diseases.
Our group previously showed that Th17 cells function MAPK function as osteoclastogenic helper T cells in bone destruction associated with inflammation, and that inhibition of Th17 development has the potential of a beneficial impact on bone diseases including rheumatoid arthritis. It is therefore important to comprehend the molecular mechanism underlying Th17 development in order to develop ideal therapeutic strategies against RA. IL 6 and TGF b induce Th17 development, in which the orphan nuclear receptors RORgt and RORa play an indispensable role. We found that the expression of a nuclear I B family member, I B, was upregulated by the combination of IL 6 and TGF b, but independently of RORgt. Not only Nfkbiz / mice but also Rag2 / mice transferred with Nfkbiz / CD4 T cells were highly resistant to experimental autoimmune encephalomyelitis, which is a mouse model of multiple sclerosis.
Nfkbiz mice were also protected from the activation of osteoclastogenesis and bone destruction in a LPS induced model of inflammatory bone destruction. When Cellular differentiation activated in vitro under Th17 polarizing conditions, IL 17 production in Nfkbiz T cells was markedly reduced compared to WT cells. Notably, the expression of RORgt and RORa was comparable between WT and Nfkbiz / T cells. Thus, it is unlikely that ROR nuclear receptors function downstream of I B or vice versa. In the absence of IL 6 and TGF b, neither the ROR nuclear receptors nor I B induced Th17 development efficiently. However, when I B was overexpressed, either RORgt or RORa strongly induced IL 17 production, even in the absence of exogenous polarizing cytokines.
In cooperation with RORgt and RORa, I B enhanced Il17a expression by directly binding to the regulatory region of the Il17a gene. In addition, the expression of Il17f, Il21 and Il23r mRNA was decreased in Nfkbiz / T cells. I B also bound fatty acid amide hydrolase inhibitors to the promoter or the enhancer region of these genes in Th17 cells. Our study demonstrates the essential role of I B in Th17 development, and points to a molecular basis for a novel therapeutic strategy against autoimmune disease.