HSP90 is required for TAK1 stability but not for its activation in the pro-inflammatory signaling pathway

Abstract 

The protein kinase transforming-growth-factor-β-activated kinase-1 (TAK1) is a key regulator in the pro-inflammatory signaling pathway and is activated by tumor necrosis factor-α, interleukin-1 (IL-1) and lipopolysaccharide (LPS). We describe the identification of TAK1 as a client protein of the 90 kDa heat-shock protein (Hsp90)/cell division cycle protein 37 (Cdc37) chaperones. However, Hsp90 is not required for the activation of TAK1 as short exposure to the Hsp90 inhibitor, 17-(allylamino)-17-demethoxygeldanamycin (17-AAG) did not affect its activation by LPS or IL-1. Prolonged treatment of cells with 17-AAG inhibits Hsp90 and downregulates TAK1. Our results suggest that Hsp90 is required for the folding and stability of TAK1 but is displaced and no longer required when TAK1 is complexed to TAK1-binding protein-1 (TAB1).

Structured summary

Abbreviations: 17-AAG, 17-(allylamino)-17-demethoxygeldanamycin, Cdc37, cell division cycle protein 37, CUE, coupling of ubiquitin conjugation to endoplasmic reticulum degradation, DMEM, Dulbecco’s modified Eagle’s medium, ELISA, enzyme-linked immunosorbent assay, FCS, foetal-calf serum, GST, glutathione S-transferase, HA, haemagglutinin, HEK293, human embryonic kidney 293 cells, Hsp90, 90kDa heat-shock protein, IκB, inhibitor of NF-κB, IKK, inhibitor of nuclear factor κB kinase, IL, interleukin, IRAK, interleukin-1 receptor-associated kinase, JNK, c-Jun N-terminal kinase, LPS, lipopolysaccharide, MAPK, mitogen-activated protein kinase, MKK, MAP kinase kinase, MyD88, myeloid differentiation factor 88, NF-κB, nuclear factor κB, RIP, receptor-interacting protein, TAB, TAK1-binding protein, TAK1, transforming-growth-factor-β-activated kinase-1, TNF, tumor necrosis factor, TRADD, TNF receptor-associated death domain, TRAF, TNF-receptor-associated factor, Ubc13, ubiquitin-conjugating enzyme 13, Uev1A, ubiquitin E2 variant 1a

Keywords: Interleukin-1, Inflammation, Tumor necrosis factor, Lipopolysaccharide, Protein kinase