NF-кB promotes aggresome formation via upregulating HDAC6 and in turn maintaining Vimentin cage

Proteasome inhibitors have been applied to anticancer therapy by accumulating toxic misfolded proteins. However, chemical inactivation of proteasome generates aggresome, a Vimentin cage-enclosed subcellular structure quarantining HDAC6-Dynein-transported misfolded proteins before the protein toxicants are degraded by autophagy. Hence, aggresome may attenuate proteasome inhibitor drugs-induced cytotoxicity. To solve the problem, it is imperative to characterize how cells assemble aggresome. By examining aggresomes in six cell lines, A549 cells were selectively studied for their bigger cell size and moderate aggresome forming activity. Aggresome grew in size upon continuous exposure of A549 cells to proteasome inhibitor MG132, and reached a mature size around 16 th to 24 th hour of treatment. Mechanistic studies revealed that NF-кB translocated to nucleus in MG132 treated cells, and chemical activation or knockdown of NF-кB enhanced or prohibited aggresome assembly. Further analyses showed that NF-кB upregulated HDAC6, and HDAC6 maintained Vimentin cage by interacting with Vimentin p72, a key modification of the intermediate filament contributing to aggresome formation. Remarkably, chemical inactivation of NF-кB synergized MG132-induced cell mortality. All the findings suggest that NF-кB dictates aggresome assembly via upregulating HDAC6, and NF-кB inhibitor may serve as a potential drug potentiating proteasome inhibitor medicine-induced cytotoxicity during the treatment of cancer cells.