부산대학교 도서관

Sterile alpha motif and histidine-aspartate (HD) domain-containing protein 1 (SAMHD1) inhibits HIV-1 replication in nondividing cells by reducing the intracellular dNTP pool. SAMHD1 also suppresses NF-κB activation induced by inflammatory stimuli and viral infections. Specifically, SAMHD1-mediated reduction of NF-κB inhibitory protein (IκBa) phosphorylation is important for the suppression of NF-κB activation. However, while the inhibitors of NF-κB kinase subunit alpha and beta (IKKa and IKKß) regulate IκBa phosphorylation, the mechanism by which SAMHD1 regulates phosphorylation of IκBa remains unclear. Here, we report that SAMHD1 suppresses phosphorylation of IKKa/ß/κ via interaction with IKKa and IKKß, thus inhibiting subsequent phosphorylation of IκBa in monocytic THP-1 cells and differentiated nondividing THP-1 cells. We show that knockout of SAMHD1 enhanced phosphorylation of IKKa, IKKß, and IKKκ in THP-1 cells treated with the NF-κB activator lipopolysaccharide or infected with Sendai virus and SAMHD1 reconstitution inhibited phosphorylation of IKKa/ß/κ in Sendai virus-infected THP-1 cells. We demonstrate that endogenous SAMHD1 interacted with IKKa and IKKß in THP-1 cells and recombinant SAMHD1 bound to purified IKKa or IKKß directly in vitro. Mapping of these protein interactions showed that the HD domain of SAMHD1 interacts with both IKKa and IKKß and that the kinase domain of IKKa and the ubiquitin-like domain of IKKß are required for their interactions with SAMHD1, respectively. Moreover, we found that SAMHD1 disrupts the interaction between upstream kinase TAK1 and IKKa or IKKß. Our findings identify a new regulatory mechanism by which SAMHD1 inhibits phosphorylation of IκBa and NF-κB activation. [ABSTRACT FROM AUTHOR]