Page 16 - H. Cell signaling

[H. Cell signaling-15]

P62 enhances the auto-ubiquitination of traf6 induced by

lipopolysaccharides

Sung-hwan Cho¹˙#, Kyung-hye Roh¹˙#, Eui-ju Choi¹˙*

¹Division of life science, Korea University, Seoul 028-41, South Korea

Lipopolysaccharides (LPS) has been shown to induce the TLR4-triggered activation of the NF-kB pathway. TRAF6,
an E3 ubiquitin ligase, catalyzes the K63-polyubiquitination of several components, including TRAF6, of the NF-kB
pathway, thereby mediating the LPS-induced activation of this signaling pathway. The TRAF6-mediated K63-

polyubiquitination can be potentiated by a scaffold protein p62, which contains a PB1 domain, a TRAF6 binding

site, and an UBA ubiquitin-associating domain. In order to better understand the mechanism by which p62 enhances
the TRAF6 activity, we investigated a role of p62 in the regulation of TRAF6 auto-ubiquitination. Our in vitro
ubiquitination assay data indicated that p62 directly acted on TRAF6 and increased the polyubiquitination of TRAF6.

Furthermore, genetic ablation of p62 in MEFs mitigated the LPS-induced oligomerization of TRAF6. Additionally,
p62 physically interacted with TRAF6, while the p62 lacking either a UBA domain or a PB1 domain failed not only

to interact with TRAF6 but also to increase its oligomerization. Taken together, our results suggested that p62
enhances the LPS-induced oligomerization and autoubiquitination of TRAF6 and that the UBA and PB1 domains

may be important for the p62-dependent regulation of TRAF6 activity.