Department of Pharmacology and Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-7365, USA.
J Biol Chem. 2010 Jan 15;285(3):2077-89. doi: 10.1074/jbc.M109.065102. Epub 2009 Nov 10.
p62/Sequestosome 1 is a scaffold protein involved in the regulation of autophagy, trafficking of proteins to the proteasome, and activation of NF-kappaB. p62 encodes an N-terminal PB1 domain in addition to the ZZ domain, TRAF6-binding domain, LC3 interaction region, and ubiquitin-associated domain, each critical for the physiological function of p62. PB1 domains have a beta-grasp topology where the front end of one PB1 domain binds the back end of a second PB1 domain. The p62 PB1 domain homodimerizes as well as heterodimerizes with other PB1 domains. The front end of the PB1 domain in p62 binds the PB1 domain of atypical protein kinases C, the MAPK kinase, MEK5, and the NBR1 protein. Other than its role in homodimerization, the rear end acidic cluster region of the p62 PB1 domain had no previous defined binding partners. Herein, we demonstrate that the rear end acidic cluster region of the p62 PB1 domain binds the front end basic region of the MAPK kinase kinase, MEKK3. p62 and MEKK3 co-localize in speckles or aggregates that are centers for organizing TRAF6-regulated NF-kappaB signaling and the assembly of polyubiquinated proteins sorting to sequestosomes and proteasomes. The p62-MEKK3 complex binds TRAF6, which regulates the ubiquitination of the IKK complex and NF-kappaB activation. p62 is required for the association of MEKK3 with TRAF6 and short hairpin RNA knockdown of p62 inhibits IL-1 and MEKK3 activation of NF-kappaB. The rear end acidic cluster of the p62 PB1 domain is used to organize cytosolic aggregates or speckles-associated TRAF6-p62-MEKK3 complex for control of NF-kappaB activation.
p62/自噬体相关蛋白 1 是一种支架蛋白，参与自噬的调节、蛋白质向蛋白酶体的运输以及 NF-kappaB 的激活。p62 编码一个 N 端 PB1 结构域，除了 ZZ 结构域、TRAF6 结合结构域、LC3 相互作用区域和泛素相关结构域外，还编码一个 N 端 PB1 结构域，每个结构域对 p62 的生理功能都很关键。PB1 结构域具有β-抓取拓扑结构，其中一个 PB1 结构域的前端与第二个 PB1 结构域的后端结合。p62 的 PB1 结构域同源二聚体以及与其他 PB1 结构域异源二聚体。p62 的 PB1 结构域前端与非典型蛋白激酶 C、MAPK 激酶、MEK5 和 NBR1 蛋白的 PB1 结构域结合。除了在同源二聚体中的作用外，p62 PB1 结构域的后端酸性簇区域以前没有定义的结合伙伴。在此，我们证明 p62 PB1 结构域的后端酸性簇区域与 MAPK 激酶激酶、MEKK3 的前端碱性区域结合。p62 和 MEKK3 在斑点或聚集体中共定位，这些斑点或聚集体是 TRAF6 调节的 NF-kappaB 信号和多泛素化蛋白分拣到自噬体和蛋白酶体的中心。p62-MEKK3 复合物与 TRAF6 结合，调节 IKK 复合物的泛素化和 NF-kappaB 的激活。p62 对于 MEKK3 与 TRAF6 的结合以及短发夹 RNA 敲低 p62 抑制 IL-1 和 MEKK3 激活 NF-kappaB 是必需的。p62 PB1 结构域的后端酸性簇用于组织细胞质聚集物或斑点相关的 TRAF6-p62-MEKK3 复合物，以控制 NF-kappaB 的激活。
