DEF pocket in p38? facilitates substrate selectivity and mediates autophosphorylation.

ABSTRACT: Signaling processes are primarily promoted by molecular recognition and corresponding protein-protein interactions. One of the key eukaryotic signaling pathways is the MAP kinase cascade involved in vital cellular processes such as cell proliferation, differentiation, apoptosis, and stress response. The principle recognition site of MAP kinases, the common docking (CD) region, forms selective interactions with substrates, upstream activators, and phosphatases. A second docking site, defined as the DEF site interaction pocket (DEF pocket), is formed subsequent to ERK2 and p38? activation. Both crystal structures of p38? in its dually phosphorylated form and of intrinsically active mutants showed the DEF pocket, giving motivation for studying its role in substrate activation and selectivity. Mutating selected DEF pocket residues significantly decreased the phosphorylation levels of three p38? substrates (ATFII, Elk-1, and MBP) with no apparent effect on the phosphorylation of MK2 kinase. Conversely, mutating the CD region gave the opposite effect, suggesting p38? substrates can be classified into DEF-dependent and DEF-independent substrates. In addition, mutating DEF pocket residues decreased the autophosphorylation capability of intrinsically active p38? mutants, suggesting DEF-mediated trans-autophosphorylation in p38?. These results could contribute to understanding substrate selectivity of p38? and serve as a platform for designing p38?-selective DEF site blockers, which partially inhibit p38? binding DEF-dependent substrates, whereas maintaining its other functions intact. In this context, preliminary results using synthetic peptides reveal significant inhibition of substrate phosphorylation by activated p38?.

SUBMITTER: Tzarum N 

PROVIDER: S-EPMC3707655 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature