Structural studies of human dual-specificity phosphatase 26

Abstract

Dual-specificity phosphatases (DUSPs) play an important role in regulating cellular signaling pathways governing cell growth, differentiation and apoptosis. Human DUSP26 inhibits apoptosis of cancer cells by dephosphorylating substrates such as p38 and p53. The crystal structures of the DUSP26 catalytic domain with its C152S mutant, DUSP26 (61-211, C152S) and DUSP26 (39-211, C152S) were determined at $2.20 \AA$ and $2.49 \AA$ resolutions, respectively. The crystal structure of DUSP26 (61-211, C152S) showed a novel type of domain-swapped dimer formed, by extensive crossover of the C-terminal $\alpha$ 7-helix. Taken together with phosphatase activity assay results, structural comparison with other DUSPs revealed that DUSP26 (61-211, C152S) adopts a catalytically inactive conformation of protein tyrosine phosphate-binding loop, which significantly deviates from canonical DUSP structures. The crystal structure of DUSP26 (39-211, C152S) contains additional N-terminal $\alpha$ -helix. DUSP26 (39-211, C152S) has active conformation of protein tyrosine phosphate-binding loop as that of VHR, which is consistent with phosphatase activity assay. In particular, noticeable difference exists between DUSP26 (61-211, C152S) and the active forms of other DUSPs at the hinge region of a swapped C-terminal domain. Additionally, two significant gaps were identified between the catalytic core and its surrounding loops in DUSP26 (61-211, C152S), which can be exploited as additional binding sites for allosteric enzyme regulation. There is only one gap between catalytic core and its surrounding loops in DUSP26 (39-211, C152S). The gap is conserved both inactive conformation of DUSP26 (61-211, C152S) and active conformation of DUSP26 (39-211, C152S). Thus, the structures of DUSP26 (61-211, C152S) and DUSP26 (39-211, C152S) may provide structural insights into the rational design of DUSP26-targeted anti-cancer drugs.