An unexpected 2-histidine phosphoesterase activity of suppressor of T-cell receptor signaling protein 1 contributes to the suppression of cell signaling

Abstract

The suppressor of T-cell receptor (TCR) signaling (Sts) proteins Sts-1 and Sts-2 suppress receptor-mediated signaling pathways in various immune cells, including the TCR pathway in T cells and the Dectin-1 signaling pathway in phagocytes. As multidomain enzymes, they contain an N-terminal ubiquitin-association domain, a central Src homology 3 domain, and a C-terminal histidine phosphatase domain. Recently, a 2-histidine (2H) phosphoesterase motif was identified within the N-terminal portion of Sts. The 2H phosphoesterase motif defines an evolutionarily ancient protein domain present in several enzymes that hydrolyze cyclic phosphate bonds on different substrates, including cyclic nucleotides. It is characterized by two invariant histidine residues that play a critical role in catalytic activity. Consistent with its assignment as a phosphoesterase, we demonstrate here that the Sts-1 2H phosphoesterase domain displays catalytic, saturable phosphodiesterase activity toward the dinucleotide 2′,3′-cyclic NADP. The enzyme exhibited a high degree of substrate specificity and selectively generated the 3′-nucleotide as the sole product. Sts-1 also had phosphodiesterase catalytic activity toward a 5-mer RNA oligonucleotide containing a 2′,3′-cyclic phosphate group at its 3′ terminus. To investigate the functional significance of Sts-1 2H phosphoesterase activity, we generated His-to-Ala variants and examined their ability to negatively regulate cellular signaling pathways. Substitution of either conserved histidine compromised the ability of Sts-1 to suppress signaling pathways downstream of both the TCR and the Dectin-1 receptor. Our results identify a heretofore unknown cellular enzyme activity associated with Sts-1 and indicate that this catalytic activity is linked to specific cell-signaling outcomes.

Rebamipide and Derivatives are Potent, Selective Inhibitors of Histidine Phosphatase Activity of the Suppressor of T Cell Receptor Signaling Proteins

“…1 the above general procedure. (6). The compound 6 was prepared by using 2-amino-3-(2-oxo-1,2-dihydroquinolin-4-yl)propanoic acid hydrochloride, NaOH, and 6-chloronicotinoyl chloride as described in the above general procedure.…”

“…Sts-1 (also called TULA-2 or UBASH3B) and Sts-2 (also called TULA-1 or UBASH3A) share a unique domain organization composed of a C-terminal histidine phosphatase (HP) domain, , an internal region recently identified as a cyclic nucleotide phosphodiesterase (PDE), and two protein–protein interacting domains, namely, ubiquitin associating (UBA) and src-homology 3 (SH3) domains. The predominant means by which the Sts proteins are known to regulate immune signaling pathways is through the activity catalyzed by the HP domain.…”

TULA Proteins in Men, Mice, Hens, and Lice: Welcome to the Family

“…The latest addition to this family's set of functional domains is a 2H phosphoesterase domain, termed this way due to the presence of two histidine residues that are essential for its phosphodiesterase activity [29]. The 2H domain of TULA-2 exhibits enzymatic activity toward 2′,3′ cyclic NADP and a 5-mer RNA oligonucleotide containing a 2′,3′ cyclic phosphate group [30]. Although natural substrates of this enzymatic domain remain The C-terminal region of TULA proteins was initially recognized as an area of homology (i) between the TULA orthologues from human, C. elegans and Drosophila [1] and (ii) to mammalian phosphoglycerate mutase [2].…”

TULA-Family Regulators of Platelet Activation

“…The N-terminal half of TULA-family proteins contains UBA and SH3 domains, which interact with ubiquitin and proline-rich-motif-containing proteins, respectively [ 4 , 5 , 15 , 16 ], and appear to regulate various cellular processes [ 4 , 5 , 12 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ] (see Figure 1 ). Finally, a domain exhibiting 2′-phosphodiestease activity has been recognized in the region between UBA and SH3 domains, although its physiological substrates remain unclear [ 22 ] (see Figure 1 ).…”