Structural insights into cGAMP degradation by Ecto-nucleotide pyrophosphatase phosphodiesterase 1

Abstract

ENPP1 (Ecto-nucleotide pyrophosphatase phosphodiesterase 1), a type II transmembrane glycoprotein, hydrolyzes ATP to produce AMP and diphosphate, thereby inhibiting bone mineralization. A recent study showed that ENPP1 also preferentially hydrolyzes 2′3′-cGAMP (cyclic GMP-AMP) but not its linkage isomer 3′3′-cGAMP, and negatively regulates the cGAS-STING pathway in the innate immune system. Here, we present the high-resolution crystal structures of ENPP1 in complex with 3′3′-cGAMP and the reaction intermediate pA(3′,5′)pG. The structures revealed that the adenine and guanine bases of the dinucleotides are recognized by nucleotide- and guanine-pockets, respectively. Furthermore, the structures indicate that 2′3′-cGAMP, but not 3′3′-cGAMP, binds to the active site in a conformation suitable for catalysis, thereby explaining the specific degradation of 2′3′-cGAMP by ENPP1. Our findings provide insights into how ENPP1 hydrolyzes both ATP and cGAMP to participate in the two distinct biological processes.

SLC19A1 transports immunoreactive cyclic dinucleotides

“…The nucleoside monophosphates AMP and GMP, the major ENPP-1 hydrolysis products of 2'3'-cGAMP, slightly inhibited [ 32 P] 2'3'-cGAMP uptake ( Fig. 4d) 24 consistent with previous observations that AMP, other nucleotides, and organic phosphates in general, inhibit SLC19A1-mediated transport 17,18 . Our findings indicated that SLC19A1 broadly interacts with CDNs irrespective of the phosphodiester linkages or the base content but that CDN breakdown products have a limited effect on CDN uptake.…”

Crystal structures of human ENPP1 in apo and bound forms

“…Overall, the human ENPP1 structures presented are similar to those of the secreted mouse ENPP1 (see Fig. 1; Kato et al, 2012Kato et al, , 2018Jansen et al, 2012). A high sequence identity (79.7%), particularly for the catalytic domain (88.4%), allowed the structure of the mouse enzyme, PDB entry 4b56, to be used to obtain the phases via molecular replacement.…”

Compound C Reducing Interferon Expression by Inhibiting cGAMP Accumulation

“…Interestingly, a recent study shows that Ecto-nucleotide pyrophosphatase phosphodiesterase 1 (ENPP1), preferentially hydrolyzes 2′3′-cGAMP, but not 3′3′-cGAMP, thereby negatively regulates the cGAS-STING pathway (Wang et al, 2018a). This preferential degradation is due to its binding to the ENPP1 active site in a conformation suitable for catalysis (Kato et al, 2018). Thus, it needs to be further clarified if Compound C can affect cGAMP degradation by modulating ENPP1 activities.…”