Zinc deficiency causes delayed ATP clearance and adenosine generation in rats and cell culture models

Abstract

Zinc deficiency causes myriad pathophysiological symptoms, but why distinct phenotypes are generated by zinc deficiency remains unclear. Considering that several ectoenzymes involved in purinergic signaling through extracellular adenine-nucleotide hydrolysis possess zinc ions in their active sites, and disorders in purinergic signaling result in diverse diseases that are frequently similar to those caused by zinc deficiency, herein we examine whether zinc deficiency affects extracellular adenine-nucleotide metabolism. Zinc deficiency severely impairs the activities of major ectoenzymes (ENPP1, ENPP3, NT5E/CD73, and TNAP), and also strongly suppresses adenine-nucleotide hydrolysis in cell-membrane preparations or rat plasma, thereby increasing ATP and ADP levels and decreasing adenosine levels. Thus, zinc deficiency delays both extracellular ATP clearance and adenosine generation, and zinc modulates extracellular adenine-nucleotide metabolism. Since the finely tuned balance between extracellular adenine nucleotides and adenosine is critical for purinergic signaling, these findings provide a novel insight into why zinc deficiency results in diverse symptoms.

Zinc deficiency exacerbates pressure ulcers by increasing oxidative stress and ATP in the skin

“…There are several evidences that Zn deficiency delays extracellular ATP clearance [16,38]. Extracellular ATP is hydrolyzed by 3 groups of molecules: ecto-nucleoside triphosphate diphosphohydrolases (ENTPDs), ectonucleotide pyrophosphatase/phosphodiesterases (ENPPs), and alkaline phosphatase (ALP) [39,40].…”

“…Similar to this previous study, our study also identified that Zn deficiency reduced the number of LCs and increased the amount of ATP in cutaneous I/R-injured skin. In addition, as ENPPs and ALP are Zn-dependent molecules, Zn deficiency severely impairs the activities of ENPPs and ALP, which leads to increased ATP levels [38]. This indicates one underlying mechanism by which ZD mice show increased ATP in I/R-injured skin.…”

Detailed analyses of the crucial functions of Zn transporter proteins in alkaline phosphatase activation

“…We have shown that ZNT5-ZNT6 heterodimers and ZNT7 homodimers are indispensable for the activation of several zinc ectoenzymes, including TNAP and PLAP, by using genetically engineered chicken DT40 cells (24)(25)(26)(27). However, a fundamental question that has remained unanswered is whether this holds true for mammalian cells, including human cells.…”

“…We addressed this question by establishing cultured human cells lacking ZNT5-ZNT6 heterodimers and ZNT7 homodimers: we disrupted ZNT5 and/or ZNT7 by using the CRISPR/Cas9 system, and we used HAP1 cells for these studies because these cells exhibit zinc-dependent TNAP activity ( Fig. 5A) (27) in addition to their unique haploid phenotype. TNAP activity was not substantially decreased in ZNT5 or ZNT7 KO HAP1 cells (HAP-Z5-KO or HAP-Z7-KO cells) ( Fig.…”

“…One of these roles of ZNT proteins is their critical function of supplying zinc to numerous proteins, including several secretory, extracellularly membrane-bound or organelle-resident enzymes biosynthesized in the compartments (hereafter zinc ectoenzymes), for their activation (20,21). In this context, we have shown that vertebrate ZNT5-ZNT6 heterodimers and ZNT7 homodimers are required for the activation of alkaline phosphatases (ALPs), such as tissue nonspecific ALP (TNAP) (22) and placental ALP (PLAP) (23), and several other ectoenzymes by using genetically engineered chicken DT40 cell mutants (24)(25)(26)(27).…”