Thiamine‐dependent regulation of mammalian brain pyridoxal kinase in vitro and in vivo. Issue 1 (23rd February 2022)

• Record Type: Journal Article
• Authors: Bunik, Victoria; Aleshin, Vasily; Nogues, Isabel; Kähne, Thilo; Parroni, Alessia; Contestabile, Roberto; Salvo, Martino Luigi; Graf, Anastasia; Tramonti, Angela
• Is Part Of: Journal of neurochemistry. Volume 161:Issue 1(2022)
• Page Start: 20
• Page End: 39
• Publication Date: 2022-02-23
• Subjects: diurnal rhythms -- MAP kinases -- Ppp1ca -- pyridoxal kinase -- thiamine antagonists -- thiamine triphosphate; Neurochemistry -- Periodicals; 616.8042
• DOI: 10.1111/jnc.15576
• Languages: English
• ISSNs: 0022-3042

Abstract

Abstract: Vitamins B1 (thiamine) and B6 (pyridox (al/ine/amine)) are crucial for central nervous system (CNS) function and neurogenesis due to the coenzyme action of their phosphorylated derivatives in the brain metabolism of glucose and neurotransmitters. Here, the non‐coenzyme action of thiamine on the major mammalian producers of pyridoxal‐5′‐phosphate (PLP), such as pyridoxal kinase (PdxK) and pyridoxine 5′‐phosphate oxidase (PNPO), is characterized. Among the natural thiamine compounds, thiamine triphosphate (ThTP) is the best effector of recombinant human PdxK (hPdxK) in vitro, inhibiting hPdxK in the presence of Mg 2+ but activating the Zn 2+ ‐dependent reaction. Inhibition of hPdxK by thiamine antagonists decreases from amprolium to pyrithiamine to oxythiamine, highlighting possible dysregulation of both the B1 ‐ and B6 ‐dependent metabolism in the chemical models of thiamine deficiency. Compared with the canonical hPdxK, the D87H and V128I variants show a twofold increase in K app of thiamine inhibition, and the V128I and H246Q variants show a fourfold and a twofold decreased K app of thiamine diphosphate (ThDP), respectively. Thiamine administration changes diurnal regulation of PdxK activity and phosphorylation at Ser213 and Ser285, expression of the PdxK‐related circadian kinases/phosphatases in the rat brain, and electrocardiography (ECG). In contrast to PdxK, PNPO is not affected by thiamine or its derivatives, either in vitro or in vivo . Dephosphorylation of the PdxK Ser285, potentially affecting mobility of the ATP‐binding loop, inversely correlates with the enzyme activity. Dephosphorylation of the PdxK Ser213, which is far away from the active site, does not correlate with the activity. The correlations analysis suggests the PdxK Ser213 to be a target of kinase MAP2K1 and phosphatase Ppp1ca. Diurnal effects of thiamine administration on the metabolically linked ThDP‐ and PLP‐dependent enzymes may support the brain homeostatic mechanisms and physiological fitness. Abstract : Pyridoxal kinase phosphorylates pyridoxal to its coenzyme form. In vitro, the Me 2+ ‐dependent regulation of pyridoxal kinase by thiamine, its antagonists, and phosphates is compared, revealing activation by thiamine triphosphate in the presence of Zn 2+ . Human variants of pyridoxal kinase with the D87H, V128I, and H246Q substitutions exhibit changed regulation by thiamine and/or derivatives. In vivo, thiamine affects diurnal regulation of the rat brain pyridoxal kinase activity and phosphorylation at Ser213 and Ser285, accompanied by changed expression of circadian kinases and phosphatases.