Pyridoxal kinase immunoreactivity in rabbit brain

MicroRNA339 Targeting PDXK Improves Motor Dysfunction and Promotes Neurite Growth in the Remote Cortex Subjected to Spinal Cord Transection

Spinal cord injury (SCI) is a fatal disease that can cause severe disability. Cortical reorganization subserved the recovery of spontaneous function after SCI, although the potential molecular mechanism in this remote control is largely unknown. Therefore, using proteomics analysis, RNA interference/overexpression, and CRISPR/Cas9 in vivo and in vitro, we analyzed how the molecular network functions in neurological improvement, especially in the recovery of motor function after spinal cord transection (SCT) via the remote regulation of cerebral cortex. We discovered that the overexpression of pyridoxal kinase (PDXK) in the motor cortex enhanced neuronal growth and survival and improved locomotor function in the hindlimb. In addition, PDXK was confirmed as a target of miR-339 but not miR-124. MiR-339 knockout (KO) significantly increased the neurite outgrowth and decreased cell apoptosis in cortical neurons. Moreover, miR-339 KO rats exhibited functional recovery indicated by improved Basso, Beattie, and Bresnehan (BBB) score. Furthermore, bioinformatics prediction showed that PDXK was associated with GAP43, a crucial molecule related to neurite growth and functional improvement. The current research therefore confirmed that miR-339 targeting PDXK facilitated neurological recovery in the motor cortex of SCT rats, and the underlying mechanism was associated with regulating GAP43 in the remote cortex of rats subjected to SCT. These findings may uncover a new understanding of remoting cortex control following SCI and provide a new therapeutic strategy for the recovery of SCI in future clinical trials.

Vitamin B-6 Metabolism and Interactions with TNAP

Two observations stimulated the interest in vitamin B-6 and alkaline phosphatase in brain: the marked increase in plasma pyridoxal phosphate and the occurrence of pyridoxine responsive seizures in hypophosphatasia. The increase in plasma pyridoxal phosphate indicates the importance of tissue non-specific alkaline phosphatase (TNAP) in transferring vitamin B-6 into the tissues. Vitamin B-6 is involved in the biosynthesis of most of the neurotransmitters. Decreased gamma-aminobutyrate (GABA) appears to be most directly related to the development of seizures in vitamin B-6 deficiency. Cytosolic pyridoxal phosphatase/chronophin may interact with vitamin B-6 metabolism and neuronal development and function. Ethanolaminephosphate phospholyase interacts with phosphoethanolamine metabolism. Extracellular pyridoxal phosphate may interact with purinoceptors and calcium channels. In conclusion, TNAP clearly influences extracellular and intracellular metabolism of vitamin B-6 in brain, particularly during developmental stages. While effects on GABA metabolism appear to be the major contributor to seizures, multiple other intra- and extra-cellular metabolic systems may be affected directly and/or indirectly by altered vitamin B-6 hydrolysis and uptake resulting from variations in alkaline phosphatase activity.

Changes in pyridoxal kinase immunoreactivity in the gerbil hippocampus following spontaneous seizure

To identify the roles of pyridoxal kinase (PLK) in epileptogenesis and the recovery mechanisms in spontaneous seizure, a chronological and comparative analysis of PLK expression in the gerbil hippocampus was conducted. PLK immunoreactivity in a pre-seizure group of seizure sensitive (SS) gerbils was more strongly detected than that in a seizure resistant (SR) group. The density of PLK immunoreactivity in a 30-min postictal group was significantly lower than that of a pre-seizure group. In a 12 h postictal group, PLK immunodensity recovered to pre-seizure level. The over-expression of PLK in the hippocampus of pre-seizure SS gerbils suggests that PLP play an important role in the modulation of GAD activity and GABA reuptake as mediated by membrane transporter via neurons.

Production and characterization of monoclonal antibodies to porcine brain pyridoxal kinase

Six monoclonal antibodies that recognize porcine brain pyridoxal kinase have been selected and designated as PK67, PK86, PK91, PK144, PK252 and PK275. A total of six monoclonal antibodies recognizing different epitopes of the enzyme were obtained, of which four inhibited the enzyme activity. When total proteins of porcine brain homogenate separated by SDS-PAGE were subjected to monoclonal antibodies, a single reactive protein band of molecular weight 39 kDa which comigrated with purified porcine pyridoxal kinase was detected. Using the anti-pyridoxal kinase antibodies as probes, the cross reactivities of brain pyridoxal kinase from human and other mammalian tissues and from avian sources were also investigated. Among human and all animal tissues tested, immunoreactive bands on Western blots appeared to have the same molecular mass of 39 kDa. These results indicate that mammalian brains contain only one major type of immunologically similar pyridoxal kinase, although some properties of the enzymes reported previously differed from one another.

Regulation of pyridoxal-5'-phosphate level by biogenic amines in mouse brain

We investigated the relationship between the concentration of pyridoxal-5'-phosphate (PLP) and biogenic amine in mouse brain. The production of PLP from pyridoxal (PL) by pyridoxal kinase (PLK) was inhibited by the addition of dopamine (DA), norepinephrine (NE) and 5-hydroxytryptamine (5-HT), but not by that of epinephrine and N-acetyl-serotonin. DA and NE were combined with PLP by a non-enzymatic reaction, whereas 5-HT was bound only slightly with PLP. The conjugated product of PLP with DA was also detected by HPLC analysis when PLK activity was assayed using PL as a substrate in the presence of DA. In an in vivo investigation, the depletion of DA and 5-HT in mouse brain after an intraperitoneal injection of 5 mg/kg reserpine, led to slight elevation of the PLP level to 120% of the control level. By contrast, the increase in DA in the brain caused by intraperitoneal administration of 150 mg/kg L-DOPA caused the PLP concentration to decrease to 70% of the control level. However, no change in PLK activity in the brain was observed when the mice were treated with either reserpine or L-DOPA. These results suggested that the level of PLP in mouse brain was partly regulated by the concentration of biogenic amines, such as DA, NE and 5-HT, without apparent induction of PLK.