No abstract

The Sox6 gene is a member of the Sox gene family, which encodes transcription factors, and previous studies have suggested that it plays an important role in the development of the central nervous system. Aggregation of embryonic carcinoma P19 cells with retinoic acid (RA) results in the development of neurons, glia, and fibroblast-like cells. Sox6 mRNA increases rapidly in P19 cells during RA induction and then decreases during differentiation into neuronal cells. To investigate whether Sox6 expression is essential for neuronal differentiation, we

We previously isolated a unique compound containing glutamate and citrate residues from the brains of newborn rats, and identified it as b-citryl-L-glutamate (b-CG).1) This compound appears in high concentrations (300-600 mM) during the period characterized by growth and differentiation of neurons in developing rats, and guinea pigs, and then decreases with maturation. [2][3][4] In another study, we found developmental changes in the concentrations of b-CG in the optic lobes of developing chick brains as well as in primary cultured neuronal cells from chick embryo optic lobes.5) A sharp peak of b-CG was shown, with a maximal concentration at 13 d of incubation in the optic lobe, while similar developmental changes were observed in primary cultured neuronal cells. In additions, the synthetic activity of b-CG was significantly increased on day 3 of the culture, whereas the hydrolyzing enzyme activity was low until day 3, and then it increased significantly until day 12.5) Together, these findings suggested that b-CG plays roles in regulating the differentiation or growth of neuronal cells. However, its functional roles in the developing brain remain unclear.The tetra-carboxyl nature of b-CG, in which a b-carboxylresidue of citrate and amino-residue of glutamate are linked with an amide bond, indicates that it may coordinate with metal ions. To evaluate that coordination, we previously performed pH titration experiments.6) The stability constant was calculated from pH titration data, which showed that b-CG forms relatively strong complexes with Fe(III), Cu(II), and Fe(II). Therefore, we examined the effects of b-CG on Fe-dependent reactive oxygen species (ROS)-generating systems, as well as the potential ROS-scavenging activities of b-CG and metal ion-(b-CG) complexes. b-CG inhibited the Fe-dependent degradation of deoxyribose, as well as Fe-dependent damage to DNA or plasmid DNA in a dose-dependent manner, whereas it had no effect on Cu-mediated DNA damage. In addition, thermodynamic data showed that b-CG in a physiological pH solution is an Fe(II) chelator rather than an Fe(III) chelator. Taken together, these findings suggest that b-CG is an endogenous low molecular weight Fe chelator.Aconitase, a critical citric acid-cycle enzyme that converts citrate to isocitrate, belongs to the family of iron-sulfur-containing dehydratases, whose activities depend on an intact 8) The active center of purified mitochondrial aconitase has been reported to be protected completely from oxidative damage by citrate, an enzyme substrate.9,10) Indeed, citrate interacts with the fourth iron atom (Fe a ) of the [4Fe-4S] 2ϩ cubane cluster, 11) prevents cluster disassembly, while it is also required for enzyme reactivation in rat cardiac mitochondria treated with H 2 O 2 .In the present study, we investigated whether b-CG could insert Fe into [3Fe-4S] 0 of aconitase. Our results showed that the [Fe(II)(b-CG)] complex plays a role as an Fe-carrier for mitochondrial aconitase, and then activates it, whereas no Fe complex with citrate, glu...

No abstract

The compound beta-citryl-L-glutamate (beta-CG) was initially isolated from developing brains, while it has also been found in high concentrations in testes and eyes. However, its functional roles are unclear. To evaluate its coordination with metal ions, we performed pH titration experiments. The stability constant, logbeta(pqr) for M(p)(beta-CG)(q)H(r) was calculated from pH titration data, which showed that beta-CG forms relatively strong complexes with Fe(III), Cu(II), Fe(II) and Zn(II). beta-CG was also found able to solubilize Fe more effectively from Fe(OH)(2) than from Fe(OH)(3). Therefore, we examined the effects of beta-CG on Fe-dependent reactive oxygen species (ROS)-generating systems, as well as the potential ROS-scavenging activities of beta-CG and metal ion-(beta-CG) complexes. beta-CG inhibited the Fe-dependent degradation of deoxyribose and Fe-dependent damage to DNA or plasmid DNA in a dose-dependent manner, whereas it had no effect on Cu-mediated DNA damage. In addition, thermodynamic data showed that beta-CG in a physiological pH solution is an Fe(II) chelator rather than an Fe(III) chelator. Taken together, these findings suggest that beta-CG is an endogenous low molecular weight Fe chelator.