Vitamin B12 deficiency reduces proliferation and promotes differentiation of neuroblastoma cells and up-regulates PP2A, proNGF, and TACE

Abstract

Vitamin B12 (cobalamin, Cbl) is indispensable for proper brain development and functioning, suggesting that it has neurotrophic effects beside its well-known importance in metabolism. The molecular basis of these effects remains hypothetical, one of the reasons being that no efficient cell model has been made available for investigating the consequences of B12 cellular deficiency in neuronal cells. Here, we designed an approach by stable transfection of NIE115 neuroblastoma cells to impose the anchorage of a chimeric B12-binding protein, transcobalamin-oleosin (TO) to the intracellular membrane. This model produced an intracellular sequestration of B12 evidenced by decreased methyl-Cbl and Sadenosylmethionine and increased homocysteine and methylmalonic acid concentrations. B12 deficiency affected the proliferation of NIE115 cells through an overall increase in catalytic protein phosphatase 2A (PP2A), despite its demethylation. It promoted cellular differentiation by improving initial outgrowth of neurites and, at the molecular level, by augmenting the levels of proNGF and p75 NTR . The up-regulation of PP2A and pro-nerve growth factor (NGF) triggered changes in ERK1/2 and Akt, two signaling pathways that influence the balance between proliferation and neurite outgrowth. Compared with control cells, a 2-fold increase of p75 NTR -regulated intramembraneous proteolysis (RIP) was observed in proliferating TO cells (P < 0.0001) that was associated with an increased expression of two tumor necrosis factor (TNF)-␣ converting enzyme (TACE) secretase enzymes, Adam 10 and Adam 17. In conclusion, our data show that B12 cellular deficiency produces a slower proliferation and a speedier differentiation of neuroblastoma cells through interacting signaling pathways that are related with increased expression of PP2A, proNGF, and TACE.homocysteine ͉ neurotrophin V itamin B12 (B12, also named cobalamin, Cbl) deficiency has long been associated with pernicious anaemia (1) and neurological disorders that range from minor behavior changes to severe neurodegenerative disorders (2). Molecular mechanisms are still lacking to explain how the deficiency can bring about all of the symptoms observed. Indeed, only two enzymes are B12-dependent in mammalian cells: the mitochondrial enzyme L-methylmalonyl-CoA mutase (EC 5.4.99.2) and the cytoplasmic homocysteine methyltransferase, also referred as methionine synthase (EC 2.1.1.13). Inferences are thus based on the two direct consequences of B12 deficiency: the accumulation of methylmalonic acid (MMA) and homocysteine (Hcy). Until now, the consequences of B12 deficiency in the brain have been difficult to evidence because of the experimental limitations of the classical cell models. Indeed, the minute amount of vitamin B12 needed by cells can be provided in vitro by B12 from the FCS, which can bind the ''autocrine'' B12 carrier protein, transcobalamin (TC) (3, 4).To delineate the role of B12 in neurological disorders, we designed a neuronal cell model made deficient in B12 through the stable ...

Luminal expression of cubilin is impaired in Imerslund-Grasbeck syndrome with compound AMN mutations in intron 3 and exon 7

“…13 IF-Cbl receptor activity was assayed in urine by radioisotope binding assay, as previously described. 4 Briefly, urine samples were concentrated 50-fold through a YM-5 membrane and urine IF-Cbl receptor activity was determined by phenyl-Sepharose radioisotope assay using 50 μL aliquots.…”

History of the therapy of pernicious anemia

“…A B 12 -(kobalamin) és a B 9 -(folsav) vitaminok sejtosztó-dást, valamint a szövetdifferenciációt szabályozó hatása lehetőséget nyújt az anaemia perniciosán túl egyéb betegségek terápiájára [36,37]. A B 12 és a folsav által irá-nyított molekuláris átalakulások elmaradásakor homocisztein és metil-malonát halmozódik fel a szervezetben, amelyeket szöveti károsodással lehetett kapcsolatba hozni.…”

A pilot clinical trial assessing the efficacy and safety of supplementation with a B complex vitamin to reduce the incidence of chemotherapy induced peripheral neuropathy in patients diagnosed with a malignancy

“…This was through interacting signalling pathways related to an increased expression of catalytic protein phosphatase 2A (PP2A), pro-nerve growth factor (proNGF) and two tumour necrosis factor alpha converting enzymes [166].…”

“…[ Table 1-5] [162][163][164]166] Peripheral neuropathy that is caused by a deficit of vitamin B12 has been reported reversed or markedly improved by administration of vitamin B12 [160,[168][169][170][171][172][173]. Even in patients with other conditions that can cause peripheral neuropathy such as type II diabetes mellitus, administration of vitamin B12 has been beneficial for nerve regeneration and myelinogenesis [167].…”

“…The combined daily dose can be seen in Table 4-1. The dose for this trial was based on research conducted on deficiency states of vitamin B1, B6 and B12 and administered dosages required to correct these deficiencies [161,162,[164][165][166][167][168]. Due to the fact that a toxicity of vitamin B6 may cause a peripheral neuropathy (dose above 95 mg a day for over a year) and that a high dose of 300 mg a day was found to interfere with tumour duration [159], the dose of vitamin B6 was suggested to be below 70 mg a day (dose in this trial is 60 mg a day).…”