Neuregulin-1/Phosphatidylinositol 3-kinase Signaling Regulates Expression of Genes Involved in Cellular Cobalamin Uptake and Processing

Nova Southeastern University, Davie, Florida, USA

Objective. To determine whether the Neuregulin-1/Phosphatidylinositol 3-kinase signaling transcriptionally regulates proteins involved with the uptake and processing of Vitamin B12 (cobalamin) in SH-SY5Y neuroblastoma cells. Background. Cobalamin is required as a cofactor for methionine synthase, which transfers folate-derived methyl groups to homocysteine to form methionine. Cobalamin must be imported and processed by cells into activated species. The antioxidant glutathione is needed to process intracellular cobalamin. Neurotrophic factors, such as neuregulin-1, increase glutathione in neurons. Neuregulin-1 and downstream phosphatidylinositol 3-kinase (PI3K) signaling promote glutathione-dependent cobalamin processing and methionine synthase activity in SH-SY5Y cells. In the work presented here, we sought to understand whether neuregulin-1/PI3K signaling might additionally regulate cobalamin status via parallel mechanisms complementary to stimulating glutathione formation. Methods. SH-SY5Y cells in 6-well plates were maintained under low-serum conditions. Cells were exposed to 1 nM neuregulin-1 for 1- or 4h. Cells were pre-treated with PI3K inhibitors pictilisib or wortmannin for 30 min and then some cells were co-treated with neuregulin-1 for 1h. Real-Time quantitative polymerase chain reaction (RT-qPCR) was used to assess gene expression of cobalamin-interacting proteins. Results. 1h neuregulin-1 generally increased expression of cobalamin processing genes, which was blocked by PI3K inhibitors. However, PI3K inhibitors increased expression when given alone. Transcripts were decreased or no longer increased after 4h exposure. Conclusion. Neuregulin-1 regulates expression of cobalamin-related genes in a temporal- and PI3K-dependent manner. Grants. This research was supported with a fellowship from the American Foundation for Pharmaceutical Education (AFPE).