Lysophosphatidylcholine (LPC) is one of the major lysophospholipids mainly generated by phospholipase A2 (PLA2)-mediated hydrolysis of phosphatidylcholine (PC). We previously found that LPC displays neurotrophin-like activity in the rat pheochromocytoma PC12 cells and in cerebellar granule neurons, but the molecular mechanism remains unclear. We report here that LPC specifically enhances nerve growth factor (NGF)-induced signals in PC12 cells. When PC12 cells were treated with NGF, MAPK was phosphorylated, but this phosphorylation was significantly elevated when LPC was added together. In accordance, NGF-induced expression of immediate early genes, c-fos and NGF-IA, was upregulated by LPC. Phosphorylation of the upstream components, MEK and NGF receptor TrkA, was also promoted by LPC, which was in line with increased phosphorylation of Akt. In contrast, LPC did not enhance epidermal growth factor (EGF)-, basic fibroblast growth factor-, or insulin-like growth factor-1-induced signals. Studies using TrkA/EGF receptor chimeras demonstrated that the extracellular domain, but not the transmembrane or intracellular domains, of TrkA is responsible for the effect of LPC. Exogenously-added secretory PLA2 (sPLA2) enhanced NGF-induced MAPK phosphorylation at a comparable level to LPC, suggesting that LPC generated in situ by sPLA2-mediated hydrolysis of membrane PC stimulated NGF-TrkA signal. Taken together, these results indicate a specific role and function of LPC on NGF-TrkA signaling pathway.

Morchella are macrofungi and are also called morels, as they exhibit a morel-like upper cap structure. Morels contain abundant essential amino acids, vitamins and biologically active compounds, which provide substantial health benefits. Approximately 80 species of Morchella have been reported, and even more species have been isolated. However, the lack of wild Morchella resources and the difficulties associated with culturing Morchella have caused a shortage in the morels available for daily consumption. Additionally, in-depth genomic and morphological studies are still needed. In this study, to provide genomic data for further investigations of culturing techniques and the biological functions of Morchella sextelata (M. sextelata), de novo genome sequencing was carried out on the Illumina HiSeq. 4000 platform using both the Illumina 150 and PacBio systems. The final estimated genome size of M. sextelata was 52.93 Mb, containing 59 contigs and a GC content of 47.37%. A total of 9,550 protein-coding genes were annotated. In addition, the repeat sequences, gene components and gene functions were analyzed using various databases. Furthermore, the secondary metabolite gene clusters and the predicted structures of their products were analyzed. Finally, a genomic comparison of different species of Morchella was performed.

We found that brain-derived neurotrophic factor (BDNF)-induced phosphorylation of mitogen-activated protein kinase (MAPK) and Akt in cerebellar granule neurons was specifically potentiated by LPC. LPC also augmented the BDNF-induced phosphorylation of TrkB, the receptor for BDNF. In TrkB-transfected CHO-K1 cells, LPC potentiated BDNF-induced MAPK phosphorylation. These results suggest that LPC plays a role in BDNF-TrkB signaling by regulating the activation of TrkB.Key words: Akt; brain-derived growth factor; cerebellar granule neurons; lysophosphatidylcholine; mitogen-activated protein kinaseNerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3, and neurotrophin-4 constitute a family of closely related small proteins that support and regulate the survival, development, and functions of neurons in the nervous system of vertebrates.1,2) BDNF is abundantly expressed in the developing and adult mammalian brains, and has been implicated in the pathophysiology of various brain diseases. The cellular actions of BDNF are mediated through two receptors, TrkB (high affinity) and p75 (low affinity). By binding to TrkB, BDNF induces the phosphorylation of TrkB and its kinase activity. Phosphorylated TrkB at tyrosine 515 activates the Rasmitogen-activated protein kinase (MAPK) signaling pathway, which induces the phosphorylation of cAMP response element-binding protein and various transcription factors involved in cell survival, as well as the phosphatidylinositol 3-kinase (PI3K)-Akt signaling cascade, which inhibits proapoptotic signals, thereby promoting the survival of cells. Activated TrkB at tyrosine 816 recruits and phosphorylates phospholipase C-1 (PLC-1), and this induces Ca 2þ /calmodulindependent kinase (Ca 2þ /CaM) activation by mobilizing Ca 2þ from the intracellular stores to the cytoplasm, which eventually promotes cell survival.Cerebellar granule neurons (CGNs) are the most abundant neurons in the brain. Cultured CGNs are a suitable model for studying cell survival and differentiation.3) BDNF and IGF-1 have been found to protect CGNs from low potassium-induced apoptosis by activating the Ras-MAPK and the PI3K-Akt signaling cascades, respectively. 11) In the present study, we aimed to determine whether LPC has a similar effect on the BDNF-TrkB pathway. This might be important in the attempt to understand the signaling mechanism of neurotrophin-like activity elicited by LPC. We found that LPC promoted BDNF-induced MAPK phosphorylation in TrkB-transfected CHO-K1 cells. LPC also enhanced BDNF-induced but not IGF-1-induced MAPK and Akt phosphorylation in CGNs that endogenously express TrkB. These findings imply a specific interaction of LPC with TrkB.LPC used in this study was 1-palmitoyl-sn-glycero-3-phosphocholine (C16:0; cat. no. 855675P; Avanti Polar Lipids, USA). Brain-derived neurotrophic factor (BDNF, PT45002) was purchased from Toyobo (Japan). Recombinant human insulin-like growth factor-1 (IGF-1, GPT-10011L) was purchased from Pepro Tech (USA). The primary antibodies used wer...