A "notch" in the cellular communication network in response to anoxia by wood frog (Rana sylvatica)

Wood frogs (Rana sylvatica) experience months of whole-body freezing during winter. Anoxia is one of the side stresses along with cell dehydration and hyperglycemia. Among multicellular organisms, communication and coordination is essential between neighbouring cells, particularly under stress conditions. Notch signaling is an effective communication channel between cells and regulates multiple pro-survival pathways. Signaling initiates when membrane-bound ligands Delta-like (DLL) or Jagged (JAG) interact with notch receptors. Activated receptor undergoes cleavage to release intracellular domain (NICD) in the cytoplasm. NICD translocates to the nucleus and forms a transcriptional complex with MAML and RBPJ that interacts with promoter regions and activates stress-specific genes. The role of notch signaling in enduring anoxia was assessed by studying the pathway components using immunoblots, TF-ELISA, and qPCR on treated samples of liver and heart. Bioinformatics tool Pymol was used to prepare structures based on available protein sequences for ligands, NOTCH receptor and the transcriptional complex. The results showed an increase in the levels of both ligands and receptors but decreased levels of RBPJ, suggesting an effective transmission of stress signal but suppressed gene transcription that goes in accordance with lowering energy expense required in energy crisis during anoxia. The study suggests Notch-independent activation of HES1 and HES5. Tissue-specific response of HES1, HES5, and MAML implies energy conservation and myocardial protection. The current study is the first analysis of the regulation of notch signaling in amphibians on encountering anoxic conditions that present multiple future directions.