Transcriptomic, proteomic, and biochemical analyses reveal a novel neuritogenesis mechanism of Naja naja venom α-elapitoxin post binding to TrkA receptor of rat pheochromocytoma cells.

Abstract

This is the first report showing unique neuritogenesis potency of Indian Cobra N. naja venom long-chain α-neurotoxin (Nn-α-elapitoxin-1) exhibiting no sequence similarity to conventional nerve growth factor, by high-affinity binding to its tyrosine kinase A (TrkA) receptor of rat pheochromocytoma (PC-12) cells without requiring low-affinity receptor p75NTR. The binding residues between Nn-α-elapitoxin-1 and mammalian TrkA receptor are predicted by in silico analysis. This binding results in a time-dependent internalization of TrkA receptor into the cytoplasm of PC-12 cells. The transcriptomic analysis has demonstrated the differential expression of 445 genes; 38 and 32 genes are up-regulated and down-regulated, respectively in the PC-12 cells post-treatment with Nn-α-elapitoxin-1. Global proteomic analysis in concurrence with transcriptomic data has also demonstrated that in addition to expression of a large number of common intracellular proteins in the control and Nn-α-elapitoxin-1-treated PC-12 cells, the latter cells also showed the expression of uniquely up-regulated and down-regulated intracellular proteins involved in diverse cellular functions. Altogether, the data from transcriptomics, proteomics, and inhibition of downstream signaling pathways by specific inhibitors, and the immunoblot analysis of major regulators of signaling pathways of neuritogenesis unambiguously demonstrate that, similar to mouse 2.5S-nerve growth factor, the activation of mitogen activated protein kinase/extracellular signal-regulated kinase is the major signaling pathway for neuritogenesis by Nn-α-elapitoxin-1. Nonetheless, fibroblast growth factor signaling and heterotrimeric G-protein signaling pathways were found to be uniquely expressed in Nn-α-elapitoxin-1-treated PC-12 cells and not in mouse 2.5S-nerve growth factor -treated cells. The TrkA binding region of Nn-α-elapitoxin-1 may be developed as a peptide-based drug prototype for the treatment of major central neurodegenerative diseases. Read the Editorial Highlight for this article on page 599.