Insights into molecular characterization of NOD1-RIPK interaction and transcriptional modulation in response to LPS in spotted snakehead, Channa punctata (Bloch, 1793).

NOD1, plays a pivotal role in immune responses against bacterial as well as viral invasions. While the downstream signaling pathway of NOD1 is well understood in mammals, its characterization in lower vertebrates remains elusive. In present study, an effort was made to identify and characterize downstream signaling cascade of NOD1 in response to LPS, a potential ligand of NOD1 in teleosts, in spotted snakehead. In addition, the temporal effect of LPS on transcriptional modulation of NOD1 and its downstream signaling molecule RIPK2 was investigated. Docking studies revealed well conserved leucine rich domains of NOD1 that could bind with LPS. Further, NACHT-ATP interactions revealed differences in ATP binding motifs within the NACHT domain in spotted snakehead compared to those reported in other fish species and mammals pointing towards species-specific nature of ATP interactions within the NACHT domain. Further, it was revealed that the ssNOD1-CARD domain interacts with the CARD domain of downstream signaling molecule ssRIPK. Interestingly, LPS treatment modulated the expression of both, ssNOD1 and ssRIPK2 in a time-dependent manner.