Comparative genomic analysis of buffalo (Bubalus bubalis) NOD1 and NOD2 receptors and their functional role in in-vitro cellular immune response.

Biswajit Brahma,Deepak Gaur,Devika Gautam,Sushil Kumar,Hrudananda Malik,Sourav Mahanty,Bidhan Chandra De,Dhruba Malakar,Sachinandan De,Tirtha Kumar Datta,Mahesh Chandra Patra,Meenu Chopra,Purusottam Mishra,Dario S Zamboni

doi:10.1371/journal.pone.0119178

Abstract

Nucleotide binding and oligomerization domain (NOD)-like receptors (NLRs) are innate immune receptors that recognize bacterial cell wall components and initiate host immune response. Structure and function of NLRs have been well studied in human and mice, but little information exists on genetic composition and role of these receptors in innate immune system of water buffalo—a species known for its exceptional disease resistance. Here, a comparative study on the functional domains of NOD1 and NOD2 was performed across different species. The NOD mediated in-vitro cellular responses were studied in buffalo peripheral blood mononuclear cells, resident macrophages, mammary epithelial, and fibroblast cells. Buffalo NOD1 (buNOD1) and buNOD2 showed conserved domain architectures as found in other mammals. The domains of buNOD1 and buNOD2 showed analogy in secondary and tertiary conformations. Constitutive expressions of NODs were ubiquitous in different tissues. Following treatment with NOD agonists, peripheral lymphocytes showed an IFN-γ response along-with production of pro-inflammatory cytokines. Alveolar macrophages and mammary epithelial cells showed NOD mediated in-vitro immune response through NF-κB dependent pathway. Fibroblasts showed pro-inflammatory cytokine response following agonist treatment. Our study demonstrates that both immune and non-immune cells could generate NOD-mediated responses to pathogens though the type and magnitude of response depend on the cell types. The structural basis of ligand recognition by buffalo NODs and knowledge of immune response by different cell types could be useful for development of non-infective innate immune modulators and next generation anti-inflammatory compounds.

Highlights

The germ line encoded pattern recognition receptors (PRRs) are innate immune sentinels that recognize conserved microbe-associated molecular patterns (MAMPs) and initiate host response against microbial invasion
Little homology was observed between NOD1 and NOD2 for the species considered in the study including buffalo (9.38%) and human (14.83%)
This is explicable since primary mode and interfaces of CARD-CARD interactions with RICK are different for NOD1 and NOD2

Summary

Introduction

The germ line encoded pattern recognition receptors (PRRs) are innate immune sentinels that recognize conserved microbe-associated molecular patterns (MAMPs) and initiate host response against microbial invasion. Nucleotide-binding and oligomerization domain (NOD)-like receptors (NLRs) were identified as intracellular PRRs in human about 15 years ago [1,2,3]. NOD1 and NOD2 are the prototypical NLRs belonging to the NLRC subgroup with a single and tandem N-terminal CARD domain(s), respectively [9] Both NOD1 and NOD2 sense bacterial peptidoglycans, but specific ligand moieties are different for these receptors. RICK promotes Lys63-linked ubiquitination of NEMO, allowing the recruitment of TAK1 that phosphorylates IKK-β, leading to degradation of the nuclear factor kappa-B (NF-κB) repressor IkB. This allows NF-κB translocation to the nucleus and initiation of transcription of pro-inflammatory genes. The complex promotes conversion of LC3 to LC3-II, leading to the autophagosome formation [18]

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