An LRR domain-containing membrane protein gene in rotifer Brachionus plicatilis: Sequence feature, expression pattern, and ligands binding activity

Abstract

Leucine-rich repeat (LRR) domains mediate multiple innate immune responses via protein-ligand and protein-protein interactions, but their exact roles in invertebrates are poorly understood. Herein, an LRR domain-containing transmembrane protein (BpLRRm) was identified in the rotifer Brachionus plicatilis. The 1069 bp BpLRRm nucleotide sequence contains a 942 bp open reading frame (ORF) encoding a 313 amino acid polypeptide with four LRR motifs harbouring the LXXLXXLXLXXNXLXXL motif, and a transmembrane domain. Treatment with 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) decreased BpLRRm mRNA levels at 3 h, but they increased thereafter and peaked at 12 h. Lipopolysaccharide (LPS) treatment first increased BpLRRm mRNA levels at 3 h, but levels returned to normal at 12 h, then increased and peaked at 24 h. Recombinant BpLRRm protein bound pathogen-related molecular patterns (PAMPs), including LPS, peptidoglycan (PGN), glucan (GLU) and polyinosinic-polycytidylic acid (poly IC), in a dose-dependent manner. Thus, BpLRRm might function as a pattern recognition receptor (PRR) in the innate immunity of B. plicatilis, and mediate responses to environmental pollution.