Molecular identification and functional analysis of two variants of myeloid differentiation factor 88 (MyD88) from disk abalone (Haliotis discus discus). (February 2018)

• Record Type: Journal Article
• Authors: Priyathilaka, Thanthrige Thiunuwan; Bathige, S.D.N.K.; Lee, Seongdo; Lee, Jehee
• Is Part Of: Developmental and comparative immunology. Volume 79(2018)
• Page Start: 113
• Page End: 127
• Publication Date: 2018-02
• Subjects: Disk abalone -- MyD88 -- Innate immune responses -- Development stages -- NF-κB activation -- Inflammatory responses; Immunology -- Periodicals; Developmental immunology -- Periodicals; 616.079
• DOI: 10.1016/j.dci.2017.10.010
• Languages: English
• ISSNs: 0145-305X

Abstract

Abstract: Myeloid differentiation factor 88 (MyD88) is a crucial adaptor protein of the Toll-like receptor (TLR)- and interleukin 1 receptor-mediated signaling pathways and is involved in a diverse array of inflammatory responses via NF-κB activation. In the present study, two MyD88 variants were identified from disk abalone ( Haliotis discus discus ) and designated AbMyD88-2 and AbMyD88-X. The deduced AbMyD88-2 and AbMyD88-X comprised 433 and 354 amino acids with predicted molecular masses of 48.85 kDa and 40.17 kDa, respectively. AbMyD88-2 and AbMyD88-X possessed typical MyD88 domain structural features including an N-terminal death domain (DD) and C-terminal toll interleukin 1 receptor (TIR) domain similar to those in mammals. Expression analysis of AbMyD88-2 and AbMyD88-X mRNA at different early embryonic developmental stages of abalone by qPCR revealed that their constitutive expression at all developmental stages analyzed with the considerably higher values at the 16-cell ( AbMyD88- 2) and morula stages ( AbMyD88-X ). In unchallenged disk abalones, AbMyD88-2 was highly expressed in muscles, while AbMyD88-X mRNA was predominantly transcribed in hemocytes. Moreover, AbMyD88-2 and AbMyD88-X mRNA were differentially modulated in abalone hemocytes after a challenge with live bacteria ( Vibrio parahaemolyticus, Listeria monocytogenes ), virus (viral hemorrhagic septicemia virus), and pathogen-associated molecular patterns (lipopolysaccharides and Poly I:C). Overexpression of AbMyD88-2 and AbMyD88-X in HEK293T cells induced the activation of the NF-κB promoter. AbMyD88-2 and AbMyD88-X involvement in inflammatory responses was characterized by their overexpression in RAW264.7 murine macrophage cells. These results revealed comparatively higher NO (Nitric oxide) production, induction of inflammatory mediator genes ( iNOS and COX2 ), and proinflammatory genes ( IL1β, IL6 and TNFα ) expression in abalone MyD88s-overexpressing cells than in mock control in the presence or absence of LPS stimulation. Altogether, these results suggest that existence of a MyD88-dependent like signaling pathway in disk abalone and that both AbMyD88-2 and AbMyD88-X might be involved in innate immune and inflammatory responses. Highlights: Two MyD88 isoforms were identified from Disk abalone (AbMyD88-2 and AbMyD88-X). AbMyD88-2 and AbMyD88-X possessed typical MyD88 domain structural features. Both MyD88 isoforms were constitutive expressed at early embryonic developmental stages of disk abalone. The mRNA expression of AbMyD88-2 and AbMyD88-X was differentially modulated upon immune stimulation in vivo. AbMyD88-2 and AbMyD88-X involved in inflammatory responses via NF-κB activation.