First Report of Invertebrate Mx: Cloning, Characterization and Expression Analysis of Mx cDNA in Disk Abalone (Haliotis Discus Discus)

Fish Shellfish Immunol. 2007 Jul;23(1):86-96. doi: 10.1016/j.fsi.2006.09.007. Epub 2006 Oct 4.

Abstract

Myxovirus resistance (Mx) protein is one of the most studied antiviral proteins. It is induced by the type I interferon system (IFN alpha/beta) in various vertebrates, but its expression has not been identified or characterized in mollusks or other multi-cellular invertebrates to date. In this study, we isolated the Mx gene from a disk abalone (Haliotis discus discus) normalized cDNA library. Mx cDNA was sequenced, cloned and compared to other known Mx proteins. The full-length 1664 bp of abalone Mx cDNA contained a 1533-bp open reading frame that codes for 511 amino acids. Within the coding sequence of abalone Mx, characteristic features were found, such as a tripartite guanosine-5'-triphosphate (GTP)-binding motif and a dynamin family signature. In addition, leucine residues in the C-terminal region displayed a special leucine domain at L(468), L(475), L(489) and L(510), suggesting that abalone Mx may have a similar oligomerization function as other leucine zipper motifs. Abalone Mx protein exhibited 44% amino acid similarity with channel catfish Mx1, rainbow trout Mx2 and Atlantic halibut Mx. Abalones were injected intramuscularly with the known IFN inducer poly I:C and RT-PCR was performed for Mx mRNA analysis. The results showed enhanced Mx expression in abalone gill and digestive tissues 24h as well as 48 h after injection of poly I:C. Mx mRNA was expressed in gill, digestive gland, mantle and foot tissues in healthy abalone, suggesting that the basal level of Mx expressed is tissue-specific. There is no known Mx protein closely related to abalone Mx according to phylogenetic analysis. Abalone Mx may have diverged from a common gene ancestor of fish and mammalian Mx proteins, since abalone Mx showed high similarity in terms of conserved tripartite GTP-binding, dynamin family signature motifs and poly I:C enhancement of Mx mRNA expression.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Cloning, Molecular
  • DNA Primers
  • DNA, Complementary / genetics
  • GTP-Binding Proteins / genetics*
  • GTP-Binding Proteins / metabolism
  • Gastropoda / genetics*
  • Molecular Sequence Data
  • Myxovirus Resistance Proteins
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sequence Alignment
  • Sequence Analysis, DNA
  • Species Specificity

Substances

  • DNA Primers
  • DNA, Complementary
  • Myxovirus Resistance Proteins
  • GTP-Binding Proteins