Defense mechanisms in insects: Certain integumental proteins and tyrosinase are responsible for nonself‐recognition and immobilization of Escherichia coli in the cuticle of developing Ceratitis capitata

Abstract

A defense mechanism in the cuticle of developing C. capitata was demonstrated using an in vitro system consisting of isolated cuticular tyrosinase from C. capitata, cuticular tyrosinase-free proteins, tyrosine, and E. coli. The simultaneous presence of the above components resulted in the formation of large immobilized E. coli aggregates. By contrast, omission of any of the above components failed to produce such aggregates. In other words, E. coli retained their mobility and viability. The results indicate that certain cuticular proteins are responsible for the nonself-recognition, since they are able to bind to the E. coli surface in vitro, and a reactive tyrosine derivative is generated by the action of cuticular tyrosinase for the immobilization and probably killing of E. coli. Based on these studies the most likely explanation for the nonself-recognition and immobilization and/or killing of bacteria is the production of E. coli-protein complexes and their crosslinking through quinone intermediate.

Covalent Association of Lipopolysaccharide at the Hemocyte Surface of Insects is an Initial Step for its Internalization

“…It must be underlined, however, that similar coupling reactions occur not only for cell-mediated defense reactions, but also for humoral defense reactions. Indeed, we have already demonstrated the formation of bacterial aggregates via the same mechanism in the integument of C. capifutu larvae (Marmaras et al, 1993;Charalambidis et al, 1994b).…”

Immune response in insects: The role of phenoloxidase in defense reactions in relation to melanization and sclerotization

“…However, cecropins as well as several other distinct groups of antibacterial peptides are mainly involved in the humoral reactions in the hemolymph (see below). At the same time we demonstrated that certain integumental proteins from Ceratitis capitata larvae have the ability to recognize and immobilize and/or kill Escherichia coli cells, by a mechanism similar to that described for hemocyte proteins (Marmaras et al, 1993;Charalambidis et al, 1995).…”

“…1). There are integumental proteins having the ability to recognize and immobilize E. Cali cells (Marmaras et al, 1993). The white pupa mutant of C. capitata which produces white puparia and lacks the ability to form E. coli aggregates (Charalambidis et al, 1994b1, lends credence to the argument regarding the participation of adduct formation between tyrosine derivatives and specific proteins in the immobilization of bacterial invaders.…”

Global gene expression analysis of Anopheles gambiae responses to microbial challenge

“…Abrasions and challenge of the ectodermally derived integument will lead to transcriptional activation of the antimicrobial cecropin gene (Brey et al, 1993). An in vitro study showed that certain cuticular proteins are implicated in non-self-recognition of E. coli through binding to its surface (Marmaras et al, 1993). Cuticle proteins are also expressed by hemocytes; one of the major immune competent cell types in invertebrates (Mun˜oz et al, 2002;Bartholomay et al, 2004).…”