Cuticular protein with a low complexity sequence becomes cross-linked during insect cuticle sclerotization and is required for the adult molt

Abstract

In the insect cuticle, structural proteins (CPs) and the polysaccharide chitin are the major components. It has been hypothesized that CPs are cross-linked to other CPs and possibly to chitin by quinones or quinone methides produced by the laccase2-mediated oxidation of N-acylcatechols. In this study we investigated functions of TcCP30, the third most abundant CP in protein extracts of elytra (wing covers) from Tribolium castaneum adults. The mature TcCP30 protein has a low complexity and highly polar amino acid sequence. TcCP30 is localized with chitin in horizontal laminae and vertically oriented columnar structures in rigid cuticles, but not in soft and membranous cuticles. Immunoblot analysis revealed that TcCP30 undergoes laccase2-mediated cross-linking during cuticle maturation in vivo, a process confirmed in vitro using recombinant rTcCP30. We identified TcCPR27 and TcCPR18, the two most abundant proteins in the elytra, as putative cross-linking partners of TcCP30. RNAi for the TcCP30 gene had no effect on larval and pupal growth and development. However, during adult eclosion, ~70% of the adults were unable to shed their exuvium and died. These results support the hypothesis that TcCP30 plays an integral role as a cross-linked structural protein in the formation of lightweight rigid cuticle of the beetle.

Suppression of Laccase 2 severely impairs cuticle tanning and pathogen resistance during the pupal metamorphosis of Anopheles sinensis (Diptera: Culicidae)

“…Subsequently, it catalyzes the oxidation of catecholamine to quinones and/or quinone methides, which are involved in cuticle pigmentation, as well as stabilizes and reinforces the cuticle structure via catalyzing the cross-linking among various cuticular components, such as proteins-proteins, proteins-melanin, or proteins-other quinones and/or quinone methides [3–5, 44, 50]. This implies that its normal function controls the supply of important materials for cuticle construction and maintenance.…”

TRE1 and CHS1 contribute to deltamethrin resistance in Culex pipiens pallens

“…The arthropod cuticle is a composite and bipartite system containing chitin filaments embedded in a proteinaceous matrix (Mun et al, ). The chitin biosynthetic pathway involves trehalase (TRE), hexokinase (HK), glucose‐6‐phosphate isomerase, fructose 6‐phosphate transaminase, glucosamine‐phosphate N ‐acetyltransferase, phosphoacetylglucosamine mutase, UDP N ‐acetylglucosamine pyrophosphorylase, and chitin synthase (CHS).…”

Inhibition of fatty acid desaturation impairs cuticle differentiation in Drosophila melanogaster

“…A central enzyme of procuticle formation is the glycosyltransferase chitin synthase that is inserted in the apical plasma membrane of epidermal cells and synthesises chitin fibres that protrude into the extracellular space. Chitin‐binding proteins of the CPR family and other cuticle proteins such as the Tweedle proteins serve to organise the cuticle (Guan, Middlebrooks, Alexander, & Wasserman, ; Mun et al, ; Noh et al, ; Noh, Muthukrishnan, Kramer, & Arakane, ; Soares et al, ). The envelope is constructed by the ABC transporter ABCH‐9C and the extracellular protein Snustorr‐snarlik (Z. Yu et al, ; Zuber et al, ).…”