Concholepas hemocyanin biosynthesis takes place in the hepatopancreas, with hemocytes being involved in its metabolism

Abstract

Hemocyanins are copper-containing glycoproteins in some molluscs and arthropods, and their best-known function is O(2) transport. We studied the site of their biosynthesis in the gastropod Concholepas concholepas by using immunological and molecular genetic approaches. We performed immunohistochemical staining of various organs, including the mantle, branchia, and hepatopancreas, and detected C. concholepas hemocyanin (CCH) molecules in circulating and tissue-associated hemocytes by electron microscopy. To characterize the hemocytes, we purified them from hemolymph. We identified three types of granular cells. The most abundant type was a phagocyte-like cell with small cytoplasmic granules. The second type contained large electron-dense granules. The third type had vacuoles containing hemocyanin molecules suggesting that synthesis or catabolism occurred inside these cells. Our failure to detect cch-mRNA in hemocytes by reverse transcription with the polymerase chain reaction (RT-PCR) led us to propose that hemocytes instead played a role in CCH metabolism. This hypothesis was supported by colloidal gold staining showing hemocyanin molecules in electron-dense granules inside hemocytes. RT-PCR analysis, complemented by in situ hybridization analyses with single-stranded antisense RNAs as specific probes, demonstrated the presence of cch-mRNA in the hepatopancreas; this was consistent with the specific hybridization signal and confirmed the hepatopancreas as the site of CCH synthesis. Finally, we investigated the possibility that CCH catabolism in hemocytes was involved in the host immune response and in the generation of secondary metabolites such as antimicrobial peptides and phenoloxidase.

A new haemocyanin in cuttlefish (Sepia officinalis) eggs: sequence analysis and relevance during ontogeny

“…The expression site of haemocyanin is not uniform among the Mollusca and ranges from the rhogocytes/pore cells in the midgut gland in many gastropods [72-74] and Nautilus (a rather ancient cephalopod, which did not evolve branchial glands [63,75]), to the branchial glands in adult coleoid cephalopods. According to Beuerlein et al [49] and Ruth et al [75], the haemocyanin of cuttlefish embryos is also expressed in the midgut gland.…”

Enhanced structural stability of Concholepas hemocyanin increases its immunogenicity and maintains its non‐specific immunostimulatory effects

“…Despite the differences between CCH and KLH, both proteins may have similar amino acid motifs and domains that drive and stimulate the immune responses toward a strong Th1 profile. This idea is based on the presence of regions of high-sequence homology in gastropod hemocyanins, which are especially clear in the active site region [1,57], and are confirmed by the presence of common or mimic epitopes that were revealed by Ab cross-reactivity among CCH and KLH [46]. Our future studies will focus on the discovery of the common immunodominant motifs of hemocyanins that are responsible for their immunomodulatory effects in mammals.…”

Synthesis of keyhole limpet hemocyanin by the rhogocytes ofMegathura crenulata

“…This conclusion will be strengthened when the cell type responsible for HCN synthesis is determined in more species (Manubens et al. ), and when further research is conducted on the regulation of KLH synthesis, the secretion of KLH from these cells, and other roles of the rhogocytes of M. crenulata .…”