Abstract
Rhogocyte is a unique molluscan cell that synthesises a supramolecular respiratory protein known as hemocyanin. Its ability to synthesise the protein has eluded the scientists despite hemocyanin’s importance as a carrier protein and complex molecule with anti-viral activity. Although a hypothetical model of hemocyanin release from the rhogocytes lacunae was proposed based on colloid-osmotic pressure mechanism, lack of in vitro studies limits further validation of this model. In this study, we aim to investigate the impact of cell culture conditions and nature of hemocyanin biosynthesis of rhogocyte cells dissociated from Haliotis laevigata mantle tissue. Population of cells with different hemocyanin expression levels was profiled using flow cytometry, while hemocyanin concentrations in the media were elucidated by ELISA assay. We demonstrated that addition of lipoprotein supplement into the media resulted in a burst secretion of hemocyanin into the culture media. Over 7 days of culture, the population of cells tagged with hemocyanin antibody increased steadily while hemocyanin release in the media decreased significantly. Variation of culture medium, temperature, growth supplement type and concentration also impacted the cell growth and hemocyanin biosynthesis. These results indicated the possibility of an active process triggered by the addition of supplement to synthesise the protein at the highest amount during the first hour. The current study provides a glimpse of the hemocyanin biosynthesis by rhogocyte that may be significant to understand the cell ability to synthesise supramolecular protein and secretion through lacunae.
Highlights
Hemocyanin biosynthesis occurs in the rhogocyte cells in all molluscan species (Haszprunar 1996; Albrecht et al 2001; Martin et al 2011)
To the best of our knowledge, the current study is the first attempt to investigate the growth of rhogocyte cells of abalone and their ability to synthesise hemocyanin in vitro
The tissue was selected because it harbours a high population of rhogocyte cells that specialise in producing type 1 hemocyanin (Sairi et al 2015)
Summary
Hemocyanin biosynthesis occurs in the rhogocyte cells in all molluscan species (Haszprunar 1996; Albrecht et al 2001; Martin et al 2011). Cell and Tissue Research one type of hemocyanin and exist in active and resting states. The active state is when the cells readily synthesizes and releases hemocyanin into the ELS, which was reflected by low hemocyanin mRNA transcription in the cytoplasm, but prominent and distributed hemocyanin signal around the cell membrane detected by immunocytochemistry. The resting rhogocyte state manifests with a high transcription hemocyanin mRNA in the cytoplasm and distinct localised hemocyanin accumulation around the cell membrane. Our findings corroborated those of Kokkinopoulou et al (2015) who proposed the colloid-osmotic pressure mechanism as a hypothetical model to explain the hemocyanin release from the rhogocyte cell. The built-up pressure induces contraction of the actin-rich peripheries of the cytoplasmic bars and releases the ELS content
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