10.6084/m9.figshare.5675068.v1
Coates C.J.
Coates
C.J.
McCulloch C.
McCulloch
C.
Betts J.
Betts
J.
Whalley T.
Whalley
T.
Supplementary Material for: Echinochrome A Release by Red Spherule Cells Is an Iron-Withholding Strategy of Sea Urchin Innate Immunity
Karger Publishers
2017
Coelomocytes
Damage response
Degranulation
Invertebrate immunity
Paracentrotus lividus
Psammechinus miliaris
2017-12-06 15:12:29
Journal contribution
https://karger.figshare.com/articles/journal_contribution/Supplementary_Material_for_Echinochrome_A_Release_by_Red_Spherule_Cells_Is_an_Iron-Withholding_Strategy_of_Sea_Urchin_Innate_Immunity/5675068
<p>Cellular immune defences in sea urchins are shared amongst the
coelomocytes - a heterogeneous population of cells residing in the
coelomic fluid (blood equivalent) and tissues. The most iconic
coelomocyte morphotype is the red spherule cell (or amebocyte), so named
due to the abundance of cytoplasmic vesicles containing the
naphthoquinone pigment echinochrome A. Despite their identification over
a century ago, and evidence of antiseptic properties, little progress
has been made in characterising the immunocompetence of these cells.
Upon exposure of red spherule cells from sea urchins, i.e., <i>Paracentrotus lividus </i>and<i> Psammechinus miliaris</i>,
to microbial ligands, intact microbes, and damage signals, we observed
cellular degranulation and increased detection of cell-free echinochrome
in the coelomic fluid ex vivo. Treatment of the cells with ionomycin, a
calcium-specific ionophore, confirmed that an increase in intracellular
levels of Ca<sup>2+</sup> is a trigger of echinochrome release.
Incubating Gram-positive/negative bacteria as well as yeast with lysates
of red spherule cells led to significant reductions in colony-forming
units. Such antimicrobial properties were counteracted by the addition
of ferric iron (Fe<sup>3+</sup>), suggesting that echinochrome acts as a primitive iron chelator in echinoid biological defences.</p>