Silvas
Tania V.
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Changes in reflectin protein phosphorylation are associated with dynamic iridescence in squid
Silvas
Tania V.
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Preprint
Many cephalopods exhibit remarkable dermal iridescence, a component of their complex,
dynamic camouflage and communication. In the species Euprymna scolopes, the light-organ iridescence
is static and is due to reflectin protein-based platelets assembled into lamellar thin-film
reflectors called iridosomes, contained within iridescent cells called iridocytes. Squid in the
family Loliginidae appear to be unique in that the dermis possesses a dynamic iridescent component,
with reflective, colored structures that are assembled and disassembled under the control of
the muscarinic cholinergic system and the associated neurotransmitter acetylcholine (Mathger et
al. 2004). Here we present the sequences and characterization of three new members of the reflectin
family associated with the dynamically changeable iridescence in Loligo and not found in
static Euprymna iridophores. In addition, we show that application of genistein, a protein tyrosine
kinase inhibitor, suppresses acetylcholine- and calcium-induced iridescence in Loligo. We
further demonstrate that two of these novel reflectins are extensively phosphorylated in concert
with the activation of iridescence by exogenous acetylcholine. This phosphorylation and the correlated
iridescence can be blocked with genistein. Our results suggest that tyrosine phosphorylation
of reflectin proteins is involved in the regulation of dynamic iridescence in Loligo.