The pro-apoptotic action of the peptide hormone, Neb-colloostatin, on insect haemocytes

Abstract

Summary The gonadoinhibitory peptide hormone, Neb-colloostatin, was first isolated from ovaries of the flesh fly Neobellieria bullata. This 19-mer peptide is thought to be a cleaved product of a collagen-like precursor molecule that is formed during remodelling of the extracellular matrix. In this study, we report that upon injection of pico- and nanomolar doses, this peptide exerts a pro-apoptotic action on haemocytes of Tenebrio molitor adults, as visualized by changes in morphology and viability. The F-actin cytoskeleton was found aggregating into distinctive patches. This may be responsible for the observed inhibition of adhesion of haemocytes and for the stimulation of filopodia formation. However, Neb-colloostatin injection did not induce the formation of authophagic vacuoles. Our results suggest that physiological concentrations of Neb-colloostatin may play an important role in controlling the quantity and activity of haemocytes in insect haemolymph. They also suggest that in periods that Neb-colloostatin is released, this peptide may cause a weakening of the insects' immune system. This is the first report that exposure to a peptide hormone causes apoptosis in insect haemocytes.