TCAP (teneurin c-terminal associated peptide), is an ancient bioactive peptide that is highly conserved in metazoans (Chand, Casatti, et al., 2013; Colacci et al., 2015). TCAP administration reduces cellular and behavioural stress in vertebrate and urochordate animal models (D’Aquila et al., 2017; Kupferschmidt, et al.,2011; Tan et al., 2009; Wang et al., 2005). We used the Sydney rock oyster (SRO) as a molluscan model to study the molecular and physiological effects of sroTCAP. We have identified a single Teneurin/TCAP gene in the SRO genome and 4 teneurin splice variants in transcriptomics analysis where the TCAP sequences of all variants are identical. We have shown for the first time that synthetic sroTCAP is bioactive on the heart and reduces the beat minute-1 by 54% when administered in the pericardium cavity or by intramuscular (IM) injection, for up to 50 min post administration. Furthermore, 5pmol IM injected sroTCAP, modulated the immune system by reducing phagocytosis activity under stress conditions (low salinity, 15 ppt and high temperature, 30°C) compared to the control. Under similar stress conditions, we have seen a significant reduction in reactive oxygen species (ROS) production in hemocytes after 48 h of stress and at ambient conditions. Additionally, to identify potential binding partners using a pull-down assay, we have found that sroTCAP binds to GAPDH and propose a mechanism modelling the capacity of TCAP to protect cells from apoptosis under oxidative stress.
The results of this study establish a role for TCAP in the modulation of several physiological and molecular functions that are involved in energy conservation, stress and cellular defence in a molluscan model.