Silencing the chicken seven transmembrane (Ch-7TM) receptor leads to apoptosis in chicken mononuclear phagocytes

The seven-transmembrane (7TM) receptors are the largest superfamily of cell-surface receptors and are involved in various physiological processes of vertebrate species. In our previous study, a new chicken 7TM receptor (Ch-7TM) was discovered in mononuclear phagocytes (MNPs) derived from chicken peripheral blood mononuclear cells (PBMCs). To explore the functions of Ch-7TM, RNA interference (RNAi) was used to silence the Ch-7TM messenger RNA (mRNA) of MNPs, using small interfering RNA (siRNA) designed with BLOCK-iT™ RNAi Designer. Herein we demonstrated that silencing of the Ch-7TM mRNA induced apoptosis of MNPs, suggesting that Ch-7TM contributed to the survival of MNPs. Moreover, chicken sera could inhibit the Ch-7TM-silencing-induced apoptosis in MNPs. The survival factor presented in fraction 16 (F16) of chicken sera was highly protective against the Ch-7TM-silencing-induced apoptosis in MNPs. The proteins from F16 were identified as vitamin D-binding protein (DBP) and apolipoprotein A-IV (ApoA-IV), which might be potential candidates for survival factors. The protective effect of vitamin D and ApoA-IV indicated that Ch-7TM might involve the intracellular oxidation-reduction balance, although more evidence is needed to confirm this function. The siRNA screening serves as an excellent model for studying the functions of chicken MNPs receptors.