Chicken leptin receptor is functional in activating JAK-STATpathway in vitro.

Leptin is a cytokine-like hormone that regulates food intake and energy homeostasis via its interaction with the leptin receptor (LEPR) located in the target tissues. Leptin-dependent signal transduction pathways have been well characterised in mammals but less is known about them in other vertebrates. In birds, although the existence of the LEPR has been confirmed, the identity of the natural ligand for the LEPR is controversial and the signalling cascade is not fully understood either. Here, we describe the in vitro expression of chicken LEPR (chLEPR), which can mediate the leptin signal. Murine leptin specifically bound with the chLEPR, which initiated the activation of luciferase in chLEPR-expressing cells. Leptin stimulation led to phosphorylation of signal transducers and activators of transcription 3 (STAT3) via chLEPR, and Janus kinase(-2) (JAK(-2)) inhibitor partially blocked leptin-induced luciferase activation in CHO-K1 cells stably expressing chLEPR (CHO-chLEPR). RNA interference for chLEPR reduced the induction rate of luciferase activity by leptin in CHO-chLEPR cells. Furthermore, we found that leptin phosphorylated STAT3 and increased luciferase activity in LMH cells, a chicken hepatoma cell line, transiently expressing chLEPR. These results strongly suggest that the chLEPR is functional in activating the JAK-STAT pathway, which may indicate that the LEPR expressed in chicken tissues is capable of binding endogenous ligand as well as exogenous mammalian leptin, leading to physiological actions.