JAK2-STAT5 signaling is insensitive to porcine growth hormone (pGH) in hepatocytes of neonatal pig

Porcine growth hormone (pGH) is most important hormone which is involved in the growth and development of pig. However, a series of studies have indicated that neonatal pig is insensitive to pGH; the reason for this phenomenon is still not fully understood. In this work, we try to investigate this issue from the angle of intracellular signaling induced by pGH. In the present study, porcine hepatocytes from neonatal pig were used as a model, and confocal laser scanning microscopy (CLSM), Western blot, co-immunoprecipitation and colocalization assay were used to study pGH’s signaling properties in hepatocytes of neonatal pig and explore the possible mechanism(s) for why intracellular signaling is insensitive to pGH. The results indicated that Janus kinase 2 and signal transducers and activators of transcription 5/3/1 (JAK2-STATs) signaling are not activated. We further investigated the possible mechanism(s) by which JAK2-STATs’ signaling is not activated by pGH and growth hormone receptor (GHR) and found that the negative regulatory molecules of JAK2-STATs signaling may be associated with this phenomenon in the hepatocytes of neonatal pig. In addition, we also explored pGH’s biology in hepatocytes from neonatal pig, it can be found that pGH/GHR could translocate into the cell nucleus, which implies that pGH/GHR may exhibit physiological roles based on their nuclear localization. We found that pGH could not trigger intracellular signaling in the hepatocytes of neonatal pigs, but not young pigs, which provides an important explanation for why the growth of neonatal pig is GH independent.