Different cellular properties and loss of nuclear signalling of porcine epidermal growth factor receptor with aging

The biological activity and signaling profile of EGF/EGFR were affected under heat stress conditions in IEC6 cells

Epidermal growth factor (EGF) is an effective cytoprotective peptide. It is the main nutritional factor involved in the development of the intestinal tract. It has many important biological effects on the intestinal mucosa. After binding to epidermal growth factor receptor (EGFR), it initiates a signal transduction cascade to jointly promote the migration, proliferation, and differentiation of various cell types. Heat stress severely affects the intestinal health of livestock and is becoming increasingly prevalent due to the yearly increase in ambient temperature and intestinal diseases. However, the effect of heat stress on the activity and signaling of EGF/EGFR in intestinal cells is still unclear. Therefore, rat intestinal crypt epithelial cell line (IEC6) was used as a model to explore this issue, and the results showed that EGF/EGFR is internalized into IEC6 cells in a time-dependent manner under physiological conditions. However, the activity of EGF/EGFR was altered under heat stress. Furthermore, we explored the effect of heat stress on EGF/EGFR-activated signaling transduction in IEC6 cells, and the results showed that levels of factors involved in EGFR-mediated intracellular signaling (such as EGFR, signal transducers and activators of transcription 3/protein kinase B, and extracellular regulatory kinase 1/2) were downregulated under heat stress. In summary, this study shows that heat stress could damage the biological activity and intracellular signaling of EGF/EGFR. These findings have scientific importance in the field of animal husbandry; and lay the foundation for the further study of the biological activities of EGF/EGFR in the intestine.

Epidermal growth factor/epidermal growth factor receptor moves into the osteoblasts' cell nuclei where it is involved to regulate STAT5's signaling

Epidermal growth factor (EGF) has vital biological impacts on the osteoblasts. However, the knowledge on the cellular properties of EGF/EGFR (epidermal growth factor receptor) on osteoblasts is scanty. As such, we explored the EGF/EGFR's cell behavior in the osteoblast (MC3T3-E1 cell) using the indirect immunofluorescence assay, Western-blot, and fluorescence resonance energy transfer. Our findings revealed that EGF could internalize into the cytoplasm under EGFR mediation. Besides, the co-localization analysis demonstrated that caveolin played a critical role in EGFR's endocytosis. We also analyzed the cytoplasmic trafficking pathway of EGF/EGFR in MC3T3-E1 cell. The colocalization analysis showed that EGFR entered into Rab5, Rab4, and Rab9-positive endosomes. More importantly, we found that EGFR could move into the MC3T3-E1 cells' nuclei. Based on this, we investigated the EGFR's nuclear-localized functions, and the results suggested that nuclear-localized EGFR has important biological functions. This work lays a foundation for further study on EGF/EGFR's biological functions on the osteoblasts.