Abstract
Purpose::
Important factors during ocular surface regeneration is EGFR activation and neurotrophic influences. However, the potential cross-talk between these two signaling pathways has not been fully investigated in cornea. Here we investigate the effect neurotrophic factors have on EGFR activation.
Methods::
Primary rabbit corneal epithelial cells (passage P0-P1) at sub-confluency were starved of FBS for 24 hours then treated with 0.1µM of one of four neuropeptides (Neuropeptide A, Neuropeptide B, Calcitonin Gene Related Protein, (CGRP) and Substance P) for varying time points. The cells were lysed in RIPA buffer plus phosphatase inhibitors for total protein and western blotting performed to detect activated (phosphorylated) EGFR. The membranes were stripped and western blotting performed to determine total EGFR .
Results::
Three of the four neuropeptides (Substance P, Neuropeptide A, and CGRP) showed a modest up-regulation in EGFR activation. Neuropeptide B showed no change in levels of EGFR activation compared to no treatment extending out to a two hour time interval. Substance P and CGRP showed the most rapid induction with an approximately a two-fold induction of EGFR activation after 10 minutes of treatment compared to no treatment cells. Neuropeptide A showed a less modest increase of ~1.5 fold induction of EGFR activation after 30 minutes of treatment.
Conclusions::
Neuropeptides are ligands for various G-protein coupled receptors (GPCRs). Here we examined the potential cross-talk between neuropeptide GPCRs and the transmembrane tyrosine kinase receptor, EGFR. Of the four neuropeptides examined three showed the capability to induce EGFR activation suggesting a signaling mechanism exist between these membrane type receptors. Deciphering this signaling pathway will further our understanding of the ocular surface regeneration process.
Keywords: cornea: basic science • cornea: epithelium • signal transduction