Hirayama, D. | bioRxiv Science

bioRxiv2024

Low-affinity ligands of the epidermal growth factor receptor are long-range signal transmitters during collective cell migration of epithelial cells

Epidermal growth factor receptor ligands (EGFRLs) consist of seven proteins. In stark contrast to the amassed knowledge concerning the epidermal growth factor receptors themselves, the extracellular dynamics of individual EGFRLs remain elusive. Here, employing fluorescent probes and a tool for triggering ectodomain shedding of EGFRLs, we show that EREG, a low-affinity EGFRL, exhibits the most rapid and efficient activation of EGFR in confluent epithelial cells and mouse epidermis. In Madin-Darby canine kidney (MDCK) renal epithelial cells, EGFR- and ERK-activation waves propagate during collective cell migration in an ADAM17 sheddase- and EGFRL-dependent manner. Upon induction of EGFRL shedding, radial ERK activation waves were observed in the surrounding receiver cells. Notably, the low-affinity ligands EREG and AREG mediated faster and broader ERK waves than the high-affinity ligands. The integrity of tight/adherens junctions was essential for the propagation of ERK activation, implying that the tight intercellular spaces prefer the low-affinity EGFRL to the high-affinity ligands for efficient signal transmission. To validate this observation in vivo, we generated EREG-deficient mice expressing the ERK biosensor and found that ERK wave propagation and cell migration were impaired during skin wound repair. In conclusion, we have quantitatively demonstrated the distinctions among EGFRLs in shedding, diffusion, and target cell activation in physiological contexts. Our findings underscore the pivotal role of low-affinity EGFRLs in rapid intercellular signal transmission.

cell biology↗

bioRxiv2021

Redundant and specific roles of EGFR ligands in the ERK activation waves during collective cell migration of MDCK cells

Epidermal growth factor receptor (EGFR) plays a pivotal role in collective cell migration by mediating cell-to-cell propagation of extracellular signal-regulated kinase (ERK) activation. Here, we aimed to determine which EGFR ligands mediate the ERK activation waves by gene knockout. Four of the seven known EGFR ligands are expressed in MDCK cells. We found that epidermal growth factor (EGF)-deficient cells exhibited lower basal ERK activity than the cells deficient in heparin-binding EGF (HBEGF), transforming growth factor alpha (TGF) or epiregulin (EREG), but all cell lines deficient in a single EGFR ligand retained the ERK activation waves. Therefore, we knocked out the EGFR ligand genes in decreasing order of expression. ERK activation waves were markedly suppressed, albeit incompletely, only when all four EGFR ligands were knocked-out. Re-expression of the EGFR ligands revealed that all but HBEGF could restore the ERK activation waves. Aiming at complete elimination of the ERK activation waves, we further attempted to knockout Nrg1, a ligand for ErbB3 and ErbB4, and found that Nrg1 deficiency induced growth arrest in the absence of all four EGFR ligand genes expressed in MDCK cells. Collectively, these results showed that EGFR ligands exhibit remarkable redundancy in the propagation of ERK activation waves during collective cell migration.

cell biology↗