EGF-R signaling through Fyn kinase disrupts the function of integrin α6β4 at hemidesmosomes

Abstract

We have examined the mechanism and functional significance of hemidesmosome disassembly during normal epithelial cell migration and squamous carcinoma invasion. Our findings indicate that a fraction of EGF receptor (EGF-R) combines with the hemidesmosomal integrin α6β4 in both normal and neoplastic keratinocytes. Activation of the EGF-R causes tyrosine phosphorylation of the β4 cytoplasmic domain and disruption of hemidesmosomes. The Src family kinase inhibitors PP1 and PP2 prevent tyrosine phosphorylation of β4 and disassembly of hemidesmosomes without interfering with the activation of EGF-R. Coimmunoprecipitation experiments indicate that Fyn and, to a lesser extent, Yes combine with α6β4. By contrast, Src and Lck do not associate with α6β4 to a significant extent. A dominant negative form of Fyn, but not Src, prevents tyrosine phosphorylation of β4 and disassembly of hemidesmosomes. These observations suggest that the EGF-R causes disassembly of hemidesmosomes by activating Fyn, which in turn phosphorylates the β4 cytoplasmic domain. Neoplastic cells expressing dominant negative Fyn display increased hemidesmosomes and migrate poorly in vitro in response to EGF. Furthermore, dominant negative Fyn decreases the ability of squamous carcinoma cells to invade through Matrigel in vitro and to form lung metastases following intravenous injection in nude mice. These results suggest that disruption of hemidesmosomes mediated by Fyn is a prerequisite for normal keratinocyte migration and squamous carcinoma invasion.

Purinoreceptor P2X7 Regulation of Ca2+ Mobilization and Cytoskeletal Rearrangement Is Required for Corneal Reepithelialization after Injury

“…31 Previously, Fyn was shown to be required for the regulation of the b4 integrin and maintenance of hemidesmosomes, structures vital for epithelial integrity. 32 Blocking the P2X7 activity with oxATP To better understand these results and further investigate the role of P2X7 in promoting cell migration at the leading edge, we examined actin cytoskeletal rearrangements and focal adhesion dynamics in live cells. A marked decrease in membrane ruffling and minimal extension of lamellipodia at the leading edge were observed in oxATP-treated cells.…”

Upregulation of integrin β4 promotes epithelial–mesenchymal transition and is a novel prognostic marker in pancreatic ductal adenocarcinoma

“…On the other hand, a number of reports have revealed that ITGB4 combines with several oncogenic receptor tyrosine kinases, including c-Met, ErbB1, and ErbB2, to amplify the signaling pathways that accelerate cancer invasion. [30][31][32] Because these growth factor receptors are overexpressed in a large number of patients with pancreatic cancers and are involved in cancer progression, 33,34 upregulated ITGB4 may associate with some of these overactive receptor tyrosine kinases, such as EGFR and c-Met, which are well-known EMT inducers, thereby promoting tumor invasion and EMT in pancreatic cancer.…”

EGF receptor (EGFR) signaling promoting invasion is disrupted in androgen‐sensitive prostate cancer cells by an interaction between EGFR and androgen receptor (AR)

“…Although internalization by endocytosis has been assumed to be a mechanism to attenuate the signaling in response to the growth factor, increasing evidence demonstrates that a correct endocytotic pathway is important for EGFR signaling by controlling the specificity of the response. 36,37 Several studies have shown that internalized EGFR are enzymatically active, are still phosphorylated and maintain association with many adaptor proteins. [43][44][45] In addition, it has been recently shown that interaction with some adaptor proteins, such as eps8, a protein involved in cytoskeletal reorganization and actin remodeling, 46 occurs only at endosomal level.…”