title: Protein kinase C-dependent mobilization of the alpha6beta4 integrin from hemidesmosomes and its association with actin-rich cell protrusions drive the chemotactic migration of carcinoma cells.
abstract: We explored the hypothesis that the chemotactic migration of carcinoma cells that assemble hemidesmosomes involves the activation of a signaling pathway that releases the alpha6beta4 integrin from these stable adhesion complexes and promotes its association with F-actin in cell protrusions enabling it to function in migration. Squamous carcinoma-derived A431 cells were used because they express alpha6beta4 and migrate in response to EGF stimulation. Using function-blocking antibodies, we show that the alpha6beta4 integrin participates in EGF-stimulated chemotaxis and is required for lamellae formation on laminin-1. At concentrations of EGF that stimulate A431 chemotaxis ( approximately 1 ng/ml), the alpha6beta4 integrin is mobilized from hemidesmosomes as evidenced by indirect immunofluorescence microscopy using mAbs specific for this integrin and hemidesmosomal components and its loss from a cytokeratin fraction obtained by detergent extraction. EGF stimulation also increased the formation of lamellipodia and membrane ruffles that contained alpha6beta4 in association with F-actin. Importantly, we demonstrate that this mobilization of alpha6beta4 from hemidesmosomes and its redistribution to cell protrusions occurs by a mechanism that involves activation of protein kinase C-alpha and that it is associated with the phosphorylation of the beta4 integrin subunit on serine residues. Thus, the chemotactic migration of A431 cells on laminin-1 requires not only the formation of F-actin-rich cell protrusions that mediate alpha6beta4-dependent cell movement but also the disruption of alpha6beta4-containing hemidesmosomes by protein kinase C.
authors.affiliation: Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA.
authors.forename: I
authors.initials: I
authors.lastname: Rabinovitz
authors.forename: A
authors.initials: A
authors.lastname: Toker
authors.forename: A M
authors.initials: AM
authors.lastname: Mercurio
mesh_terms: D000199:Actins / Q000378:metabolism*; D000954:Antigens, Surface / Q000378:metabolism*; D002227:Carbazoles / Q000494:pharmacology; D002294:Carcinoma, Squamous Cell / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects; D002633:Chemotaxis / Q000187:drug effects; D003896:Desmosomes / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D039161:Integrin alpha6beta4; D016023:Integrins / Q000378:metabolism*; D007633:Keratins / Q000378:metabolism; D007797:Laminin / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism; D019000:Phosphotyrosine / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011554:Pseudopodia / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D014407:Tumor Cells, Cultured
chemical_list: D000199:Actins; D000954:Antigens, Surface; D002227:Carbazoles; D007211:Indoles; D039161:Integrin alpha6beta4; D016023:Integrins; D007797:Laminin; C081021:Go 6976; D010768:Phosphoserine; D019000:Phosphotyrosine; D004815:Epidermal Growth Factor; D007633:Keratins; D066246:ErbB Receptors; D011493:Protein Kinase C