INTRODUCTION The extracellular matrix glycoprotein laminin mediates adhesion events that are critical to a number of fundamental biological phenomena, including cell migration, neurite outgrowth and angiogenesis (see for review Yamada and Kleinman, 1992). Although these events take hours for com- pletion, they may be composed of a series of rapid and reversible cellular interactions with laminin. Such reversible or dynamic interactions are suggested, for example, by the rapid lamellipod extensions that occur during translocation of myoblasts on laminin (Goodman et al., 1989). The mechanisms that regulate the dynamic interactions of cells with laminin or other matrix proteins have not been examined. Based on existing data, it can be postulated that dynamic interactions involve a cycle of integrin-mediated attachment to and detach- ment from matrix proteins and that this cycle is regulated by the rapid modulation of integrin function (Regen and Horwitz, 1992). The principal epithelial and carcinoma cell surface adhesion receptors that interact with laminin are integrins α 2 β 1 , α 6 β 1 and α 6 β 4 (Sonnenberg et al., 1990; Lotz et al., 1990; Lee et al., 1992). Although some carcinoma cells also express α 3 β 1 , an established laminin and collagen receptor (Carter et al., 1990; Kramer et al., 1990; Hynes, 1992), they do not appear to use it in adhesion to laminin (Lotz et al., 1990). The α 2 β 1 integrin laminin receptor functions as a collagen receptor in a number of epithelial and carcinoma cells (Carter et al., 1990; Elices and Hemler, 1989; Lotz et al., 1990). Integrins α 6 β 4 and α 6 β 1 bind to laminin and to laminin subfragment E8, the distal stem and proximal half of the large globule of the long arm (Kramer et al., 1990; Elices et al., 1991; Lee et al., 1992). The β 4 integrin subunit, which is probably the most structurally complex of all integrins associates with variants of the α 6 integrin (Quaranta and Jones, 1991). The α 6 integrin subunit has a higher binding affinity for β 4 than for β 1 integrin (Giancotti et al., 1992). As a result, in cells expressing both β 1 and β 4 integrins, α 6 integrin preferentially associates with β 4 integrin (Hemler et al., 1989; Kajiji et al., 1989; Simon-Assmann et al., 1994). In a variety of cell types that express large amounts of the α 6 β 4 integrin, it has not been possible to assign a distinct adhesive function to α 6 β 4 using conventional adhesion tests (Sonnenberg et al., 1990). Only recently, with the use of clone A colon carcinoma cells that express α 6 β 4 but not α 6 β 1 and are highly motile on laminin, was integrin α 6 β 4 shown to be a laminin receptor (Lee et al., 1992). These authors also illus- trated that carcinoma cell lines that express both α 6 β 4 and α 6 β 1 or exclusively α 6 β 1 (RKO human rectal carcinoma cells) adhere to laminin with slower kinetics than the clone A cells. The capacity for rapid attachment and motility on laminin suggests a dynamic mode of interaction that is distinct and perhaps more significant biologically than from more static 3153 We present here a novel form of dynamic adhesion in which both the integrin receptor and the ligand supporting dynamic adhesion have been identified. Laminar flow assays showed that laminin supported attachment of α 6 β 4 - positive cells in the presence of fluid shear stress (τ≤2 dyn/cm 2 ), indicating that these cells adhered to laminin within a fraction of a second. Further increases in flow rate (3.5 dyn/cm 2 ≤τ≤100 dyn/cm 2 ) initiated rolling of attached cells in the direction of flow, suggesting that rapidly formed adhesion is reversible and repeatable. Laminin fragment E8, which interacts with α 6 integrins, supported dynamic attachment and rolling but extracellular matrix glycopro- tein fibronectin did not. In cell lines that express α 6 β 4 but not α 6 β 1 an anti-α 6 monoclonal antibody inhibited attach- ment to laminin in the presence of flow and following 5 minutes of static incubation. Infusion of this antibody onto cells adherent to laminin-coated slides led to rapid detach- ment of cells from the substratum. An anti-β 1 monoclonal antibody diminished adhesion strength following static incubation but did not inhibit rapid attachment and flow- initiated rolling. These results indicate that in some α 6 β 4 - expressing epithelial and carcinoma cell lines, integrin α 6 β 4 mediates rapidly formed dynamic interactions with laminin. Key words: laminin, integrin, α6β4, dynamics, adhesion SUMMARY Integrin α 6 β 4 mediates dynamic interactions with laminin Aydin Tözeren 1, *, Hynda K. Kleinman 2 , Stephen Wu 1 , Arthur M. Mercurio 3 and Stephen W. Byers 4 1 Department of Mechanical Engineering, The Catholic University of America, Washington, DC 20064, USA 2 Laboratory of Developmental Biology, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892, USA 3 Laboratory of Cancer Biology, Deaconess Hospital, Harvard Medical School, Boston, MA 02115, USA 4 Department of Cell Biology and Lombardi Cancer Research Center, Georgetown University, Washington, DC 20007, USA *Author for correspondence Journal of Cell Science 107, 3153-3163 (1994) Printed in Great Britain © The Company of Biologists Limited 1994