Integrin αE(CD103)β7 influences cellular shape and motility in a ligand-dependent fashion

Abstract

While the extravasation cascade of lymphocytes is well characterized, data on their intraepithelial positioning and morphology are scant. However, the latter process is presumably crucial for many immune functions. Integrin ␣ E (CD103)␤ 7 has previously been implicated in epithelial retention of some T cells through binding to E-cadherin. Our current data suggest that ␣ E (CD103)␤ 7 also determines shape and motility of some lymphocytes. Time-lapse microscopy showed that wild-type ␣ E (CD103)␤ 7 conferred the ability to form cell protrusions/filopodia and to move in an amoeboid fashion on E-cadherin, an activity that was abrogated by ␣ E (CD103)␤ 7 -directed antibodies or cytochalasin D. The ␣ E -dependent motility was further increased (P < .001) when point-mutated ␣ E (CD103) locked in a constitutively active conformation was expressed. Moreover, different yellow fluorescent protein-coupled ␣ E (CD103) species demonstrated that the number and length of filopodia extended toward purified E-cadherin, cocultured keratinocytes, cryostat-cut skin sections, or epidermal sheets depended on functional ␣ E (CD103). The in vivo relevance of these findings was demonstrated by wild-type dendritic epidermal T cells (DETCs), which showed significantly more dendrites and spanned larger epidermal areas as compared with DETCs of ␣ E (CD103)-deficient mice (P < .001). Thus, integrin ␣ E (CD103)␤ 7 is not only involved in epithelial retention, but also in shaping and proper intraepithelial morphogenesis of some leukocytes. IntroductionPositioning and locomotion of leukocytes within tissues provide the basis for the molecular crosstalk with other cells and are prerequisites for a functional immune system. To date, the recruitment cascade of initial endothelial adhesion, activation, firm adhesion, transmigration, and subsequent localization into the connective tissue is one of the best established concepts in leukocyte biology. 1,2 However, many effector functions of immunocytes are exerted within parenchymatous organs, mostly epithelia. It is therefore somewhat surprising that we know relatively little about locomotion and function-determining morphogenesis of lymphocytes within epithelial tissues, such as the epidermis of the skin. 3 An adhesion receptor that is thought to mediate retention of lymphocytes within epithelial tissues is integrin ␣ E (CD103)␤ 7 . 4 First described 2 decades ago as a selective marker for intestinal intraepithelial lymphocytes, 5 ␣ E (CD103)␤ 7 has been implicated in epithelial T-cell retention through binding to E-cadherin. 6,7 Indeed, ␣ E (CD103)-deficient mice exhibited a reduced number of mucosal intraepithelial T cells. 8 However, ␣ E (CD103)␤ 7 has later been found to be also expressed by some lymphocytes within other epithelia, such as the epidermis of the skin, 9 where it presumably contributes to recruitment of T cells in inflamed human skin 10 as well as dendritic epidermal T cells (DETCs) in murine skin. 11 Thymic DETC precursor cells express integrin ␣ E (CD103)␤ 7 before their migration ...

Role for E-Cadherin as an Inhibitory Receptor on Epidermal γδ T Cells

“…Membrane staining of b-catenin was also reduced in the rounded DETCs (data not shown). Although a E b 7 integrin has a role for cellular shape of DETCs (32) and was reported to be downregulated on DETC activation (38), we could not find apparent downregulation of a E b 7 integrin on the rounded DETCs (Fig. 2).…”

“…In addition to homophilic E-cadherin binding that controls cellular shape through connection to the actin cytoskeleton (2), heterophilic binding of a E b 7 integrin to E-cadherin also influences cellular shape (32). Therefore, the morphological change of DETCs during wound healing in vivo could result from disruption of E-cadherin-mediated homophilic binding and/or a E b 7 integrin-mediated heterophilic binding caused by downregulation of E-cadherin on DETCs, keratinocytes, or both.…”

“…6). Although DETCs adhered equally well to uncoated and E-cadherin-coated slides 24 h after seeding, only DETCs cultured on the E-cadherin-coated slides extended cellular protrusions, which is mediated by interactions of a E b 7 integrin with E-cadherin (32). Accumulation of E-cadherin at the bottom surface of DETCs was observed only when cultured on the Ecadherin-coated slides for 24 h (Fig.…”

“…This possibility is unlikely, however, because we found that homophilic E-cadherin binding cannot compensate for DETC adhesion to keratinocytes in vitro when interactions of a E b 7 integrin with E-cadherin are blocked. Stable homophilic Ecadherin binding may also contribute to retention of DETCs in the epidermis, but presumably in a different way from a E b 7 integrinmediated rapid adhesion that regulates cell motility (32).…”

“…In addition, a recent study showed that a E b 7 integrin influences cellular shape and motility of DETCs (32). However, roles of a E b 7 integrin in the adhesion of DETCs to keratinocytes, in the DETC-mediated lysis of keratinocytes, or in the costimulation of DETC activation have not been elucidated.…”