Interactions between Candida albicans and the Human Extracellular Matrix Component Tenascin-C Jose ´ L. Lo ´pez-Ribot,* , † Joseba Bikandi,* ,1 Rosario San Milla ´ n,* ,1 and W. LaJean Chaffin* ,2 *Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, Texas 79430; and †Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78284 Received July 23, 1999 Tenascins are large multimeric proteins that con- tain repeated structural motifs that include epidermal growth factor (EGF)-like repeats, fibronectin type III repeats and a globular fibrinogen-like domain, and are involved in tissue and organ morphogenesis, as well as in adhesion and migration of cells. C. albicans germ- tubes, but not blastospores, were able to bind to solu- ble human tenascin-C as revealed by an indirect im- munofluorescence assay. However, materials present in cell wall extracts from both morphologies attached to tenascin-C immobilized in wells of a microtiter plate. The binding specificity was demonstrated by the inhibitory effect of antibodies against C. albicans cell wall components and an anti-tenascin antibody, but not anti-laminin antibody. Fibronectin, but not fibrin- ogen, inhibited binding, thus indicating a role of the fibronectin type III repeats in the interaction between the fungus and tenascin-C. Binding of C. albicans cell wall materials to tenascin was RGD- and divalent cation-independent. © 1999 Academic Press Key Words: Candida albicans; tenascin-C; adhesion. Candida albicans is a dimorphic fungus that is both a commensal and opportunistic pathogen of man. De- pending on the underlying host defect, the fungus is able to cause a variety of infections that range from mucosal to life-threatening disseminated candidiasis. Adhesion of the fungus to host cells and tissues is considered the initial step leading to establishment of infection (1–3). Adherence is mediated by complemen- tary molecules on the surface of the fungus and the host. Host structures supporting attachment of C. al- bicans include the extracellular matrix (ECM) and dif- ferent groups have described binding of C. albicans to individual ECM components including laminin, fi- bronectin, fibrinogen, collagens, entactin, vitronectin, and thrombospondin (4 –14). The tenascins, a family of large multimeric glyco- proteins with typical multidomain structures, are an- other component of ECM (15). The four members of this family are tenascin-C, tenascin-R, tenascin-X, and tenascin-Y (15, 16). Tenascin-C is found in a large number of developing tissues and is frequently overex- pressed in tumor cells. It can have profound regulatory effects on cell adhesion since it displays both pro- adhesive and anti-adhesive properties, interacts with surface receptors (including integrins) on the surface of different cell types and also binds to other ECM pro- teins such as fibronectin (15, 17–25). Tenascin-C is secreted as a disulfide-linked hexameric protein. Each subunit consists of amino-terminal heptad repeats, fol- lowed by a domain of epidermal growth factor (EGF)- type repeats, a variable number (due to alternative splicing) of fibronectin type-III repeats, and a terminal fibrinogen-like domain (15) (Fig. 1). In the present study we describe the binding of sol- uble human tenascin-C to intact C. albicans cells, as well as the interactions between fungal cell wall com- ponents and immobilized tenascin-C. The ability of C. albicans to interact with tenascin-C expands the num- ber of ECM components to which the fungus is able to bind specifically and may be important in colonization and disseminated infection. MATERIALS AND METHODS Organism and culture conditions. C. albicans strain 3153A was maintained on Sabouraud medium containing 2% (w/v) agar. Yeast cells (blastoconidia or blastospores) were grown in suspension culture in the medium of Lee et al. (26) at 22°C in an orbital shaker at 180 –200 rpm. Germ tubes (germinated blasto- conidia) were induced from stationary phase yeast cells that were resuspended at 5  10 7 cells per ml in fresh prewarmed medium and incubated at 37°C for 4 h with shaking. 1 Present address: Departamento de Microbiologı ´a, Facultad de Medicina y Odontologı ´a, Universidad del Paı ´s Vasco, Campus de Leioa s/n 48080 Leioa, Bizkaia, Spain. 2 Corresponding author. Department of Microbiology and Immunol- ogy, Texas Tech University Health Sciences Center, 3601 4th Street, Lubbock, Texas 79430. Fax: 806-743-2334. E-mail: micwlc@ttuhsc.edu. Molecular Cell Biology Research Communications 2, 58 – 63 (1999) Article ID mcbr.1999.0152, available online at http://www.idealibrary.com on 58 1522-4724/99 $30.00 Copyright © 1999 by Academic Press All rights of reproduction in any form reserved.