Meet the Tenascins: Multifunctional and Mysterious

Abstract

The tenascins are a highly conserved family of large oligomeric glycoproteins found in the extracellular matrix (ECM) 1 of vertebrate organisms. Two decades ago, the molecule now known as tenascin-C was among the first proteins shown to have an adhesion modulatory role antagonizing cell attachment to fibronectin (1). Cells that normally demonstrate a stationary phenotype on the fibronectin-containing matrix by spreading out and forming cortical actin stress fibers (Fig. 1A) will show morphological changes when tenascin-C is included in the matrix by extending membrane protrusions and exhibiting decreased stress fiber formation (Fig. 1B), characteristics more typical of a migratory phenotype (2). The presence of ECM proteins such as tenascins during developmental and pathological states is now well recognized if still not well understood. Although each type has a distinctive expression pattern, the tenascins share the characteristic of having tightly regulated expression during development and throughout an organism's life. Tenascins also share the characteristic of modulating cell-matrix interactions and mediating a state of matrix attachment that promotes motility while also influencing other cell functions. As such, this protein family has important functions not only during development but also during pathological states in the adult such as tissue injury and tumorigenesis where remodeling processes are prominent. Reviews in recent years have covered pertinent aspects of tenascin biology including domain structure, modulation of cell functions, in vivo null deletion phenotypes, and contributions to human pathology (3-10). This minireview will provide a concise summary of information from these reviews, which the reader is encouraged to refer to for greater detail, and will also discuss a few of the more recent developments in the field.