Laminins and Their Ligands

Involvement of Carbohydrates in Formation of the Extracellular Matrix and in Cell Adhesion

Abstract

The extracellular matrix serves as a scaffold for cell attachment (for review: Gumbiner, 1996), growth cone guidance during neurite outgrowth (for review: Luckenbill-Edds, 1997), cell migration (for review: Lauffenberger and Horwitz, 1996), cell polarity (for review: Drubin and Nelson, 1996) and cell death (for review: Adams and Watt, 1993) all underlying critical events in ontogenetic development and differentiation (for review: Adams and Watt, 1993). The molecular architecture of the extracellular matrix is created through specific interactions between laminins, collagen type IV, nidogen/entactin, and heparan- and chondroitin sulfate proteoglycans (Sanes, 1989; Timpl, 1989; Timpl and Brown, 1994; Yurchenco and O'Rear, 1994; Timpl and Brown, 1996; Timpl, 1996). Crucial molecules involved in the architecture of this defined supra-molecular assembly are members of the steadily growing laminin family (Burgeson et al., 1994; Engvall and Wewer, 1996).
In this review we will focus on the unique molecular structure of laminins which enable self-interactions as well as interactions with different types of ligands, such as sulfated carbohydrates, other members of the extracellular matrix (nidogen/entactin, fibulins, perlecan, agrin and α-dystroglycan/cranin) and glycoproteins involved in cell adhesion (integrins and cell adhesion glycoproteins of the immunoglobulin superfamily). In particular, the involvement of carbohydrates in the interactions between laminin and its ligands will be discussed.