Specialized molecules on the surface of cells serve to mediate information transfer from the extracellular to the intracellular compartments. Most of these molecules are receptors that bind soluble stimuli such as hormones and growth factors, whereas others are molecules that interact with components fixed either to other cells or to extracellular matricides and serve to mediate cell adhesion or cell movement. Together, these various types of interactions are critical to many processes growth, development and repair of injury. Therefore, the identification of receptors involved in cell-cell and cell-matrix interactions has become an important goal of cell biology. Our recent studies have focused on the identification and characterization of a cell surface receptor that binds both elastin and laminin, and plays a role in matrix assembly and cell migration. This receptor on elastin-producing cells is a complex of three proteins: two transmembrane subunits of 61 and 55 kDa with a cytoplasmic domain(s) that interacts with the cytoskeleton, and an extracellular domain that binds a 67 kDa subunit. The 67 kDa component contains a protein binding site that recognizes galactoside sugars, and a cell binding site that binds one or both of the transmembrane subunits. The overall objective of this proposal is to characterize better the structure and function of this receptor.
The specific aims are to purify and characterize the receptor subunits and to ascertain the role played by the receptor complex in matrix assembly. We also wish to identify possible functions of the receptor in regulating cellular phenotypes. A further aim will be to better define the amino acid sequences in laminin and elastin recognized by the receptor, and determine how alterations in the amino acid sequences alter receptor-ligand binding. Finally, we plan to develop molecular clones of the elastin/laminin receptor complex and its genes.
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