Extracellular matrix protein receptors in Drosophila melanogaster

Abstract

The extracellular matrix (ECM) is defined as the many different proteins and secreted substances between cells. The ECM plays a major role in the signaling pathways that stimulate cells to perform many varied functions, ranging from control of gene expression at the cellular level to differentiation and development of tissues, organs, and ultimately the entire organism. A portion of this work describes the identification of the division abnormally delayed gene, which encodes a proteoglycan, that is involved in growth factor reception with important developmental consequences in Drosophila melanogaster. The remainder of this work deals with three Drosophila homologs of vertebrate proteins that may interact with integrins, a family of cell surface receptors for extracellular matrix ligands. The three integrin-interacting proteins are referred to by their vertebrate names, and include CD81, a member of the tetraspanin family, ILK, integrin-linked kinase, and CD98hc, a type II transmembrane glycoprotein which is the heavy chain of a multi-protein complex. In this work, the mutant phenotype of CD98hc is larval lethal and not temperature sensitive. Clonal analyses of CD98hc mutants show no phenotype of mutant clones in the eye. Genetic interactions in adult tissues or interactions affecting larval lethality between CD98hc and Drosophila integrin mutants were not observed, and it remains unclear whether CD98hc physically interacts with Drosophila integrins in tissue culture cells. Since no correlation was seen between the interactions of CD98hc and integrins in vertebrate cells and similar putative interactions in flies, this raises the question as to what role, if any, does CD98hc play as an integrin modulator in this organism.