Analysis of Laminin - alpha7beta1 Integrin Interactions: Ligand specificity and Binding sites

• Applicant: Professor Klaus von der Mark, Ph.D.
• Subject Area: Dermatology
• Term: from 2002 to 2008
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5394214

Alpha7beta1 integrin is - besides a-dystroglycan - the major laminin receptor in skeletal, cardiac and smooth muscle. Focussed to myotendinous junctions and neuromuscular synapses, is has been shown to be essential for functional maintenance and regeneration of skeletal muscle. Thus, disruption of the a7 gene itga7 in mice and men leads to progressive muscular dystrophy and myopathy. Furthermore, it has been localized on certain melanoma cells and glioblastoma cells, as well as in embryonic trophectoderm cells where it is responsible for blastocyst impantation. Integrin a7b1, a transmembrane protein complex, exists in alternatively spliced forms affecting the extracellular and intracellular domains, which are tissue specifically and developmentally regulated. Little is known, however, on the specific roles of these splice variants and their interaction with the different laminin isoforms. Previously we could demonstrate that the two extracellular splice variants a7X1 and a7X2 show selective binding to the laminin isoforms laminin-8 and -10 versus laminin-1. The aim of this project is to identify the exact laminin binding sites by swapping putative binding domains between the X1 and X2 domains predicted from the crystallographic structure of av integrin and from interspecies conserved sequences. Further approaches include site directed mutagenesis and swapping domains with the related a6X1 and a6X2 domains. Antibodies against the a7X1 and a7X2 splice variants will be prepared in order to localize the splice variants in relation to their laminin isoform ligands in embryonic and adult tissues. With these studies we propose to elucidate the mechanism of integrin-laminin interactions and to gain insight into the differential functions of a7 splice variants and their corresponding laminin isoforms in skeletal muscle and other tissues.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1086: Genetic and Molecular Analysis of Basement Membranes and Basement Membrane Anchorage
• Participating Person: Dr. Harald Lanig