Alternative splice variants of alpha(7)beta(1) integrin selectively recognize different laminin isoforms

Helga von der Mark, Inka Williams, Olaf Wendler, Lydia Sorokin, Klaus von der Mark, Ernst Pöschl

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The integrin α7β1 occurs in several cytoplasmic (α7A, α7B) and extracellular splice variants (α7X1, α7X2), which are differentially expressed during development of skeletal and heart muscle. The extracellular variants result from the alternative splicing of exons X1 and X2, corresponding to a segment within the putative ligand binding domain. To study the specificity and affinity of the X1/X2 variants to different laminin isoforms, soluble α7β1 complexes were prepared by recombinant coexpression of the extracellular domains of the α- and β-subunits. The binding of these complexes to purified ligands was measured by solid phase binding assays. Surprisingly, the alternative splice variants revealed different and specific affinities to different laminin isoforms. While the α7X2 variant bound much more strongly to laminin-1 than the α7X1 variant, the latter showed a high affinity binding to laminins-8 and -10/11. Laminin-2, the major laminin isoform in skeletal muscle, was recognized by both variants, whereas none of the two variants were able to interact with laminin-5. A specific blocking antibody inhibited the binding of both variants to all laminins tested, indicating the involvement of common epitopes in α7X1β1 and α7X2β1. Because laminin-8 and -10/11 as well as α7X1 are expressed in developing skeletal and cardiac muscle, these findings suggest that α7X1β1 may represent a physiological receptor with novel specificities for laminin-8 and -10.
Original languageEnglish
Pages (from-to)6012-6016
Number of pages5
JournalJournal of Biological Chemistry
Issue number8
Publication statusPublished - 2002

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