Alternative RNA splicing that determines agrin activity regulates binding to heparin and alpha-dystroglycan.

Development

Howard Hughes Medical Institute, Department of Molecular and Cellular Physiology, Stanford University, CA 94305, USA.

Published: May 1996

Agrin is a component of the extracellular matrix that regulates aspects of neuromuscular junction differentiation. Identification of agrin-binding proteins has lead to the suggestion that alpha-dystroglycan is a muscle cell surface proteoglycan that mediates agrin activity. To further test this hypothesis, we have compared the ability of differentially active agrin isoforms to interact with a model component of proteoglycans, heparin, as well as with the putative proteoglycan alpha-dystroglycan. We demonstrate that an alternately spliced exon (encoding the sequence lysine, serine, arginine, lysine: Y site) is necessary for agrin-heparin interactions. We also show that alternate splicing at another site (Z site) dramatically affects interaction of alpha-dystroglycan with agrin. We propose a model in which multiple distinct domains of agrin interact with both protein and sugar moieties of alpha-dystroglycan. The isoform-specific binding of agrin to alpha-dystroglycan is consistent with a functional role for this interaction during synaptogenesis.

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http://dx.doi.org/10.1242/dev.122.5.1663DOI Listing

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