Laminins promote postsynaptic maturation by an autocrine mechanism at the neuromuscular junction

Hiroshi Nishimune, Gregorio Valdez, George Jarad, Casey L. Moulson, Ulrich Müller, Jeffrey H. Miner, Joshua R. Sanes

Research output: Contribution to journalArticle

88 Scopus citations

Abstract

A prominent feature of synaptic maturation at the neuromuscular junction (NMJ) is the topological transformation of the acetylcholine receptor (AChR)-rich postsynaptic membrane from an ovoid plaque into a complex array of branches. We show here that laminins play an autocrine role in promoting this transformation. Laminins containing the α4, α5, and β2 subunits are synthesized by muscle fibers and concentrated in the small portion of the basal lamina that passes through the synaptic cleft at the NMJ. Topological maturation of AChR clusters was delayed in targeted mutant mice lacking laminin α5 and arrested in mutants lacking both α4 and α5. Analysis of chimeric laminins in vivo and of mutant myotubes cultured aneurally demonstrated that the laminins act directly on muscle cells to promote postsynaptic maturation. Immunohistochemical studies in vivo and in vitro along with analysis of targeted mutants provide evidence that laminin-dependent aggregation of dystroglycan in the postsynaptic membrane is a key step in synaptic maturation. Another synaptically concentrated laminin receptor, Bcam, is dispensable. Together with previous studies implicating laminins as organizers of presynaptic differentiation, these results show that laminins coordinate post- with presynaptic maturation.

Original languageEnglish
Pages (from-to)1201-1215
Number of pages15
JournalJournal of Cell Biology
Volume182
Issue number6
DOIs
StatePublished - Sep 22 2008

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