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EMBO J. 2009 Oct 21;28(20):3244-55. doi: 10.1038/emboj.2009.249. Epub 2009 Sep 3.

Neuroligin-1 performs neurexin-dependent and neurexin-independent functions in synapse validation.

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  • 1Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute, Stanford University School of Medicine, Palo Alto, CA 94304 5543, USA.

Abstract

Postsynaptic neuroligins are thought to perform essential functions in synapse validation and synaptic transmission by binding to, and dimerizing, presynaptic alpha- and beta-neurexins. To test this hypothesis, we examined the functional effects of neuroligin-1 mutations that impair only alpha-neurexin binding, block both alpha- and beta-neurexin binding, or abolish neuroligin-1 dimerization. Abolishing alpha-neurexin binding abrogated neuroligin-induced generation of neuronal synapses onto transfected non-neuronal cells in the so-called artificial synapse-formation assay, even though beta-neurexin binding was retained. Thus, in this assay, neuroligin-1 induces apparent synapse formation by binding to presynaptic alpha-neurexins. In transfected neurons, however, neither alpha- nor beta-neurexin binding was essential for the ability of postsynaptic neuroligin-1 to dramatically increase synapse density, suggesting a neurexin-independent mechanism of synapse formation. Moreover, neuroligin-1 dimerization was not required for either the non-neuronal or the neuronal synapse-formation assay. Nevertheless, both alpha-neurexin binding and neuroligin-1 dimerization were essential for the increase in apparent synapse size that is induced by neuroligin-1 in transfected neurons. Thus, neuroligin-1 performs diverse synaptic functions by mechanisms that include as essential components of alpha-neurexin binding and neuroligin dimerization, but extend beyond these activities.

PMID:
19730411
[PubMed - indexed for MEDLINE]
PMCID:
PMC2771087
Free PMC Article

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