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Original Article |
Correspondence to: Lawrence Shapiro, Structural Biology Program, Department of Physiology and Biophysics, The Mount Sinai School of Medicine, 1425 Madison Avenue, NY, NY 10029. Tel:(212) 659-8651 Fax:(212) 849-2456 E-mail:shapiro{at}anguilla.physbio.mssm.edu.
Classical cadherins form parallel cis-dimers that emanate from a single cell surface. It is thought that the cis-dimeric form is active in cellcell adhesion, whereas cadherin monomers are likely to be inactive. Currently, cis-dimers have been shown to exist only between cadherins of the same type. Here, we show the specific formation of cis-heterodimers between N- and R-cadherins. E-cadherin cannot participate in these complexes. Cells coexpressing N- and R-cadherins show homophilic adhesion in which these proteins coassociate at cellcell interfaces. We performed site- directed mutagenesis studies, the results of which support the strand dimer model for cis-dimerization. Furthermore, we show that when N- and R-cadherins are coexpressed in neurons in vitro, the two cadherins colocalize at certain neural synapses, implying biological relevance for these complexes. The present study provides a novel paradigm for cadherin interaction whereby selective cis-heterodimer formation may generate new functional units to mediate cellcell adhesion.
Key Words: cadherins, cell adhesion, heterophilic binding, synaptic adhesion, dimerization
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