Cell Adhesion and Specificity
RESEARCH ARTICLE Molecular basis of sidekick-mediated cell- cell adhesion and specificity Kerry M Goodman1†, Masahito Yamagata2,3†, Xiangshu Jin1,4‡, Seetha Mannepalli1, Phinikoula S Katsamba4,5, Go¨ ran Ahlse´ n4,5, Alina P Sergeeva4,5, Barry Honig1,4,5,6,7*, Joshua R Sanes2,3*, Lawrence Shapiro1,5,7* 1Department of Biochemistry and Molecular Biophysics, Columbia University, New York, United States; 2Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States; 3Center for Brain Science, Harvard University, Cambridge, United States; 4Howard Hughes Medical Institute, Columbia University, New York, United States; 5Department of Systems Biology, Columbia University, New York, United States; 6Department of Medicine, Columbia University, New York, United States; 7Zuckerman Mind Brain and Behavior Institute, Columbia University, New York, United States *For correspondence: bh6@cumc. Abstract Sidekick (Sdk) 1 and 2 are related immunoglobulin superfamily cell adhesion proteins columbia.edu (BH); sanesj@mcb. required for appropriate synaptic connections between specific subtypes of retinal neurons. Sdks harvard.edu (JRS); shapiro@ mediate cell-cell adhesion with homophilic specificity that underlies their neuronal targeting convex.hhmi.columbia.edu (LS) function. Here we report crystal structures of Sdk1 and Sdk2 ectodomain regions, revealing similar †These authors contributed homodimers mediated by the four N-terminal immunoglobulin domains (Ig1–4), arranged in a equally to this work horseshoe conformation. These Ig1–4 horseshoes interact in a novel back-to-back orientation in both homodimers through Ig1:Ig2, Ig1:Ig1 and Ig3:Ig4 interactions. Structure-guided mutagenesis Present address: ‡Department results show that this canonical dimer is required for both Sdk-mediated cell aggregation (via trans of Chemistry, Michigan State interactions) and Sdk clustering in isolated cells (via cis interactions).
[Show full text]