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Title: Molecular basis of sidekick-mediated cell-cell adhesion and specificity

Journal Article · · eLife
DOI:https://doi.org/10.7554/elife.19058· OSTI ID:1328787

Sidekick (Sdk) 1 and 2 are related immunoglobulin superfamily cell adhesion proteins required for appropriate synaptic connections between specific subtypes of retinal neurons. Sdks mediate cell-cell adhesion with homophilic specificity that underlies their neuronal targeting function. Here we report crystal structures of Sdk1 and Sdk2 ectodomain regions, revealing similar homodimers mediated by the four N-terminal immunoglobulin domains (Ig1–4), arranged in a 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 results show that this canonical dimer is required for both Sdk-mediated cell aggregation (via trans interactions) and Sdk clustering in isolated cells (via cis interactions). Sdk1/Sdk2 recognition specificity is encoded across Ig1–4, with Ig1–2 conferring the majority of binding affinity and differential specificity. We suggest that competition between cis and trans interactions provides a novel mechanism to sharpen the specificity of cell-cell interactions.

Research Organization:
Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Organization:
National Institutes of Health (NIH); Howard Hughes Medical Institute (HHMI); National Science Foundation (NSF)
Grant/Contract Number:
P41 GM103403; MCB-1412472; NS029169; EY022073
OSTI ID:
1328787
Journal Information:
eLife, Vol. 5; ISSN 2050-084X
Publisher:
eLife Sciences Publications, Ltd.Copyright Statement
Country of Publication:
United States
Language:
ENGLISH
Citation Metrics:
Cited by: 24 works
Citation information provided by
Web of Science

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Cited By (6)

Architecture of cell–cell adhesion mediated by sidekicks journal August 2018
The tricellular vertex-specific adhesion molecule Sidekick facilitates polarised cell intercalation during Drosophila axis extension posted_content July 2019
The tricellular vertex-specific adhesion molecule Sidekick facilitates polarised cell intercalation during Drosophila axis extension journal December 2019
The tricellular vertex-specific adhesion molecule Sidekick facilitates polarised cell intercalation during Drosophila axis extension. text January 2019
The tricellular vertex-specific adhesion molecule Sidekick facilitates polarised cell intercalation during Drosophila axis extension. text January 2019
Drosophila Sidekick is required in developing photoreceptors to enable visual motion detection journal January 2018

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