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J Biol Chem. 2016 Mar 11;291(11):5788-802. doi: 10.1074/jbc.M115.705681. Epub 2015 Dec 31.

Structural Characterization of the Extracellular Domain of CASPR2 and Insights into Its Association with the Novel Ligand Contactin1.

Author information

1
From the Child Health Institute of New Jersey and Departments of Neuroscience and Cell Biology and.
2
the School of Molecular Bioscience, University of Sydney, New South Wales 2006, Australia.
3
the Structural Biology Programme, Central European Institute of Technology, Masaryk University, 62500 Brno, Czech Republic.
4
the Department of Biochemistry, The University of Texas Health Science Center, San Antonio, Texas 78229.
5
the Department of Biology and Biotechnologies "Charles Darwin" and Pasteur Institute-Cenci Bolognetti Foundation, Sapienza University of Rome, Rome, Italy 00185.
6
the National Center for Microscopy and Imaging Research, University of California San Diego, La Jolla, California 92093, and.
7
the School of Molecular Bioscience, University of Sydney, New South Wales 2006, Australia, the Department of Chemistry, University of Utah, Salt Lake City, Utah 84112.
8
From the Child Health Institute of New Jersey and Departments of Neuroscience and Cell Biology and Pediatrics, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, New Jersey 08901, comoleda@rwjms.rutgers.edu.

Abstract

Contactin-associated protein-like 2 (CNTNAP2) encodes for CASPR2, a multidomain single transmembrane protein belonging to the neurexin superfamily that has been implicated in a broad range of human phenotypes including autism and language impairment. Using a combination of biophysical techniques, including small angle x-ray scattering, single particle electron microscopy, analytical ultracentrifugation, and bio-layer interferometry, we present novel structural and functional data that relate the architecture of the extracellular domain of CASPR2 to a previously unknown ligand, Contactin1 (CNTN1). Structurally, CASPR2 is highly glycosylated and has an overall compact architecture. Functionally, we show that CASPR2 associates with micromolar affinity with CNTN1 but, under the same conditions, it does not interact with any of the other members of the contactin family. Moreover, by using dissociated hippocampal neurons we show that microbeads loaded with CASPR2, but not with a deletion mutant, co-localize with transfected CNTN1, suggesting that CNTN1 is an endogenous ligand for CASPR2. These data provide novel insights into the structure and function of CASPR2, suggesting a complex role of CASPR2 in the nervous system.

KEYWORDS:

analytical ultracentrifugation; ligand-binding protein; molecular cell biology; protein structure; small-angle x-ray scattering (SAXS)

PMID:
26721881
PMCID:
PMC4786715
DOI:
10.1074/jbc.M115.705681
[Indexed for MEDLINE]
Free PMC Article

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