Project description:Contactin-2 (CNTN2), an immunoglobulin cell adhesion molecule (IgCAM) expressed on the neural cell surface, regulates the formation of myelin sheaths, facilitates communication between neurons and axoglial cells, and coordinates the migration of neural cells. However, the assembly of full-length CNTN2 is still not fully elucidated. Here, we found that the full-length human CNTN2 forms a concentration-dependent homodimer. We further determined the cryo-EM structures of the full-length CNTN2, revealing a novel bowknot-shaped scaffold constituted of the Ig1-6 repeats from two protomers, with the flexible ribbon-like FNIII repeats extending outward in opposite directions. The Ig1-6 domains, rather than the previously proposed Ig1-4 domains, have an indispensable role in mediating CNTN2-dependent cell adhesion and clustering. Moreover, structure-guided mutagenesis analyses supported the idea that CNTN2 homodimerization observed in our structure is essential for cell adhesion. Our findings offer novel insights into the mechanism through which CNTN2 forms a homodimer to maintain cell-cell contacts in the nervous system.
Project description:Transient receptor potential (TRP) proteins form a superfamily Ca(2+)-permeable cation channels regulated by a range of chemical and physical stimuli. Structural analysis of a 'minimal' TRP vanilloid subtype 1 (TRPV1) elucidated a mechanism of channel activation by agonists through changes in its outer pore region. Though homologous to TRPV1, other TRPV channels (TRPV2-6) are insensitive to TRPV1 activators including heat and vanilloids. To further understand the structural basis of TRPV channel function, we determined the structure of full-length TRPV2 at ∼5 Å resolution by cryo-electron microscopy. Like TRPV1, TRPV2 contains two constrictions, one each in the pore-forming upper and lower gates. The agonist-free full-length TRPV2 has wider upper and lower gates compared with closed and agonist-activated TRPV1. We propose these newly revealed TRPV2 structural features contribute to diversity of TRPV channels.
Project description:Heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) is a multifunctional RNA-binding protein that is associated with neurodegenerative diseases, such as amyotrophic lateral sclerosis and multisystem proteinopathy. In this study, we have used cryo-electron microscopy to investigate the three-dimensional structure of amyloid fibrils from full-length hnRNPA1 protein. We find that the fibril core is formed by a 45-residue segment of the prion-like low-complexity domain of the protein, whereas the remaining parts of the protein (275 residues) form a fuzzy coat around the fibril core. The fibril consists of two fibril protein stacks that are arranged into a pseudo-21 screw symmetry. The ordered core harbors several of the positions that are known to be affected by disease-associated mutations, but does not encompass the most aggregation-prone segments of the protein. These data indicate that the structures of amyloid fibrils from full-length proteins may be more complex than anticipated by current theories on protein misfolding.