γ-Protocadherin structural diversity and functional implications

• Main Authors: Kerry Marie Goodman, Rotem Rubinstein, Chan Aye Thu, Seetha Mannepalli, Fabiana Bahna, Göran Ahlsén, Chelsea Rittenhouse, Tom Maniatis, Barry Honig, Lawrence Shapiro
• Format: Article
• Language: English
• Published: eLife Sciences Publications Ltd 2016-10-01
• Series: eLife
• Subjects: clustered protocadherins; crystal structure; protein-protein recognition; protein diversity; neuronal self-avoidance
• Online Access: https://elifesciences.org/articles/20930

Stochastic cell-surface expression of α-, β-, and γ-clustered protocadherins (Pcdhs) provides vertebrate neurons with single-cell identities that underlie neuronal self-recognition. Here we report crystal structures of ectodomain fragments comprising cell-cell recognition regions of mouse γ-Pcdhs γA1, γA8, γB2, and γB7 revealing trans-homodimers, and of C-terminal ectodomain fragments from γ-Pcdhs γA4 and γB2, which depict cis-interacting regions in monomeric form. Together these structures span the entire γ-Pcdh ectodomain. The trans-dimer structures reveal determinants of γ-Pcdh isoform-specific homophilic recognition. We identified and structurally mapped cis-dimerization mutations to the C-terminal ectodomain structures. Biophysical studies showed that Pcdh ectodomains from γB-subfamily isoforms formed cis dimers, whereas γA isoforms did not, but both γA and γB isoforms could interact in cis with α-Pcdhs. Together, these data show how interaction specificity is distributed over all domains of the γ-Pcdh trans interface, and suggest that subfamily- or isoform-specific cis-interactions may play a role in the Pcdh-mediated neuronal self-recognition code.