Structural basis of the strong cell‐cell junction formed by cadherin‐23

Abstract

Cadherin-23, a giant atypical cadherin, form homophilic interactions at the cell-cell junction of epithelial cells and heterophilic interactions with protocadherin-15 at the tip links of neuroepithelial cells. While the molecular structure of the heterodimer is solved, the homodimer structure is yet to be resolved. The homodimers play an essential role in cell-cell adhesion as the downregulation of cadherin-23 in cancers loosen the intercellular junction resulting in faster migration of cancer cells and a significant drop in patient survival. In vitro studies have measured a stronger aggregation propensity of cadherin-23 compared to typical E-cadherin. Here, we deciphered the unique trans-homodimer structure of cadherin-23 in solution and show that it consists of two electrostatic-based interfaces extended up to two terminal domains. The interface is robust, with a low off-rate of~8 9 10 À4 s À1 that supports its strong aggregation propensity. We identified a point mutation, E78K, that disrupts this binding. Interestingly, a mutation at the interface was reported in skin cancer. Overall, the structural basis of the strong cadherin-23 adhesion may have far-reaching applications in the fields of mechanobiology and cancer.

Cis-Clustering of Cadherin-23 Controls the Kinetics of Cell-Cell Adhesion

“…Cadherins generally form anchoring junctions with the neighboring cells. Cdh23 is no different from the other family members and mediates vital cell-cell adhesion junctions in several tissues like the kidney, muscle, testes, and heart (Singaraju et al, 2019, Sotomayor et al, 2012. We, therefore, verified the effect of the liquid condensates of Cdh23 mediated by cis-clustering in cell-cell adhesion, more importantly where cis-clustering precedes the trans-interactions.…”

“…It was, therefore, necessary to block the interference of the trans-interactions to measure the strength of cis-binding. Notably, the heterophilic trans-interaction with Pcdh15 has the highest affinity in the list (Choudhary et al, 2020, Singaraju et al, 2019, Sotomayor et al, 2012. We, therefore, used excess Pcdh15 (5 µM Pcdh15 EC1-2) in the experiment buffer to neutralize the trans-binding interface of Cdh23 and predominantly measured the homophilic cis-interactions (Materials and methods).…”

“…Cdh23 is one of the long non-classical classes of cadherins with 27 extracellular domains. It mediates strong cell-cell adhesion among tissues like the heart, kidney, muscle, and testis through homophilic interactions (Sannigrahi et al, 2019, Singaraju et al, 2019, Sotomayor et al, 2012, and heterophilic interactions with protocadherin-15 in neuroepithelial cells (Sotomayor et al, 2010). Interestingly, with the potential for multivalent lateral interactions, Cdh23 engages in a stable spiral cisdimerization (Kachar et al, 2000).…”

Weakening of interaction networks with aging in tip-link protein induces hearing loss

“…The recombinant proteins are expressed in E. coli BL21 Codon Plus (DE3)-RIPL (Stratagene, U.S.A.) cells as reported previously [ 26 ]. The proteins are first affinity-purified using Ni-NTA beads (Qiagen) and refolded from 8 to 0 M urea buffer using a reported refolding protocol [ 29 ]. Finally, the refolded fractions are re-filtered using size exclusion chromatography in 25 m M HEPES 25 mM KCl, 100 mM NaCl, and 2 mM CaCl 2 (pH 7.5) buffer using Superdex 200 column (GE Healthcare) ( Supplementary Figure S3c ).…”

Cis-clustering of cadherin-23 controls the kinetics of cell-cell adhesion

“…Cdh23 is one of the long non-classical classes of cadherins with 27 extracellular domains. It mediates strong cell-cell adhesion among tissues like the heart, kidney, muscle, and testis through homophilic interactions (Sannigrahi et al, 2019, Singaraju et al, 2019, Sotomayor et al, 2012, and heterophilic interactions with protocadherin-15 in neuroepithelial cells (Sotomayor et al, 2010). Interestingly, with the potential for multivalent lateral interactions, Cdh23 engages in a stable spiral cisdimerization (Kachar et al, 2000).…”