Disulfide Bond Formation Promotes the cis- and trans-Dimerization of the E-cadherin-derived First Repeat

Abstract

Cadherin is a cell adhesion molecule crucial for epithelial and endothelial cell monolayer integrity. The previously solved x-ray crystallographic structure of the E-CAD12 cis-dimer displayed an unpaired Cys 9 , which protruded away from the Cys 9 on the other protomer. To investigate the possible biological function of Cys 9 within the first repeat (the E-cadherin-derived Nterminal repeat), E-CAD1 was overexpressed and secreted into the periplasmic space of Escherichia coli cells. Recombinant E-CAD1 produced a mixed monomer and dimer in an equilibrium fashion. The dimer was linked by a disulfide through Cys 9 pairing. Analysis by high pressure liquid chromatography and electron microscopy suggested the existence of oligomeric complexes. Mutation at Trp 2 appears to indicate that these oligomeric complexes trans-dimerize. Interestingly, mutation of Cys 9 affected not only the cis-dimerization, but also the trans-oligomerization of E-CAD1. Accordingly, it is plausible that, under oxidative stress, the homophilic interactions of E-cadherin through E-CAD1 may be promoted and stabilized by this disulfide bond.E-cadherin, a Ca 2ϩ -dependent member of the cadherin family of cell adhesion molecules, is crucial in providing cell polarity, tightness, and integrity of the intercellular junctions (1, 2). In most cancerous tissues, nonfunctional E-cadherin leads to the disturbance of the integrity of the intercellular junctions and consequentially promotes higher mobility and invasiveness of the cancer cells (3-5).In recent years, considerable information has been gathered on the adhesion mechanism of classical cadherins from both structural and functional studies. The modular architecture of classical cadherins is characterized by the five repeats in the extracellular domain (6). The N-terminal of the extracellular domain is believed to be critical for homophilic cadherin interactions. The structure of the N-terminal fragment derived from the first repeat of the neuronal N-cadherin (N-CAD1) (7) and the epithelial E-cadherin (E-CAD1) (8) displays a resemblance to the structural fold of immunoglobulin.Biochemical analysis of the first extracellular repeat E-CAD1 revealed only the presence of monomers (8). The solution structure of this monomer form was indeed determined by nuclear magnetic resonance (9, 10). This is in contrast with the crystal lattice structure of N-CAD1 (7), which contains a unique mixture of two different populations. One population consists of monomers interacting closely to form cis-dimers (parallel), which are stabilized by the exchange between the N-terminal ␤A-strand and the intercalation of Trp 2 into the partnering hydrophobic core. The other population reveals the pairing between antiparallel-oriented cisdimers, designated as trans-dimers to reflect the possible head-to-head contacts between two cadherin molecules of the apposing cells. Alternating the cis-and trans-interactions forms a zipper-like structure (7). Crystallographic analysis of E-CAD12 also showed cis-dimers linked together by calciu...

Oligomeric Structure and Minimal Functional Unit of the Electrogenic Sodium Bicarbonate Cotransporter NBCe1-A

“…In the absence of all native cysteine residues, NBCe1-A monomers are retained intracellularly presumably because of abnormal folding of the protein (63,64,69,70). In addition, the importance of S-S bond formation in mediating the oligomerization of membrane proteins as a requirement for normal transport function has been shown for sodium-dependent neurotransmitter transporters (71), SGLT1 (72), and for the oligomerization of mouse and human resistins (73), E-cadherin (74), and hyaluronan-binding protein 1 (75).…”

Critical Role of the Fifth Domain of E-Cadherin for Heterophilic Adhesion with αEβ7, But Not for Homophilic Adhesion

“…Substantial evidence suggests that the combination of cis-dimerization of two cadherin molecules on the same cell surface and trans-interactions between cadherin dimers on opposing cell surfaces maximizes homophilic adhesion. The widely accepted linear zipper model attributes the adhesive interfaces in the cis-and trans-interactions to EC1 (6,7,36). However, recent studies have introduced a new model for homophilic adhesion.…”

Calsyntenin-3 Molecular Architecture and Interaction with Neurexin 1α

“…Strikingly, intersubunit disulfide bonds interconnect and stabilize the Cstn3 tetramer. Intersubunit disulfide bonds in the extracellular space are also known to stabilize the cisdimer of E-cadherin, promoting homophilic adhesion (44), and cis-tetramers of ␥-protocaderins (45). Calsyntenins play a role in cognition, and an increasing body of work suggests a link between oxidative status and neurodegenerative disorders (46), so it is tantalizing to speculate that oxidative stress in the brain might shift the balance between Cstn3 monomers and tetramers in the synaptic cleft by promoting intersubunit disulfide bond formation, thereby altering Cstn3 function.…”