Linking molecular affinity and cellular specificity in cadherin-mediated adhesion

Abstract

Many cell-cell adhesive events are mediated by the dimerization of cadherin proteins presented on apposing cell surfaces. Cadherinmediated processes play a central role in the sorting of cells into separate tissues in vivo, but in vitro assays aimed at mimicking this behavior have yielded inconclusive results. In some cases, cells that express different cadherins exhibit homotypic cell sorting, forming separate cell aggregates, whereas in other cases, intermixed aggregates are formed. A third pattern is observed for mixtures of cells expressing either N-or E-cadherin, which form distinct homotypic aggregates that adhere to one another through a heterotypic interface. The molecular basis of cadherin-mediated cell patterning phenomena is poorly understood, in part because the relationship between cellular adhesive specificity and intermolecular binding free energies has not been established. To clarify this issue, we have measured the dimerization affinities of N-cadherin and E-cadherin. These proteins are similar in sequence and structure, yet are able to mediate homotypic cell patterning behavior in a variety of tissues. N-cadherin is found to form homodimers with higher affinity than does E-cadherin and, unexpectedly, the N/Ecadherin heterophilic binding affinity is intermediate in strength between the 2 homophilic affinities. We can account for observed cell aggregation behaviors by using a theoretical framework that establishes a connection between molecular affinities and cell-cell adhesive specificity. Our results illustrate how graded differences between different homophilic and heterophilic cadherin dimerizaton affinities can result in homotypic cell patterning and, more generally, show how proteins that are closely related can, nevertheless, be responsible for highly specific cellular adhesive behavior.binding affinities ͉ cadherins ͉ cell adhesion ͉ differential adhesion hypothesis ͉ surface plasmon resonance E xpression of different cadherins has been associated with the sorting of cells into distinct layers or compartments (1, 2). This behavior is often viewed as a manifestation of homotypic cell-sorting behavior-like cells adhere to one another. However, cell layers characterized by the expression of different cadherins sometimes remain in contact with one another, suggesting that heterotypic adhesion may also be of physiological relevance. Consistent with in vivo observations, in vitro aggregation assays have shown that cells expressing different classical cadherins can adhere to one another (3, 4). In some such instances, cells form distinct aggregates that possess a common interface, whereas in others, cells are completely mixed. Thus, cells expressing cadherins can exhibit homotypic and/or heterotypic adhesive properties, albeit for reasons that remain to be explained. Here, we probe the molecular basis of this behavior.Cadherins constitute a large family of cell surface adhesion receptors that can be grouped into numerous subfamilies (5). The type I and type II ''classical cadherins'' are found ...

Structural basis of oligomerization in septin-like GTPase of immunity-associated protein 2 (GIMAP2)

“…GTP-induced stabilization of switch I leads to low affinity dimerization of GIMAP2 via the G interface. Such low affinity interaction is typical for proteins that are locally concentrated on a membrane surface and thereby restricted in their mobility (36,37). Switch II, on the other hand, is not involved in the G interface, unlike in the corresponding G interfaces of septin2 (25), Toc34 (23,24), and dynamin (28) (Fig.…”

Spontaneous assembly and active disassembly balance adherens junction homeostasis

“…To exclude this possibility, we compared the stability of the Ec-KL-Dendra and Ec-Δ748-KLDendra clusters in cadherin-deficient CHO cells-a classic model in cadherin studies (22). For this work, we produced CHO cell subclones expressing comparable levels of these two mutants (Fig.…”

Mechanisms of protein oligomerization, the critical role of insertions and deletions in maintaining different oligomeric states

“…Mechanisms of homooligomerization are not very well understood although recent studies have shed some light on their main principles. For example, it has been shown how lowaffinity cadherin dimers formed through β-strand swapping can mediate and control highly specific intercellular adhesion (10,27). In another study it was proposed that β-barrel membrane proteins can oligomerize through the weakly stable interfacial beta-strands (28), while the C-terminal helix in certain p53 proteins might be essential for stabilizing tetramers (29).…”