Phylogenetic analysis of the cadherin superfamily
ABSTRACT Cadherins are a multigene family of proteins which mediate homophilic calcium-dependent cell adhesion and are thought to play an important role in morphogenesis by mediating specific intercellular adhesion. Different lines of experimental evidence have recently indicated that the site responsible for mediating adhesive interactions is localized to the first extracellular domain of cadherin. Based upon an analysis of the sequence of this domain, I show that cadherins can be classified into three groups with distinct structural features. Furthermore, using this sequence information a phylogenetic tree relating the known cadherins was assembled. This is the first such tree to be published for the cadherins. One cadherin subtype, neural cadherin (N-cadherin), shows very little sequence divergence between species, whereas all other cadherin subtypes show more substantial divergence, suggesting that selective pressure upon this domain may be greater for N-cadherin than for other cadherins. Phylogenetic analysis also suggests that the gene duplications which established the main branches leading to the different cadherin subtypes occurred very early in their history. These duplications set the stage for the diversified superfamily we now observe.
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ABSTRACT: Members of the cadherin superfamily of proteins are involved in diverse biological processes such as morphogenesis, sound transduction, and neuronal connectivity. Key to cadherin function is their extracellular domain containing cadherin repeats, which can mediate interactions involved in adhesion and cell signaling. Recent cellular, biochemical, and structural studies have revealed that physical interaction among cadherins is more complex than originally thought. Here we review work on new cadherin complexes and discuss how the classification of the mammalian family can be used to search for additional cadherin-interacting partners. We also highlight some of the challenges in cadherin research; namely, the characterization of a cadherin connectome in biochemical and structural terms, as well as the elucidation of molecular mechanisms underlying the functional diversity of nonclassical cadherins in vivo.Trends in cell biology 04/2014; 24(9). DOI:10.1016/j.tcb.2014.03.007 · 12.12 Impact Factor
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ABSTRACT: Metazoans and transporting epithelia (TE) kept a strict correlation throughout evolution because a cell lodged in an intimate tissue and surrounded by an extracellular space less than a micron thick would quickly perish were it not for the intense and highly selective exchange of substances across TE. The main cellular features of TE are tight junctions and apical/basolateral polarity involving close to a hundred molecular species exquisitely assembled. Even when at the dawn of metazoan, junctions and polarity must have been much simpler, it is hard to imagine how the molecules that are involved might have coincided in the same organism and within a few minutes. The present chapter attempts to solve this conundrum by discussing several clues. 1. Polarity, as well as certain molecules involved in its generation and maintenance, are even present in unicellulars. 2. Molecular species belonging to septate and occluding junctions can be found in unicellulars, albeit fulfilling different roles.3 Primitive metazoan might have had very simple epithelia of a transient nature, that helped to retain nutrients and signal molecules for short periods, then opened to allow the whole mass of cells to be flushed by the environment (“Thrifty sponge”). 4. Early metazoan might have compensated the inefficiency of their primitive epithelia with a large surface-to-volume ratio. 5. Finally, the possibility exists that cells might have proliferated without completely detaching from each other, and preserving the orientation of their mitotic spindle, thereby generating an ample overall polarized epithelium that would create an internal environment even before an internal body of somatic cells would grow inside (“the mare nostrum metazoan”).
Progress in Retinal and Eye Research 01/1996; 15(2). DOI:10.1016/1350-9462(96)00008-0 · 9.90 Impact Factor