A novel cell-cell junction system: thecortex adhaerensmosaic of lens fiber cells

Abstract

The anucleate prismoid fiber cells of the eye lens are densely packed to form a tissue in which the plasma membranes and their associated cytoplasmic coat form a single giant cell-cell adhesive complex, the cortex adhaerens. Using biochemical and immunoprecipitation methods in various species (cow, pig, rat), in combination with immunolocalization microscopy, we have identified two different major kinds of cortical complex. In one, the transmembrane glycoproteins N-cadherin and cadherin-11 [which also occur in heterotypic (`mixed') complexes] are associated with α- and β-catenin, plakoglobin (proportions variable among species), p120ctn and vinculin. The other complex contains ezrin, periplakin, periaxin and desmoyokin (and so is called the EPPD complex), usually together with moesin, spectrin(s) and plectin. In sections through lens fiber tissue, the short sides of the lens fiber hexagons appear to be enriched in the cadherin-based complexes, whereas the EPPD complexes also occur on the long sides. Moreover, high resolution double-label fluorescence microscopy has revealed, on the short sides, a finer, almost regular mosaicism of blocks comprising the cadherin-based, catenin-containing complexes, alternating with patches formed by the EPPD complexes. The latter, a new type of junctional plaque ensemble of proteins hitherto known only from certain other cell types, must be added to the list of major lens cortex proteins. We here discuss its possible functional importance for the maintenance of lens structure and functions, notably clear and sharp vision.

Loss of ephrin-A5 function disrupts lens fiber cell packing and leads to cataract

“…In the WT lens, N-cadherin is mostly localized to the short ends of the lens fiber cell hexagonal faces as previously reported (Fig. 3A) (15). In the mutant lens, N-cadherin became internalized from the cell membrane into the cytoplasm (Fig.…”

“…Gap junctions were detected using antibodies against either Cx46 or the Cx46 interacting protein ZO-1 (26). In P21 WT lenses, the majority of the gap junctions were located on the broad side of the fiber cell hexagonal profile as previously reported (15,26). In contrast, Cx46 was randomly distributed in the mutant lens, possibly resulting from cell shape alterations [supporting information (SI) Fig.…”

“…As the lens is completely enclosed by an acellular, avascular capsule, it is believed that these cell-cell junctions are critical for providing nutrient transport, removal of metabolic wastes, and maintenance of homeostasis (11,12). In addition to gap junctions, widespread adherens junctions containing N-cadherin and its associated protein ␤-catenin exist between lens fiber cells (13)(14)(15)(16), and may play important roles in lens development and function.…”

Processus and recessus adhaerentes: giant adherens cell junction systems connect and attract human mesenchymal stem cells

“…The molecular composition of these junctions is simple. Apparently, the coexistence of N-cadherin and cadherin-11 is typical for puncta adhaerentia of diverse mesenchymal cells and tissues (e.g., Okazaki et al 1994;Hoffmann and Balling 1995;Kimura et al 1995;Simonneau and Thiery 1998;Hinz et al 2004), as are cytoplasmic plaques comprising α-and β-catenin, together with protein p120 and afadin, whereas appreciable amounts of other plaque proteins seem to be lacking (for references, see Straub et al 2003;Godsel et al 2004;Irie et al 2004; for a possible role of gelsolin in the anchorage of the actin filaments at adhering junctions of fibroblasts and probably also other mesenchymally derived cells, see Chan et al 2004). The functional importance of the molecular complement of these puncta adhaerentia in the differentiation of mesenchymal cells and tissue formation is indicated by the developmental defects described for mice lacking N-cadherin or cadherin-11 or both (Radice et al 1997;Horikawa et al 1999;Luo et al 2004;Kostetskii et al 2005) and by the general importance of cadherin-11 in the regulation of cell motility and cell-cell interaction in the dynamics of mesenchymal cells (cf.…”

The pulling, pushing and fusing of lens fibers

“…These morphological changes are associated with extensive membrane and cortical cytoskeletal remodeling, actomyosin reorganization and cell adhesion turnover. [5][6][7][8][9][10][11][12][13][14][15][16][17] Additionally, the tips of the elongating fiber cells at both the anterior and posterior terminals slide along the lens epithelium and capsule, respectively, as these cells migrate inward, and finally detach at the suture, where they form contacts with their counterparts from the opposite side of the lens. 4,12 These cell movements are fundamental for maintaining distinct lens fiber cell polarity and are temporally and spatially regulated as the lens grows continuously throughout life.…”