A novel cell-cell junction system: the cortex adhaerens mosaic of lens fiber cells.
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 alpha- and beta-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.
Straub
Beate K
BK
Division of Cell Biology, German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany.
Boda
Judit
J
Kuhn
Caecilia
C
Schnoelzer
Martina
M
Korf
Ulrike
U
Kempf
Tore
T
Spring
Herbert
H
Hatzfeld
Mechthild
M
Franke
Werner W
WW
D000818:Animals; D015820:Cadherins / Q000378:metabolism*; D051177:Catenins; D002417:Cattle; D015815:Cell Adhesion Molecules / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D051180:Desmoplakins; D007365:Intercellular Junctions / Q000378:metabolism*; D007381:Intermediate Filament Proteins / Q000378:metabolism; D007908:Lens, Crystalline / Q000166:cytology / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D009363:Neoplasm Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D051179:Plakins; D051190:Plectin; D051381:Rats; D013049:Spectrin / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013552:Swine; D015534:Trans-Activators / Q000378:metabolism*; D016596:Vinculin / Q000378:metabolism; D051178:alpha Catenin; D051176:beta Catenin; D051185:gamma Catenin; D000095002:Delta Catenin; D000099149:Ezrin
D015820:Cadherins; D051177:Catenins; D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; D051180:Desmoplakins; D007381:Intermediate Filament Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D009363:Neoplasm Proteins; D010750:Phosphoproteins; D051179:Plakins; D051190:Plectin; D013049:Spectrin; D015534:Trans-Activators; D016596:Vinculin; D051178:alpha Catenin; D051176:beta Catenin; D051185:gamma Catenin; D000095002:Delta Catenin; D000099149:Ezrin; C489572:Ahnak protein, mouse; C489573:Ahnak protein, rat; C495267:CTNNB1 protein, mouse; C495272:Ctnna1 protein, mouse; C495268:Ctnnb1 protein, rat; C491674:PPL protein, human; C495333:Plec protein, mouse; C495334:Plec protein, rat; C110037:Ppl protein, mouse; C071058:moesin; C086960:osteoblast cadherin