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Adherens junctions, desmosomes and hemidesmosomes (anchoring junctions) Gap junctions [5] (communicating junction) Tight junctions (occluding junctions) Invertebrates have several other types of specific junctions, for example septate junctions (a type of occluding junction) [4] or the C. elegans apical junction.
In desmosomes, plakoglobin and plakophilin help to anchor desmoplakin and keratin filaments to the desmosome structure. Plakoglobin has 12-arm repeats with a head and tail structure. Plakophilins have 9-arm repeats, and exist in two isoforms: a shorter "a" form and longer "b" form. [citation needed]
Gap junctions were first described as close appositions as other tight junctions, but following electron microscopy studies in 1967, they were renamed gap junctions to distinguish them from tight junctions. [2] They bridge a 2-4 nm gap between cell membranes. [3] Gap junctions use protein complexes known as connexons to
Gap junctions are the main site of cell-cell signaling or communication that allow small molecules to diffuse between adjacent cells. In vertebrates, gap junctions are composed of transmembrane proteins called connexins. They form hexagonal pores or channels through which ions, sugars, and other small molecules can pass.
When the membranes of two animal cells are close, they may form special types of cell junctions, which come in three broad types: occluding junctions (such as tight junctions and septate junctions), anchoring junctions (such as adherens junctions, desmosomes, focal adhesions, and hemidesmosomes), and communicating junctions (such as gap ...
Desmosomes prevent separation during contraction by binding intermediate filaments, anchoring the cell membrane to the intermediate filament network, joining the cells together. [ 2 ] [ 3 ] Gap junctions connect the cytoplasms of neighboring cells electrically allowing cardiac action potentials to spread between cardiac cells by permitting the ...
Each gap junction (sometimes called a nexus) contains numerous gap junction channels that cross the plasma membranes of both cells. [11] With a lumen diameter of about 1.2 to 2.0 nm, [2] [12] the pore of a gap junction channel is wide enough to allow ions and even medium-size molecules like signaling molecules to flow from one cell to the next, [2] [13] thereby connecting the two cells' cytoplasm.
Connexins are commonly named according to their molecular weights, e.g. Cx26 is the connexin protein of 26 kDa. A competing nomenclature is the gap junction protein system, where connexins are sorted by their α (GJA) and β (GJB) forms, with additional connexins grouped into the C, D and E groupings, followed by an identifying number, e.g. GJA1 corresponds to Cx43.