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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.
A desmosome (/ ˈ d ɛ z m ə ˌ s oʊ m /; [1] [2] "binding body"), also known as a macula adherens (plural: maculae adherentes) (Latin for adhering spot), is a cell structure specialized for cell-to-cell adhesion. A type of junctional complex, they are localized spot-like adhesions randomly arranged on the lateral sides of plasma membranes.
The three types of cell junction recognised as making up an intercalated disc are desmosomes, fascia adherens junctions, and gap junctions. [2] Fascia adherens are anchoring sites for actin, and connect to the closest sarcomere. [3]
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 ...
TEM of rat kidney tissue shows a protein dense tight junction (three dark lines) at ~55,000x magnification.. Tight junctions provide endothelial and epithelial cells with barrier function, which can be further subdivided into protective barriers and functional barriers serving purposes such as material transport and maintenance of osmotic balance.
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
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.
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.