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Hemidesmosomes form rivet-like links between cytoskeleton and extracellular matrix components such as the basal laminae that underlie epithelia. Like desmosomes, they tie to intermediate filaments in the cytoplasm, but in contrast to desmosomes, their transmembrane anchors are integrins rather than cadherins.
Hemidesmosomes can be categorized into two types based on their protein constituents. Type 1 hemidesmosomes are found in stratified and pseudo-stratified epithelium.Type 1 hemidesmosomes have five main elements: integrin α6 β4, plectin in its isoform 1a, i. e. P1a, tetraspanin protein CD151, BPAG1e, or bullous pemphigoid antigen isoform e, and BPAG2 (also known as BP180 or type 17 collagen). [2]
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]
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 also provide strength and durability to cells and tissues and are located just below adherens junctions. They are sites of adhesion and do not encircle the cell. They are made of two specialized cadherins, desmoglein and desmocollin. These proteins have extracellular domains that interact with each other on adjacent cells.
Schematic of cell adhesion. Cell adhesion is the process by which cells interact and attach to neighbouring cells through specialised molecules of the cell surface. This process can occur either through direct contact between cell surfaces such as cell junctions or indirect interaction, where cells attach to surrounding extracellular matrix, a gel-like structure containing molecules released ...
Basal cells are bound to each other by desmosomes, and to the basal lamina of the basement membrane by hemidesmosomes. These junctions help to create one tightly bound, continuous tissue layer that can endure mechanical stress and effectively function as a connection between the basement membrane and remaining epithelial tissue. [4]
Tight junctions are a pair of trans-membrane protein fused on outer plasma membrane. Adherens junctions are a plaque (protein layer on the inside plasma membrane) which attaches both cells' microfilaments. Desmosomes attach to the microfilaments of cytoskeleton made up of keratin protein. Hemidesmosomes resemble desmosomes on a section.