Adherens junctions (or zonula adherens, intermediate junction, or "belt desmosome") are protein complexes that occur at cell–cell junctions, cell–matrix junctions in epithelial and endothelial tissues, usually more basal than
tight junctions
Tight junctions, also known as occluding junctions or ''zonulae occludentes'' (singular, ''zonula occludens''), are multiprotein junctional complexes whose canonical function is to prevent leakage of solutes and water and seals between the epith ...
. An adherens junction is defined as a cell junction whose cytoplasmic face is linked to the
actin
Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of over ...
cytoskeleton.
They can appear as bands encircling the cell (zonula adherens) or as spots of attachment to the extracellular matrix (focal adhesion).
Adherens junctions uniquely disassemble in uterine epithelial cells to allow the blastocyst to penetrate between epithelial cells.
A similar cell junction in non-epithelial, non-endothelial cells is the
fascia adherens
In anatomy for cardiac muscle, fascia adherens are ribbon-like structures that stabilize non-epithelial tissue. They are similar in function and structure to the zonula adherens or adherens junction of epithelial cells. It is a broad intercellular ...
. It is structurally the same, but appears in ribbonlike patterns that do not completely encircle the cells. One example is in
cardiomyocytes
Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle tha ...
.
Proteins
Adherens junctions are composed of the following proteins:
*
cadherins
Cadherins (named for "calcium-dependent adhesion") are a type of cell adhesion molecule (CAM) that is important in the formation of adherens junctions to allow cells to adhere to each other . Cadherins are a class of type-1 transmembrane proteins, ...
. The cadherins are a family of transmembrane proteins that form homodimers in a calcium-dependent manner with other cadherin molecules on adjacent cells.
* p120 (sometimes called
delta catenin
Delta-1-catenin and Delta-2-catenin are members of a subfamily of proteins with ten Armadillo-repeats. Delta-2-catenin is expressed in the brain where it is important for normal cognitive development. Like beta-catenin and gamma-catenin, delta-c ...
) binds the juxtamembrane region of the cadherin.
*
γ-catenin
Plakoglobin, also known as junction plakoglobin or gamma-catenin, is a protein that in humans is encoded by the ''JUP'' gene. Plakoglobin is a member of the catenin protein family and homologous to β-catenin. Plakoglobin is a cytoplasmic compone ...
or gamma-catenin (
plakoglobin
Plakoglobin, also known as junction plakoglobin or gamma-catenin, is a protein that in humans is encoded by the ''JUP'' gene. Plakoglobin is a member of the catenin protein family and homologous to β-catenin. Plakoglobin is a cytoplasmic compone ...
) binds the catenin-binding region of the cadherin.
*
α-catenin
Alpha-catenin functions as the primary protein link between cadherins and the actin cytoskeleton. It has been reported that the actin binding proteins vinculin and alpha-actinin can bind to alpha-catenin. It has been suggested that alpha-caten ...
or alpha-catenin binds the cadherin indirectly via
β-catenin
Catenin beta-1, also known as beta-catenin (β-catenin), is a protein that in humans is encoded by the ''CTNNB1'' gene.
Beta-catenin is a dual function protein, involved in regulation and coordination of cell–cell adhesion and gene transcripti ...
or
plakoglobin
Plakoglobin, also known as junction plakoglobin or gamma-catenin, is a protein that in humans is encoded by the ''JUP'' gene. Plakoglobin is a member of the catenin protein family and homologous to β-catenin. Plakoglobin is a cytoplasmic compone ...
and links the actin cytoskeleton with cadherin. Significant
protein dynamics Proteins are generally thought to adopt unique structures determined by their amino acid sequences. However, proteins are not strictly static objects, but rather populate ensembles of (sometimes similar) conformations. Transitions between these stat ...
is thought to be involved.
Models
Adherens junctions were, for many years, thought to share the characteristic of
anchor cells through their cytoplasmic
actin
Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of over ...
filaments.
Adherens junctions may serve as a regulatory module to maintain the actin
contractile ring
In molecular biology, an actomyosin contractile ring is a prominent structure during cytokinesis.Cheffings TH, Burroughs NJ, Balasubramanian MK. (2016). Actomyosin Ring Formation and Tension Generation in Eukaryotic Cytokinesis. Curr Biol. 26(15): ...
with which it is associated in microscopic studies.
References
External links
MBInfo - Adherens JunctionMBInfo - Adherens Junction Assembly*
*
{{Authority control
Cell anatomy