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Cadherin-2 also known as Neural cadherin (N-cadherin), is a protein that in humans is encoded by the ''CDH2''
gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
. CDH2 has also been designated as CD325 ( cluster of differentiation 325). Cadherin-2 is a
transmembrane A transmembrane protein is a type of integral membrane protein that spans the entirety of the cell membrane. Many transmembrane proteins function as gateways to permit the transport of specific substances across the membrane. They frequently u ...
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
expressed in multiple tissues and functions to mediate cell–cell adhesion. In cardiac muscle, Cadherin-2 is an integral component in adherens junctions residing at intercalated discs, which function to mechanically and electrically couple adjacent cardiomyocytes. Alterations in expression and integrity of Cadherin-2 has been observed in various forms of disease, including human dilated cardiomyopathy. Variants in ''CDH2'' have also been identified to cause a syndromic
neurodevelopmental disorder Neurodevelopmental disorders are a group of mental conditions negatively affecting the development of the nervous system, which includes the brain and spinal cord. According to the American Psychiatric Association Diagnostic and Statistical Manu ...
.


Structure

Cadherin-2 is a
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
with molecular weight of 99.7 kDa, and 906
amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...
s in length. Cadherin-2, a classical
cadherin Cadherins (named for "calcium-dependent adhesion") are cell adhesion molecules important in forming adherens junctions that let cells adhere to each other. Cadherins are a class of type-1 transmembrane proteins, and they depend on calcium (Ca2+) ...
from the cadherin superfamily, is composed of five extracellular cadherin repeats, a transmembrane region and a highly conserved
cytoplasm The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...
ic tail. Cadherin-2, as well as other cadherins, interact with Cadherin-2 on an adjacent cell in an anti-parallel conformation, thus creating a linear, adhesive "zipper" between cells.


Function

Cadherin-2, originally named Neural cadherin for its role in neural tissue, plays a role in
neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...
s and later was found to also play a role in cardiac muscle and in cancer
metastasis Metastasis is a pathogenic agent's spreading from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, ...
. Cadherin-2 is a
transmembrane A transmembrane protein is a type of integral membrane protein that spans the entirety of the cell membrane. Many transmembrane proteins function as gateways to permit the transport of specific substances across the membrane. They frequently u ...
, homophilic glycoprotein belonging to the calcium-dependent cell adhesion molecule family. These proteins have extracellular domains that mediate homophilic interactions between adjacent cells, and C-terminal,
cytoplasm The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...
ic tails that mediate binding to catenins, which in turn interact with 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 ...
cytoskeleton The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells, including those of bacteria and archaea. In eukaryotes, it extends from the cell nucleus to the cell membrane and is compos ...
.


Role in development

Cadherin-2 plays a role in development as a calcium dependent cell–cell adhesion glycoprotein that functions during
gastrulation Gastrulation is the stage in the early embryonic development of most animals, during which the blastula (a single-layered hollow sphere of cells), or in mammals, the blastocyst, is reorganized into a two-layered or three-layered embryo known as ...
and is required for establishment of left-right asymmetry. Cadherin-2 is widely expressed in the
embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...
post- implantation, showing high levels in the
mesoderm The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical ...
with sustained expression through adulthood. Cadherin-2 mutation during development has the most significant effect on cell adhesion in the primitive heart; dissociated
myocyte A muscle cell, also known as a myocyte, is a mature contractile Cell (biology), cell in the muscle of an animal. In humans and other vertebrates there are three types: skeletal muscle, skeletal, smooth muscle, smooth, and Cardiac muscle, cardiac ...
s and abnormal heart tube development occur. Cadherin-2 plays a role in the development of the vertebrate heart at the transition of
epithelial cell Epithelium or epithelial tissue is a thin, continuous, protective layer of Cell (biology), cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial (Mesothelium, mesothelial) tissues line ...
s to trabecular and compact myocardial cell layer formation. An additional study showed that
myocyte A muscle cell, also known as a myocyte, is a mature contractile Cell (biology), cell in the muscle of an animal. In humans and other vertebrates there are three types: skeletal muscle, skeletal, smooth muscle, smooth, and Cardiac muscle, cardiac ...
s expressing a dominant negative Cadherin-2 mutant showed significant abnormalities in
myocyte A muscle cell, also known as a myocyte, is a mature contractile Cell (biology), cell in the muscle of an animal. In humans and other vertebrates there are three types: skeletal muscle, skeletal, smooth muscle, smooth, and Cardiac muscle, cardiac ...
distribution and migration towards the endocardium, resulting in defects in trabecular formation within the myocardium.


Role in cardiac muscle

In cardiac muscle, Cadherin-2 is found at intercalated disc structures which provide end-on cell–cell connections that facilitate mechanical and electrical coupling between adjacent cardiomyocytes. Within intercalated discs are three types of junctions: adherens junctions, desmosomes and
gap junction Gap junctions are membrane channels between adjacent cells that allow the direct exchange of cytoplasmic substances, such small molecules, substrates, and metabolites. Gap junctions were first described as ''close appositions'' alongside tight ...
s; Cadherin-2 is an essential component in adherens junctions, which enables cell–cell adhesion and force transmission across the
sarcolemma The sarcolemma (''sarco'' (from ''sarx'') from Greek; flesh, and ''lemma'' from Greek; sheath), also called the myolemma, is the cell membrane surrounding a skeletal muscle fibre or a cardiomyocyte. It consists of a lipid bilayer and a thin ...
. Cadherin-2 complexed to catenins has been described as a master regulator of intercalated disc function. Cadherin-2 appears at cell–cell junctions prior to
gap junction Gap junctions are membrane channels between adjacent cells that allow the direct exchange of cytoplasmic substances, such small molecules, substrates, and metabolites. Gap junctions were first described as ''close appositions'' alongside tight ...
formation, and is critical for normal myofibrillogenesis. Expression of a mutant form of Cadherin-2 harboring a large deletion in the extracellular domain inhibited the function of endogenous Cadherin-2 in adult ventricular cardiomyocytes, and neighboring cardiomyocytes lost cell–cell contact and
gap junction Gap junctions are membrane channels between adjacent cells that allow the direct exchange of cytoplasmic substances, such small molecules, substrates, and metabolites. Gap junctions were first described as ''close appositions'' alongside tight ...
plaques as well. Mouse models employing transgenesis have highlighted the function of N-cadherin in cardiac muscle. Mice with altered expression of N-cadherin and/or E-cadherin showed a dilated cardiomyopathy phenotype, likely due to malfunction of intercalated discs. In agreement with this, mice with ablation of N-cadherin in adult hearts via a cardiac-specific tamoxifen-inducible Cre N-cadherin transgene showed disrupted assembly of intercalated discs, dilated cardiomyopathy, impaired cardiac function, decreased
sarcomere A sarcomere (Greek σάρξ ''sarx'' "flesh", μέρος ''meros'' "part") is the smallest functional unit of striated muscle tissue. It is the repeating unit between two Z-lines. Skeletal striated muscle, Skeletal muscles are composed of tubular ...
length, increased Z-line thickness, decreases in connexin 43, and a loss in muscular tension. Mice died within two months of transgene expression, mainly due to spontaneous Ventricular tachycardia. Further analysis of N-cadherin knockout mice revealed that the arrhythmias were likely due to
ion channel Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by Gating (electrophysiol ...
remodeling and aberrant Kv1.5 channel function. These animals showed a prolonged
action potential An action potential (also known as a nerve impulse or "spike" when in a neuron) is a series of quick changes in voltage across a cell membrane. An action potential occurs when the membrane potential of a specific Cell (biology), cell rapidly ri ...
duration, reduced density of inward rectifier potassium channel and decreased expression of Kv1.5, KCNE2 and cortactin combined with disrupted
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 ...
cytoskeleton The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells, including those of bacteria and archaea. In eukaryotes, it extends from the cell nucleus to the cell membrane and is compos ...
at the
sarcolemma The sarcolemma (''sarco'' (from ''sarx'') from Greek; flesh, and ''lemma'' from Greek; sheath), also called the myolemma, is the cell membrane surrounding a skeletal muscle fibre or a cardiomyocyte. It consists of a lipid bilayer and a thin ...
.


Role in neurons

In neural cells, at certain central nervous system
synapse In the nervous system, a synapse is a structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or a target effector cell. Synapses can be classified as either chemical or electrical, depending o ...
s, presynaptic to postsynaptic
adhesion Adhesion is the tendency of dissimilar particles or interface (matter), surfaces to cling to one another. (Cohesion (chemistry), Cohesion refers to the tendency of similar or identical particles and surfaces to cling to one another.) The ...
is mediated at least in part by Cadherin-2. N-cadherins interact with catenins to play an important role in learning and memory (''For full article see Cadherin-catenin complex in learning and memory''). Loss of N-cadherin is also associated with attention-deficit hyperactivity disorder in humans, and impaired synaptic functioning.


Role in cancer metastasis

Cadherin-2 is commonly found in cancer cells and provides a mechanism for transendothelial migration. When a cancer cell adheres to the endothelial cells of a blood vessel it up-regulates the src kinase pathway, which phosphorylates
beta-catenin Catenin beta-1, also known as β-catenin (''beta''-catenin), is a protein that in humans is encoded by the ''CTNNB1'' gene. β-Catenin is a dual function protein, involved in regulation and coordination of cell–cell adhesion and gene transcrip ...
s attached to both Cadherin-2 (this protein) and E-cadherins. This causes the intercellular connection between two adjacent endothelial cells to fail and allows the cancer cell to slip through.


Clinical significance

Variants in ''CDH2'' have been identified to cause a syndromic
neurodevelopmental disorder Neurodevelopmental disorders are a group of mental conditions negatively affecting the development of the nervous system, which includes the brain and spinal cord. According to the American Psychiatric Association Diagnostic and Statistical Manu ...
characterized by
Corpus callosum The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain. The corpus callosum is only found in placental ...
, axon, cardiac, ocular, and genital differences. One study investigating genetic underpinnings of obsessive-compulsive disorder and Tourette disorder found that while ''CDH2'' variants are likely not disease-causing as single entities, they may confer risk when examined as part of a panel of related cell–cell adhesion genes. Further studies in larger cohorts will be required to unequivocally determine this. In human dilated cardiomyopathy, it was shown that Cadherin-2 expression was enhanced and arranged in a disarrayed fashion, suggesting that disorganization of Cadherin-2 protein in
heart disease Cardiovascular disease (CVD) is any disease involving the heart or blood vessels. CVDs constitute a class of diseases that includes: coronary artery diseases (e.g. angina pectoris, angina, myocardial infarction, heart attack), heart failure, ...
may be a component of remodeling.


Interactions

Cadherin-2 has been shown to interact with: *
Beta-catenin Catenin beta-1, also known as β-catenin (''beta''-catenin), is a protein that in humans is encoded by the ''CTNNB1'' gene. β-Catenin is a dual function protein, involved in regulation and coordination of cell–cell adhesion and gene transcrip ...
, * CDH11, * type IIb RPTPs including PTPmu ( CTNND1), * CTNNA1, * LRRC7, * PTPRM) * PTPrho ( PTPRT), and * Plakoglobin. * XIRP1 * SCARB2


See also

* ADH-1


References


Further reading

* * * * * * * * * * * * * * * * * *


External links

* * * {{Cell adhesion molecules Clusters of differentiation