Cell adhesion molecule
Encyclopedia
Cell Adhesion Molecules are protein
s located on the cell surface involved with the binding with other cells or with the extracellular matrix
(ECM) in the process called cell adhesion
.
These proteins are typically transmembrane receptors and are composed of three domains: an intracellular domain that interacts with the cytoskeleton
, a transmembrane domain, and an extracellular domain that interacts either with other CAMs of the same kind (homophilic binding) or with other CAMs or the extracellular matrix (heterophilic binding).
s, the cadherin
s, and the selectin
s.
One classification system involves the distinction between calcium-independent CAMs and calcium-dependent CAMs.
CAMs (IgSF CAMs) are either homophilic or heterophilic and bind integrins or different IgSF CAMs.
s. Two well known examples are CD34
and GLYCAM-1.
s are a family of homophilic CAMs, Ca2+
-dependent. The most important members of this family are E-cadherins (epithelial
), P-cadherins (placenta
l), and N-cadherins (neural
).
s are a family of heterophilic CAMs that bind fucosylated carbohydrates, e.g., mucin
s. The three family members are E-selectin
(endothelial
), L-selectin
(leukocyte), and P-selectin
(platelet
). The best-characterized ligand for the three selectins is P-selectin glycoprotein ligand-1 (PSGL-1), which is a mucin-type glycoprotein expressed on all white blood cells.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s located on the cell surface involved with the binding with other cells or with the extracellular matrix
Extracellular matrix
In biology, the extracellular matrix is the extracellular part of animal tissue that usually provides structural support to the animal cells in addition to performing various other important functions. The extracellular matrix is the defining feature of connective tissue in animals.Extracellular...
(ECM) in the process called cell adhesion
Cell adhesion
Cellular adhesion is the binding of a cell to a surface, extracellular matrix or another cell using cell adhesion molecules such as selectins, integrins, and cadherins. Correct cellular adhesion is essential in maintaining multicellular structure...
.
These proteins are typically transmembrane receptors and are composed of three domains: an intracellular domain that interacts with the cytoskeleton
Cytoskeleton
The cytoskeleton is a cellular "scaffolding" or "skeleton" contained within a cell's cytoplasm and is made out of protein. The cytoskeleton is present in all cells; it was once thought to be unique to eukaryotes, but recent research has identified the prokaryotic cytoskeleton...
, a transmembrane domain, and an extracellular domain that interacts either with other CAMs of the same kind (homophilic binding) or with other CAMs or the extracellular matrix (heterophilic binding).
Families of CAMs
Most of the CAMs belong to four protein families: Ig (immunoglobulin) superfamily (IgSF CAMs), the integrinIntegrin
Integrins are receptors that mediate attachment between a cell and the tissues surrounding it, which may be other cells or the ECM. They also play a role in cell signaling and thereby regulate cellular shape, motility, and the cell cycle....
s, the cadherin
Cadherin
Cadherins are a class of type-1 transmembrane proteins. They play important roles in cell adhesion, ensuring that cells within tissues are bound together. They are dependent on calcium ions to function, hence their name.The cadherin superfamily includes cadherins, protocadherins, desmogleins, and...
s, and the selectin
Selectin
Selectins are a family of cell adhesion molecules . All selectins are single-chain transmembrane glycoproteins that share similar properties to C-type lectins due to a related amino terminus and calcium-dependent binding...
s.
One classification system involves the distinction between calcium-independent CAMs and calcium-dependent CAMs.
IgSF CAMs
Immunoglobulin superfamilyImmunoglobulin superfamily
The immunoglobulin superfamily is a large group of cell surface and soluble proteins that are involved in the recognition, binding, or adhesion processes of cells. Molecules are categorized as members of this superfamily based on shared structural features with immunoglobulins ; they all possess a...
CAMs (IgSF CAMs) are either homophilic or heterophilic and bind integrins or different IgSF CAMs.
Lymphocyte homing receptors
These are also known as addressinAddressin
Addressin also known as mucosal vascular addressin cell adhesion molecule 1 is a protein that in humans is encoded by the MADCAM1 gene....
s. Two well known examples are CD34
CD34
CD34 molecule is a cluster of differentiation molecule present on certain cells within the human body. It is a cell surface glycoprotein and functions as a cell-cell adhesion factor. It may also mediate the attachment of stem cells to bone marrow extracellular matrix or directly to stromal cells...
and GLYCAM-1.
Integrins
The Integrins are a family of heterophilic CAMs that bind IgSF CAMs or the extracellular matrix. They are heterodimers, called alpha and beta. Eighteen different alpha subunits that combine with 8 different beta subunits to form twenty-four known integrins; however not all combinations are observed.Cadherins
The cadherinCadherin
Cadherins are a class of type-1 transmembrane proteins. They play important roles in cell adhesion, ensuring that cells within tissues are bound together. They are dependent on calcium ions to function, hence their name.The cadherin superfamily includes cadherins, protocadherins, desmogleins, and...
s are a family of homophilic CAMs, Ca2+
Calcium in biology
Calcium plays a pivotal role in the physiology and biochemistry of organisms and the cell. It plays an important role in signal transduction pathways, where it acts as a second messenger, in neurotransmitter release from neurons, contraction of all muscle cell types, and fertilization...
-dependent. The most important members of this family are E-cadherins (epithelial
Epithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...
), P-cadherins (placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
l), and N-cadherins (neural
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...
).
Selectins
The selectinSelectin
Selectins are a family of cell adhesion molecules . All selectins are single-chain transmembrane glycoproteins that share similar properties to C-type lectins due to a related amino terminus and calcium-dependent binding...
s are a family of heterophilic CAMs that bind fucosylated carbohydrates, e.g., mucin
Mucin
Mucins are a family of high molecular weight, heavily glycosylated proteins produced by epithelial tissues in most metazoans. Mucins' key characteristic is their ability to form gels; therefore they are a key component in most gel-like secretions, serving functions from lubrication to cell...
s. The three family members are E-selectin
E-selectin
E-selectin, also known as CD62 antigen-like family member E , endothelial-leukocyte adhesion molecule 1 , or leukocyte-endothelial cell adhesion molecule 2 , is a cell adhesion molecule expressed only on endothelial cells activated by cytokines. Like other selectins, it plays an important part in...
(endothelial
Endothelium
The endothelium is the thin layer of cells that lines the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. These cells are called endothelial cells. Endothelial cells line the entire circulatory system, from the heart...
), L-selectin
L-selectin
L-selectin, also known as CD62L, is a cell adhesion molecule found on leukocytes. It belongs to the selectin family of proteins, which recognize sialylated carbohydrate groups...
(leukocyte), and P-selectin
P-selectin
P-selectin is a cell adhesion molecule on the surfaces of activated endothelial cells, which line the inner surface of blood vessels, and activated platelets...
(platelet
Platelet
Platelets, or thrombocytes , are small,irregularly shaped clear cell fragments , 2–3 µm in diameter, which are derived from fragmentation of precursor megakaryocytes. The average lifespan of a platelet is normally just 5 to 9 days...
). The best-characterized ligand for the three selectins is P-selectin glycoprotein ligand-1 (PSGL-1), which is a mucin-type glycoprotein expressed on all white blood cells.
See also
- Cell membraneCell membraneThe cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
- cell migrationCell migrationCell migration is a central process in the development and maintenance of multicellular organisms. Tissue formation during embryonic development, wound healing and immune responses all require the orchestrated movement of cells in particular directions to specific locations...
- Immunological synapseImmunological synapseIn immunology, an immunological synapse is the interface between an antigen-presenting cell and a lymphocyte. It was first discovered by Abraham Kupfer at the National Jewish Medical and Research Center in Denver and the term was coined by Michael Dustin at NYU who studied it in further detail...
- trogocytosisTrogocytosisTrogocytosis is a process whereby lymphocytes conjugated to antigen-presenting cells extract surface molecules from these cells and express them on their own surface...