Cell adhesion

Cell Adhesion

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Cell adhesion

Cellular adhesion is the binding of a cell

Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
to another cell or to a surface

Surface

In mathematics, specifically in topology, a surface is a two-dimensional topological manifold. The most familiar examples are those that arise as the boundaries of solid objects in ordinary three-dimensional Euclidean space E3....
or matrix

Extracellular matrix

In biology, the extracellular matrix is the extracellular part of animal tissue that usually provides structural support to the animal Cell in addition to performing various other important functions....
. Cellular adhesion is regulated by specific cell adhesion molecule

Cell adhesion molecule

Cell Adhesion Molecules are proteins located on the Cell surface involved with the binding with other cells or with the extracellular matrix in the process called cell adhesion....
s that interact with other molecules. They are hydrolyzed by extracellular hydrolytic enzymes

Hydrolase

In biochemistry, a hydrolase is an enzyme that catalyzes the hydrolysis of a chemical bond. For example, an enzyme that catalyzed the following reaction is a hydrolase:...
. This will tear away the layer unneeded for molecular distibution of arion cells. Then from out of the adhesion protein from the fragile cell membrane. Often the connection between the cell adhesion proteins and the cytoskeleton is not as direct as shown in the diagram.

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Adhesion in Prokaryotes

Prokaryotes have adhesion molecules usually termed "adhesins". Adhesins may occur on pili

Pili

Pili may refer to:Common names:* Pilus is a cellular organelle* Pili, a Philippine Tree that is a source of the Pili nut* Pili is a Hawaiian grass used to thatch structures...
(fimbriae), flagellae, or the cell surface. Adhesion of bacteria is the first step in colonization and regulates tropism

Tropism

A tropism is a biological phenomenon, indicating growth or turning movement of a biological organism, usually a plant, in response to an environmental stimulus ....
(tissue- or cell-specific interactions).

Adhesion in Viruses

Viruses also have adhesion molecules required for viral binding to host cells. For example, influenza

Influenza

Influenza, commonly known as the flu, is an infectious disease that affects birds and mammals caused by RNA viruses of the biological family Orthomyxoviridae ....
virus has a hemagglutinin

Hemagglutinin

Influenza hemagglutinin or haemagglutinin is a type of hemagglutinin found on the surface of the influenza viruses. It is an antigenic glycoprotein....
on its surface that is required for recognition of the sugar

Sugar

Sugar is a class of edible crystalline substances, mainly sucrose, lactose, and fructose. Human taste buds interpret its flavor as sweet. Sugar as a basic food carbohydrate primarily comes from sugar cane and from sugar beet, but also appears in fruit, honey, sorghum, sugar maple , and in many other sources....
sialic acid

Sialic acid

Sialic acid is a generic term for the N- or O-substituted derivatives of neuraminic acid, a monosaccharide with a nine-carbon backbone....
on host cell surface molecules. HIV

HIV

Human immunodeficiency virus is a lentivirus that can lead to AIDS , a condition in humans in which the immune system begins to fail, leading to life-threatening opportunistic infections....
has an adhesion molecule termed gp120

Gp120

gp120 is a glycoprotein exposed on the surface of the HIV structure and genome. The 120 in its name comes from its molecular weight of 120 Dalton ....
that binds to its ligand CD4

CD4

CD4 is a glycoprotein expressed on the surface of T helper cells, regulatory T cells, monocytes, macrophages, and dendritic cells. It was discovered in the late 1970s and was originally known as leu-3 and T4 before being named CD4 in 1984....
, which is expressed on lymphocytes.

Adhesion in Eukaryotes

Eukaryotic protozoans also express multiple adhesion molecules. An example of a pathogenic protozoan is the malaria

Malaria

Malaria is a Vector -borne infectious disease caused by protozoan parasites. It is widespread in Tropics and subtropical regions, including parts of the Americas, Asia, and Africa....
l parasite (Plasmodium falciparum), which uses one adhesion molecule called the circumsporozoite protein to bind to liver cells, and another adhesion molecule called the merozoite surface protein to bind red blood cells. In human

Human

A human being, also human or man, is a member of a species of bipedalism primates in the family Hominidae . Mitochondrial DNA evidence indicates that modern humans originated in east Africa about 200,000 years ago....
cells, which have many different types of adhesion molecules, the major classes are named integrins, Ig superfamily members

Immunoglobulin superfamily

The immunoglobulin superfamily is a large group of cell surface and soluble proteins that are involved in the recognition, binding, or cell adhesion processes of Cell ....
, cadherins, and selectins. Each of these adhesion molecules has a different function and recognizes different ligands. Defects in cell adhesion are usually attributable to defects in expression of adhesion molecules.

Human Genetic Diseases

There are the human genetic

Genetics

Genetics , a discipline of biology, is the science of heredity and Genetic variation in living organisms. The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding....
diseases caused by inability to express a specific adhesion molecule. An example is leukocyte adhesion deficiency

Leukocyte adhesion deficiency

Leukocyte-adhesion deficiency , is a rare autosomal recessive disorder characterized by immunodeficiency resulting in recurrent infections. The disorder is often divided into two separate genotypes called type I and type II, with type II being associated with fewer infections but more developmental delay....
-I (LAD-I), where patients do not express the ß2-integrin subunit precursor. This integrin is required for leukocytes to adhere to the blood vessel wall during inflammation

Inflammation

Inflammation is the complex biological response of Blood vessel tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. It is a protective attempt by the organism to remove the injurious stimuli as well as initiate the healing process for the tissue....
in order to fight infection. The leukocytes from LAD-I patients fail to adhere and patients exhibit serious episodes of infection

Infection

An infection is the detrimental colonization of a host organism by a foreign species. In an infection, the infecting organism seeks to utilize the host resources to multiply ....
that can be life threatening.

Tumor adhesion

Cancer metastasis tumors that spread through the circulatory system use mechanisms of cell adhesion to establish new tumors in the body. Release of epoxyeicosatrienoic acid

Epoxyeicosatrienoic acid

The Epoxyeicosatrienoic acids or EETs are signaling molecules formed by the action of Cytochrome P450 oxidase on 20-carbon essential fatty acids, such as arachidonic acid, from which it is produced by the enzyme epoxygenase....
is believed to increase this propensity.

Differential Adhesion Hypothesis

The differential adhesion hypothesis (sometimes called the "thermodynamic hypothesis") is a theory of cell adhesion

Cell adhesion

Cellular adhesion is the binding of a cell to another cell or to a surface or extracellular matrix. Cellular adhesion is regulated by specific cell adhesion molecules that interact with other molecules....
advanced by Malcolm Steinberg in 1964 to explain the mechanism by which heterotypic cells in mixed aggregates sort out into isotypic territories

Holotype

A holotype is one of several possible biological types. A type is what fixes a name to a taxon. A holotype is a single physical example of an organism, known to have been used when the species was formally described....
. The DAH postulates that tissues are viscoelastic liquids, and as such possess measurable tissue surface tensions. These surface tensions have been determined for a variety of tissues, including embryonic tissues and cell lines. The surface tensions correspond to the mutual sorting behavior: the tissue type with the higher surface tension will occupy an internal position relative to a tissue with a lower surface tension (if these tissues can interact with each other through their adhesion machinery). Quantitative differences in homo and heterotypic adhesion are supposed to be sufficient to account for the phenomenon without the need to postulate cell type specific adhesion systems: fairly generally accepted, although some tissue

Biological tissue

Tissue is a cellular organizational level intermediate between cells and a complete organism. Hence, a tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function....
specific cell adhesion molecules are now known to exist.

External links

by G. Cooper (online textbook)
by Lodish et al. (online textbook)
by Alberts et al. (online textbook) no anda