Cell–cell interaction
In epithelial cells, they function also to separate the extracellular fluid surrounding their apical and basolateral membranes.
[1] These junctions exist as a continuous band located just below the apical surface between the membranes of neighboring epithelial cells.
The tight junctions on adjacent cells line up so as to produce a seal between different tissues and body cavities.
For example, the apical surface of gastrointestinal epithelial cells serve as a selective permeable barrier that separates the external environment from the body.
On the cytoplasmic side, plakins form plaques which anchor the desmosomes to intermediate filaments composed of keratin proteins.
[4] Gap junctions are the main site of cell-cell signaling or communication that allow small molecules to diffuse between adjacent cells.
The extracellular face of the plasma membrane has a variety of proteins, carbohydrates, and lipids which project outward and act as signals.
[5] Synaptic signaling, an integral part of nervous system activity, occurs between neurons and target cells.
Protocadherins, a member of the cadherin family, mediate the adhesion of neurons to their target cells at synapses otherwise known as synaptic junctions.
These neurotransmitters bind and activate receptors on the post-synaptic neuron thereby transmitting the signal to the target cell.
Small molecules (<1000 Da), such as ions, amino acids, and sugars, can diffuse freely through plasmodesmata.
The cell-cell interactions facilitated by plasmodesmata play an important role in development of plant cells and tissues and defense against viral infection.
It requires successive forming and breaking of cell-cell interactions between the leukocytes and the endothelial cells that line blood vessels.
These cell-cell interactions are mediated mainly by a group of Cell Adhesion Molecules (CAMs) called selectins.
When the endothelium or the lining of a blood vessel is damaged, connective tissue including collagen fibers is locally exposed.
They communicate through physical interactions and signaling molecules such as homoserine lactones and peptides as a means to control metabolism and regulate growth .
Contact inhibition is thought to be mediated by cadherins, proteins that play an important role in cell adhesion.
Strong anchoring, a characteristic that determines virulence, prevents the bacteria from being washed away before infection occurs.
Many pathogens have Type III secretion systems which can directly inject protein toxins into the host cells.
Dysregulation that leads to leukocyte migration into healthy tissues can cause conditions such as acute respiratory distress syndrome and some types of arthritis.
[12] The autoimmune disease pemphigus vulgaris results from autoantibodies to desmoglein and other normal body proteins.
Mutations in the connexin genes cause 8 human diseases including heart malformations and neurosensory deafness.
