Intercellular communication
Different types of cells use different proteins and mechanisms to communicate with one another using extracellular signalling molecules or electric fluctuations which could be likened to an intercellular ethernet.
In this article, intercellular communication has been further collated into various areas of research rather than by functional or structural characteristics.
Single-celled organisms sense their environment to seek food and may send signals to other cells to behave symbiotically or reproduce.
Using a chemical gradient to coordinate cell growth and differentiation continues to be important as multicellular animals and plants become more complex.
Gap junctions allow neighboring cells to directly exchange small molecules.
[9] Pannexins, connexins, and innexins are transmembrane proteins that are all named after the Latin term nexus, meaning to connect.
The connexon pairs form ICCs that can transport water, many other molecules up to around 1000 atoms in size[18] and can be very rapidly signaled to turn on and off as required.
To add to their versatility there are a range of these ICC types due to their being over 20 different connexins with different properties that can combine with each other in a variety of ways.
They are found in Prokaryotes for exchanging DNA, small organisms such as Pinnularia, Valonia ventricosa, Volvox, C. elegans[22] and mitosis generally (Cytokinesis),[23] Blepharisma for sexual reproduction and during Meiosis including Spermatocytogenesis to synchronise development of germ cells and oogenesis in larger organisms.
Using an electrical nerve impulse from a neuron of a neuromuscular junction to stimulate a muscle to contract is an example of very small[26] (about 0.05μm) vesicles being directly involved in regulating intercellular communication.
When activated by a nerve impulse more than 100 vesicles will be released at once, hundreds of thousands of signalling molecules, causing a significant contraction of the muscle fiber.
[31] Vesicles are also associated with the transport of materials outside of the cell to enable growth and repair of tissues in the extracellular matrix.
Examples of larger vesicles are in regulatory secretary pathways in endocrine, exocrine tissues,[34] transcytosis[35][36] and the vesiculo-vacuolar organelle (VVO) in endothelial and perhaps other cell types.
[38] Some large intercellular vesicles also appear to stay intact as they transport their contents from one part of a tissue to another and involve gap junction plaques.
Nerves made up of many cells in vertebrates are typically highly specialized in form and function usually being the most complex in the brain.
Being "accessory" cells that pass on the message they require an additional space and can consume a lot of energy within an organism.
[41] When groups of nerve cells form another type of intercellular communication called ephaptic coupling can arise.
There are reductionist attempts to associate particular groups of nerve cells exhibiting ephaptic coupling with particular functions in the brain.
[43] As yet there are no studies on the simplest neural systems such as the polar bodies of Ctenophores to see if ephaptic coupling may explain some of their more complex behaviors.
[13] In-water reproduction often involves vast synchronized release of gametes called spawning.
[45] Over large distances cells in one plant will communicate with cells in another plant of the same species and other species by releasing signals into the air such as green leaf volatiles that can, among other things, pre-warn neighbors of herbivores or in the case of ethylene gas the signal triggers ripening in fruits.
The innexin helps ensure the wasp egg is neutralized, saving the caterpillar from the parasite.
