Neurexin
Encyclopedia
A neurexin is a presynaptic protein that helps to glue together neurons at the synapse
. Neurexins are type I membrane protein
s that can be classified into two types, α-NRXNs and β-NRXNs. The α-NRXNs are larger and have different amino-terminal extracellular sequences. Neurexins mediate signaling across the synapse, and affect the properties of neural networks by specifying synaptic functions. In humans, alterations in genes encoding neurexins are implicated in autism and other cognitive diseases.
Neurexins were discovered as receptors for α-latrotoxin, a toxin in black widow spider
venom. Their functional roles in insects are likely similar to those in vertebrates.
β-Neurexins (located presynaptically) act as receptors for neuroligin (located postsynaptically). Neurexin and neuroligin "shake hands," resulting in the connection between the two neurons and the production of a synapse. Additionally, β-Neurexin has also been found to play a role in angiogenesis
.
The neurexin gene
s are NRXN1
, NRXN2
, and NRXN3
.
Synapse
In the nervous system, a synapse is a structure that permits a neuron to pass an electrical or chemical signal to another cell...
. Neurexins are type I membrane protein
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 that can be classified into two types, α-NRXNs and β-NRXNs. The α-NRXNs are larger and have different amino-terminal extracellular sequences. Neurexins mediate signaling across the synapse, and affect the properties of neural networks by specifying synaptic functions. In humans, alterations in genes encoding neurexins are implicated in autism and other cognitive diseases.
Neurexins were discovered as receptors for α-latrotoxin, a toxin in black widow spider
Black widow spider
Latrodectus mactans, the Southern black widow, is a highly venomous species of spider in the genus Latrodectus. They are well known for the distinctive black and red coloring of the female of the species and for the fact that she will occasionally eat her mate after reproduction. The species is...
venom. Their functional roles in insects are likely similar to those in vertebrates.
β-Neurexins (located presynaptically) act as receptors for neuroligin (located postsynaptically). Neurexin and neuroligin "shake hands," resulting in the connection between the two neurons and the production of a synapse. Additionally, β-Neurexin has also been found to play a role in angiogenesis
Angiogenesis
Angiogenesis is the physiological process involving the growth of new blood vessels from pre-existing vessels. Though there has been some debate over terminology, vasculogenesis is the term used for spontaneous blood-vessel formation, and intussusception is the term for the formation of new blood...
.
The neurexin gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s are NRXN1
NRXN1
Neurexin-1-alpha is a protein that in humans is encoded by the NRXN1 gene.-Genomics:The gene is found in a single copy on the short arm of chromosome 2 . The gene is 1,112,187 bases in length, is located on the Crick strand and encodes a protein of 1,477 amino acids .-Further reading:...
, NRXN2
NRXN2
Neurexin-2-alpha is a protein that in humans is encoded by the NRXN2 gene.-Further reading:...
, and NRXN3
NRXN3
Neurexin-3-alpha is a protein that in humans is encoded by the NRXN3 gene.-Further reading:...
.