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Neuroligin
Neuroligin (NLGN), a type I membrane protein, is a cell adhesion protein on the postsynaptic membrane that mediates the formation and maintenance of synapses between neurons. Neuroligins act as ligands for β-Neurexins, which are cell adhesion proteins located presynaptically. Neuroligin and β-neurexin "shake hands," resulting in the connection between two neurons and the production of a synapse. Neuroligins also affect the properties of neural networks by specifying synaptic functions, and they mediate signalling by recruiting and stabilizing key synaptic components. Neuroligins interact with other postsynaptic proteins to localize neurotransmitter receptors and channels in the postsynaptic density as the cell matures.〔 Additionally, neuroligins are expressed in human peripheral tissues and have been found to play a role in angiogenesis. In humans, alterations in genes encoding neuroligins are implicated in autism and other cognitive disorders.
== Structure ==
Neuroligins bind with the aid of Ca2+ to the α-neurexin LNS (laminin, neurexin and sex hormone-binding globulin-like folding units) domains and to the β-neurexin LNS domain which then establishes a heterophilic trans-synaptic recognition code.〔Igor P. Fabrichny, Philippe Leone, Gerlind Sulzenbacher, Davide Comoletti, Meghan T. Miller, Palmer Taylor, Yves Bourne, Pascale Marchot (December 2007) Neuron. 56(6): 979–991. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2703725/PMCID: PMC2703725 NIHMSID: NIHMS109548〕 Through the observation of the crystal structure of neuroligin-1, it was determined that neuroligin-1 forms a protein dimer when two neurexin-1 beta monomers bind to the neuroligin-1’s two opposite surfaces. This forms a heterotetramer, which contains an interface for binding Ca2+. The interaction of neuroligin and neurexin to form a heterotetramer is monitored by alternatively spliced sites located near the binding interface for Ca2+ in both the neuroligin-1 and the neurexin-1 beta.〔Araç D, Boucard AA, Ozkan E, Strop P, Newell E, Südhof TC, Brunger AT (December 2007) Neuron. 56(6):992-1003. http://www.ncbi.nlm.nih.gov/pubmed/18093522〕 Subsequently, the presence of native neuroligin dimers was confirmed in neurons through biochemical detection, which included heterodimers composed of different neuroligin species, increasing the potential heterogeneity of endogenous neuroligin core dimer complexes.
The extracellular domain of NLGN consists mostly of a region that is homologous to acetylcholinesterases, but the amino acids important for catalysis in AChE are not conserved in NLGN, which lack esterase activity. Furthermore, this AChE homologous region is crucial for the proper function of NLGN.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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