User:Mrilliant/sandbox

Structure
The presynaptic membrane and the postsynaptic membrane of neuronal synapses are joined to each other via adhesion molecules. Two specific pairs of adhesion molecules involved with synaptic connections are the presynaptic proteins neurexins and the postsynaptic proteins neuroligins.

Neurexins are made up of three genes (NRXN1, 2, and 3), each of which produces both an α-neurexin and a β-neurexin. The transmembrane domain of neurexins are specialized to aid in the localizing of voltage-gated Ca2+ channels which ensures that synaptic vesicles are properly released (book). On the surface of the membrane of α-neurexins there are six LNS domains (laminin, neurexin and sex hormone-binding globulin-like folding units) and on the surface of β-neurexins there is one LNS domain. Neuroligins bind with the aid of Ca2+ to the α-neurexin LNS domains and to the β-neurexin LNS domain which then establishes a heterophilic trans-synaptic recognition code

Function
Neurexins function as trans-synaptic receptors while synapses are differentiated. The presynaptic neurexins bind to postsynaptic neuroligins, and this process suggests that neurexins help signal down a pathway that regulates synapse formation and stabilization. Presenilins (PS) are thought to process the regulation of neurexins at glutamatergic synapses and prevent the undue accumulation of neurexins at the presynaptic terminal.