Gene selection, alternative splicing, and post-translational processing regulate neuroligin selectivity for beta-neurexins.
Neuroligins 1-4 are postsynaptic transmembrane proteins capable of initiating presynaptic maturation via interactions with beta-neurexin. Both neuroligins and beta-neurexins have alternatively spliced inserts in their extracellular domains. Using analytical ultracentrifugation, we determined that the extracellular domains of the neuroligins sediment as dimers, whereas the extracellular domains of the beta-neurexins appear monomeric. Sedimentation velocity experiments of titrated stoichiometry ratios of beta-neurexin and neuroligin suggested a 2:2 complex formation. The recognition properties of individual neuroligins toward beta-neurexin-1 (NX1beta), along with the influence of their splice inserts, were explored by surface plasmon resonance and affinity chromatography. Different neuroligins display a range of NX1beta affinities spanning more than 2 orders of magnitude. Whereas splice insert 4 in beta-neurexin appears to act only as a modulator of the neuroligin/beta-neurexin association, splice insert B in neuroligin-1 (NL1) is the key element regulating the NL1/NX1beta binding. Our data indicate that gene selection, mRNA splicing, and post-translational modifications combine to give rise to a controlled neuroligin recognition code with a rank ordering of affinities for particular neurexins that is conserved for the neuroligins across mammalian species.
Comoletti
Davide
D
Department of Pharmacology, University of California-San Diego, La Jolla, California 92093-0636, USA.
Flynn
Robyn E
RE
Boucard
Antony A
AA
Demeler
Borries
B
Schirf
Virgil
V
Shi
Jianxin
J
Jennings
Lori L
LL
Newlin
Helen R
HR
Südhof
Thomas C
TC
Taylor
Palmer
P
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D002846:Chromatography, Affinity; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005786:Gene Expression Regulation; D014644:Genetic Variation; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010957:Plasmids; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D020349:Surface Plasmon Resonance
D018076:DNA, Complementary; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; C086959:neurexin Ibeta