TY - JOUR
T1 - Neurexophilin binding to α-neurexins. A single LNS domain functions as an independently folding ligand-binding unit
AU - Missler, Markus
AU - Hammer, Robert E
AU - Südhof, Thomas C.
PY - 1998/12/25
Y1 - 1998/12/25
N2 - α-Neurexins (Iα, IIα, and IIIα) are receptor-like proteins expressed in hundreds of isoforms on the neuronal cell surface. The extracellular domains of α-neurexins are composed of six LNS repeats, named after homologous sequences in the Laminin A G domain, Neurexins, and Sex hormone- binding globulin, with three interspersed epidermal growth factor-like domains. Purification of neurexin Iα revealed that it is tightly complexed to a secreted glycoprotein called neurexophilin 1. Neurexophilin 1 is a member of a family of at least four genes and resembles a neuropeptide, suggesting a function as an endogenous ligand for α-neurexins. We have now used recombinant proteins and knockout mice to investigate which isoforms and domains of different neurexins and neurexophilins interact with each other. We show that neurexophilins 1 and 3 but not 4 (neurexophilin 2 is not expressed in rodents) bind to a single individual LNS domain, the second overall LNS domain in all three α-neurexins. Although this domain is alternatively spliced, all splice variants bind, suggesting that alternative splicing does not regulate binding. Using homologous recombination to disrupt the neurexophilin 1 gene, we generated mutant mice that do not express detectable neurexophilin 1 mRNA. Mice lacking neurexophilin 1 are viable with no obvious morbidity or mortality. However, homozygous mutant mice exhibit male sterility, probably because homologous recombination resulted in the co- insertion into the neurexophilin gene of herpes simplex virus thymidine kinase, which is known to cause male sterility. In the neurexophilin 1 knockout mice, neurexin Iα is complexed with neurexophilin 3 but not neurexophilin 4, suggesting that neurexophilin 1 is redundant with neurexophilin 3 and that neurexophilins 1 and 3 but not 4 bind to neurexins. This hypothesis was confirmed using expression experiments. Our data reveal that the six LNS and three epidermal growth factor domains of neurexins are independently folding ligand-binding domains that may interact with distinct targets. The results support the notion that neurexophilins represent a family of extracellular signaling molecules that interact with multiple receptors including all three α-neurexins.
AB - α-Neurexins (Iα, IIα, and IIIα) are receptor-like proteins expressed in hundreds of isoforms on the neuronal cell surface. The extracellular domains of α-neurexins are composed of six LNS repeats, named after homologous sequences in the Laminin A G domain, Neurexins, and Sex hormone- binding globulin, with three interspersed epidermal growth factor-like domains. Purification of neurexin Iα revealed that it is tightly complexed to a secreted glycoprotein called neurexophilin 1. Neurexophilin 1 is a member of a family of at least four genes and resembles a neuropeptide, suggesting a function as an endogenous ligand for α-neurexins. We have now used recombinant proteins and knockout mice to investigate which isoforms and domains of different neurexins and neurexophilins interact with each other. We show that neurexophilins 1 and 3 but not 4 (neurexophilin 2 is not expressed in rodents) bind to a single individual LNS domain, the second overall LNS domain in all three α-neurexins. Although this domain is alternatively spliced, all splice variants bind, suggesting that alternative splicing does not regulate binding. Using homologous recombination to disrupt the neurexophilin 1 gene, we generated mutant mice that do not express detectable neurexophilin 1 mRNA. Mice lacking neurexophilin 1 are viable with no obvious morbidity or mortality. However, homozygous mutant mice exhibit male sterility, probably because homologous recombination resulted in the co- insertion into the neurexophilin gene of herpes simplex virus thymidine kinase, which is known to cause male sterility. In the neurexophilin 1 knockout mice, neurexin Iα is complexed with neurexophilin 3 but not neurexophilin 4, suggesting that neurexophilin 1 is redundant with neurexophilin 3 and that neurexophilins 1 and 3 but not 4 bind to neurexins. This hypothesis was confirmed using expression experiments. Our data reveal that the six LNS and three epidermal growth factor domains of neurexins are independently folding ligand-binding domains that may interact with distinct targets. The results support the notion that neurexophilins represent a family of extracellular signaling molecules that interact with multiple receptors including all three α-neurexins.
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U2 - 10.1074/jbc.273.52.34716
DO - 10.1074/jbc.273.52.34716
M3 - Article
C2 - 9856994
AN - SCOPUS:0032567532
SN - 0021-9258
VL - 273
SP - 34716
EP - 34723
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 52
ER -