The Nogo-66 receptor homolog NgR2 is a sialic acid-dependent receptor selective for myelin-associated glycoprotein.
The Nogo-66 receptor (NgR1) is a promiscuous receptor for the myelin inhibitory proteins Nogo/Nogo-66, myelin-associated glycoprotein (MAG), and oligodendrocyte myelin glycoprotein (OMgp). NgR1, an axonal glycoprotein, is the founding member of a protein family composed of the structurally related molecules NgR1, NgR2, and NgR3. Here we show that NgR2 is a novel receptor for MAG and acts selectively to mediate MAG inhibitory responses. MAG binds NgR2 directly and with greater affinity than NgR1. In neurons NgR1 and NgR2 support MAG binding in a sialic acid-dependent Vibrio cholerae neuraminidase-sensitive manner. Forced expression of NgR2 is sufficient to impart MAG inhibition to neonatal sensory neurons. Soluble NgR2 has MAG antagonistic capacity and promotes neuronal growth on MAG and CNS myelin substrate in vitro. Structural studies have revealed that the NgR2 leucine-rich repeat cluster and the NgR2 "unique" domain are necessary for high-affinity MAG binding. Consistent with its role as a neuronal MAG receptor, NgR2 is an axonassociated glycoprotein. In postnatal brain NgR1 and NgR2 are strongly enriched in Triton X-100-insoluble lipid rafts. Neural expression studies of NgR1 and NgR2 have revealed broad and overlapping, yet distinct, distribution in the mature CNS. Taken together, our studies identify NgRs as a family of receptors (or components of receptors) for myelin inhibitors and provide insights into how interactions between MAG and members of the Nogo receptor family function to coordinate myelin inhibitory responses.
Venkatesh
Karthik
K
Center for Aging and Developmental Biology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.
Chivatakarn
Onanong
O
Lee
Hakjoo
H
Joshi
Pushkar S
PS
Kantor
David B
DB
Newman
Barbara A
BA
Mage
Rose
R
Rader
Christoph
C
Giger
Roman J
RJ
D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000378:metabolism; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology; D002522:Chlorocebus aethiops; D006224:Cricetinae; D003412:Cricetulus; D058851:GPI-Linked Proteins; D021962:Membrane Microdomains / Q000378:metabolism; D009185:Myelin Proteins; D018992:Myelin-Associated Glycoprotein / Q000378:metabolism* / Q000502:physiology; D019158:N-Acetylneuraminic Acid / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D016501:Neurites / Q000502:physiology; D000070816:Nogo Receptor 1; D011485:Protein Binding; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018000:Receptors, Peptide / Q000378:metabolism
D058851:GPI-Linked Proteins; D009185:Myelin Proteins; D018992:Myelin-Associated Glycoprotein; D009419:Nerve Tissue Proteins; D000070816:Nogo Receptor 1; D011956:Receptors, Cell Surface; D018000:Receptors, Peptide; C486581:Rtn4r protein, rat; D019158:N-Acetylneuraminic Acid