MAG

The protein encoded by this gene is a type I membrane protein and member of the immunoglobulin superfamily. It is thought to be involved in the process of myelination. It is a lectin that binds to sialylated glycoconjugates and mediates certain myelin-neuron cell-cell interactions. Three alternatively spliced transcripts encoding different isoforms have been described for this gene. [provided by RefSeq, Nov 2010]

Full Name

Myelin Associated Glycoprotein

Function

Adhesion molecule that mediates interactions between myelinating cells and neurons by binding to neuronal sialic acid-containing gangliosides and to the glycoproteins RTN4R and RTN4RL2 (By similarity).
Not required for initial myelination, but seems to play a role in the maintenance of normal axon myelination. Protects motoneurons against apoptosis, also after injury; protection against apoptosis is probably mediated via interaction with neuronal RTN4R and RTN4RL2. Required to prevent degeneration of myelinated axons in adults; this probably depends on binding to gangliosides on the axon cell membrane (By similarity).
Negative regulator of neurite outgrowth; in dorsal root ganglion neurons the inhibition is mediated primarily via binding to neuronal RTN4R or RTN4RL2 and to a lesser degree via binding to neuronal gangliosides. In cerebellar granule cells the inhibition is mediated primarily via binding to neuronal gangliosides. In sensory neurons, inhibition of neurite extension depends only partially on RTN4R, RTN4RL2 and gangliosides. Inhibits axon longitudinal growth (By similarity).
Inhibits axon outgrowth by binding to RTN4R (By similarity).
Preferentially binds to alpha-2,3-linked sialic acid. Binds ganglioside Gt1b (By similarity).

Biological Process

Axon regenerationIEA:Ensembl
Cell adhesionISS:UniProtKB
Cell-cell adhesion via plasma-membrane adhesion moleculesISS:UniProtKB
Cellular response to mechanical stimulusIEA:Ensembl
Central nervous system myelin formationIEA:Ensembl
Negative regulation of axon extensionISS:UniProtKB
Negative regulation of neuron apoptotic processISS:UniProtKB
Negative regulation of neuron differentiationIEA:Ensembl
Negative regulation of neuron projection developmentISS:UniProtKB
Positive regulation of astrocyte differentiationIEA:Ensembl
Positive regulation of myelinationIEA:Ensembl
Substantia nigra developmentHEP:UniProtKB
Transmission of nerve impulseIEA:Ensembl

Cellular Location

Cell membrane
Membrane raft

Involvement in disease

Spastic paraplegia 75, autosomal recessive (SPG75):
A form of spastic paraplegia, a neurodegenerative disorder characterized by a slow, gradual, progressive weakness and spasticity of the lower limbs. Rate of progression and the severity of symptoms are quite variable. Initial symptoms may include difficulty with balance, weakness and stiffness in the legs, muscle spasms, and dragging the toes when walking. In some forms of the disorder, bladder symptoms (such as incontinence) may appear, or the weakness and stiffness may spread to other parts of the body. SPG75 is characterized by onset in early childhood and is associated with mild to moderate cognitive impairment.

Topology

Extracellular: 20-516
Helical: 517-536
Cytoplasmic: 537-626

PTM

N-glycosylated.
Phosphorylated on tyrosine residues.
Ubiquitinated, leading to proteasomal degradation.