The small myelin-associated glycoprotein binds to tubulin and microtubules.
The myelin-associated glycoprotein (MAG) exists as two isoforms, differing only by their respective cytoplasmic domains, that have been suggested to function in the formation and maintenance of myelin. In the present study, a 50 kDa protein binding directly to the small MAG (S-MAG) cytoplasmic domain was detected and identified as tubulin, the core component of the microtubular cytoskeleton. In vitro, the S-MAG cytoplasmic domain slowed the polymerization rate of tubulin and co-purified with assembled microtubules. A significant sequence homology was found between the tau family tubulin-binding repeats and the carboxy-terminus of S-MAG. Our results indicate that S-MAG is the first member of the Ig superfamily that can be classified as a microtubule-associated protein, and place S-MAG in a dynamic structural complex that could participate in linking the axonal surface and the myelinating Schwann cell cytoskeleton.
Kursula
P
P
Department of Pathology, University of Oulu, P.O. Box 5000, FIN-90014, Oulu, Finland. petri.kursula@oulu.fi
Lehto
V P
VP
Heape
A M
AM
D000818:Animals; D001932:Brain Neoplasms; D005910:Glioma; D066298:In Vitro Techniques; D008870:Microtubules / Q000378:metabolism*; D008969:Molecular Sequence Data; D018992:Myelin-Associated Glycoprotein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009413:Nerve Fibers, Myelinated / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012583:Schwann Cells / Q000378:metabolism; D012584:Sciatic Nerve / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014404:Tubulin / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D018992:Myelin-Associated Glycoprotein; D011994:Recombinant Proteins; D014404:Tubulin