Myelin proteolipid protein (PLP), but not DM-20, is an inositol hexakisphosphate-binding protein.
Myelin proteolipid protein (PLP) and its alternatively spliced isoform, DM-20, are the major integral membrane proteins of central nervous system myelin. It is known that PLP and DM-20 are delivered to myelin by a finely regulated vesicular transport system in oligodendrocytes. Evolutionarily, it is believed that ancestral DM-20 acquired a PLP-specific exon to create PLP, after which PLP/DM-20 became a major component of central nervous system myelin. We purified PLP as an inositol 1,3,4,5-tetrakisphosphate-binding protein after solubilization in a non-organic solvent. However, under the isotonic condition, PLP binds inositol hexakisphosphate (InsP6) significantly, not inositol 1,3,4,5-tetrakisphosphate. Most of the InsP6-binding proteins are involved in vesicular transport, suggesting the involvement of PLP in vesicular transport. We separated DM-20 from PLP by CM-52 chromatography and showed that DM-20 has no InsP6 binding activity. These findings indicate that the PLP-specific domain confers the InsP6 binding activity and this interaction may be important for directing PLP transport to central nervous system myelin.
Laboratory of Neural Information, National Institute for Physiological Sciences, Okazaki National Research Institutes, Okazaki, Aichi 444, Japan. ikenaka@nips.ac.jp
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Yamaguchi
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Ikenaka
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Niinobe
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Yamada
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Mikoshiba
D000818:Animals; D001667:Binding, Competitive; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D002531:Cerebellum / Q000378:metabolism*; D002846:Chromatography, Affinity; D002848:Chromatography, DEAE-Cellulose; D007295:Inositol Phosphates / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D018991:Myelin Proteolipid Protein / Q000302:isolation & purification / Q000378:metabolism*; D009419:Nerve Tissue Proteins; D010833:Phytic Acid / Q000378:metabolism*; D013379:Substrate Specificity
D007295:Inositol Phosphates; D018991:Myelin Proteolipid Protein; D009419:Nerve Tissue Proteins; C047516:Plp1 protein, mouse; C081655:inositol-1,3,4,5-tetrakisphosphate; D010833:Phytic Acid