title: Tight binding of NAP-22 with acidic membrane lipids.
abstract: Recovery of various signal transduction molecules in the detergent-resistant membrane microdomain (DRM) fraction suggests the importance of this region in cellular functions. Insolubility of the outer leaflet of DRM to the non-ionic detergent is ascribed to the tight association of cholesterol and sphingolipid. Since, poor localization of sphingolipid is observed in the inner leaflet, the physicochemical background of the insolubility of the inner leaflet is hence still an enigma. NAP-22 (also called BASP1 or CAP-23) is a neuron-enriched calmodulin-binding protein and one of the major proteins in the DRM of the neuronal cell membrane. A previous study showed the presence of several lipids in a NAP-22 fraction after the process of extraction and column chromatography. In this study, the effect of lipid extraction on NAP-22 was studied through native-gel electrophoresis, ultracentrifugation, and electron microscopic observation. The mobility of NAP-22 in native-PAGE was shifted from low to high after delipidation. Delipidated NAP-22 bound phosphatidylserine (PS), phosphatidylinosotol, and ganglioside. Some part of the mixture of PS and NAP-22 was recovered in the insoluble fraction after Triton X-100 treatment and the addition of cholesterol enhanced the amount of NAP-22 in the insoluble fraction.
authors.affiliation: Divison of Biology, Graduate School of Science, Kobe-University, Kobe 657-8501, Japan. Electronic address: smaekawa@kobe-u.ac.jp.
authors.forename: Shohei
authors.initials: S
authors.lastname: Maekawa
authors.affiliation: Divison of Biology, Graduate School of Science, Kobe-University, Kobe 657-8501, Japan.
authors.forename: Yuumi
authors.initials: Y
authors.lastname: Kobayashi
authors.affiliation: Divison of Biology, Graduate School of Science, Kobe-University, Kobe 657-8501, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Morita
authors.affiliation: Divison of Biology, Graduate School of Science, Kobe-University, Kobe 657-8501, Japan.
authors.forename: Toshinobu
authors.initials: T
authors.lastname: Suzaki
mesh_terms: D000096:Acetone; D000818:Animals; D002148:Calmodulin-Binding Proteins / Q000737:chemistry*; D002725:Chloroform; D003598:Cytoskeletal Proteins / Q000737:chemistry*; D008563:Membrane Lipids / Q000737:chemistry*; D000432:Methanol; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D011485:Protein Binding; D051381:Rats; D012997:Solvents
chemical_list: D002148:Calmodulin-Binding Proteins; D003598:Cytoskeletal Proteins; D008563:Membrane Lipids; D009419:Nerve Tissue Proteins; D012997:Solvents; C066853:Basp1 protein, rat; D000096:Acetone; D002725:Chloroform; D000432:Methanol
keywords: Cholesterol; Ganglioside; Lipid raft; NAP-22; Neuron; Phosphatidylserine