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The Journal of Neuroscience, April 15, 2009, 29(15):4794-4807; doi:10.1523/JNEUROSCI.3955-08.2009

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Cellular/Molecular
Phosphatidylinositol 4,5-Bisphosphate-Dependent Interaction of Myelin Basic Protein with the Plasma Membrane in Oligodendroglial Cells and Its Rapid Perturbation by Elevated Calcium

Schanila Nawaz,¹ Angelika Kippert,¹ Aiman S. Saab,¹ Hauke B. Werner,¹ Thorsten Lang,³ Klaus-Armin Nave,¹ and Mikael Simons^1,2,4

¹Max Planck Institute of Experimental Medicine and ²Department of Neurology, University of Göttingen, D-37075 Göttingen, Germany, ³Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany, and ⁴Center for Biochemistry and Molecular Cell Biology, University of Göttingen, D-37073 Göttingen, Germany

Correspondence should be addressed to Dr. Klaus-Armin Nave, Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3, D-37073 Göttingen, Germany. Email: nave{at}em.mpg.de

Myelin basic protein (MBP) is an essential structural component of CNS myelin. The electrostatic association of this positively charged protein with myelin-forming membranes is a crucial step in myelination, but the mechanism that regulates myelin membrane targeting is not known. Here, we demonstrate that phosphatidylinositol 4,5-bisphosphate (PIP2) is important for the stable association of MBP with cellular membranes. In oligodendrocytes, overexpression of synaptojanin 1-derived phosphoinositide 5-phosphatase, which selectively hydrolyzes membrane PIP2, causes the detachment of MBP from the plasma membrane. In addition, constitutively active Arf6/Q67L induces the formation of PIP2-enriched endosomal vacuoles, leading to the redistribution of MBP to intracellular vesicles. Fluorescence resonance energy transfer imaging revealed an interaction of the PIP2 sensing probe PH-PLC1 with wild-type MBP, but not with a mutant MBP isoform that fails to associate with the plasma membrane. Moreover, increasing intracellular Ca²⁺, followed by phospholipase C-mediated PIP2 hydrolysis, as well as reduction of the membrane charge by ATP depletion, resulted in the dissociation of MBP from the glial plasma membrane. When the corpus callosum of mice was analyzed in acute brain slices by electron microscopy, the reduction of membrane surface charge led to the loss of myelin compaction and rapid vesiculation. Together, these results establish that PIP2 is an essential determinant for stable membrane binding of MBP and provide a novel link between glial phosphoinositol metabolism and MBP function in development and disease.

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Received Aug. 19, 2008; revised Dec. 9, 2008; accepted Jan. 7, 2009.

Correspondence should be addressed to Dr. Klaus-Armin Nave, Department of Neurogenetics, Max Planck Institute of Experimental Medicine, Hermann-Rein-Strasse 3, D-37073 Göttingen, Germany. Email: nave{at}em.mpg.de

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