Myelin basic protein co-distributes with other PI(4,5)P2-sequestering proteins in Triton X-100 detergent-resistant membrane microdomains

The 18.5 kDa isoform of myelin basic protein (MBP) has recently been shown to sequester phosphatidylinositol-(4,5)-bis-phosphate (PI(4,5)P₂) in vesicular membranes in vitro, as do domains of other membrane- and cytoskeleton-associated proteins such as MARCKS (myristoylated alanine-rich C kinase substrate) and GAP-43 (growth-associated protein of 43 kDa), known collectively as “PI(4,5)P₂-modulins” [Musse et al., Biochemistry, 47 (2008) 10372–10382 (doi:10.1021/bi801302b)]. Here, we demonstrate co-localisation of MBP and MARCKS in primary rat oligodendrocytes, and co-distribution of MBP, MARCKS, and GAP-43 in lipid raft fractions recovered from Triton X-100 detergent-extracted isolated myelin and brain homogenates. The results lend further support to MBP's multifunctionality, particularly as an additional modulator of PI(4,5)P₂ availability in myelin.