Biochemical and morphologic evidence of the interaction of oligodendrocyte membrane rafts with actin filaments.

Cytoskeletal structures under the cell membrane carry out pivotal roles in the maintenance and remodeling of the cell structures. Reforming of the cytoskeletal networks after partial extraction of membrane components could be a good clue to identify molecular components pertaining the interaction of cytoskeleton with membrane. A detergent extract from 3-week-old rat brain membrane fraction was found to make an actin-based gel upon incubation at 25 degrees C. Some protein components of the gelation products were recovered in a Triton-insoluble low-density microdomain fraction (raft) after depolymerization of actin filaments. Some of these proteins were identified as 2',3'-cyclic nucleotide-3'-phosphodiesterase (CNPase), proteolipid protein (PLP), and myelin oligodendrocyte glycoprotein (MOG) through electrospray time-of-flight (ESI-TOF) analysis and Western blotting. Because these proteins are well-known marker proteins of oligodendrocytes, localization of these proteins and cholesterol, a raft-localized lipid, with actin filaments was studied using cultured oligodendrocytes. Clear colocalization of these proteins and cholesterol with actin filaments was observed after Triton treatment at 4 degrees C before fixation. These results indicate that raft microdomains participate in the formation of cell shape through interaction with microfilaments in oligodendrocytes.