Involvement of membrane skeletal molecules in the Schmidt-Lanterman incisure in Schwann cells.

Membrane skeletal networks form a two-dimensional lattice structure beneath erythrocyte membranes. 4.1R-MPP (membrane palmitoylated protein) 1-glycophorin C is one of the basic molecular complexes of the membrane skeleton. An analogous molecular complex, 4.1G-MPP6-cell adhesion molecule 4 (CADM4), is incorporated into the Schmidt-Lanterman incisure (SLI), a truncated cone shape in the myelin internode that is a specific feature of myelinated nerve fibers formed in Schwann cells in the peripheral nervous system. In this review, the dynamic structure of peripheral nerve fibers under stretching conditions is demonstrated using in vivo cryotechnique. The structures of nerve fibers had a beaded appearance, and the heights of SLI circular-truncated cones increased at the narrow sites of nerve fibers under the stretched condition. The height of SLI-truncated cones was lower in 4.1G-deficient nerve fibers than in wild-type nerve fibers. 4.1G was essential for the molecular targeting of MPP6 and CADM4 in SLI. The signal transduction protein, Src, was also involved in the 4.1G-MPP6-CADM4 molecular complex. The phosphorylation of Src was altered by the deletion of 4.1G. Thus, we herein demonstrate a membrane skeletal molecular complex in SLI that has potential roles in the regulation of adhesion and signal transduction as well as in structural stability in Schwann cells.