Variability in Membrane Continuity Between Schwann Cells and Neurons

Abstract

Both Schwann cells (SCs) and neurons dynamically expand and contract their plasma membrane during their extension of projections and movement. However, these cell types have very different motility profiles and physiological function. We developed methods to measure the correlated movement of regions of plasma membrane, based on quantitative analysis of the movement of fluorescently labeled wheat-germ agglutinin (WGA) bound to the extracellular membrane. WGA trajectories were compared between SCs and neurons isolated from neonatal SpragueDawley rats, using both cross-correlation and regression analysis. Schwann cellular membranes exhibited significantly higher correlation (42.37 ± 5.87%, mean ± SEM) compared to neurons (24.51 ± 3.52%). Additionally, Schwann cellular membranes were more mobile (À0.165 ± 0.099 lm/min average velocity) compared to neurons (0.052 ± 0.032 lm/s). Comparison of both cell types upon establishment of contact with another neuron failed to identify any difference with the non-contacting state. Our results are suggestive of a role for forces generated by mobility on the biomechanical continuity of plasma membrane. Such forces are likely to interact with factors, including the cytoskeletal framework and adhesion proteins. This work has implications for interactions of neurons and SCs during development and neuronal regeneration.

Ribosomal trafficking is reduced in Schwann cells following induction of myelination

“…Structurally, neuronal contact alters the nucleation, polarity, and distribution of microtubules within myelinating Schwann cells (Kidd et al, 1994 ). In addition, consistent with reduced cellular extension and crawling during neuronal interactions, mobility of Schwann cell membranes and their associated cytoskeleton is reduced and adhesion is enhanced (Feltri et al, 1994 ; Nobes and Hall, 1999 ; Love et al, 2012 ). Alternatively, cell morphological changes may reflect a redistribution or change in the stability of microtubules, which may result from Schwann cell differentiation and maturation.…”

“…The summation of net velocity for each individual L4-GFP particle within a given movie offers a summary of directionality and extent of movement within a cell during our imaging period. Normalization of this displacement to the imaging duration yields net velocity, which enables comparison with bulk transport rates captured over a longer time frame (Love et al, 2012 ; Pathak et al, 2013 ). There are significant differences in net velocity of ribosomes over the course of Schwann cell development ( p = 0.0038, One-Way ANOVA, Figure 6A ).…”

“…Immunocytochemistry was performed at various developmental time points, using published protocols (Love et al, 2012 ). Samples were labeled with one or a combination of the following primary antibodies: mouse anti-S100 (Sigma-Aldrich S2532), mouse anti-SMI31 (abcam ab24573), mouse anti-MBP, human anti-Ribo-P (Immunovision HPO-0100), mouse anti-RPL4 (Sigma-Aldrich WH0006124M1), mouse anti-tubulin (Sigma-Aldrich T9026).…”

“…Custom Matlab (Mathworks, Inc.) programs were modified from previous studies (Chetta and Shah, 2011 ; Love et al, 2012 ) to convert time course images into a kymograph. Kymographs allow for visualization of changes in an intensity profile of a 1-dimensional trace over time with the time variable displayed along the y-axis and cellular position along the x-axis.…”

Combinatorial influences of paclitaxel and strain on axonal transport

“…Movies of axonal transport were then assembled with frames taken every 5 seconds for 5 minutes for mitochondria and actin-GFP transport, and every 5 seconds for 90 seconds for synaptophysin-RFP transport. Kymographs were generated from movies using a custom MATLAB script to allow for visualization of mobile and stationary tracks and computation of velocity, movement time, and distance travelled (procedure adopted with modifications from 26 ). All transport related parameters were calculated over the entire duration of each movie.…”