Myelin Proteomics: Molecular Anatomy of an Insulating Sheath

Fast-transmitting vertebrate axons are electrically insulated with multiple layers of nonconductive plasma membrane of glial cell origin, termed myelin. The myelin membrane is dominated by lipids, and its protein composition has historically been viewed to be of very low complexity. In this review, we discuss an updated reference compendium of 342 proteins associated with central nervous system myelin that represents a valuable resource for analyzing myelin biogenesis and white matter homeostasis. Cataloging the myelin proteome has been made possible by technical advances in the separation and mass spectrometric detection of proteins, also referred to as proteomics. This led to the identification of a large number of novel myelin-associated proteins, many of which represent low abundant components involved in catalytic activities, the cytoskeleton, vesicular trafficking, or cell adhesion. By mass spectrometry-based quantification, proteolipid protein and myelin basic protein constitute 17% and 8% of total myelin protein, respectively, suggesting that their abundance was previously overestimated. As the biochemical profile of myelin-associated proteins is highly reproducible, differential proteome analyses can be applied to material isolated from patients or animal models of myelin-related diseases such as multiple sclerosis and leukodystrophies

Salt-dependent compaction of di- and trinucleosomes studied by small-angle neutron scattering.

Using small-angle neutron scattering (SANS), we have measured the salt-dependent static structure factor of di- and trinucleosomes from chicken erythrocytes and from COS-7 cells. We also determined the sedimentation coefficients of these dinucleosomes and dinucleosomes reconstituted on a 416-bp DNA containing two nucleosome positioning sequences of the 5S rDNA of Lytechinus variegatus at low and high salt concentrations. The internucleosomal distance d was calculated by simulation as well as Fourier back-transformation of the SANS curves and by hydrodynamic simulation of sedimentation coefficients. Nucleosome dimers from chicken erythrocyte chromatin show a decrease in d from approximately 220 A at 5 mM NaCl to 150 A at 100 mM NaCl. For dinucleosomes from COS-7 chromatin, d decreases from 180 A at 5 mM to 140 A at 100 mM NaCl concentration. Our measurements on trinucleosomes are compatible with a compaction through two different mechanisms, depending on the salt concentration. Between 0 and 20 mM NaCl, the internucleosomal distance between adjacent nucleosomes remains constant, whereas the angle of the DNA strands entering and leaving the central nucleosome decreases. Above 20 mM NaCl, the adjacent nucleosomes approach each other, similar to the compaction of dinucleosomes. The internucleosomal distance of 140-150 A at 100 mM NaCl is in agreement with distances measured by scanning force microscopy and electron microscopy on long chromatin filaments

Temporal profile of matrix metalloproteinases and their inhibitors in a human endothelial cell culture model of cerebral ischemia.

The objective of our study was to determine the contribution of human BMECs to the MMP metabolism under in vitro OGD conditions simulating ischemic stroke. Our results suggest that human BMECs switch to a proinflammatory state by means of an enhanced production of MMP-2, attenuated release of TIMP-1, and unaffected production of TIMP-2. Thus, human BMECs might participate in the MMP-mediated BBB breakdown during ischemic stroke. However, our data does not support human BMECs to be a source of MMP-9