The Presence of Aldehyde‐Reacted Proteins in Normal and Multiple Sclerosis White Matter

Abstract

The incorporation of tritium from NaB3H4 into the major protein components of myelin and the presence of weak fluorescence emission bands at wavelengths of approximately 440 and 500 nm from sodium dodecyl sulfate-solubilized, delipidated white matter are indicative of the presence of the products of aldehyde reactions with proteins. The incorporation of tritium from NaB3H4 into myelin proteins was confirmed by reaction with purified components of myelin basic protein or with lipophilin, a purified fraction of proteolipid protein. From the extent of tritium incorporation into the purified proteins, it is estimated that approximately 0.2 mol of tritium is incorporated/mol of myelin basic protein and approximately 0.4 mol of tritium/mol of proteolipid protein. There is approximately 50% greater incorporation of tritium into a more degraded, less positively charged form of the basic protein. The incorporation of tritium into normal and multiple sclerosis white matter was compared. There is a small but statistically significant difference in the percentage of the total counts incorporated into the major protein fractions for the two groups, with the multiple sclerosis samples showing a higher percentage of the counts in the Wolfgram protein and a lower percentage in the myelin basic protein compared with the normal samples.

Topology of CNS Myelin Proteolipid Protein: Evidence for the Nonenzymic Glycosylation of Extracytoplasmic Domains in Normal and Diabetic Animals

“…Presence of Borohydride-Reducible Groups in PLP. Vlassara et al (1983) and Epand et al (1985) found evidence for the presence of aldehyde-reacted proteins in the central nervous system myelin. In both studies the incorporation of radioactivity into myelin proteins after treatment with (2 3H)NaBH4 was observed.…”

“…Vlassara et al (1983) demonstrated that glycosylated lysine residues and their rearrangement products are the major borohydride-reducible adducts present in total myelin proteins and that their amount increases in diabetic rats. Epand et al (1985) speculated that unsaturated fatty acids which are linked to PLP could also be reduced by (3H)NaBH4. To discriminate between these possibilities, we incubated myelin proteins, radioactively labeled with (3H)NaBH4 as above, under denaturating conditions (2% SDS, 6 M urea) with 0.4 M hydroxylamine, pH 7.4, and 50 mM dithiothreitol for 2 h at 37 °C to cleave the thioester-linked fatty acids completely (Weimbs & Stoffel, 1993).…”