Dolichyl phosphate: rapid increase and predominant form of brain dolichol compounds during early brain development

Of brain dolichol compounds, dolichyl phosphate is most critical since it serves as the carrier of saccharide moieties to be utilized for N-linked protein glycosylation. The objectives of the current study were to determine (1) whether the proportion of dolichyl phosphate to dolichol in brain is relatively large and/or changes with development, and (2) whether the subcellular distribution of these isoprenoid compounds differs and/or changes with development. A recently described, improved technique for isolation and quantitation of dolichyl phosphate was employed. The data show that in the first 4 weeks of postnatal life in the rat dolichyl phosphate is, in fact, the predominant form of total dolichol compounds in brain. Subsequently, concentrations of dolichol exceeded those of dolichyl phosphate in adult brain, particularly with aging. Dolichyl phosphate was found to be localized primarily in microsomes; dolichol was found in only small amounts in microsomes but was enriched in the fraction that contained lysosomes. The observations indicate that during early brain development, an active time period for differentiating events, many of which are mediated by glycoproteins, dolichyl phosphate is present in high concentration at the subcellular site of N-linked glycoprotein synthesis, i.e., endoplasmic reticulum.