No abstract

One of the main targets of pp60v-src tyrosine kinase is a 34 to 39-kilodalton protein of chicken embryo fibroblasts called p36 or calpactin I. We have previously reported an association of the cytoplasmic fraction of p36 (10-20% of the total cellular p36) with three chicken polypeptides named p32, p48, and p54. We have now raised and affinity-purified antibodies against each of these proteins. This has allowed their identification: p32 is lactate dehydrogenase, p48 is enolase, and p54 is phosphoglucose isomerase. An association between p36 and two other known substrates of pp60v-src, the glycolytic enzymes enolase and lactate dehydrogenase, suggests a cellular organization of the various targets of the oncogene tyrosine kinases. Furthermore, a possible relationship between p36 and glycolysis is questioned.

The uptake of radioactive ethanolamine has been studied in exclusively neuronal and glial cell cultures from dissociated cerebral hemispheres of chick embryos. Both cell types show saturable kinetics; neurons have an apparent Km of 6.7 microM, Vmax 41.4 pmol mg prot.-1 min-1 and glial cells a Km of 119.6 microM, Vmax 3,917 pmol mg prot-1 min-1. The lower affinity of the transport and the 100 fold increase in Vmax observed in glial cells correlated with a more important accumulation of free ethanolamine found in glial cells and with a higher degree of phosphorylation of ethanolamine. The uptake appeared to be temperature and Na+ ions dependent but was not affected by CN- or ouabain. Monomethyl-, dimethylethanolamine and choline were effective in inhibiting the uptake. Little or no effect was observed with serine, methionine, carnitine, alanine or glutamate.

No abstract

Fetal rat brain aggregating cell cultures were exposed to varying concentrations of [3H]monomethylethanolamine (MME) and [3H] dimethylethanolamine (DME). The rate of labeling of water-soluble compounds was more rapid and the amount of radioactivity present was greater than in the lipids. After a 72 hour incubation in the presence of millimolar concentrations of these nitrogenous bases, the major water-soluble products were the phosphorylated form of the bases. Little label was associated with the free bases or their cytidyl derivative. In the phospholipids, 97% of the radioactivity was recovered in phosphatidylmonomethylethanolamine (PMME) and 3% in phosphatidyldimethylethanolamine (PDME) or 95% in PDME and 5% in phosphatidylcholine (PC) after growth in presence of [3H]MME and [3H]DME respectively. The rate of formation of the radioactive products increased as function of the concentration of the nitrogenous base added up to 4 mM, the highest concentration employed. There was no significant difference in the pattern of labeling with cells grown in media devoid of methionine or choline. The turnover of the water-soluble metabolites was more rapid than in the phospholipids where an apparent half-life of 24 hours was calculated.