Figure 4.
PI4KIIα accounts for the great majority of the PI 4-kinase activity present on synaptic vesicles. (A) CPG leading to a highly purified synaptic vesicle fraction (30). (Upper) Protein content (A280 readings) and the PI kinase activity (TLC analysis) of the fractions in arbitrary units. (Lower) Levels of PI4KIIα and synaptophysin in the same fractions (Western blotting). (B) Synaptic vesicle-containing fractions were pooled, solubilized in Triton X-100 (SM, starting material), and subjected to immunoprecipitation with anti-PI4KIIα Abs or control IgGs. (Upper) Depletion of PI4KIIα, but not of the control protein synaptophysin, from the extract as revealed by Western blotting. (Lower) Drastic decrease in PI kinase activity in the PI4KIIα-depleted extract. X denotes an unidentified spot.