Figure 3.
PI(4)P 5-Kinase α is downstream of ARNO/ARF6 during axonal elongation and branching. Morphometric analysis of the effect of expression of PI(4)P 5-kinase α on axonal outgrowth and branching. (a) Effect on total axonal length. Expression of PI(4)P 5-Kinase α alone resulted in no quantifiable effects upon axonal length compared with control, whereas coexpression of PI(4)P 5-Kinase α reversed the effect of expression of ARNO-E156K or ARF6-T27N upon axonal length. (b) Effect on the number of axonal branch points. Expression of PI(4)P 5-Kinase α resulted in no quantifiable effects upon the number of axonal branch points, and coexpression of PI(4)P 5-Kinase α reversed the effect of expression of ARNO-E156K or ARF6-T27N upon axonal branching. Data are presented as the means ± SD (n = 10). p < 0.0001 (****). (c and d) Hippocampal neurons transfected with PI(4)P 5-Kinase α (c) and ARNO-E156K and PI(4)P 5-Kinase α (d) were visualized by confocal microscopy. (c) Cell expressing PI(4)P 5-Kinase α. The axon (arrow) is short with very few collateral branches. (d) Cell expressing ARNO-E156K and PI(4)P 5-Kinase α. The axonal process (arrow) is short with fewer collateral branches compared with cells expressing ARNO-E156K (compare with Figure 1e). Bars, 25 μm (e–g).