Evidence for phosphatidylinositol 4-kinase and actin involvement in the regulation of ¹²⁵I-β-nerve growth factor retrograde axonal transport

The signaling events regulating the retrograde axonal transport of neurotrophins are poorly understood, but a role for phosphatidylinositol kinases has been proposed. In this study, we used phenylarsine oxide (PAO) to examine the participation of phosphatidylinositol 4-kinases in nerve growth factor (NGF) retrograde axonal transport within sympathetic and sensory neurons. The retrograde transport of ¹²⁵I-labeled βNGF was inhibited by PAO (0.5-2 nmol/eye), and this effect was diminished by dilution. Coinjection of 2,3-dimercaptopropanol with PAO reduced its ability to inhibit ¹²⁵I- βNGF retrograde transport. PAO (20 nM to 200 μM) also inhibited NGF- dependent survival of both sympathetic and sensory neuronal populations. F- actin staining in sympathetic and sensory neuronal growth cones was disrupted by PAO at 10 and 2 nM, respectively, and occurred within 5 min of exposure to the drug. The actin inhibitor latrunculin A also rapidly affected F-actin staining in vitro and reduced ¹²⁵I-βNGF retrograde axonal transport in vivo to the same extent as PAO. These results suggest that both phosphatidylinositol 4-kinase isoforms and the actin cytoskeleton play significant roles in the regulation of ¹²⁵I-βNGF retrograde axonal transport in vivo.