Interplay between phosphorylation and palmitoylation mediates plasma membrane targeting and sorting of GAP43.
Bottom Line: Plasma membrane association decreased the diffusion constant fourfold in neuritic shafts.Simulations confirmed that a combination of diffusion, dynamic plasma membrane interaction and active transport of a small fraction of GAP43 suffices for efficient sorting to growth cones.Our data demonstrate a complex interplay between phosphorylation and lipidation in mediating the localization of GAP43 in neuronal cells.
Affiliation: Department of Neurobiology, University of Osnabrück, 49076 Osnabrück, Germany.Show MeSH
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Mentions: Pharmacologic inhibition of transport indicated that a fraction of GAP43 is anterogradely transported. If true, a flux of GAP43 toward the tip of the process should be observed. To test this hypothesis, we photoactivated a population of GAP43 in the middle of the process and recorded changes in the fluorescence distal to and proximal from the center of activation (Figure 7A, top). Flux should then become evident by a ratio of distal/proximal fluorescence higher than one in the majority of the processes. Indeed, we observed increased distal/proximal ratios for GAP43wt, which became significant at 25 min (Figure 7A, middle). No flux was observed with the cytosolic control protein (3×PAGFP). Treatment with brefeldin A abolished distal flux, supporting a requirement for vesicle transport in trafficking of GAP43. Distal flux was also observed with the phosphoblocking GAP43 construct (GAP43S41A), supporting that phosphorylation-mediated membrane reaction is not required for transport of GAP43 (Figure 7A, bottom, right).
Affiliation: Department of Neurobiology, University of Osnabrück, 49076 Osnabrück, Germany.