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: To determine whether phosphorylation of GAP43 at Ser-41 is sufficient to induce plasma membrane association, we created a palmitoylation-deficient GAP43 construct by mutating the two cysteine residues at positions 3 and 4 to serine (GAP43C3,4S; Liu et al., 1994) and also as a combination with the two phosphomutations at Ser-41. None of the three constructs showed detectable enrichment at the cell periphery in living cells (Figure 3A, left). Quantification by densitometric analysis confirmed the absence of peripheral enrichment (Figure 3A, right), indicating an absolute requirement for palmitoylation for plasma membrane association. The fact that all palmitoylation-deficient GAP43 constructs exhibited a significant lower peripheral enrichment than the respective palmitoylatable counterparts indicates that palmitoylation alone mediates some, albeit apparently weak, association with the plasma membrane, which is increased after phosphorylation. This is also detectable in the images of the single focal plane of the respective nonphosphorylatable but palmitoylatable GAP43S41A-expressing cells (e.g., arrows in Figure 2A).
Affiliation: Department of Neurobiology, University of Osnabrück, 49076 Osnabrück, Germany.