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: Posttranslational modifications can dramatically change the function and interactions of cytosolic proteins and are likely to contribute to protein sorting. This is of particular importance for highly polarized cells such as neurons. An instructive example is GAP43, which is synthesized on free ribosomes in the neuronal cell body, is susceptible to phosphorylation and lipidation, and becomes highly enriched in the tips of extending neurites. To scrutinize how phosphorylation and lipidation mediate sorting of GAP43, we used a combination of biochemical, genetic, and imaging approaches. Our results are summarized in Figure 9 and demonstrate a complex interplay of phosphorylation and palmitoylation in plasma membrane targeting and sorting of GAP43. In particular, we showed that 1) phosphorylation at Ser-41 directs palmitoylated GAP43 to the plasma membrane, 2) plasma membrane association decreases diffusion of GAP43 in the cell body and neuritic shaft, and 3) S-palmitoylation tags GAP43 for global sorting by inducing piggybacking on exocytic vesicles. Furthermore, we showed that plasma membrane association exhibits an absolute requirement for palmitoylation and that palmitoylation-mediated sorting to the growth cone is increased by phosphorylation-mediated membrane reaction.
Affiliation: Department of Neurobiology, University of Osnabrück, 49076 Osnabrück, Germany.