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[摘要]：GAP-43 (growth-associated protein-43) is it dually palmitoylated protein, at cysteine residues at positions 3 and 4, that mostly localizes in plasma membrane both in neural and non-neural cells. In the present study, we have examined membrane association., subcellular distribution and intracellular trafficking of GAP-43 in CHO (Chinese hamster ovary)-K1 cells. Using biochemical assays and confocal and video microscopy in living cells we demonstrated that GAP-43, at steady state, localizes at the recycling endosome in addition to the cytoplasmic leaflet of the plasma membrane and TGN (trans-Golgi network). Pharmacological inhibition of newly synthesized GAP-43 acylation or double mutation of Cys(3) and Cys(4) of GAP-43 completely disrupts TGN, plasma membrane and recycling endosome association. A combination of selective photobleaching techniques and time-lapse fluorescence microscopy reveals a dynamic association of GAP-43 with recycling endosomes in equilibrium with the plasma membrane pool. Newly synthesized GAP-43 is found mainly associated with the TGN, but not with the pericentriolar recycling endosome, and traffics to the plasma membrane by a brefeldin A-insensitive pathway. Impairment of plasma membrane fusion and internalization by treatment with tannic acid (foes affect the trafficking of GAP-43 from plasma membrane to recycling endosomes which reveals a vesicle-mediated retrograde trafficking of GAP-43. Here, we also show that internalization of GAP-43 is regulated by Arf (ADP-ribosylation factor) 6. Taken together. these results demonstrate that dual acylation is required for sorting of peripheral membrane-associated GAP-43 to recycling endosome via in Arf6-associated endocytic vesicular pathway. |
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