The tetraspanin CD63/ lamp3 cycles between endocytic and secretory compartments in human endothelial cells.
In the present study, we show that in human endothelial cells the tetraspanin CD63/ lamp3 distributes predominantly to the internal membranes of multivesicular-multilamellar late endosomes, which contain the unique lipid lysobisphosphatidic acid. Some CD63/ lamp3 is also present in Weibel-Palade bodies, the characteristic secretory organelle of these cells. We find that CD63/ lamp3 molecules can be transported from late endosomes to Weibel-Palade bodies and thus that CD63/ lamp3 cycles between endocytic and biosynthetic compartments; however, movement of CD63/ lamp3 is much slower than that of P-selectin, which is known to cycle between plasma membrane and Weibel-Palade bodies. When cells are treated with U18666A, a drug that mimics the Niemann-Pick type C syndrome, both proteins accumulate in late endosomes and fail to reach Weibel-Palade bodies efficiently, suggesting that P-selectin, like CD63/ lamp3, cycles via late endosomes. Our data suggest that CD63/ lamp3 partitions preferentially within late endosome internal membranes, thus causing its accumulation, and that this mechanism contributes to CD63/ lamp3 retention in late endosomes; however, our data also indicate that the protein can eventually escape from these internal membranes and recycle toward Weibel-Palade bodies to be reused. Our observations thus uncover the existence of a selective trafficking route from late endosomes to Weibel-Palade bodies.[1]References
- The tetraspanin CD63/lamp3 cycles between endocytic and secretory compartments in human endothelial cells. Kobayashi, T., Vischer, U.M., Rosnoblet, C., Lebrand, C., Lindsay, M., Parton, R.G., Kruithof, E.K., Gruenberg, J. Mol. Biol. Cell (2000) [Pubmed]
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