Rab11 Promotes Docking and Fusion of Multivesicular Bodies in a Calcium‐Dependent Manner
Open Access
- 2 December 2004
- Vol. 6 (2), 131-143
- https://doi.org/10.1111/j.1600-0854.2004.00257.x
Abstract
Multivesicular bodies (MVBs) are membranous structures within 60–100 nm diameter vesicles accumulate. MVBs are generated after invagination and pinching off of the endosomal membrane in the lumen of the vacuole. In certain cell types, fusion of MVBs with the plasma membrane results in the release of the internal vesicles called exosomes. In this report we have examined how an increase in cytosolic calcium affects the development of MVBs and exosome release in K562 cells overexpressing GFP-Rab11 wt or its mutants. In cells overexpressing the Rab11Q70 L mutant or Rab11 wt, an increase in the cytosolic calcium concentration induced by monensin caused a marked enlargement of the MVBs. This effect was abrogated by the membrane permeant calcium chelator BAPTA-AM. We also examined the behavior of MVBs in living cells by time lapse confocal microscopy. Many MVBs, decorated by wt or Q70L mutant GFP-Rab11, were docked and ready to fuse in the presence of a calcium chelator. This observation suggests that Rab11 is acting in the tethering/docking of MVBs to promote homotypic fusion, but that the final fusion reaction requires the presence of calcium. Additionally, a rise in intracellular calcium concentration enhanced exosome secretion in Rab11 wt overexpressing cells and reversed the inhibition of the mutants. The results suggest that both Rab11 and calcium are involved in the homotypic fusion of MVBs.Keywords
This publication has 57 references indexed in Scilit:
- Membrane FusionCell, 2003
- Indirect activation of naïve CD4+ T cells by dendritic cell–derived exosomesNature Immunology, 2002
- Characteristics of the Interaction between Hsc70 and the Transferrin Receptor in Exosomes Released during Reticulocyte MaturationPublished by Elsevier BV ,2001
- Na+–Ca2+ exchange and its implications for calcium homeostasis in primary cultured rat brain microvascular endothelial cellsThe Journal of Physiology, 1999
- Rab11 Is Associated with Transferrin-Containing Recycling Compartments in K562 CellsBiochemical and Biophysical Research Communications, 1997
- B lymphocytes secrete antigen-presenting vesicles.The Journal of Experimental Medicine, 1996
- Rab GTPases: master regulators of membrane traffickingCurrent Opinion in Cell Biology, 1994
- Rab11, a small GTPase associated with both constitutive and regulated secretory pathways in PC12 cellsFEBS Letters, 1993
- The fate of the transferrin receptor during maturation of sheep reticulocytes in vitroCanadian Journal of Biochemistry and Cell Biology, 1984
- Receptor-mediated endocytosis of transferrin and recycling of the transferrin receptor in rat reticulocytes.The Journal of cell biology, 1983