|
||

* Department of Cell Biology, Lysosomes are considered to be a terminal
degradative compartment of the endocytic pathway,
into which transport is mostly unidirectional. However,
specialized secretory vesicles regulated by Ca2+, such as
neutrophil azurophil granules, mast cell-specific granules, and cytotoxic lymphocyte lytic granules, share
characteristics with lysosomes that may reflect a common biogenesis. In addition, the involvement of Ca2+
transients in the invasion mechanism of the parasite
Trypanosoma cruzi, which occurs by fusion of lysosomes with the plasma membrane, suggested that lysosome exocytosis might be a generalized process present
in most cell types.
Here we demonstrate that elevation in the intracellular free Ca2+ concentration of normal rat kidney
(NRK) fibroblasts induces fusion of lysosomes with the
plasma membrane. This was verified by measuring the
release of the lysosomal enzyme These findings highlight a novel role for lysosomes in
cellular membrane traffic and suggest that fusion of lysosomes with the plasma membrane may be an ubiquitous form of Ca2+-regulated exocytosis.
Department of Ophthalmology, Yale University School of Medicine, New Haven,
Connecticut 06520
-hexosaminidase, the
appearance on the plasma membrane of the lysosomal
glycoprotein lgp120, the release of fluid-phase tracers
previously loaded into lysosomes, and the release of the
lysosomally processed form of cathepsin D. Exposure
to the Ca2+ ionophore ionomycin or addition of Ca2+containing buffers to streptolysin O-permeabilized
cells induced exocytosis of ~10% of the total lysosomes
of NRK cells. The process was also detected in other
cell types such as epithelial cells and myoblasts. Lysosomal exocytosis was found to require micromolar levels of Ca2+ and to be temperature and ATP dependent,
similar to Ca2+-regulated secretory mechanisms in specialized cells.
This article has been cited by other articles:
|
|