In:
Journal of Cell Science, The Company of Biologists, Vol. 121, No. 19 ( 2008-10-01), p. 3261-3270
Abstract:
Macrophages express the P2X7 receptor and other nucleotide (P2) receptors, and display the phenomenon of extracellular ATP (ATPe)-induced P2X7-dependent membrane permeabilization, which occurs through a poorly understood mechanism. We used patch-clamp recordings, cytoplasmic Ca2+ measurements and fluorescent dye uptake assays to compare P2X7-associated transport phenomena of macrophages and HEK-293 cells transfected with P2X7 receptors (HEK-P2X7 cells). Both cell types showed inward currents, increase of free cytoplasmic Ca2+ concentration and the uptake of cationic dyes upon exposure to ATPe, as previously described. However, in contrast to the macrophages, HEK-P2X7 cells did not take up anionic dyes and did not display the 440 pS channels (Z pores) under cell-attached patch-clamping conditions. In addition, the transport mechanism of anionic dyes displayed by macrophages was also able to support dye efflux and, once activated at 37°C, it remained active at 4°C, whereas uptake of cationic dyes was temperature-dependent and unidirectional. Our results indicate that the mechanism of ATPe-induced dye uptake, usually called a `permeabilization phenomenon' and associated with a `permeabilization pore' can be ascribed to at least two distinct mechanisms in macrophages: a diffusional pathway, possibly associated with the 440 pS Z pores, and a cation uptake mechanism that is not diffusional and should be ascribed to an, as yet, unidentified transport mechanism.
Type of Medium:
Online Resource
ISSN:
1477-9137
,
0021-9533
Language:
English
Publisher:
The Company of Biologists
Publication Date:
2008
detail.hit.zdb_id:
219171-4
detail.hit.zdb_id:
1483099-1
SSG:
12
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