Produção Nacional
Revisado por pares
ATP-induced P2X7-associated uptake of large molecules involves distinct mechanisms for cations and anions in macrophages
2008; The Company of Biologists; Volume: 121; Issue: 19 Linguagem: Inglês
10.1242/jcs.029991
ISSN1477-9137
AutoresJulieta Schachter, Andressa Piedade Motta, Aliane de Souza Zamorano, Hercules Antônio da Silva-Souza, Marília Zaluar P. Guimarães, Pedro M. Persechini,
Tópico(s)Mast cells and histamine
ResumoMacrophages 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.
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