Dimensions and ion selectivity of recombinant AMPA and kainate receptor channels and their dependence on Q/R site residues.
AUTOR(ES)
Burnashev, N
RESUMO
1. Recombinant alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor (AMPAR) subunits (GluR-A or GluR-B) and kainate receptor (KAR) subunit (GluR-6) in their unedited (Q)- and edited (R)-forms were expressed in HEK 293 cells. To estimate the dimensions of the narrow portion of these channels, biionic reversal potentials for organic cations of different mean diameters were determined with Cs+ as the internal reference ion. 2. Homomeric channels assembled from Q-form subunits were cation selective. The relation between the relative permeability and the mean size of different organic cations suggests that the diameter of the narrow portion of Q-form channels is approximately 0.78 nm for AMPAR and 0.75 nm for KAR channels. 3. Homomeric channels assembled from R-form subunits were permeant for anions and cations. When probed with CsC1 gradients the relative chloride permeability (PC1/PCs) was estimated as 0.14 for GluR-B(R) and 0.74 for GluR-6(R)-subunit channels. The permeability versus mean size relation for large cations measured with the weakly permeant F- as anion, indicates that for the R-form KAR channels the apparent pore diameter is close to 0.76 nm. 4. Heteromeric AMPAR and KAR channels co-assembled from Q- and R-form subunits were cation selective. The diameter of the narrow portion of these channels is estimated to be in the range between 0.70 and 0.74 nm. 5. The results indicated that the diameters of the narrow portion of AMPAR and KAR channels of different subunit composition and of widely different ion selectivity are comparable. Therefore, the differences in the anion versus cation selectivity, in Ca2+ permeability and in channel conductance are likely to be determined by the difference in charge density of the channel.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1160833Documentos Relacionados
- Q/R site editing in kainate receptor GluR5 and GluR6 pre-mRNAs requires distant intronic sequences.
- The AMPA receptor subunit GluR-B in its Q/R site-unedited form is not essential for brain development and function
- Fractional calcium currents through recombinant GluR channels of the NMDA, AMPA and kainate receptor subtypes.
- Block of open channels of recombinant AMPA receptors and native AMPA/kainate receptors by adamantane derivatives.
- Calcium influx through subunits GluR1/GluR3 of kainate/AMPA receptor channels is regulated by cAMP dependent protein kinase.