Calcium Influx Through AMPA Receptors and Through Calcium Channels Is Regulated by Protein Kinase C in Cultured Retina Amacrine-Like Cells |
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Authors: | Ana Luísa Carvalho Carlos B Duarte Carlos J Faro Arsélio P Carvalho Euclides V Pires |
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Institution: | Center for Neuroscience of Coimbra, Departments of Biochemistry and; Zoology, University of Coimbra, Portugal |
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Abstract: | Abstract: The functional modulation of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors by protein kinase C (PKC) was investigated in cultures enriched in retinal amacrine-like cells. The kainate-evoked Ca2+]i increase is due to Ca2+ entry through open AMPA receptor channels, because it was blocked by the active isomer of a 2,3-benzodiazepine (LY 303070), an AMPA receptor antagonist. The AMPA receptor response to kainate was potentiated by phorbol 12-myristate 13-acetate, which specifically stimulates PKC, and it was decreased by bisindolylmaleimide I, a selective inhibitor of PKC, as well as by PKC down-regulation. The results indicate not only that the AMPA receptor activation has a PKC requirement, but also that PKC amplifies maximal receptor activation by 100 µ M kainate. The effect of PKC activation or inhibition on voltage-gated Ca2+-channel activity was also investigated. Activation of PKC caused inhibition of Ca2+ channels, and the same effect was produced by inhibition of PKC, whereas the inactive analogue of the phorbol ester did not affect channel activity. Our results show an important role for PKC in regulating the function of both AMPA receptors and Ca2+ channels in cultured retina cells. |
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Keywords: | Protein kinase C AMPA receptors Calcium channels Retina Amacrine cells |
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