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Protein kinase C enhances glycine‐insensitive desensitization of NMDA receptors independently of previously identified protein kinase C sites
Author(s) -
Jackson Michael F.,
Konarski Jakub Z.,
Weerapura Manjula,
Czerwinski Waldemar,
MacDonald John F.
Publication year - 2006
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2006.03651.x
Subject(s) - protein kinase c , desensitization (medicine) , nmda receptor , homologous desensitization , protein subunit , receptor , microbiology and biotechnology , biology , agonist , kinase , protein kinase a , phorbol , chemistry , biochemistry , gene
Protein kinase C (PKC) phosphorylates the NR1 and NR2A subunits of NMDARs at consensus sites located within their intracellular C‐terminal tails. However, the functional consequences of these biochemical events are not well understood. In HEK293 cells expressing NR1/NR2A, activation of endogenous PKC by 4β‐phorbol 12‐myristate 13‐acetate (PMA) increased NMDAR desensitization as evidenced by a reduced steady‐state current without any change in peak. The effects of PMA on NMDAR‐mediated responses were prevented by specific PKC inhibitors and were not mimicked by an inactive enantiomer of PMA. The effects of PMA were preserved despite mutagenesis of the major PKC sites on the NR1 subunit (S889A, S890A, S896A and S897A) or removal of the entire NR1 C‐terminal tail (NR1 stop838 ). When co‐expressing NR1 stop838 /NR2A the effects of PMA could only be observed with agonist concentrations sufficient to induce glycine‐insensitive desensitization. Moreover, the effects of PMA were observed in receptors composed of NR1/NR2A and NR1/NR2B, but not NR1/NR2C, a subunit combination in which desensitization is absent. The NR2 subunit dependence suggested that the actions of PMA might require specific PKC sites previously identified within NR2A. However, a C‐terminal truncated form of NR2A (NR2A stop905 ) remained responsive to PMA. We conclude that activation of PKC increases NMDAR glycine‐insensitive desensitization independently of previously identified sites located within the NR1 C‐terminus and distal segment of the NR2A C‐terminus.