Regulation of N-methyl-D-aspartate receptor function by constitutively active protein kinase C.
The ability of the constitutively active fragment of protein kinase C (PKM) to modulate N-methyl-D-aspartate (NMDA)-activated currents in cultured mouse hippocampal neurons and acutely isolated CA1 hippocampal neurons from postnatal rats was studied using patch-clamp techniques. The responses of two heterodimeric combinations of recombinant NMDA receptors (NR1a/NR2A and NR1a/NR2B) expressed in human embryonic kidney 293 cells were also examined. Intracellular applications of PKM potentiated NMDA-evoked currents in cultured and isolated CA1 hippocampal neurons. This potentiation was observed in the absence or presence of extracellular Ca2+ and was prevented by the coapplication of the inhibitory peptide protein kinase inhibitor(19-36). Furthermore, the PKM-induced potentiation was not a consequence of a reduction in the sensitivity of the currents to voltage-dependent blockade by extracellular Mg2+. We also found different sensitivities of the responses of recombinant NMDA receptors to the intracellular application of PKM. Some potentiation was observed with the NR1a/NR2A subunits, but none was observed with the NR1a/NR2B combination. Applications of PKM to inside-out patches taken from cultured neurons increased the probability of channel opening without changing single-channel current amplitudes or channel open times. Thus, the activation of protein kinase C is associated with potentiation of NMDA receptor function in hippocampal neurons largely through an increase in the probability of channel opening.
Xiong
Z G
ZG
Department of Physiology and Pharmacology, University of Toronto, Toronto, Ontario, Canada, M5S 1A8.
Raouf
R
R
Lu
W Y
WY
Wang
L Y
LY
Orser
B A
BA
Dudek
E M
EM
Browning
M D
MD
MacDonald
J F
JF
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005071:Evoked Potentials; D006624:Hippocampus / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*; D006801:Humans; D008274:Magnesium / Q000378:metabolism; D051379:Mice; D016202:N-Methylaspartate; D009474:Neurons / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D017966:Pyramidal Cells / Q000378:metabolism; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000737:chemistry / Q000378:metabolism*
D004791:Enzyme Inhibitors; D010455:Peptides; D016194:Receptors, N-Methyl-D-Aspartate; C061479:protein kinase inhibitor peptide; D016202:N-Methylaspartate; D011493:Protein Kinase C; D008274:Magnesium; D002118:Calcium