Inhibitory interactions between phosphorylation sites in the C terminus of α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptor GluA1 subunits.
The C terminus of AMPA-type glutamate receptor (AMPAR) GluA1 subunits contains several phosphorylation sites that regulate AMPAR activity and trafficking at excitatory synapses. Although many of these sites have been extensively studied, little is known about the signaling mechanisms regulating GluA1 phosphorylation at Thr-840. Here, we report that neuronal depolarization in hippocampal slices induces a calcium and protein phosphatase 1/2A-dependent dephosphorylation of GluA1 at Thr-840 and a nearby site at Ser-845. Despite these similarities, inhibitors of NMDA-type glutamate receptors and protein phosphatase 2B prevented depolarization-induced Ser-845 dephosphorylation but had no effect on Thr-840 dephosphorylation. Instead, depolarization-induced Thr-840 dephosphorylation was prevented by blocking voltage-gated calcium channels, indicating that distinct Ca(2+) sources converge to regulate GluA1 dephosphorylation at Thr-840 and Ser-845 in separable ways. Results from immunoprecipitation/depletion assays indicate that Thr-840 phosphorylation inhibits protein kinase A (PKA)-mediated increases in Ser-845 phosphorylation. Consistent with this, PKA-mediated increases in AMPAR currents, which are dependent on Ser-845 phosphorylation, were inhibited in HEK-293 cells expressing a Thr-840 phosphomimetic version of GluA1. Conversely, mimicking Ser-845 phosphorylation inhibited protein kinase C phosphorylation of Thr-840 in vitro, and PKA activation inhibited Thr-840 phosphorylation in hippocampal slices. Together, the regulation of Thr-840 and Ser-845 phosphorylation by distinct sources of Ca(2+) influx and the presence of inhibitory interactions between these sites highlight a novel mechanism for conditional regulation of AMPAR phosphorylation and function.
From the Department of Physiology and Interdepartmental Ph.D. Program for Neuroscience at UCLA, and.
Erin E
EE
Gray
From the Department of Physiology and Interdepartmental Ph.D. Program for Neuroscience at UCLA, and.
Ryan
R
Guglietta
From the Department of Physiology and Department of Neurobiology, David Geffen School of Medicine at UCLA.
Baljit S
BS
Khakh
From the Department of Physiology and UCLA Integrative Center for Learning and Memory, Los Angeles, California 90095 todell@mednet.ucla.edu.
Thomas J
TJ
O'Dell
D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D057809:HEK293 Cells; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D006801:Humans; D008297:Male; D008387:Marine Toxins; D008564:Membrane Potentials / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000378:metabolism*; D019319:Okadaic Acid / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism; D054645:Protein Phosphatase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D018091:Receptors, AMPA / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000378:metabolism*; D013912:Threonine / Q000378:metabolism*
D015220:Calcium Channels; D008387:Marine Toxins; D010080:Oxazoles; D021122:Protein Subunits; D018091:Receptors, AMPA; D019319:Okadaic Acid; D013912:Threonine; D012694:Serine; C059041:calyculin A; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D002118:Calcium
AMPA Receptor; GluA1 Subunits; Glutamate Receptors Ionotropic (AMPA, NMDA); Hippocampus; Protein Kinases; Protein Phosphatase; Protein Phosphorylation; Synaptic Plasticity