title: Stable membrane expression of postsynaptic CaV1.2 calcium channel clusters is independent of interactions with AKAP79/150 and PDZ proteins.
abstract: In neurons L-type calcium currents contribute to synaptic plasticity and to activity-dependent gene regulation. The subcellular localization of Ca(V)1.2 and its association with upstream and downstream signaling proteins is important for efficient and specific signal transduction. Here we tested the hypothesis that A-kinase anchoring proteins (AKAPs) or PDZ-proteins are responsible for the targeting and anchoring of Ca(V)1.2 in the postsynaptic compartment of glutamatergic neurons. Double-immunofluorescence labeling of hippocampal neurons transfected with external HA epitope-tagged Ca(V)1.2 demonstrated that clusters of membrane-incorporated Ca(V)1.2-HA were colocalized with AKAP79/150 but not with PSD-95 in the spines and shafts of dendrites. To disrupt the interactions with these scaffold proteins, we mutated known binding sequences for AKAP79/150 and PDZ proteins in the C terminus of Ca(V)1.2-HA. Unexpectedly, the distribution pattern, the density, and the fluorescence intensity of clusters were similar for wild-type and mutant Ca(V)1.2-HA, indicating that interactions with AKAP and PDZ proteins are not essential for the correct targeting of Ca(V)1.2. In agreement, brief treatment with NMDA (a chemical LTD paradigm) caused the degradation of PSD-95 and the redistribution of AKAP79/150 and alpha-actinin from dendritic spines into the shaft, without a concurrent loss or redistribution of Ca(V)1.2-HA clusters. Thus, in the postsynaptic compartment of hippocampal neurons Ca(V)1.2 calcium channels form signaling complexes apart from those of glutamate receptors and PSD-95. Their number and distribution in dendritic spines is not altered upon NMDA-induced disruption of the glutamate receptor signaling complex, and targeting and anchoring of Ca(V)1.2 is independent of its interactions with AKAP79/150 and PDZ proteins.
authors.affiliation: Department of Physiology and Medical Physics, Innsbruck Medical University, A-6020 Innsbruck, Austria.
authors.forename: Valentina
authors.initials: V
authors.lastname: Di Biase
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Obermair
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Szabo
authors.forename: Christophe
authors.initials: C
authors.lastname: Altier
authors.forename: Juan
authors.initials: J
authors.lastname: Sanguesa
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Bourinet
authors.forename: Bernhard E
authors.initials: BE
authors.lastname: Flucher
mesh_terms: D054758:A Kinase Anchor Proteins / Q000378:metabolism*; D000185:Actinin / Q000378:metabolism; D000818:Animals; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D049229:Dendritic Spines / Q000187:drug effects / Q000378:metabolism*; D000076122:Disks Large Homolog 4 Protein; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D015870:Gene Expression; D049452:Green Fluorescent Proteins / Q000235:genetics; D051528:Guanylate Kinases; D006624:Hippocampus / Q000166:cytology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D046912:Multiprotein Complexes / Q000378:metabolism / Q000648:ultrastructure; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D054731:PDZ Domains / Q000502:physiology; D010316:Particle Size; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection
chemical_list: D054758:A Kinase Anchor Proteins; C520665:Akap5 protein, mouse; C514350:CACNA1C protein, mouse; D020746:Calcium Channels, L-Type; D000076122:Disks Large Homolog 4 Protein; C501447:Dlg4 protein, mouse; D018690:Excitatory Amino Acid Agonists; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D011993:Recombinant Fusion Proteins; D000185:Actinin; D049452:Green Fluorescent Proteins; D016202:N-Methylaspartate; D051528:Guanylate Kinases