Ribosomal S6 kinase 2 interacts with and phosphorylates PDZ domain-containing proteins and regulates AMPA receptor transmission

Abstract

These results suggest that binding of RSK2 to PDZ domain proteins and phosphorylation of these proteins or their binding partners regulates excitatory synaptic transmission. extracellular signal-regulated kinase ͉ glutamate receptors ͉ RAS ͉ synaptic plasticity S everal forms of synaptic plasticity, including hippocampal long-term potentiation (a cellular model of learning and memory) require signaling through extracellular signalregulated kinase (ERK) (1-4). ERK signaling also regulates two cellular processes closely associated with plasticity: synaptic delivery of AMPA-type glutamate receptors (AMPA-Rs) (3), and activity-dependent dendritic spine modifications (5, 6).ERK phosphorylates and activates the p90 ribosomal S6 kinase (RSK) family of protein kinases in vitro (7,8) and in vivo (9, 10). Of the four mammalian RSK isoforms, RSK1-RSK4 (11-13), RSK2 and RSK3 are prominent in brain regions, such as cortex and hippocampus, which are important for learning and memory (14). In humans, RSK2 gene mutations cause CoffinLowry syndrome, a condition characterized by psychomotor retardation (15), whereas RSK2 knockout mice perform poorly in a watermaze spatial learning task and display poor coordination (16). These findings suggest that RSK2 is required for correct neuronal development and͞or function and that other RSKs cannot compensate for the loss of RSK2.Interactions with specific binding partners target many protein kinases to precise cellular locations. In neurons, kinase targeting of this type may control phosphorylation-dependent synapsespecific modifications that in turn underlie many forms of synaptic plasticity (17,18). Scaffold proteins for elements of the ERK cascade have been described (19,20), but it is unclear whether and how ERK signaling is targeted to subcellular regions, such as synapses in neurons.Here we report that RSKs contain C-terminal sequences that bind PDZ [postsynaptic density fraction (PSD)95͞discs large͞ ZO-1] domains, protein-protein interaction domains found in many synaptic proteins (21,22). RSK2 binds several PDZ domain proteins in vitro and in vivo. The RSK2 C-terminal PDZ ligand is essential not only for binding to these interactors but also for RSK2 to efficiently phosphorylate them. Furthermore, interactions with PDZ domain proteins are important for RSK2's effects on synaptic function because kinase-dead RSK2 dramatically affects frequency of AMPA-R-mediated miniature excitatory postsynaptic currents (mEPSC) in a PDZ liganddependent manner. Materials and MethodsAntibodies. The following antibodies were used: anti-Shank1 (Chemicon), anti-pan-Shank (M. Sheng, Massachusetts Institute of Technology, Cambridge), anti-Shank3 (P. Worley and J.-C. Tu, The Johns Hopkins University), anti-membrane-associated guanylate kinase with inverted orientation (anti-MAGI-1; Sigma), anti-hemagglutinin (anti-HA) (Roche Applied Science); anti-myc (Covance, Richmond, CA); anti-phospho-RxRxxS͞T-(P), anti-phosphoERK, anti-panERK, anti-phosphoRSK S380 (Cell Signaling Technology, Beverly, MA); sheep anti...

The Coffin–Lowry syndrome-associated protein RSK2 is implicated in calcium-regulated exocytosis through the regulation of PLD1

“…It has been recently reported that RSKs contain C-terminal sequences that bind PDZ-containing proteins (32), which are in neurons often enriched in synaptic active zones (33). In PC12 and chromaffin cells, we recently described that the PDZ-containing protein Scribble present at the plasma membrane is critical for exocytosis (34).…”

Regulation of Protein Kinase A Activity by p90 Ribosomal S6 Kinase 1

“…An interesting aspect of the extreme C terminus of RSKs is that all of them have a PDZ domain binding region. It has been suggested that, because these regions are different, the different RSK isoforms may interact with different PDZ domain-containing proteins (23). In this context, because RSK1, but not the other RSK isoforms, also interacts with PKAc via its extreme C terminus that contains the PDZ binding residues (732STTL-COO Ϫ ), it is possible that interaction with PKAc also modulates association of RSK1 with proteins containing PDZ domains.…”

p90 ribosomal S6 kinase 2 exerts a tonic brake on G protein-coupled receptor signaling

“…*Statistically different from RSK2ϩ͞ϩ fibroblasts, P Ͻ 0.05. Interestingly, RSK2 has recently been demonstrated to contain C-terminal sequences that bind PDZ domains, and the interaction of RSK2 with PDZ domain-containing proteins has been demonstrated to be important for the role of RSK2 in synaptic function (9). The possibility that PDZ domain-containing proteins, GPCRs, and RSK2 form large synaptic signaling complexes is an intriguing possibility that warrants further study.…”

“…Because RSK2 has a broad range of substrates and actions, it is likely to participate in many other cellular processes. Intriguingly, RSK2 has also been found in association with NMDA and ␣-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors (8,9), which also interact with postsynaptic density protein 95 (10) and have been implicated in the etiology of psychotic disorders (11). Recently, RSK2 has also been demonstrated to regulate excitatory synaptic transmission via AMPA receptors (9).…”