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Biomedical subjects

Gareth M Thomas

Publications and source records attributed to Gareth M Thomas.

4 recordsLinked to original sources
PubMed2006

Targeted in vivo mutations of the AMPA receptor subunit GluR2 and its interacting protein PICK1 eliminate cerebellar long-term depression.

Cerebellar long-term depression (LTD) is a major form of synaptic plasticity that is thought to be critical for certain types of motor learning. Phosphorylation of the AMPA receptor subunit GluR2 on serine-880 as well as interaction of GluR2 with PICK1 have been suggested to contribute to the endocytic removal of postsynaptic AMPA receptors during LTD. Here, we show that targeted mutation of PICK1, the GluR2 C-terminal PDZ ligand, or the GluR2 PKC phosphorylation site eliminates cerebellar LTD in mice. LTD can be rescued in cerebellar cultures from mice lacking PICK1 by transfection of wild-type PICK1 but not by a PDZ mutant or a BAR domain mutant deficient in lipid binding, indicating the importance of these domains in PICK1 function. These results demonstrate that PICK1-GluR2 PDZ-based interactions and GluR2 phosphorylation are required for LTD expression in the cerebellum.

Age Factors↗
PubMed2005

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

Extracellular signal-regulated kinase (ERK) signaling is important for neuronal synaptic plasticity. We report here that the protein kinase ribosomal S6 kinase (RSK)2, a downstream target of ERK, uses a C-terminal motif to bind several PDZ domain proteins in heterologous systems and in vivo. Different RSK isoforms display distinct specificities in their interactions with PDZ domain proteins. Mutation of the RSK2 PDZ ligand does not inhibit RSK2 activation in intact cells or phosphorylation of peptide substrates by RSK2 in vitro but greatly reduces RSK2 phosphorylation of PDZ domain proteins of the Shank family in heterologous cells. In primary neurons, NMDA receptor (NMDA-R) activation leads to ERK and RSK2 activation and RSK-dependent phosphorylation of transfected Shank3. RSK2-PDZ domain interactions are functionally important for synaptic transmission because neurons expressing kinase-dead RSK2 display a dramatic reduction in frequency of AMPA-type glutamate receptor-mediated miniature excitatory postsynaptic currents, an effect dependent on the PDZ ligand. These results suggest that binding of RSK2 to PDZ domain proteins and phosphorylation of these proteins or their binding partners regulates excitatory synaptic transmission.

Adaptor Proteins, Signal Transducing↗
PubMed2004

Stress- and mitogen-induced phosphorylation of the synapse-associated protein SAP90/PSD-95 by activation of SAPK3/p38gamma and ERK1/ERK2.

SAPK3 (stress-activated protein kinase-3, also known as p38gamma) is a member of the mitogen-activated protein kinase family; it phosphorylates substrates in response to cellular stress, and has been shown to bind through its C-terminal sequence to the PDZ domain of alpha1-syntrophin. In the present study, we show that SAP90 [(synapse-associated protein 90; also known as PSD-95 (postsynaptic density-95)] is a novel physiological substrate for both SAPK3/p38gamma and the ERK (extracellular-signal-regulated protein kinase). SAPK3/p38gamma binds preferentially to the third PDZ domain of SAP90 and phosphorylates residues Thr287 and Ser290 in vitro, and Ser290 in cells in response to cellular stresses. Phosphorylation of SAP90 is dependent on the binding of SAPK3/p38gamma to the PDZ domain of SAP90. It is not blocked by SB 203580, which inhibits SAPK2a/p38alpha and SAPK2b/p38beta but not SAPK3/p38gamma, or by the ERK pathway inhibitor PD 184352. However, phosphorylation is abolished when cells are treated with a cell-permeant Tat fusion peptide that disrupts the interaction of SAPK3/p38gamma with SAP90. ERK2 also phosphorylates SAP90 at Thr287 and Ser290 in vitro, but this does not require PDZ-dependent binding. SAP90 also becomes phosphorylated in response to mitogens, and this phosphorylation is prevented by pretreatment of the cells with PD 184352, but not with SB 203580. In neurons, SAP90 and SAPK3/p38gamma co-localize and they are co-immunoprecipitated from brain synaptic junctional preparations. These results demonstrate that SAP90 is a novel binding partner for SAPK3/p38gamma, a first physiological substrate described for SAPK3/p38gamma and a novel substrate for ERK1/ERK2, and that phosphorylation of SAP90 may play a role in regulating protein-protein interactions at the synapse in response to adverse stress- or mitogen-related stimuli.

Amino Acid Sequence↗