Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Some membrane proteins must be clustered at target sites to efficiently perform their functions. PDZ domain-containing scaffold proteins bind to the tails of target membrane proteins and promote their localization and clustering on the cell surface. This chapter describes the experimental details of the clustering assay, using the interaction between potassium channels and PSD-95, an abundant PDZ domain protein in neuronal synapses, as a model.
Methods Mol Biol 2006
PMID:Clustering assay for studying the interaction of membrane proteins with PDZ domain proteins. 1687 97

Mutations in cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-regulated chloride channel, cause cystic fibrosis. To investigate interactions of CFTR in living cells, we measured the diffusion of quantum dot-labeled CFTR molecules by single particle tracking. In multiple cell lines, including airway epithelia, CFTR diffused little in the plasma membrane, generally not moving beyond 100-200 nm. However, CFTR became mobile over micrometer distances after 1) truncations of the carboxy terminus, which contains a C-terminal PDZ (PSD95/Dlg/ZO-1) binding motif; 2) blocking PDZ binding by C-terminal green fluorescent protein fusion; 3) disrupting CFTR association with actin by expression of a mutant EBP50/NHERF1 lacking its ezrin binding domain; or 4) skeletal disruption by latrunculin. CFTR also became mobile when the cytoskeletal adaptor protein binding capacity was saturated by overexpressing CFTR or its C terminus. Our data demonstrate remarkable and previously unrecognized immobilization of CFTR in the plasma membrane and provide direct evidence that C-terminal coupling to the actin skeleton via EBP50/ezrin is responsible for its immobility.
Mol Biol Cell 2006 Dec
PMID:Tracking of quantum dot-labeled CFTR shows near immobilization by C-terminal PDZ interactions. 1698 54

The postsynaptic density protein PSD-95 and related membrane-associated guanylate kinases are scaffolding proteins, whose modular interaction motifs organize protein complexes at cell junctions. The signature guanylate kinase domain (GK) contains elements of the protein's GMP-binding site but does not bind nucleotide. Instead, the GK domain has evolved from an enzyme to a protein-protein interaction motif. Here, we show that this canonical GMP-binding region interacts with microtubule-associated protein-1a (MAP1a) and we present a structural model. We determine the consensus GK-binding sequence in MAP1a and demonstrate that PSD-95 can use a similar interaction mode to bind diverse protein partners. Furthermore, we show that PSD-95 GK has adopted the conformational flexibility of the ancestral enzyme to bind its varied ligands, which suggests a mechanism of regulation.
Nat Struct Mol Biol 2007 Feb
PMID:The guanylate kinase domain of the MAGUK PSD-95 binds dynamically to a conserved motif in MAP1a. 1722 Aug 95

Using phage display, we identified Na+/H+ exchanger regulatory factor (NHERF)-2 as a novel binding partner for the cadherin-associated protein, beta-catenin. We showed that the second of two PSD-95/Dlg/ZO-1 (PDZ) domains of NHERF interacts with a PDZ-binding motif at the very carboxy terminus of beta-catenin. N-cadherin expression has been shown to induce motility in a number of cell types. The first PDZ domain of NHERF is known to bind platelet-derived growth factor-receptor beta (PDGF-Rbeta), and the interaction of PDGF-Rbeta with NHERF leads to enhanced cell spreading and motility. Here we show that beta-catenin and N-cadherin are in a complex with NHERF and PDGF-Rbeta at membrane ruffles in the highly invasive fibrosarcoma cell line HT1080. Using a stable short hairpin RNA system, we showed that HT1080 cells knocked down for either N-cadherin or NHERF had impaired ability to migrate into the wounded area in a scratch assay, similar to cells treated with a PDGF-R kinase inhibitor. Cells expressing a mutant NHERF that is unable to associate with beta-catenin had increased stress fibers, reduced lamellipodia, and impaired cell migration. Using HeLa cells, which express little to no PDGF-R, we introduced PDGF-Rbeta and showed that it coimmunoprecipitates with N-cadherin and that PDGF-dependent cell migration was reduced in these cells when we knocked-down expression of N-cadherin or NHERF. These studies implicate N-cadherin and beta-catenin in cell migration via PDGF-R-mediated signaling through the scaffolding molecule NHERF.
Mol Biol Cell 2007 Apr
PMID:NHERF links the N-cadherin/catenin complex to the platelet-derived growth factor receptor to modulate the actin cytoskeleton and regulate cell motility. 1722 87

The localization of RNA/mRNA in dendrites plays a role in both local and temporal regulation of protein synthesis, which is required for certain forms of synaptic plasticity. A key molecule in these processes is the fragile X mental retardation protein (FMRP). Using in situ hybridization coupled to immunofluorescence confocal microscopy, we find that the FMRP-RNP particle contains alphaCaMKII and BC1 RNAs as well as Staufen and CPEB proteins. Furthermore, following mGluR activation, the FMRP-mRNP complex moves into spines as shown by co-localization with the PSD-95 and Shank proteins. This study shows, for the first time, that the translationally inactive FMRP-mRNP complex relocates into neuronal spines after stimulation and that de novo protein synthesis mainly contributes to the pool of FMRP at synapses.
Mol Cell Neurosci 2007 Mar
PMID:The fragile X mental retardation protein-RNP granules show an mGluR-dependent localization in the post-synaptic spines. 1725 95

Membrane palmitoylated protein 4 (Mpp4) is a member of the membrane-associated guanylate kinase family. We show that Mpp4 localizes specifically to the plasma membrane of photoreceptor synaptic terminals. Plasma membrane Ca(2+) ATPases (PMCAs), the Ca(2+) extrusion pumps, interact with an Mpp4-dependent presynaptic membrane protein complex that includes Veli3 and PSD95. In mice lacking Mpp4, PMCAs were lost from rod photoreceptor presynaptic membranes. Synaptic ribbons were enlarged, a phenomenon known to correlate with higher Ca(2+). SERCA2 (sarcoplasmic-endoplasmic reticulum Ca(2+) ATPase, type 2), which pumps cytosolic Ca(2+) into intracellular Ca(2+) stores and localizes next to the ribbons, was increased. The distribution of IP(3)RII (InsP(3) receptor, type 2), which releases Ca(2+) from the stores, was shifted away from the synaptic terminals. Synaptic transmission to second-order neurons was maintained but was reduced in amplitude. These data suggest that loss of Mpp4 disrupts a Ca(2+) extrusion mechanism at the presynaptic membranes, with ensuing adaptive responses by the photoreceptor to restore Ca(2+) homeostasis. We propose that Mpp4 organizes a presynaptic protein complex that includes PMCAs and has a role in modulating Ca(2+) homeostasis and synaptic transmission in rod photoreceptors.
Hum Mol Genet 2007 May 01
PMID:Mpp4 is required for proper localization of plasma membrane calcium ATPases and maintenance of calcium homeostasis at the rod photoreceptor synaptic terminals. 1734 88

The ubiquitin-proteasome system (UPS) actively controls protein dynamics and local abundance via regulated protein degradation. This study investigates UPS' roles in the regulation of postsynaptic function and molecular composition in the Drosophila neuromuscular junction (NMJ) genetic system. To specifically impair UPS function postsynaptically, the UAS/GAL4 transgenic method was employed to drive postsynaptic expression of proteasome beta2 and beta6 subunit mutant proteins, which operate through a dominant negative mechanism to block proteasome function. When proteasome mutant subunits were constitutively expressed, excitatory junctional current (EJC) amplitudes were increased, demonstrating that postsynaptic proteasome function limits neurotransmission strength. Interestingly, the alteration in synaptic strength was calcium-dependent and miniature EJCs had significantly smaller mean amplitudes and more rapid mean decay rates. Postsynaptic levels of the Drosophila PSD-95/SAP97 homologue, discs large (DLG), and the GluRIIB-containing glutamate receptor were increased, but GluRIIA-containing receptors were unaltered. With acute postsynaptic proteasome inhibition using an inducible transgenic system, neurotransmission was similarly elevated with the same specific increase in postsynaptic GluRIIB abundance. These findings demonstrate postsynaptic proteasome regulation of glutamatergic synaptic function that is mediated through specific regulation of GluRIIB-containing glutamate receptors.
Mol Cell Neurosci 2007 May
PMID:The ubiquitin-proteasome system postsynaptically regulates glutamatergic synaptic function. 1736 64

Emerging evidence has suggested that glycogen synthase kinase 3 (GSK-3) is a key regulatory kinase involved in a plethora of processes in the nervous system, including neuronal development, mood stabilization, and neurodegeneration. However, the cellular mechanisms underlying the actions of GSK-3 remain to be identified. In this study, we examined the impact of GSK-3 on the N-methyl-D-aspartate (NMDA) receptor channel, a central player involved in cognitive and emotional processes. We found that application of various structurally different GSK-3 inhibitors caused a long-lasting reduction of NMDA receptor-mediated ionic and synaptic current in cortical pyramidal neurons. Cellular knockdown of GSK-3beta in neuronal cultures with a small interfering RNA led to smaller NMDA receptor current and loss of its regulation by GSK-3 inhibitors. The NR2B subunit-containing NMDA receptor was the primary target of GSK-3, but the GSK-3 modulation of NMDAR current did not involve the motor protein kinesin superfamily member 17-based transport of NR2B-containing vesicles along microtubules. Combined electrophysiological, immunocytochemical, and biochemical evidence indicated that GSK-3 inhibitors induced the down-regulation of NMDAR current through increasing the Rab5-mediated and PSD-95-regulated NMDAR internalization in a clathrin/dynamin-dependent manner.
Mol Pharmacol 2007 Jul
PMID:Glycogen synthase kinase 3 regulates N-methyl-D-aspartate receptor channel trafficking and function in cortical neurons. 1740 Jul 62

In this article we analyze the mechanisms by which the C-terminal four amino acids of inducible nitric oxide synthase (NOS2) interact with proteins that contain PDZ (PSD-95/DLG/ZO-1) domains resulting in the translocation of NOS2 to the cellular apical domain. It has been reported that human hepatic NOS2 associates to EBP50, a protein with two PDZ domains present in epithelial cells. We describe herein that NOS2 binds through its four carboxy-terminal residues to CAP70, a protein that contains four PDZ modules that is targeted to apical membranes. Interestingly, this interaction augments both the cytochrome c reductase and .NO-synthase activities of NOS2. Binding of CAP70 to NOS2 also results in an increase in the population of active NOS2 dimers. In addition, CAP70 participates in the correct subcellular targeting of NOS2 in a process that is also dependent on the acylation state of the N-terminal end of NOS2. Hence, nonpalmitoylated NOS2 is unable to progress toward the apical side of the cell despite its interaction with either EBP50 or CAP70. Likewise, if we abrogate the interaction of NOS2 with either EBP50 or CAP70 by fusing the GFP reporter to the carboxy-terminal end of NOS2 palmitoylation is not sufficient to confer an apical targeting.
Mol Biol Cell 2007 Jul
PMID:Binding of CAP70 to inducible nitric oxide synthase and implications for the vectorial release of nitric oxide in polarized cells. 1750 52

Mutations in the parkin gene result in an autosomal recessive juvenile-onset form of Parkinson's disease. As an E3 ubiquitin-ligase, parkin promotes the attachment of ubiquitin onto specific substrate proteins. Defects in the ubiquitination of parkin substrates are therefore believed to lead to neurodegeneration in Parkinson's disease. Here, we identify the PSD-95/Discs-large/Zona Occludens-1 (PDZ) protein PICK1 as a novel parkin substrate. We find that parkin binds PICK1 via a PDZ-mediated interaction, which predominantly promotes PICK1 monoubiquitination rather than polyubiquitination. Consistent with monoubiquitination and recent work implicating parkin in proteasome-independent pathways, parkin does not promote PICK1 degradation. However, parkin regulates the effects of PICK1 on one of its other PDZ partners, the acid-sensing ion channel (ASIC). Overexpression of wild-type, but not PDZ binding- or E3 ubiquitin-ligase-defective parkin abolishes the previously described, protein kinase C-induced, PICK1-dependent potentiation of ASIC2a currents in non-neuronal cells. Conversely, the loss of parkin in hippocampal neurons from parkin knockout mice unmasks prominent potentiation of native ASIC currents, which is normally suppressed by endogenous parkin in wild-type neurons. Given that ASIC channels contribute to excitotoxicity, our work provides a mechanism explaining how defects in parkin-mediated PICK1 monoubiquitination could enhance ASIC activity and thereby promote neurodegeneration in Parkinson's disease.
Mol Biol Cell 2007 Aug
PMID:Parkin-mediated monoubiquitination of the PDZ protein PICK1 regulates the activity of acid-sensing ion channels. 1755 32


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