The Ras guanine nucleotide exchange factor CDC25Mm is present at the synaptic junction (original) (raw)
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The Role of the Ras Guanyl-Nucleotide Exchange Factor Rasgrp1 in Synaptic Transmission
Official Symbol Name Other designations, notes Calb1 Calbindin D-28K, calbindin D28 Calb2 Calretinin, Calbindin2 CR Camk2a calcium/calmodulin-dependent protein kinase II alpha CamkII subunit alpha Canx Calnexin Cnx Creb1 cAMP responsive element binding protein 1 Dab2ip disabled homolog 2 (Drosophila) interacting protein Dgkz diacylglycerol kinase zeta Diap1 diaphanous homolog 1 Dia1 Dlg2 disks large homolog 2 PSD-93, Psd93, Chapsyn-110 Dlg4 disks large homolog 4 PSD-95, Psd95 Eea1 early endosome antigen 1 Egf Epidermal growth factor Gad1 glutamic acid decarboxylase 1 EP10, GAD25, GAD44, GAD67 Gad2 glutamic acid decarboxylase 2 GAD65 Golgb1 Giantin, golgi autoantigen, golgin subfamily b, macrogolgin 1 Gm6840 Grb2 growth factor receptor-bound protein 2 Gria1 glutamate receptor, ionotropic, AMPA1 (alpha 1) GluR1, GluA1, GluRA Gria2 glutamate receptor, ionotropic, AMPA2 (alpha 2) GluR2, GluA2, GluR-B, Glur-Diese Studie enthält die ersten Beweise für eine spezifische neuronale Funktion von Rasgrp1. Sie zeigt, dass Rasgrp1 selektiv die postsynaptische Sensitivität an glutamatergen Synapsen reguliert. Diese Studie zeigt, dass die selektive Veränderung der Regulation von Ras eine hilfreiche Methode ist, um die vielfältigen Effekte der Ras Signaltransduktion in Neuronen verstehen zu können. represent the postsynapse. Upon binding of Glutamate, the receptors open and allow Sodium to enter the cell. Upon this influx of cations, the cell depolarizes locally. This electrical signal propagates as the depolarization passively spreads through the dendrites. Spine shape, dendrite caliber and branching influence signal propagation as it travels to the soma. In the soma, final integration of all incoming signals takes place. If the resulting depolarization passes a certain threshold, a new action potential is generated in an all-or-none fashion. Postsynaptic spines, dendrites, the soma, the axon and presynaptic boutons represent highly specialized compartments that are part of the complex morphology of neurons. In fact, without knowledge of ion channels or biophysical properties of the Rho family G proteins regulate cytoskeletal rearrangements through actin binding proteins such as Wasl (Wiskott-Aldrich syndrome-like, also known as N-WASP) and Diap1 (diaphanous homolog 1, also known as Dia1). In this way, they function in the formation of stress fibers, lamellipodia and other morphological processes. In addition, they also regulate gene expression and signal via Pi3k (Takai et al., 2001). Rab family G proteins function in protein sorting, intracellular vesicle trafficking, targeting, docking and fusion. Their mechanism is to activate effectors that directly influence vesicular membrane shape, vesicle tethering or vesicle motility. (Stenmark, 2009; Takai et al., 2001). By similar mechanisms, Arf G proteins function in intracellular trafficking, in particular in vesicle budding from endomembranes, in II.2.2. The Classical Ras Signaling Cascade The first findings indicating a neuronal involvement of the classical Ras G proteins came from experiments using the pheochromocytoma cell line (PC12). Overexpression of Hras, Nras or infection with the Kirsten murine sarcoma virus led to neuronal differentiation of these cells, which was recognized by the outgrowth of II.3. Controversies in the Research of Neuronal Ras Signaling Since publication of the findings described above, research on neuronal Ras signaling has led to many controversies. In this regard, one experimental system in particular appears to have given rise to most of the controversies in the field. Extensive research on Ras signaling is conducted using activated mutants of Ras proteins. The activated mutated protein is able to bind GTP, but unable to hydrolyze it to GDP and therefore remains in a constitutively active state (Karnoub and Weinberg, 2008). The corresponding frequently used Glycine to Valine mutation at amino acid (aa) position 12 (G12V) is normally found in oncogenic Hras. II.5.1. Specificity of Ras GEFs GEFs that activate classical Ras G proteins in the brain belong to three families, the Sos, Rasgrf and Rasgrp family. In case of the Rasgrf and Rasgrp proteins, an activity towards the Rras/Mras subfamily besides the classical Ras G proteins seems to be a general pattern of specificity. The activity of Sos GEFs seems to be restricted Rasgrp1, Rasgrp2a, Rasgrp2b and Rasgrp3. Rasgrp1 mRNA and protein are highly expressed in the brain. It is found in the olfactory bulb, cortex, caudo-putamen (including striatum), hippocampus and thalamus, but only at very low levels in midbrain, cerebellum, pons and medulla
Signaling Proteins in the Post-Synaptic Density
2011
The ability of an organism to respond to its environment stems from synapses and signaling in the post-synaptic density (PSD). Neurological disorders often occur at the level of faulty signal transduction in the PSD. Here we describe the behavioral characterization of Densin 180, a PSD-enriched scaffold protein. We also report on the regulation of Ras guanine release factor1 (RasGRF1), a guanine exchange factor that promotes activation of Ras and thus the ERK pathway as part of an NMDA (N-methyl-D-aspartate) receptor complex with CaMKII (Ca2+/calmodulin-dependent kinase). The Densin KO exhibits severe nest building deficits, elevated anxiety and aggressiveness, impaired sensorimotor gating, hyperlocomotion to novel objects, and short-term memory (hippocampal- and cortical- dependent) deficits. These behavioral abnormalities resemble schizophrenia and autism. Decreases in the schizophrenia susceptibility gene products, DISC1 and mGluR5, are observed in the KO relative to the WT and m...
Proceedings of the National Academy of Sciences, 1991
A neuron-specific Ca2_/calmodulin-dependent protein kinase, CaM kinase Gr, phosphorylates selectively a Ras-related GTP-binding protein (Rap-lb) that is enriched in brain tissue. The phosphorylation reaction achieves a stoichiometry of about 1 and involves a serine residue near the carboxyl terminus of the substrate. Both CaM kinase Gr and cAMP-dependent protein kinase, but not CaM kinase II, phosphorylate identical or contiguous serine residues in Raplb. The rate of phosphorylation of Rap-lb by CaM kinase Gr is enhanced following autophosphorylation of the protein kinase. Other low molecular weight GTP-binding proteins belonging to the Ras superfamily, including Rab-3A, Rap-2b, and c-Ha-ras p21, are not phosphorylated by CaM inase Gr. The phosphorylation of Rap-lb itself can be reversed by an endogenous brain phosphoprotein phosphatase. These observations provide a potential connection between a neuronal Ca2+signaling pathway and a specific low molecular weight GTPbinding protein that may regulate neuronal trnnsmembrane signaling, vesicle transport, or neurotransmitter release. Neuronal Ca2+-signaling is partly mediated by two neuronspecific Ca2_/calmodulin-dependentprotein kinases, CaM
The Journal of biological chemistry, 2014
SynGAP is a neuron-specific Ras and Rap GTPase-activating protein (GAP) found in high concentration in the postsynaptic density (PSD) fraction from mammalian forebrain. We have previously shown that, in situ in the PSD fraction or in recombinant form in Sf9 cell membranes, synGAP is phosphorylated by Ca2+/calmodulin-dependent protein kinase II (CaMKII), another prominent component of the PSD. Here we show that recombinant synGAP (r-synGAP), lacking 102 residues at the N-terminus, can be purified in soluble form and is phosphorylated by cyclin-dependent kinase 5 (CDK5) as well as by CaMKII. Phos-phorylation of r-synGAP by CaMKII increases its HRas GAP activity by 25% and its Rap1 GAP activity by 76%. Conversely, phosphorylation by CDK5 increases r-synGAPs HRas GAP activity by 98% and its Rap1 GAP activity by 20%. Thus, phosphorylation by both kinases increases synGAP activity, but CaMKII shifts the relative GAP activity toward inactivation of Rap1; whereas CDK5 shifts the relative ac...
Involvement of CDC25Mm/Ras-GRF1-Dependent Signaling in the Control of Neuronal Excitability
Molecular and Cellular Neuroscience, 2001
Ras-GRF1 is a neuron-specific guanine nucleotide exchange factor for Ras proteins. Mice lacking Ras-GRF1 (؊/؊) are severely impaired in amygdala-dependent longterm synaptic plasticity and show higher basal synaptic activity at both amygdala and hippocampal synapses (Brambilla et al., 1997). In the present study we investigated the effects of Ras-GRF1 deletion on hippocampal neuronal excitability. Electrophysiological analysis of both primary cultured neurons and adult hippocampal slices indicated that Ras-GRF1؊/؊ mice displayed neuronal hyperexcitability. Ras-GRF1؊/؊ hippocampal neurons showed increased spontaneous activity and depolarized resting membrane potential, together with a higher firing rate in response to injected current. Changes in the intrinsic excitability of Ras-GRF1؊/؊ neurons can entail these phenomena, suggesting that Ras-GRF1 deficiency might alter the balance between ionic conductances. In addition, we showed that mice lacking Ras-GRF1 displayed a higher seizure susceptibility following acute administration of convulsant drugs. Taken together, these results demonstrated a role for Ras-GRF1 in neuronal excitability.
Proceedings of the National Academy of Sciences, 1992
We have examined the isolated postsynaptic density (PSD) fraction for the presence of a G protein. First, we found specific binding of guanosine 5'-[-[35S~thio]triphosphate to the PSD. Second, pertussis toxin-activated ADPribosylation of the isolated PSD fraction resulted in the appearance of a G protein with an apparent molecular mass of 41 kDa, and two G proteins with apparent molecular masses of 41 kDa and 39 kDa in synaptic membrane (SM) fraction and total homogenate (H). The amount of the 41-kDa G protein per unit protein was in the order of SM > H > PSD. Anti-G1 antibodies recognized the 41-kDa G protein in both PSD and SM, whereas anti-GO antibodies reacted with the 39-kDa G protein in the SM. The absence of G. protein in the PSD suggested that there was no contamination with SM. Moreover, unlabeled PSD incubated with an extract of SM that contained the labeled G proteins resulted in no label in the subsequently reisolated PSD, suggesting that the G protein found in the PSD was not due to adsorption of the G protein onto the PSD during its isolation from the SM. PSD pretreated with EGTA gave an 11-fold increase in the ADP-ribosylation reaction of the G, protein; similar effects on the G, and Go proteins of SM were obtained. Restoration of Ca2+/calmodulin to the PSD, but not of either Ca2+ or calmodulin alone, removed the effect of EGTA, indicating a strong complex formation between G1 and Ca2+/calmodulin that decreased the ADP-ribosylation reaction. Preincubation with the Ca2+-channel blocker nifedipine decreased the ADP-ribosylation reaction in the PSD. We conclude that Gi is present in the PSD, that it may interact with calmodulin and that it is involved in the regulation of voltagedependent Ca2+ channel. We present a theory of the involvement of the G protein and calmodulin in postsynaptic neurophysiological events.
Proceedings of the National Academy of Sciences, 1996
The alpha subunit of type II calcium/calmodulin-dependent protein kinase (CAM II kinase-alpha) plays an important role in longterm synaptic plasticity. We applied preembedding immunocytochemistry (for CAM II kinase-alpha) and postembedding immunogold labeling [for glutamate or gamma-aminobutyric acid (GABA)] to explore the subcellular relationships between transmitter-defined axon terminals and the kinase at excitatory and inhibitory synapses in thalamus and cerebral cortex. Many (but not all) axon terminals ending in asymmetric synapses contained presynaptic CAM II kinase-alpha immunoreactivity; GABAergic terminals ending in symmetric synapses did not. Postsynaptically, CAM II kinase-alpha immunoreactivity was associated with postsynaptic densities of many (but not all) glutamatergic axon terminals ending on excitatory neurons. CAM II kinase-alpha immunoreactivity was absent at postsynaptic densities of all GABAergic synapses. The findings show that CAM II kinase-alpha is selective...
Molecular Brain Research, 1996
A full-length cDNA for a novel isoform of the human receptor tyrosine phosphatase y gene d'I l'I«,\ was overexpressed in Sf9 insect cells, and the gene product. PTPy, was purified and characterized. The protein was expressed as a Mr~185,000 protein accompanied by a Mr â€"¿ 120,000 putative cleavage product on SDS-PAGE analysis. The protein undergoes jV-linked glycosylation and constitutive phosphorylation of serine resi dues. When assayed for tyrosine-specific phosphatase activity, PTPy dephosphorylatcd myelin basic protein at a pH optimum of 7.5 and a A,„ of 12.6 UM; reduced carboxyamidomethylated and maleylated lysozyme (RCM-lysozyme) at a pH optimum of 6.0 and a k,,, of 12 UM; and p-nitrophenylphosphate with a pH optimum of 5.5 and a A,,, of 3.5 HIM.
Journal of Neuroscience, 2010
In contrast to chemical transmission, few proteins have been shown associated with gap junctionmediated electrical synapses. Mixed (electrical and glutamatergic) synaptic terminals on the teleost Mauthner cell known as "Club endings" constitute because of their unusual large size and presence of connexin 35 (Cx35), ortholog of the widespread mammalian Cx36, a valuable model for the study of electrical transmission. Remarkably, both components of their mixed synaptic response undergo activity-dependent potentiation. Changes in electrical transmission result from interactions with colocalized glutamatergic synapses, the activity of which leads to the activation of Ca ++ /calmodulindependent kinase II (CaM-KII), required for the induction of changes in both forms of transmission. However, the distribution of this kinase and potential localization to electrical synapses remains undetermined. Taking advantage of the unparalleled experimental accessibility of Club endings, we explored the presence and intraterminal distribution of CaM-KII within these terminals. Here we show: 1) unlike other proteins, both CaM-KII labeling and distribution were highly variable between contiguous contacts, and 2) CaM-KII was not restricted to the periphery of the terminals, where glutamatergic synapses are located, but also was present at the center where gap junctions predominate. Accordingly, double-immunolabeling indicated that Cx35 and CaM-KII were colocalized and biochemical analysis showed that these proteins associate. Because CaM-KII characteristically undergoes activity-dependent translocation, the observed variability of labeling likely reflects physiological differences between electrical synapses of contiguous Club endings, which remarkably co-exist with differing degrees of conductance. Taken together, our results indicate that CaM-KII should be considered a component of electrical synapses although its association is non-obligatory and likely driven by activity.