The C2 domain of SynGAP is essential for stimulation of the Rap GTPase reaction

Peña, Vladimir; Hothorn, Michael; Eberth, Alexander; Kaschau, Nikolai; Parret, Annabel; Gremer, Lothar; Bonneau, Fabien; Ahmadian, Mohammad Réza; Scheffzek, Klaus

doi:10.1038/embor.2008.20

Cited by 89 publications

(88 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Mutation of the arginine finger in the GAP domain of CAPRI inactivates both RasGAP and Rap1GAP activities (20,23), which is similar to the effects of mutating the arginine finger of GAP1 IP4BP (20) or SynGAP (11,38). This observation indicates that the Rap1-binding site within the catalytic domain of CAPRI is the same as for Ras.…”

Section: Discussionsupporting

confidence: 62%

“…However, mutation of the asparagine thumb or glutamine residues within the GAP domain in GAP1 IP4PB failed to inhibit Rap1GAP activity (21). In contrast, mutation of the corresponding asparagine in SynGAP significantly reduced its Rap1GAP activity but did not affect binding affinity (38). These data imply that each of these dual Ras-and Rap-GAPs employs its own mechanism to act on Rap1.…”

Section: Discussionmentioning

confidence: 64%

See 1 more Smart Citation

Ca2+-dependent Monomer and Dimer Formation Switches CAPRI Protein between Ras GTPase-activating Protein (GAP) and RapGAP Activities

Dai

Walker

Vet

et al. 2011

Journal of Biological Chemistry

View full text Add to dashboard Cite

CAPRI is a member of the GAP1 family of GTPase-activating proteins (GAPs) for small G proteins. It is known to function as an amplitude sensor for intracellular Ca 2؉ levels stimulated by extracellular signals and has a catalytic domain with dual Ras-GAP and RapGAP activities. Here, we have investigated the mechanism that switches CAPRI between its two GAP activities. We demonstrate that CAPRI forms homodimers in vitro and in vivo in a Ca 2؉ -dependent manner. The site required for dimerization was pinpointed by deletion and point mutations to a helix motif that forms a hydrophobic face in the extreme C-terminal tail of the CAPRI protein. Deletion of this helix motif abolished dimer formation but did not affect translocation of CAPRI to the plasma membrane upon cell stimulation with histamine. We found that dimeric and monomeric CAPRI coexist in cells and that the ratio of dimeric to monomeric CAPRI increases upon cell stimulation with histamine. Free Ca 2؉ at physiologically relevant concentrations was both necessary and sufficient for dimer formation. Importantly, the monomeric and dimeric forms of CAPRI exhibited differential GAP activities in vivo; the wild-type form of CAPRI had stronger RapGAP activity than RasGAP activity, whereas a monomeric CAPRI mutant showed stronger RasGAP than RapGAP activity. These results demonstrate that CAPRI switches between its dual GAP roles by forming monomers or homodimers through a process regulated by Ca 2؉ . We propose that Ca 2؉ -dependent dimerization of CAPRI may serve to coordinate Ras and Rap1 signaling pathways.The closely related small G proteins (GTPases) Ras and Rap1 are conserved molecular switches that couple extracellular signals to a wide range of cellular responses through different signaling networks (1). Ras plays a central role in cell proliferation and cell survival and is a major oncogene (2). Rap1 was originally identified as a protein that reverts the effects of active Ras, such as the loss of adhesion accompanying cell transformation by oncogenic K-Ras (3) or the activation of ERK and ELK1 (4, 5). However, subsequent studies showed that Rap1 is not a mere anti-Ras protein but has discrete functions, notably in integrinmediated cell adhesion and spreading, formation of cell/cell contacts (6), superoxide formation, and cAMP-induced neurite outgrowth (1, 7). These distinct physiological roles of Ras and Rap1 are mediated by their differential use of effector proteins and also through differential subcellular localizations of their effectors (8).As is typical for small G proteins, the biological activities of both Ras and Rap1 are controlled by a GDP/GTP cycle; they are active in their GTP-bound form and inactive in their GDPbound form (1). Guanine nucleotide exchange factors activate them by promoting the dissociation of GDP, allowing excess free cellular GTP to bind, whereas GAPs 2 inactivate them by stimulating their intrinsic GTPase activity. A number of guanine nucleotide exchange factors and GAPs for Ras and Rap have been identified. In general, t...

show abstract

Section: Discussionsupporting

confidence: 62%

Section: Discussionmentioning

confidence: 64%

Ca2+-dependent Monomer and Dimer Formation Switches CAPRI Protein between Ras GTPase-activating Protein (GAP) and RapGAP Activities

Dai

Walker

Vet

et al. 2011

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…The GAP domain in this structure however exhibits an inactive conformation, representing an autoinhibited state of the plexin intracellular region. In contrast, structures of several other Ras GAP domains all show the active conformation (13,24,25), and regulation of their activity often involves direct blocking of the active site by regulatory domains in the proteins (28). The observations of both active and inactive conformations suggest a distinct regulation mechanism for Ras GAPs.…”

Section: Discussionmentioning

confidence: 87%

“…S1), the two GAP homologous regions C1 and C2 of plexin A3 form a GAP domain with an overall fold similar to canonical Ras GAPs such as p120 Ras GAP ( Fig. 1 B and C) (12,24,25). The two catalytically critical arginine residues in plexin A3, Arg-1407 and Arg-1724, superimpose precisely with those in p120 Ras GAP (Fig.…”

Section: Resultsmentioning

confidence: 93%

Crystal structure of the plexin A3 intracellular region reveals an autoinhibited conformation through active site sequestration

He¹,

Yang

Terman

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

113

View full text Add to dashboard Cite

Plexin cell surface receptors bind to semaphorin ligands and transduce signals for regulating neuronal axon guidance. The intracellular region of plexins is essential for signaling and contains a R-Ras/M-Ras GTPase activating protein (GAP) domain that is divided into two segments by a Rho GTPase-binding domain (RBD). The regulation mechanisms for plexin remain elusive, although it is known that activation requires both binding of semaphorin to the extracellular region and a Rho-family GTPase (Rac1 or Rnd1) to the RBD. Here we report the crystal structure of the plexin A3 intracellular region. The structure shows that the N-and C-terminal portions of the GAP homologous regions together form a GAP domain with an overall fold similar to other Ras GAPs. However, the plexin GAP domain adopts a closed conformation and cannot accommodate R-Ras/M-Ras in its substrate-binding site, providing a structural basis for the autoinhibited state of plexins. A comparison with the plexin B1 RBD/Rnd1 complex structure suggests that Rnd1 binding alone does not induce a conformational change in plexin, explaining the requirement of both semaphorin and a Rho GTPase for activation. The structure also identifies an N-terminal segment that is important for regulation. Both the N-terminal segment and the RBD make extensive interactions with the GAP domain, suggesting the presence of an allosteric network connecting these three domains that integrates semaphorin and Rho GTPase signals to activate the GAP. The importance of these interactions in plexin signaling is shown by both cell-based and in vivo axon guidance assays.autoinhibition ͉ axon guidance ͉ signaling ͉ structure

show abstract

“…Additionally, Rap2, a member of the Ras family of GTPases, indirectly activates JNK (Figure 3), and Rap2-JNK interactions traffic AMPA receptors away from the synapse during LTD, or bidirectionally in an activity dependent manner (Hussain et al, 2010;Thomas et al, 2008;Zhu et al, 2005). Interestingly, Rap2 function is modulated by SynGAP, a Ras and Rap GTPase-activating-protein, by its C2 domain (Funk et al, 2009;Pena et al, 2008). Recently reported decreases in SynGAP (Funk et al, 2009), together with decreased expression of Rap2, JNK1/2, and PSD-95, suggests abnormal AMPAR localization and trafficking in schizophrenia.…”

Section: Discussionmentioning

confidence: 99%

Abnormal Activity of the MAPK- and cAMP-Associated Signaling Pathways in Frontal Cortical Areas in Postmortem Brain in Schizophrenia

Funk

McCullumsmith

Haroutunian

et al. 2011

Neuropsychopharmacol

136

102

View full text Add to dashboard Cite

Recent evidence suggests that schizophrenia may result from alterations of integration of signaling mediated by multiple neurotransmitter systems. Abnormalities of associated intracellular signaling pathways may contribute to the pathophysiology of schizophrenia. Proteins and phospho-proteins comprising mitogen activated protein kinase (MAPK) and 3 0 -5 0 -cyclic adenosine monophosphate (cAMP)-associated signaling pathways may be abnormally expressed in the anterior cingulate (ACC) and dorsolateral prefrontal cortex (DLPFC) in schizophrenia. Using western blot analysis we examined proteins of the MAPK-and cAMP-associated pathways in these two brain regions. Postmortem samples were used from a well-characterized collection of elderly patients with schizophrenia (ACC ¼ 36, DLPFC ¼ 35) and a comparison (ACC ¼ 33, DLPFC ¼ 31) group. Near-infrared intensity of IR-dye labeled secondary antisera bound to targeted proteins of the MAPK-and cAMP-associated signaling pathways was measured using LiCor Odyssey imaging system. We found decreased expression of Rap2, JNK1, JNK2, PSD-95, and decreased phosphorylation of JNK1/2 at T183/Y185 and PSD-95 at S295 in the ACC in schizophrenia. In the DLPFC, we found increased expression of Rack1, Fyn, Cdk5, and increased phosphorylation of PSD-95 at S295 and NR2B at Y1336. MAPK-and cAMP-associated molecules constitute ubiquitous intracellular signaling pathways that integrate extracellular stimuli, modify receptor expression and function, and regulate cell survival and neuroplasticity. These data suggest abnormal activity of the MAPK-and cAMP-associated pathways in frontal cortical areas in schizophrenia. These alterations may underlie the hypothesized hypoglutamatergic function in this illness. Together with previous findings, these data suggest that abnormalities of intracellular signaling pathways may contribute to the pathophysiology of schizophrenia.

show abstract

The C2 domain of SynGAP is essential for stimulation of the Rap GTPase reaction

Cited by 89 publications

References 35 publications

Ca2+-dependent Monomer and Dimer Formation Switches CAPRI Protein between Ras GTPase-activating Protein (GAP) and RapGAP Activities

Ca2+-dependent Monomer and Dimer Formation Switches CAPRI Protein between Ras GTPase-activating Protein (GAP) and RapGAP Activities

Crystal structure of the plexin A3 intracellular region reveals an autoinhibited conformation through active site sequestration

Abnormal Activity of the MAPK- and cAMP-Associated Signaling Pathways in Frontal Cortical Areas in Postmortem Brain in Schizophrenia

Contact Info

Product

Resources

About