Nedd4 Regulates Ubiquitination and Stability of the Guanine-Nucleotide Exchange Factor CNrasGEF

Pham, Nam; Rotin, Daniela

doi:10.1074/jbc.m108373200

Cited by 45 publications

(48 citation statements)

References 35 publications

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“…Similarly, neither Cb1 nor Parkin and Mdm2 copurified with EAAC1 in the same experiment (data not shown). These data provide strong evidence that EAAC1 and Nedd4 interact in C6 glioma cells, which is consistent with previous reports suggesting a possible role of a Nedd4 family member (Nedd4-2) in the regulation of EAAC1 function (42,43) and dopamine transporter ubiquitination (44).…”

Section: Nedd4 Is the E3 Ligase Associated With Eaac1supporting

confidence: 81%

Morphine Induces Ubiquitin-Proteasome Activity and Glutamate Transporter Degradation

Yang

Wang

Sung

et al. 2008

Journal of Biological Chemistry

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Glutamate transporters play a crucial role in physiological glutamate homeostasis, neurotoxicity, and glutamatergic regulation of opioid tolerance. However, how the glutamate transporter turnover is regulated remains poorly understood. Here we show that chronic morphine exposure induced posttranscriptional downregulation of the glutamate transporter EAAC1 in C6 glioma cells with a concurrent decrease in glutamate uptake and increase in proteasome activity, which were blocked by the selective proteasome inhibitor MG-132 or lactacystin but not the lysosomal inhibitor chloroquin. At the cellular level, chronic morphine induced the PTEN (phosphatase and tensin homolog deleted on chromosome Ten)-mediated up-regulation of the ubiquitin E3 ligase Nedd4 via cAMP/protein kinase A signaling, leading to EAAC1 ubiquitination and proteasomal degradation. Either Nedd4 or PTEN knockdown with small interfering RNA prevented the morphine-induced EAAC1 degradation and decreased glutamate uptake. These data indicate that cAMP/protein kinase A signaling serves as an intracellular regulator upstream to the activation of the PTEN/ Nedd4-mediated ubiquitin-proteasome system activity that is critical for glutamate transporter turnover. Under an in vivo condition, chronic morphine exposure also induced posttranscriptional down-regulation of the glutamate transporter EAAC1, which was prevented by MG-132, and transcriptional up-regulation of PTEN and Nedd4 within the spinal cord dorsal horn. Thus, inhibition of the ubiquitin-proteasome-mediated glutamate transporter degradation may be an important mechanism for preventing glutamate overexcitation and may offer a new strategy for treating certain neurological disorders and improving opioid therapy in chronic pain management.Glutamate transporters play a crucial role in physiological glutamate homeostasis, neurotoxicity, and glutamatergic regulation of opioid tolerance (1-5). However, how the glutamate transporter degradation is regulated remains unclear (6 -8). The ubiquitin-proteasome system (UPS) 2 is a major non-lysosomal proteolytic pathway that degrades cellular proteins including those with important roles in the regulation of cell growth and function (9 -11). In addition, activation of UPS has been shown to regulate the PSD-95 degradation and ␣-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor surface expression (12), suggesting a possible relationship between UPS and glutamatergic activities. Ubiquitination is a process involving three enzymes: E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3 (ubiquitin ligase) (13,14). Interactions between an E3 ligase and its target molecule are considered a key step in determining the selectivity of UPS for a target molecule and its subsequent proteasomal degradation, a process that is subject to intracellular modulation by various upstream regulators (14). PTEN (phosphatase and tensin homolog deleted on chromosome Ten) is a tumor suppressor and lipid phosphatase, which has been shown to regulate cell surviva...

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Section: Nedd4 Is the E3 Ligase Associated With Eaac1supporting

confidence: 81%

Morphine Induces Ubiquitin-Proteasome Activity and Glutamate Transporter Degradation

Yang

Wang

Sung

et al. 2008

Journal of Biological Chemistry

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“…Interestingly, mutation of the cdc25 domain to disrupt Ras binding also eliminated ubiquitination of GRF2 (65). Degradation of the Rap GEF, PDZ-GEF1, following NEDD4-mediated ubiquitination also required Rap1 binding (38). Although no well conserved D box could be identified in Epac2, sequence alignment identified a KEN box (67) between residues 176 and 186 that may alternatively target the GEF for ubiquitination.…”

Section: Discussionmentioning

confidence: 99%

“…Epac2 also possesses a second, lower affinity cAMPbinding domain (36). Based on CDC25 homology domain alignment, four additional exchange factors belong to the Epac subfamily, namely PDZ-/RA-GEFs 1 and 2 that possess low affinity cAMP binding sites (37)(38)(39)(40), MR-GEF (36,41,42), and a putative GEF, Link II (GenBank accession number NM016339) that lack cAMP-binding domains (Fig. 1A).…”

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confidence: 99%

The RAP1 Guanine Nucleotide Exchange Factor Epac2 Couples Cyclic AMP and Ras Signals at the Plasma Membrane

Liu

Asuri

Rebhun

et al. 2006

Journal of Biological Chemistry

105

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Epac-1 and -2 (exchange proteins directly activated by cyclic AMP) are guanine-nucleotide exchange factors for the GTPases Rap1 and -2. Epac2 but not Epac1 was found to possess a RA (Ras association) domain similar to that found in the Ras effector Ral-GDS. This domain specifically bound Ras-GTP, enabling oncogenic Ras to translocate Epac2 from the cytosol to the plasma membrane. Consequently, a small pool of plasma membrane-bound Rap1 was activated at the expense of bulk Rap1 located on intracellular organelles. Whereas translocation of Epac2 was not mimicked by challenge with epidermal growth factor alone, costimulation with forskolin, prostaglandin E 2 , or an Epac-selective cyclic AMP analoginduced rapid relocation of GFP-Epac2 but not -Epac1 to the plasma membrane in a Ras-dependent manner. Deletion of the cyclic AMP-binding domain overcame the need for nucleotide, suggesting that this domain normally masked the RA domain in the resting GEF. Thus, Epac2 can respond to costimulation by agonists that jointly elevate Ras-GTP and cyclic AMP levels, activating a specific pool of Rap1 at the plasma membrane. Therefore, despite its previous description as a Ras antagonist or independently functioning GTPase, Rap1/Krev-1 may additionally act downstream of Ras in cells that express the cyclic AMP-regulated GEF, Epac2.

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“…The event is important for regulation of endocytosis of the receptor (Mosesson et al, 2003;Soubeyran et al, 2002) and for lysosomal degradation (Longva et al, 2002). Furthermore, some of the GEFs, namely Vav and CNrasGEF (for 'cyclic nucleotide ras GEF'), are ubiquitylated by Cbl and Nedd4, respectively (Miura-Shimura et al, 2003;Pham and Rotin, 2001). Finally, it has been suggested that ubiquitin-dependent protein degradation regulates actin cytoskeletal reorganisation.…”

Section: Introductionmentioning

confidence: 99%

Elmo1 inhibits ubiquitylation of Dock180

Makino

Tsuda

Ichihara

et al. 2006

Journal of Cell Science

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Dock180, a member of the CDM family of proteins, plays roles in biological processes such as phagocytosis and motility through its association with the signalling adaptor protein Crk. Recently, the complex formation between Dock180 and Elmo1 was reported to function as a bipartite guanine nucleotide exchange factor for Rac. In this study, we demonstrated that the amount of Dock180 increased when Elmo1 was co-expressed. Dock180 was found to be ubiquitylated and Dock180 protein levels could be augmented by treatment with proteasome inhibitor. The ubiquitylation of Dock180 was enhanced by epidermal growth factor (EGF), Crk and adhesion-dependent signals. Furthermore, Elmo1 inhibited ubiquitylation of Dock180, resulting in the increase in Dock180 levels. The Elmo1 mutant Δ531, which encompasses amino acids required for Dock180 binding, preserved the inhibitory effects on ubiquitylation of Dock180. Upon EGF stimulation, both Dock180 and ubiquitin were demonstrated to translocate to the cell periphery by immunofluorescence, and we found ubiquitylation of Dock180 and its inhibition by Elmo1 to occur in cellular membrane fractions by in vivo ubiquitylation assay. These data suggest that Dock180 is ubiquitylated on the plasma membrane, and also that Elmo1 functions as an inhibitor of ubiquitylation of Dock180. Therefore, an ubiquitin-proteasome-dependent protein degradation mechanism might contribute to the local activation of Rac on the plasma membrane.

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Nedd4 Regulates Ubiquitination and Stability of the Guanine-Nucleotide Exchange Factor CNrasGEF

Cited by 45 publications

References 35 publications

Morphine Induces Ubiquitin-Proteasome Activity and Glutamate Transporter Degradation

Morphine Induces Ubiquitin-Proteasome Activity and Glutamate Transporter Degradation

The RAP1 Guanine Nucleotide Exchange Factor Epac2 Couples Cyclic AMP and Ras Signals at the Plasma Membrane

Elmo1 inhibits ubiquitylation of Dock180

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