A stimulatory GDP/GTP exchange protein for smg p21 is active on the post-translationally processed form of c-Ki-ras p21 and rhoA p21.

Mizuno, Takakazu; Kaibuchi, Kozo; Yamamoto, Takakazu; Kawamura, M.; Sakoda, Tsuyoshi; Fujioka, Hiroyuki; Matsuura, Yoshiharu; Takai, Yoshimi

doi:10.1073/pnas.88.15.6442

Cited by 188 publications

(150 citation statements)

References 33 publications

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“…Non-prenylated small GTPases migrate slower than prenylated small GTPases in SDS-PAGE gels (11,26). We found that Rac1 and Rac1(PBRQ) proteins exhibit similar rates of migration on SDS-PAGE gels (Fig.…”

Section: Smggds Has a Nuclear Export Signal Sequence-becausementioning

confidence: 67%

“…Our demonstration that Rac1 and RhoA regulate the nucleocytoplasmic shuttling of SmgGDS and p120ctn raises the intriguing possibility that these GTPases affect the nuclear localization of other ARM proteins. Other small GTPases with a PBR, which have been reported to interact with SmgGDS, include Cdc42 (13,14), K-Ras4B (11,14), Rap1A (18), Rap1B (11,14), and RalA (18). The PBRs of these GTPases may have functions similar to those of Rac1 and RhoA.…”

Section: Discussionmentioning

confidence: 99%

“…SmgGDS interacts with nuclear proteins (23,24) and cytoplasmic proteins (11)(12)(13)(14)(15)18), we looked for sequences in SmgGDS that might promote nucleocytoplasmic shuttling. Although classic NLS sequences are not apparent in SmgGDS, putative NES sequences, consisting of LX (2)(3) LXXLXL in which the leucines are sometimes replaced by isoleucines (reviewed in Ref.…”

Section: Smggds Has a Nuclear Export Signal Sequence-becausementioning

confidence: 99%

“…SmgGDS promotes guanine nucleotide exchange by small GTPases containing a C-terminal polybasic region (PBR), which is a series of adjacent lysines or arginines (11)(12)(13)(14)(15)18). We noticed a striking sequence similarity between the PBR of small GTPases that interact with Smg-GDS and the NLS sequence of proteins that associate with the ARM protein karyopherin ␣.…”

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confidence: 99%

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Novel Mechanism of the Co-regulation of Nuclear Transport of SmgGDS and Rac1

Lanning

Ruiz-Velasco

Williams

2003

Journal of Biological Chemistry

131

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The armadillo protein SmgGDS promotes guanine nucleotide exchange by small GTPases containing a C-terminal polybasic region (PBR), such as Rac1 and RhoA. Because the PBR resembles a nuclear localization signal (NLS) sequence, we investigated the nuclear transport of SmgGDS with Rac1 or RhoA. We show that the Rac1 PBR has significant NLS activity when it is fused to green fluorescent protein (GFP) or in the context of full-length Rac1. In contrast, the RhoA PBR has very poor NLS activity when it is fused to GFP or in the context of full-length RhoA. The nuclear accumulation of both Rac1 and SmgGDS is enhanced by Rac1 activation and diminished by mutation of the Rac1 PBR. Conversely, SmgGDS nuclear accumulation is diminished by interactions with RhoA. An SmgGDS nuclear export signal sequence that we identified promotes SmgGDS nuclear export. These results suggest that SmgGDS⅐ Rac1 complexes accumulate in the nucleus because the Rac1 PBR has NLS activity and because Rac1 supplies the appropriate GTP-dependent signal. In contrast, SmgGDS⅐RhoA complexes accumulate in the cytoplasm because the RhoA PBR does not have NLS activity. This model may be applicable to other armadillo proteins in addition to SmgGDS, because we demonstrate that activated Rac1 and RhoA also provide stimulatory and inhibitory signals, respectively, for the nuclear accumulation of p120 catenin. These results indicate that small GTPases with a PBR can regulate the nuclear transport of armadillo proteins.Armadillo (ARM) 1 family proteins that contain multiple copies of the ϳ42-amino acid (aa) ARM motif include SmgGDS, p120 catenin (p120ctn), ␤-catenin, plakoglobin, APC, karyopherin ␣ (also known as importin ␣), and several other proteins (reviewed in Refs. 1-3). Nucleocytoplasmic shuttling by many ARM proteins allows them to regulate events in different cellular compartments, including gene transcription and cell adhesion (reviewed in Refs. 2-7). ARM proteins enter the nucleus by different mechanisms (reviewed in Refs. 2-7). Karyopherin ␣ enters the nucleus when it associates with proteins containing a nuclear localization signal (NLS) sequence consisting of a series of adjacent lysines or arginines (reviewed in Ref. 3). The NLS sequence is believed to anchor within the long surface groove formed by the multiple ARM repeats of karyopherin ␣, promoting the nuclear import of both the NLS-containing protein and karyopherin ␣ (3, 5). APC possesses two NLS sequences and may enter the nucleus by associating with karyopherin ␣ or related proteins (4, 7). The mechanisms by which other ARM proteins enter the nucleus are less clear, because some of these proteins neither possess classic NLS sequences, nor have they been reported to associate with NLS-containing proteins.Several ARM proteins interact with the Rho family of small GTPases (8 -15) or with guanine nucleotide exchange factors (GEFs) for these GTPases (16,17). SmgGDS promotes guanine nucleotide exchange by small GTPases containing a C-terminal polybasic region (PBR), which is a series of adjacent l...

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Section: Smggds Has a Nuclear Export Signal Sequence-becausementioning

confidence: 67%

Section: Discussionmentioning

confidence: 99%

Section: Smggds Has a Nuclear Export Signal Sequence-becausementioning

confidence: 99%

mentioning

confidence: 99%

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Novel Mechanism of the Co-regulation of Nuclear Transport of SmgGDS and Rac1

Lanning

Ruiz-Velasco

Williams

2003

Journal of Biological Chemistry

131

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“…Recombinant isoprenylated RhoA was prepared from Sf9 cells expressing human RhoA as described by Mizuno et al (29).…”

Section: Preparation Of S Pombe Extract and Cellmentioning

confidence: 99%

Cloning, Expression, and Characterization of a Novel Phospholipase D Complementary DNA from Rat Brain

Kodaki

Yamashita

1997

Journal of Biological Chemistry

219

165

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Here we report the cloning and characterization of cDNA for a different type of PLD (rat PLD2 (rPLD2)) from rat brain. We synthesized highly degenerate amplimers corresponding to the conserved regions of eukaryote PLDs and performed polymerase chain reaction on a rat brain cDNA library. Using the amplified sequence as the probe, we cloned a rat brain cDNA clone that contained an open reading frame of 933 amino acids with an M r of 105,992. The deduced amino acid sequence showed significant similarity to hPLD1 with a large deletion in the middle of the sequence. When the sequence was expressed in the fission yeast Schizosaccharomyces pombe, PLD activity was greatly increased. The activity was markedly stimulated by phosphatidylinositol 4,5-bisphosphate, but not by ADPribosylation factor 1 and RhoA. Rat brain cytosol known to stimulate small GTP-binding protein-dependent PLD did not stimulate rPLD2 expressed in S. pombe. The transcript was detected at significant levels in brain, lung, heart, kidney, stomach, small intestine, colon, and testis, but at low levels in thymus, liver, and muscle. Only a negligible level was found in spleen and pancreas. Thus rPLD2 is a novel type of PLD dependent on phosphatidylinositol 4,5-bisphosphate, but not on the small GTP-binding proteins ADP-ribosylation factor 1 and RhoA. Phospholipase D (PLD)1 catalyzes the hydrolysis of phosphatidylcholine (PC) to phosphatidic acid and choline (1). A variety of signal molecules such as hormones, neurotransmitters, and growth factors are known to induce the activation of PLD in a wide range of cell types. Hence PLD is implicated in a broad spectrum of physiological processes and diseases, including metabolic regulation, inflammation, secretion, mitogenesis, oncogenesis, neural and cardiac stimulation, diabetes, and senescence (for reviews, see Ref.2). Despite its crucial importance in signal transduction, the molecular structure and characteristics of PLD enzyme are only poorly understood.Multiple PLD isoforms exist in mammalian tissues. Several factors were reported to stimulate PLD activity in vitro, including unsaturated fatty acid (3), phosphatidylinositol 4,5-bisphosphate (PIP 2 ) (4), monomeric GTP-binding proteins (G proteins) such as ADP-ribosylation factor 1 (ARF1) (5, 6) and RhoA (7, 8), protein kinase C (9), and calmodulin (10). Massenburg et al. (11) showed that two major forms of PLD activity in rat brain membranes can be separated into ARF-dependent and oleate-dependent enzymes, clearly indicating that these are distinct isoforms. Both oleate-dependent and ARF-dependent types of PLD were recently highly purified from pig lung and brain, respectively (12, 13). In addition, there may be multiple forms of small G protein-dependent PLD including ARF-sensitive, RhoA-sensitive, and ARF-, RhoA-sensitive PLDs. Siddiqi et al. (14) reported that the cytosolic fraction of HL-60 cells contained a soluble PLD activated by ARF, but not RhoA. Malcolm et al. (8) showed rat liver plasma membrane PLD to be sensitive to RhoA, but not to ARF. PL...

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