Function of the Small Guanosine Triphosphate-Binding Protein RhoA in the Process of Implantation

The homotypic fusion of yeast vacuoles requires Sec18p (NSF)-driven priming to allow vacuole docking, but the mechanism that links priming and docking is unknown. We find that a large multisubunit protein called the Vam2/6p complex is bound to cis-paired SNAP receptors (SNAREs) on isolated vacuoles. This association of the Vam2/6p complex with the cis-SNARE complex is disrupted during priming. The Vam2/6p complex then binds to Ypt7p, a guanosine triphosphate binding protein of the Rab family, to initiate productive contact between vacuoles. Thus, cis-SNARE complexes can contain Rab/Ypt effectors, and these effectors can be mobilized by NSF/Sec18p-driven priming, allowing their direct association with a Rab/Ypt protein to activate docking.

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Islet activating protein-sensitive guanosine triphosphate-binding protein regulates K+-channels coupled with FMRFamide receptors.

The Japanese Journal of Physiology ◽

10.2170/jjphysiol.37.551 ◽

1987 ◽

Vol 37 (3) ◽

pp. 551-557 ◽

Cited By ~ 9

Author(s):

Kazuhiko SASAKI ◽

Junko TAKAHASHI ◽

Mitsuhiko MATSUMOTO ◽

Koichiro TAKASHIMA ◽

Seishi HAKOZAKI ◽

...

Keyword(s):

Binding Protein ◽

Guanosine Triphosphate ◽

K Channels

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Role of pertussis toxin-sensitive guanosine triphosphate-binding proteins in the response of erythroblasts to erythropoietin

Blood ◽

10.1182/blood.v77.3.486.486 ◽

1991 ◽

Vol 77 (3) ◽

pp. 486-492 ◽

Cited By ~ 16

Author(s):

BA Miller ◽

K Foster ◽

JD Robishaw ◽

CF Whitfield ◽

L Bell ◽

...

Keyword(s):

Adenylate Cyclase ◽

Pertussis Toxin ◽

Binding Proteins ◽

Binding Protein ◽

Cyclase Activity ◽

Adenylate Cyclase Activity ◽

Guanosine Triphosphate ◽

Gtp Binding Protein ◽

Gtp Binding

Abstract Human progenitor-derived erythroblasts have been recently shown to respond to erythropoietin (Epo) with an increase in intracellular free calcium concentration [Cac]. To explore the role of guanosine triphosphate (GTP)-binding proteins in mediating the rise in [Cac], single day 10 erythroid burst forming unit (BFU-E)-derived erythroblasts loaded with Fura-2 were pretreated with pertussis toxin (PT), stimulated with Epo, and [Cac] measured over 18 minutes with fluorescence microscopy coupled to digital video imaging. The [Cac] increase in day 10 erythroblasts stimulated with Epo was blocked by pretreatment with PT in a dose-dependent manner but not by heat- inactivated PT. These observations provided strong evidence that a PT- sensitive GTP-binding protein is involved. To further characterize the GTP-binding protein, day 10 erythroblast membrane preparations were solubilized, electrophoresed, and immunoblotted with antibodies specific for the known PT-sensitive G-protein subunits: the three subtypes of Gia (1,2, and 3) and Goa, Gia1 or Gia3 and Gia2 were identified but no Goa was found. To examine the influence of Epo on adenylate cyclase activity, day 10 erythroblasts were initially treated with Epo, isolated membrane preparations made, and cyclic adenosine monophosphate (cAMP) production by adenylate cyclase in membrane preparations in the presence of theophylline measured. Epo did not inhibit but significantly stimulated adenylate cyclase activity. However, the mechanism of increase of [Cac] appears to be independent of adenylate cyclase stimulation because treatment of erythroblasts with the cell-permeant dibutyryl cAMP failed to increase [Cac]. In summary, pertussis toxin blocks the increase in [Cac] in erythroblasts after Epo stimulation suggesting that this response is mediated through a pertussis toxin-sensitive GTP-binding protein. Candidate PT-sensitive GTP-binding proteins identified on day 10 erythroblasts were Gia 1, 2, or 3, but not Goa.

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Variation in the Small Guanosine Triphosphate (GTP)-Binding Protein, Secretion-Associated and RAS-Related (SAR1A) Gene and Response to Hydroxyurea Treatment in Sickle Cell Disease.

Blood ◽

10.1182/blood.v110.11.3392.3392 ◽

2007 ◽

Vol 110 (11) ◽

pp. 3392-3392

Author(s):

Chutima Kumkhaek ◽

Jianqiong Zhu ◽

James G. Taylor ◽

Carolyn Hoppe ◽

Gregory J. Kato ◽

...

Keyword(s):

Sickle Cell Disease ◽

Confidence Interval ◽

Sickle Cell ◽

Protein Secretion ◽

Binding Protein ◽

Erythroid Cell ◽

Cell Disease ◽

Guanosine Triphosphate ◽

Gtp Binding Protein ◽

Gtp Binding

Abstract Hydroxyurea (HU) is a well-known chemotherapeutic agent and a potent ribonuclease reductase inhibitor that induces Hb F synthesis in sickle cell disease and some thalassemia syndromes. Our group has shown that the HU-inducible small guanosine triphosphate (GTP)-binding protein, secretion-associated and RAS-related (SAR) protein plays a role in g-globin gene induction and erythroid cell maturation by causing cell apoptosis and G1/S-phase arrest through the reduction of PI3 kinase and ERK phosphorylation and increased p21 and GATA2 expression. Our preliminary analysis indicates that HU inducibility is mediated at the transcriptional level, and is localized to elements in the SAR1A promoter. The aim of this study was to assess whether polymorphisms in the SAR1A gene promoter are associated with Hb F levels or HU therapeutic responses. We studied 386 sickle cell disease patients consisting of 269 adults treated with or without HU and 117 newborns with sickle cell disease identified from a newborn screening program. Twenty point mutations, including one nonsynonymous variant, were identified in SAR1A, including nine previously reported in SNP databases. A difference in genotype frequencies was observed between adults and newborns for rs2310991 in the 5′UTR (odd ratio [OR] = 1.9, 95% confidence interval [CI] = 1.1–3.2, P=0.009) and +31 T>C in 5′UTR (odd ratio [OR] 9.8 [ 1.3–73.9]; confidence interval [CI] 95%; P<0.001). Three previously unknown SNPs in the upstream 5′UTR (−809 C>T, −502 G>T and −385 C>A) were significantly associated with the HbF response in Hb SS patients treated with HU (P<0.05). Our data suggest that the SAR1A polymorphism might contribute to the regulation of HbF expression and modulate patient responses to HU in sickle cell disease.

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