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At least 19 recordsLinked to original sources
PubMed1992

Effects of phospholipid and GTP on recombinant ADP-ribosylation factors (ARFs). Molecular basis for differences in requirements for activity of mammalian ARFs.

ADP-ribosylation factors (ARFs) are highly conserved approximately 20-kDa guanine nucleotide-binding proteins that were first identified based on their ability to stimulate the cholera toxin-catalyzed ADP-ribosylation of Gs alpha and thus activate adenylyl cyclase. Proteins with ARF activity have been characterized from different mammalian tissues and exhibited different requirements for activity, stability, and phospholipid. Based on molecular cloning and mRNA distribution, at least six mammalian ARFs, which fall into three classes, have been identified. To test whether individual ARFs might have different requirements for optimal activity, as judged by their ability to enhance cholera toxin ADP-ribosyltransferase activity, four ARFs from classes I, II, and III were produced as recombinant proteins in Escherichia coli and characterized. Recombinant bovine ARF 2 (rARF 2) and human ARF 3 (rARF 3) (class I), human ARF 5 (rARF 5, class II), and human ARF 6 (rARF 6, class III) differed in the effects of phospholipid and detergent on their ability to enhance cholera toxin activity; rARFs 2, 3, and 5 required dimyristoylphosphatidylcholine (DMPC) and cholate, whereas rARF 6 did not require phospholipid/detergent for activity. Further characterization of two of the more divergent ARFs (ARFs 2 and 6) showed that both exhibited guanosine 5'-O-(3-thio)triphosphate binding which was enhanced by DMPC/cholate. In the transferase assay, rARF 2 required approximately 4 microM GTP for half-maximal stimulation of toxin activity, whereas rARF 6 required 0.05 microM GTP. rARF 6 exhibited a delay in activation of toxin not detected with rARF 2 that may be related to a requirement for guanine nucleotide exchange and/or GTP binding. These findings are consistent with the conclusion that the highly conserved members of the ARF family have different requirements for optimal activity.

ADP-Ribosylation Factor 6↗
PubMed1992

Human and Giardia ADP-ribosylation factors (ARFs) complement ARF function in Saccharomyces cerevisiae.

ADP-ribosylation factors (ARFs) are approximately 20-kDa guanine nucleotide-binding proteins that stimulate the ADP-ribosyltransferase activity of cholera toxin in vitro. ARFs are highly conserved, ubiquitously expressed in eukaryotic cells and appear to be involved in vesicular protein transport. The two yeast ARFs are > 60% identical to mammalian ARFs and are essential for cell viability (Stearns, T., Kahn, R. A., Botstein, D., and Hoyt, M. A. (1990) Mol. Cell. Biol. 10, 6690-6699). Although the two yeast ARF proteins are 96% identical in amino acid sequence, the yeast ARF1 gene is constitutively expressed, whereas the ARF2 gene is repressed by glucose. Human ARF5 and ARF6 and a Giardia ARF differ substantially in size and amino acid identity from other mammalian and eukaryotic ARFs but will, as befits their designation, activate cholera toxin. Expression of human ARF5, ARF6, or Giardia ARF cDNA rescued the lethal yeast ARF double mutant (arf1, arf2). Strains rescued by human ARF5, ARF6, or Giardia ARF grew much more slowly than wild-type yeast or strains rescued with yeast ARF1. We infer from the impaired growth of these rescued strains that the homologous ARFs may have specific targeting information that does not interact effectively or efficiently with the yeast protein membrane trafficking system.

ADP-Ribosylation Factor 1↗
PubMed1992

Regulation of ADP-ribosylation factor (ARF) expression. Cross-species conservation of the developmental and tissue-specific alternative polyadenylation of ARF 4 mRNA.

ADP-ribosylation factors (ARFs), approximately 20-kDa guanine nucleotide-binding proteins, are involved in protein trafficking and enhance cholera toxin ADP-ribosyltransferase activity. Expression of six ARF genes was examined in mammalian tissues; only ARF 4 mRNA was detected in rat testis in forms considerably shorter than those in other tissues. Testis-specific expression of short forms of ARF 4 mRNA was observed in several mammalian species. On Northern analysis of the developmental expression of rat ARF 4 mRNA, appearance of the shorter species was consistent with its involvement in a late stage of spermatogenesis. Sequences of products of rapid amplification of cDNA ends (RACE-polymerase chain reaction) of rat ARF 4 mRNA revealed that different mRNAs resulted from the use of three polyadenylation signals, one AUUAAA and two AAUAAA. Sequences of 3'-untranslated regions of rat and human ARF 4 mRNA were very similar with identical polyadenylation signals at similar positions. Of the ARF 4 mRNAs identified by RACE-PCR, with sizes of 1.1, 1.3, and 1.8 kb, the 1.1-kb mRNA was predominant in adult testis. By in situ hybridization, the 1.1-kb mRNA was identified primarily in mature sperm, consistent with the developmental studies. Shorter mRNAs, thought to be more stable, may compensate for cessation of transcription at late stages of spermatogenesis.

ADP-Ribosylation Factors↗
PubMed1992

The amino terminus of ADP-ribosylation factor (ARF) is a critical determinant of ARF activities and is a potent and specific inhibitor of protein transport.

Deletion of the amino-terminal 17 residues from human ADP-ribosylation factor (ARF) resulted in a protein ([delta 1-17]mARF1p) devoid of ARF activity but which retained the ability to bind guanine nucleotides with high affinity. Unlike the wild type, the binding of guanine nucleotides to this deletion mutant was found to be independent of added phospholipids. A chimeric protein was produced, consisting of 10% (the amino-terminal 17 amino acids) human ARF1p and 90% ARL1p, an ARF-like protein (55% identical protein sequence) from Drosophila. This chimera was found to have ARF activity, lacking in the parental ARL1 protein. Thus, the amino terminus of ARF1p was shown to be a critical component of ARF activity. A synthetic peptide, derived from the amino terminus of ARF1p, has no ARF activity. Rather, the peptide was found to be a specific inhibitor of ARF activities. This peptide was also found to be a potent and specific inhibitor of both an in vitro intra-Golgi transport assay and the guanosine 5'-3-O-(thio)triphosphate-stimulated accumulation of coated vesicles and buds from Golgi preparations. We conclude that ARF is required for the budding of coated vesicles from the Golgi stacks and serves a regulatory role in protein secretion through the Golgi in eukaryotic cells.

ADP-Ribosylation Factor 1↗
PubMed1990

Mechanism of activation of cholera toxin by ADP-ribosylation factor (ARF): both low- and high-affinity interactions of ARF with guanine nucleotides promote toxin activation.

Activation of adenylyl cyclase by cholera toxin A subunit (CT-A) results from the ADP-ribosylation of the stimulatory guanine nucleotide binding protein (GS alpha). This process requires GTP and an endogenous guanine nucleotide binding protein known as ADP-ribosylation factor (ARF). One membrane (mARF) and two soluble forms (sARF I and sARF II) of ARF have been purified from bovine brain. Because the conditions reported to enhance the binding of guanine nucleotides by ARF differ from those observed to promote optimal activity, we sought to characterize the determinants influencing the functional interaction of guanine nucleotides with ARF. High-affinity GTP binding by sARF II (apparent KD of approximately 70 nM) required Mg2+, DMPC, and sodium cholate. sARF II, in DMPC/cholate, also enhanced CT-A ADP-ribosyltransferase activity (apparent EC50 for GTP of approximately 50 nM), although there was a delay before achievement of a maximal rate of sARF II stimulated toxin activity. The delay was abolished by incubation of sARF II with GTP at 30 degrees C before initiation of the assay. In contrast, a maximal rate of activation of toxin by sARF II, in 0.003% SDS, occurred without delay (apparent EC50 for GTP of approximately 5 microM). High-affinity GTP binding by sARF II was not detectable in SDS. Enhancement of CT-A ADP-ribosyltransferase activity by sARF II, therefore, can occur under conditions in which sARF II exhibits either a relatively low affinity or a relatively high affinity for GTP. The interaction of GTP with ARF under these conditions may reflect ways in which intracellular membrane and cytosolic environments modulate GTP-mediated activation of ARF.

ADP-Ribosylation Factors↗
PubMed1986

Loss of glomerular responses to vasoconstrictor agents in rabbits recovering from ARF.

Glomerular responses to angiotensin II (AII), arginine vasopressin (AVP), and norepinephrine (NE) were estimated in rabbits recovering from uranium-mediated nephropathy or ischemic acute renal failure (ARF) to examine roles of intraglomerular events in resistance to ARF. Uranyl acetate (UA, 0.8 mg/kg) produced ARF in some animals but did not in others. Rabbits recovering from UA-induced ARF were highly resistant to a rechallenge with a larger dose of the agent (2 mg/kg). Their glomeruli did not respond to AII, AVP and NE in vitro. In animals having not experienced ARF following the initial insult, however, resistance to the rechallenge was lower than in animals recovering from ARF, and the glomerular response to contractile stimuli was well sustained. A two hour clamping of the renal artery induced ARF in uninephrectomized rabbits. These animals were not resistant to an additional ischemia in the recovery phase, despite inhibited glomerular contractile responses to AII. These data indicate a nonspecific inhibition of glomerular responses to contractile stimuli in the recovery phase of ARF. It is unlikely, however, that resistance to ARF can be attributed to the loss of the glomerular contractile response.

Acute Kidney Injury↗
PubMed1979

The diagnosis of acute renal failure (ARF) following cardiac surgery with cardio-pulmonary bypass.

The diagnostic value of renal concentrating capacity expressed as free water clearance (CH2O), in comparison with other routine criteria for the early identification of acute renal failure (ARF), was evaluated in 1,203 adult patients undergoing cardiac surgical procedures. On the basis of the appearance of pathologic CH2O values in the range of -20 to 0 ml/hour or more positive, reversible or irreversible ARF was observed in 90 (= 7.5%) of our patients. Mortality in the presence of ARF was 47%; total ARF mortality was 3.5%. CH2O was pathologic for the first time on an average of 1.6 days after operation. In contrast, routine ARF criteria reported in the literature, such as serum urea and creatinine at varying substrate levels or oliguria, allowed diagnosis 1 to 5.5 days later. Moreover, these parameters only partially and less frequently met the criteria for ARF at the different levels. Likewise, the incidence of ARF decreased to a minimum of 1.7% and the total ARF mortality to 1.3%, depending on the severity of the criteria used. Altogether, the occurrence of pathologic CH2O values proved to be the earliest, most frequent and most reliable criterion for the recognition of ARF following cardiac surgery with cardiac-pulmonary bypass.

Acute Kidney Injury↗
PubMed1992

Inhibition by brefeldin A of a Golgi membrane enzyme that catalyses exchange of guanine nucleotide bound to ARF.

A wide variety of membrane transformations important in intracellular transport are inhibited by the fungal metabolite brefeldin A (refs 1-4), implying that the target for this drug is central to the formation and maintenance of subcellular compartments. Brefeldin A added to cells causes the rapid and reversible dissociation of a Golgi-associated peripheral membrane protein (M(r) 110,000) which was found to be identical to one of the subunits of the coat of Golgi-derived (non-clathrin) coated vesicles, beta-COP, implying that brefeldin A prevents transport by blocking the assembly of coats and thus the budding of enclosed vesicles. In addition to the coatomer (a cytosol-derived complex of seven polypeptide chains, one of which is beta-COP), the non-clathrin (COP) coat of Golgi-derived vesicles contains stoichiometric amounts of a small (M(r) approximately 20,000) GTP-binding protein, the ADP-ribosylation factor (ARF). Binding of ARF to Golgi membranes is necessary before coatomer/beta-COP can bind these membranes (ref. 12; and D. J. Palmer et al., manuscript submitted), so the primary effect of brefeldin A seems to be on the reaction responsible for ARF binding. Indeed, like beta-COP, ARF is dissociated from the Golgi complex by treatment with brefeldin A and brefeldin A prevents ARF from associating in vitro, but the mechanism of this action by brefeldin A has been unclear. Here we report the discovery of an enzyme in a Golgi-enriched fraction that catalyses guanine nucleotide (GDP-GTP) exchange on ARF-1 protein, and which is inhibited by brefeldin A. We suggest that activation of ARF proteins for membrane localization by compartmentalized exchange enzymes is in general the first committed step in membrane transformation pathways.

ADP-Ribosylation Factors↗
PubMed1992

Evidence for ADP-ribosylation factor (ARF) as a regulator of in vitro endosome-endosome fusion.

We have used an in vitro endosome fusion assay, recombinant ARF, synthetic peptides, and guanosine 5'-3-O-(thio)triphosphate (GTP gamma S) to study the role of ARF during endocytosis. Previous work has shown that GTP gamma S stimulates in vitro endosome fusion in dilute cytosol (less than 0.5 mg/ml) but inhibits fusion in concentrated cytosol (greater than 1.0 mg/ml). Two peptides corresponding to the NH2-terminal 16 amino acids of human ARF1 and ARF4 blocked GTP gamma S stimulation of fusion in dilute cytosol and reversed GTP gamma S inhibition of fusion in concentrated cytosol. The addition of recombinant human ARF1 to endosomes in dilute or concentrated cytosol resulted in GTP gamma S-dependent inhibition of fusion. Only the myristoylated form of ARF inhibited fusion. The NH2-terminal ARF1 peptide reversed inhibition by recombinant ARF1. Preincubation experiments showed that endosomes could form an ARF-resistant intermediate during the fusion process. Western blot analysis revealed clathrin-coated vesicles extracted with detergent retained ARF. The results suggest that ARF is involved in both the stimulatory and inhibitory effects of GTP gamma S in dilute and concentrated cytosol, respectively. Furthermore, myristoylation, the NH2-terminal domain, and binding to GTP appear to be critical for ARF activity during an early prefusion step required for endocytosis.

ADP-Ribosylation Factor 1↗
PubMed1992

[Mechanisms and therapeutic effect of Cordyceps sinensis (CS) on aminoglycoside induced acute renal failure (ARF) in rats].

Nephrotoxic ARF model of rat was induced by IP injection of either Gentamycin or Kanamycin and treated with CS. The results of study showed that the simultaneous administration of CS with Gentamycin could protect the proximal tubular cells from Gentamycin toxicity and the use of CS after the establishment of Kanamycin nephrotoxic ARF could prompt an earlier recovery from ARF as compared with the control group. The possible mechanisms of CS on ARF include: (1) protecting tubular cell sodium pump activity; (2) attenuating tubular cell lysosome overfunction stimulated by phagocytosis of aminoglycoside; (3) decreasing tubular cell lipoperoxidation in response to toxic injury.

Acute Kidney Injury↗
PubMed1985

Comparison of the effects of argon fluoride (ArF) and krypton fluoride (KrF) excimer lasers on ocular structures.

We evaluated the effects of argon fluoride (ArF) and krypton fluoride (KrF) excimer lasers on ocular structures. We produced corneal incisions, optical iridotomy, capsulotomy, and retinotomy with these lasers. Incisions produced with ArF showed sharply defined borders with minimal coagulative effects to the adjacent structures. Cuts created with KrF showed coagulative necrosis of the wound edges ranging from two to five um in width. From our study it appears that ArF has photoablative action and KrF has a predominantly photoablative action with minimal photocoagulative effect on the tissue.

Animals↗
PubMed1992

Brefeldin A inhibits Golgi membrane-catalysed exchange of guanine nucleotide onto ARF protein.

The fungal metabolite brefeldin A is a powerful tool for investigating membrane traffic in eukaryotic cells. The effects of brefeldin A on traffic are partly explained by its ability to prevent binding of cytosolic coat proteins onto membranes. The non-clathrin coatomer complex binds reversibly to Golgi membranes in a GTP-controlled cycle. The low-molecular-mass GTP-binding protein ADP-ribosylation factor (ARF), which also associates reversibly with Golgi membranes, is required for coatomer binding and probably accounts for the control by guanine nucleotide of the coatomer-membrane interaction. Brefeldin A prevents the assembly of coatomer onto the membrane by inhibiting the GTP-dependent interaction of ARF with the Golgi membrane, but the nature of this interaction has not been established. Here we demonstrate that Golgi membranes can specifically catalyse the exchange of GTP onto ARF and that brefeldin A prevents this function.

ADP-Ribosylation Factors↗
PubMed2026

Auxin-induced ARF transcription factor degradation defines tissue boundaries.

How organs partition themselves into discrete domains with distinct functions is a fundamental question in biology. The gynoecium of flowering plants provides an excellent system to address this question. Here, we show that the boundary between the stigma and style at the gynoecium apex is established by the complementary distribution of the phytohormone auxin and the Auxin Response Factor (ARF), ETTIN (ETT). Mechanistically, auxin induces ETT protein destabilization via the ubiquitin-proteasome pathway. A short sequence motif within an intrinsically disordered region is required for this auxin-triggered degradation. Disruption of this motif leads to ectopic ETT accumulation at the gynoecium apex and consequently abolishes stigma-style boundary development. We further demonstrate that this previously unrecognized mode of auxin-induced ARF instability is evolutionarily conserved among ETT orthologs across angiosperms. In summary, this study reveals how graded auxin distribution affects ARF transcription factor activity, contributing to the establishment of the stigma-style boundary, ensuring correct gynoecium formation and reproductive success in flowering plants.

Indoleacetic Acids↗
PubMed1992

Clinical significance of kidney biopsy in acute renal failure (ARF).

Out of 152 cases of Acute renal failure (ARF) 32 patients (21%) were subjected to kidney biopsy. All patients had intrinsic ARF. Prerenal azotemia and obstructive uropathy were excluded. Histologic observations were: Crescentric glomerulonephritis in 7 (21.9%), acute endocapillary proliferative glomerulonephritis 5 (15.6%), acute interstitial nephritis 7 (21.9%), necrotizing vasculitis 4 (12.5%), acute tubular necrosis in 5 (15.6%) and membrano-proliferative GN with superimposed crescent in 2 (6.2%) while renal cortical necrosis was seen in 6.2% of cases. Prebiopsy diagnosis was correct in only 10 (31.25%) cases. The result of biopsy had altered clinical diagnosis in 22 (68.75%) patients and precise renal biopsy diagnosis resulted in therapeutic changes in 54.8% of patients with ARF.

Acute Kidney Injury↗
PubMed1988

Persistence of heart reactive antibodies (HRA) in acute rheumatic fever (ARF) and rheumatic heart disease (RHD) patients.

Heart Reactive Antibodies (HRA) of IgG and IgM classes were investigated in 79 patients in four clinically classified groups. Group I comprised of 16 children with Acute Rheumatic Fever (ARF) and Group II consisted of 15 cases with active Rheumatic Heart Disease (RHD). Twenty seven cases of ARF and RHD in remission and 21 adults with quiescent RHD were included in Groups III and IV respectively. Control groups comprised of 14 normal, healthy, donors and eight Post Streptococcal Acute Glomerular Nephritis (PSAGN) cases. Low levels of HRA of IgG and IgM classes were detected in control groups. The overall incidence of HRA of IgG and IgM classes was 82.28 and 39.24% respectively in the patient group. An increased frequency of HRA-IgM antibodies was observed in Groups I, III and IV (p less than 0.01, 0.001 and 0.025 respectively). All the four groups demonstrated a highly significant increase in incidence of HRA--IgG class (p less than 0.0005). Persistence of high titres of HRA-IgG class in ARF and RHD is reported in the paper.

Adolescent↗
PubMed1977

Reduction in severity of acute renal failure (ARF) in rats by dopamine.

Dopamine was administered to rats at the time of initiation of anoxic acute renal failure. Dopamine partially reduced the severity of ARF as evidenced by a reduction in blood urea, serum creatinine as well as an increase in glomerular filtration rate (GFR). (UNaV) in dopamine treated ARF was similar to sham operated animals and both were significantly lower than control ARF.

Acute Kidney Injury↗
PubMed2026

Integrated analysis of ATAC-seq and RNA-seq reveals the TCP-ARF molecular module related to pathogenic process of phytoplasma infection in Paulownia fortunei.

BACKGROUND: Witches’ broom is an important disease of the Paulownia fortunei. Understanding the pathogenesis of witches’ broom is a prerequisite for its prevention and control. Phytoplasma is the pathogen of Paulownia witches’ broom. RESULTS: We investigated the changes in chromatin accessibility before and after phytoplasma infection in Paulownia fortunei by analyzing the DNA accessibility (ATAC-seq). In phytoplasma-infected P. fortunei (PFI) compared to healthy samples (PF), the closed regions of chromatin(1187 regions) were three times more than the open regions (352 regions). Fifty one percent of the accessible chromatin regions were overlapped with either H3K27ac or H3K9ac peaks. The closed regions were enriched in the conserved motif TGGGC[CT] that is recognized by the TCP transcription factor family. The closed regions in PFI are intersected with ARF family gene locus. The gene PfARF3 was verified to interact with the PfTCP23 transcription factor. The PfTCP23 was predicted to be interacted with the effector pawb44 in the pathogen of phytoplasma. CONCLUSIONS: The phytoplasma infection in P. fortunei is involved in the chromatin changes of the DNA accessibility and histone modification. The binding regions of TCP23 were found to be changed mostly in the accessibility between PFI and PF. The TCP-ARF module was found to be the possible regulatory module inducing the crinkled leaf trait.

RNA-Seq↗
PubMed1991

Selectivity, efficiency, and surface characteristics of hard dental tissues ablated with ArF pulsed excimer lasers.

Lasers are finding expanding applications in the field of dentistry. Cutting in soft tissue, hard dental material ablation, caries removal, and root canal therapy are only a few examples of dental laser uses. In this article, the application of short pulse ArF excimer laser to ablation of dentin and enamel is investigated. In particular, the effect of laser pulse repetition rates (PRR) and fluence levels on the efficiency of the ablation process and on the average thermal response of ablated surfaces is investigated. Ablation of dentin was found to be considerably more efficient than the ablation of enamel and depends exponentially on the laser fluence. Both dentin and enamel surfaces showed an increase in surface temperature with repetition rate. At lower PRR, however, temperature increases are very small. Surface temperature was also found to increase with laser fluence, although this increase is very small at laser PRR of 5 Hz or less. Tissue ablation rates were found to be comparable to or better than other nanosecond lasers, and left smooth surfaces, free of thermal damage. Microscopic examination of the ablated surface shows no crack formation, charring, discoloration, or any other thermal damage. The ablated surfaces appear to be very smooth, highly polished, and glossy looking as if they were subjected to thermal melting. This observation is indeed confirmed under scanning electron microscopy (SEM), where evidence of localized melting of the tissue is observed. Furthermore, a close SEM examination of the dentin surface reveals a selectively ablated intertubular dentin, while the remaining pillar-like dentin tubules are sealed off with fused peritubular dentin. At all fluence levels and PRR, the first three to four pulses impinging on an untreated enamel surface produced unusually large plumes of debris which were different in size, texture, and fluorescence emission characteristics from the ablation products of subsequent pulses. It is believed that these different ablation characteristics are a consequence of the pulsed ArF laser's ability to selectively remove residual matter from the more resistant enamel surface.

Acid Etching, Dental↗