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Biomedical subjects

M Sacher

Publications and source records attributed to M Sacher.

At least 19 recordsLinked to original sources
PubMed2000

TRAPP stimulates guanine nucleotide exchange on Ypt1p.

TRAPP, a novel complex that resides on early Golgi, mediates the targeting of ER-to-Golgi vesicles to the Golgi apparatus. Previous studies have shown that YPT1, which encodes the small GTP-binding protein that regulates membrane traffic at this stage of the secretory pathway, interacts genetically with BET3 and BET5. Bet3p and Bet5p are 2 of the 10 identified subunits of TRAPP. Here we show that TRAPP preferentially binds to the nucleotide-free form of Ypt1p. Mutants with defects in several TRAPP subunits are temperature-sensitive in their ability to displace GDP from Ypt1p. Furthermore, the purified TRAPP complex accelerates nucleotide exchange on Ypt1p. Our findings imply that Ypt1p, which is present on ER-to-Golgi transport vesicles, is activated at the Golgi once it interacts with TRAPP.

Carrier Proteins↗
PubMed2000

TRAPP stably associates with the Golgi and is required for vesicle docking.

Bet3p, a component of a large novel complex called TRAPP, acts upstream of endoplasmic reticulum (ER)-Golgi SNAREs. Unlike the SNAREs, which reside on multiple compartments, Bet3p is localized exclusively to Golgi membranes. While other proteins recycle from the Golgi to the ER, Bet3p and other TRAPP subunits remain associated with this membrane under conditions that block anterograde traffic. We propose that the persistent localization of TRAPP to the Golgi may be important for its role in docking vesicles to this membrane. Consistent with this proposal, we find that transport vesicles fail to bind to Golgi membranes in vitro in the absence of Bet3p. Binding is restored by the addition of cytosol containing Bet3p. These findings indicate that TRAPP stably associates with the Golgi and is required for vesicle docking.

Animals↗
PubMed2000

Protein complexes in transport vesicle targeting.

The transport of material between membrane-bounded organelles in eukaryotic cells requires the accurate delivery of different classes of carrier vesicles to specific target compartments. Recent studies indicate that different targeting reactions involve distinct protein complexes that act to mark the target organelle for incoming vesicles. This review focuses on the proteins and protein complexes that have been implicated in various targeting reactions.

Biological Transport↗
PubMed2000

Identification and characterization of five new subunits of TRAPP.

TRAPP (transport protein particle), a multiprotein complex containing ten subunits, plays a key role in the late stages of endoplasmic reticulum to Golgi traffic in the yeast Saccharomyces cerevisiae. We previously described the identification of five TRAPP subunits (Bet5p, Trs20p, Bet3p, Trs23p and Trs33p). Now we report the identification of the remaining five subunits (Trs31p, Trs65p, Trs85p, Trs120p and Trs130p) as well as an initial characterization of the yeast complex and its human homologue. We find that three of the subunits are dispensable for growth and a novel sequence motif is found in Bet3p, Trs31p and Trs33p. Furthermore, biochemical characterization of both yeast and human TRAPP suggests that this complex is anchored to a Triton X-100 resistant fraction of the Golgi. Differences between yeast and human TRAPP as well as the relationship of TRAPP subunits to other docking/tethering factors are discussed.

Amino Acid Sequence↗
PubMed1999

[Long central apnea as the chief symptom of aseptic meningoencephalitis in a 6-week-old infant].

Viral infections can cause apnoea, bradycardia, and desaturation events in preterm and new born infants. These symptoms do not always occur in older infants. A link between virus infection, apnoea, apparent life threatening events (ALTE) and sudden infant death (SID) is speculated. We report a 6-week-old infant with long central apnoea as the first and main symptom of meningoencephalitis caused by enterovirus.

Enterovirus Infections↗
PubMed1999

High-copy suppressor analysis reveals a physical interaction between Sec34p and Sec35p, a protein implicated in vesicle docking.

A temperature-sensitive mutant, sec34-2, is defective in the late stages of endoplasmic reticulum (ER)-to-Golgi transport. A high-copy suppressor screen that uses the sec34-2 mutant has resulted in the identification of the SEC34 structural gene and a novel gene called GRP1. GRP1 encodes a previously unidentified hydrophilic yeast protein related to the mammalian Golgi protein golgin-160. Although GRP1 is not essential for growth, the grp1Delta mutation displays synthetic lethal interactions with several mutations that result in ER accumulation and a block in the late stages of ER-to-Golgi transport, but not with those that block the budding of vesicles from the ER. Our findings suggest that Grp1p may facilitate membrane traffic indirectly, possibly by maintaining Golgi function. In an effort to identify genes whose products physically interact with Sec34p, we also tested the ability of overexpressed SEC34 to suppress known secretory mutations that block vesicular traffic between the ER and the Golgi. This screen revealed that SEC34 specifically suppresses sec35-1. SEC34 encodes a hydrophilic protein of approximately 100 kDa. Like Sec35p, which has been implicated in the tethering of ER-derived vesicles to the Golgi, Sec34p is predominantly soluble. Sec34p and Sec35p stably associate with each other to form a multiprotein complex of approximately 480 kDa. These data indicate that Sec34p acts in conjunction with Sec35p to mediate a common step in vesicular traffic.

Amino Acid Sequence↗
PubMed1999

Volume of ventricular blood is an important determinant of outcome in supratentorial intracerebral hemorrhage.

OBJECTIVE: To determine the prognostic significance and pathophysiologic implication of intraventricular extension of supratentorial intracerebral hemorrhage. DESIGN: Prospective study. SETTING: Acute stroke and neurointensive care units of a tertiary care hospital. PATIENTS: One hundred twenty-nine patients with supratentorial intracerebral hemorrhage, managed medically. INTERVENTIONS: Two patients had intraventricular catheters placed for external drainage. No patient received thrombolytics or surgical evacuation of clot. MEASUREMENTS AND MAIN RESULTS: Of the 129 patients, 47 had intraventricular extension of their hemorrhages. These patients had larger intraparenchymal hemorrhages (36.6 cm3 vs. 15.0 cm3) and lower initial Glasgow Coma Scale scores (mean, 9.6 vs. 13.7). Their 30-day mortality rate was 43% compared with only 9% among those without ventricular extension. Univariate and multivariate logistic regression modeling was used to assess the prognostic significance of various measures of intraventricular hemorrhage. The presence of intraventricular hemorrhage, the number of ventricles containing blood, fourth ventricular blood, and intraventricular hemorrhage volume were each related to 30-day mortality in a univariate analysis, but only intraventricular hemorrhage volume contributed significantly to outcome prediction in the presence of Glasgow Coma Scale score. CONCLUSIONS: Volume of intraventricular hemorrhage is an important determinant of outcome in supratentorial intracerebral hemorrhage.

Blood Volume↗
PubMed1998

TRAPP, a highly conserved novel complex on the cis-Golgi that mediates vesicle docking and fusion.

We previously identified BET3 by its genetic interactions with BET1, a gene whose SNARE-like product acts in endoplasmic reticulum (ER)-to-Golgi transport. To gain insight into the function of Bet3p, we added three c-myc tags to its C-terminus and immunopurified this protein from a clarified detergent extract. Here we report that Bet3p is a member of a large complex ( approximately 800 kDa) that we call TRAPP (transport protein particle). We propose that TRAPP plays a key role in the targeting and/or fusion of ER-to-Golgi transport vesicles with their acceptor compartment. The localization of Bet3p to the cis-Golgi complex, as well as biochemical studies showing that Bet3p functions on this compartment, support this hypothesis. TRAPP contains at least nine other constituents, five of which have been identified and shown to be highly conserved novel proteins.

Amino Acid Sequence↗
PubMed1998

Special compression sutures: a new surgical technique to achieve a quick decrease in shunt volume caused by diffuse hemangiomatosis of the liver.

A new surgical technique for the management of shunting liver hemangiomas that otherwise would rapidly lead to intractable cardiac failure is presented. Rapid, significant reduction of shunt volume was achieved surgically by transhepatic compression sutures using PTFE pledgets and selective ligation of a large feeding vessel from the right hepatic artery.

Constriction↗
PubMed1998

Thallium-201 retention in focal intracranial lesions for differential diagnosis of primary lymphoma and nonmalignant lesions in AIDS patients.

UNLABELLED: The purpose of this study was to determine whether 201Tl retention in focal intracranial lesions can help distinguish central nervous system (CNS) lymphoma from toxoplasmosis and other nonmalignant CNS lesions in patients with acquired immunodeficiency syndrome. METHODS: Forty-nine patients who presented with focal lesions on CT and/or MRI had 201Tl brain SPECT studies (early and delayed image sets) performed shortly after admission. Early and delayed 201Tl uptake ratios were obtained for the positive studies, and the retention index of thallium was calculated (delayed/early target-to-background mean count ratio). RESULTS: Twenty-nine patients had foci of significantly increased 201Tl uptake on the early images in regions of corresponding CT/MRI lesions. Ten of these patients had biopsy-proven lymphomas. Another patient was found to have metastatic adenocarcinoma. Twelve additional patients had a response to radiation therapy or a clinical course consistent with lymphoma and six patients had a false-positive SPECT study. The early uptake ratio could not separate malignant from nonmalignant lesions. The 201Tl retention index in patients with lymphomas (1.18 +/- 0.16) was significantly higher than the retention index in adenocarcinoma (0.24) and in the six nonmalignant lesions (0.62 +/- 0.07). The lowest retention index in patients with lymphoma was 1.07, and the highest retention index in nonmalignant lesions was 0.70. Twenty patients showed no 201Tl uptake in the regions of CT/MRI lesions. Three of them had biopsies consistent with a benign etiology, and one patient was diagnosed with tuberculosis. Fifteen patients improved clinically on antitoxoplasmosis medications alone, and one patient had CNS lymphoma. The overall sensitivity of 201Tl brain SPECT was 96%. The specificity was 76% by counting all studies with abnormal 201Tl uptake, but it increased to 100% when the retention index was also considered. CONCLUSION: The retention index increases the specificity of 201Tl brain SPECT in human immunodeficiency virus patients. In the presence of abnormal early 201Tl uptake, it is essential to perform delayed imaging and calculate the retention index to distinguish nonmalignant lesions from lymphoma. The absence of 201Tl uptake on early images at the site of a CT/MRI abnormality excludes the diagnosis of lymphoma with a high degree of confidence and delayed imaging is unnecessary.

AIDS-Related Opportunistic Infections↗
PubMed1997

The synaptobrevin-related domains of Bos1p and Sec22p bind to the syntaxin-like region of Sed5p.

SNAREs (soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptors) are cytoplasmically oriented membrane proteins that reside on vesicular carriers (v-SNARE) and target organelles (t-SNARE). The pairing of a stage-specific v-SNARE with its cognate t-SNARE may mediate the specificity of membrane traffic. In the yeast Saccharomyces cerevisiae transport between the endoplasmic reticulum and Golgi complex employs two v-SNAREs, Bos1p and Sec22p, each containing a domain that is related to the neuronal v-SNARE synaptobrevin. Sed5p, which is homologous to syntaxin, is the t-SNARE that functions at this stage of the secretory pathway. Here we report that regions of Bos1p and Sec22p, which are homologous to synaptobrevin, bind to the syntaxin-like domain of Sed5p. Furthermore, we demonstrate that efficient v-SNARE/t-SNARE interactions require the participation of both v-SNAREs, indicating that, unlike post-Golgi membrane traffic, the active form of the endoplasmic reticulum to Golgi v-SNARE is a heteromeric complex.

Binding Sites↗
PubMed1997

Bet1p activates the v-SNARE Bos1p.

Bet1p is a type II membrane protein that is required for vesicular transport between the endoplasmic reticulum and Golgi complex in the yeast Saccharomyces cerevisiae. A domain of Bet1p, that shows potential to be involved in a coiled-coil interaction, is homologous to a region of the neuronal protein SNAP-25. Here, we used in vitro binding studies to demonstrate that Bet1p plays a role in potentiating soluble NSF attachment protein receptor (SNARE) interactions. Mutational analysis points to the coiled-coil region as necessary for Bet1p function, and circular dichroism experiments support this theory. In vitro binding studies were also used to demonstrate that a direct interaction between Bet1p and Bos1p is required for the efficient interaction of the vesicle SNARE with its SNARE target. Genetic studies suggest that the interactions of Bet1p with Bos1p are regulated by the small GTP-binding protein Ypt1p.

Amino Acid Sequence↗
PubMed1997

False-positive uptake of TI-201 by an intracranial inflammatory pseudotumor.

A 28-year-old man had recurrent episodes of headache, ophthalmoplegia, and ptosis. MR imaging showed a mass within the sphenoid sinus. TI-201 imaging showed intense uptake in the region of the sphenoid sinus and right middle fossa with moderate retention of activity, suggesting the diagnosis of a viable tumor. A biopsy specimen from the sphenoid sinus revealed dense inflammatory infiltrate dominated by plasma cells, consistent with inflammatory pseudotumor. After radiation therapy, the mass showed no significant change on MR imaging, but regressed in size and uptake on the follow-up TI-201 scan. TI-201 may accumulate in nonmalignant inflammatory lesions and could mimic a viable tumor. It is, therefore, suggested that before surgery and histologic diagnosis, any abnormal intracranial accumulation of TI-201 should be interpreted with caution.

Adult↗
PubMed1997

Renal pyelectasis in fetuses and neonates: diagnostic value of renal pelvis diameter in pre- and postnatal sonographic screening.

OBJECTIVE: Pre- and postnatal pyelectasis detected by sonographic screening is of questionable pathologic importance. Therefore, we defined the natural course and diagnostic value of renal pelvis diameter (RPD) during fetal life and the neonatal period as such dilatation was revealed on routine sonography. MATERIALS AND METHODS: Routine sonography in pregnant women was obtained between gestational weeks 22 and 30. Sonograms were obtained for 1021 fetuses, of which 15 could not be followed up as neonates. The remaining 1006 fetuses also underwent neonatal sonography. All neonates with an RPD larger than 5 mm were followed up sonographically. Neonates with an RPD larger than 9 mm or persistent widening (> 5-9 mm) were examined by voiding cystourethrogram, radionuclide renogram, or both. RESULTS: Thirty fetuses (3%) had an RPD larger than 5 mm. Nine of these fetuses also had an RPD larger than 5 mm as neonates. Of these nine neonates, one had bilateral grade II vesicoureteric reflux (VUR) and two had urinary tract obstructions (one posterior urethral valve and one ureteropelvic junction obstruction). Forty-nine neonates whose results on fetal sonograms had been normal showed an RPD larger than 5 mm on neonatal sonograms. Grade III VUR was found in one boy, and ureteropelvic junction obstruction was found in two boys. The kidneys of 54 neonates who showed an RPD larger than 5 mm without urinary tract obstruction were followed up until an RPD of 0-5 mm was evident. RPD normalized within 1 year of birth, whether VUR was present or not. Symptomatic urinary tract infection was diagnosed in 17 infants who had no renal pelvis dilatation seen on pre-or postnatal screening during the observation period. Seven of the 17 neonates had VUR. Conversely, none of the infants with pre- postnatal dilatation presented with symptomatic urinary tract infection. However, in one neonate an asymptomatic urinary tract infection without VUR was diagnosed by routine urinalysis. CONCLUSION: In our study, we linked renal pelvis dilatation on pre- and postnatal sonograms to obstructive uropathies rather than to vesicoureteric reflux. Prenatal sonography proved less sensitive than postnatal sonography in revealing obstructive uropathies. An RPD smaller than 10 mm on neonatal sonography was of no pathologic significance because renal collecting systems normalized spontaneously in all infants within 1 year of birth. These neonates and infants had no significant risk for urinary tract infection and did not need further evaluation.

Dilatation, Pathologic↗
PubMed1996

Brain perfusion imaging during preoperative temporary balloon occlusion of the internal carotid artery.

UNLABELLED: The main objective of this study was to assess whether 99mTc-HMPAO brain SPECT imaging can identify patients at high risk of developing an infarct following permanent carotid occlusion in the course of brain surgery. METHODS: Test balloon occlusion of the internal carotid artery was performed in 44 patients with a variety of head and neck tumors or aneurysms. Technetium-99m-HMPAO was injected intravenously while the balloon was initiated and a SPECT study was obtained 30 min later. Follow-up CT scans were obtained routinely for all patients at 2 wk and 1 mo following surgery, or earlier when necessary. Thirty patients and five normal volunteers had semiquantitative analysis of cerebral perfusion. RESULTS: Twenty-six patients demonstrated ipsilateral perfusion abnormalities during trial occlusion. Eight patients in this group underwent bypass grafting prior to sacrifice of the artery: two resulting in infarcts. Eighteen patients had symmetric cerebral perfusion during occlusion and four of these patients underwent permanent therapeutic carotid occlusion; three patients had subsequent infarcts and the fourth patient had an impending stroke. CONCLUSION: Patients with symmetric cerebral perfusion measured by 99mTc-HMPAO SPECT may still have a high long-term complication rate following carotid sacrifice. The scan findings in these patients were not predictive of the outcome. Patients with asymmetric cerebral perfusion had alternative therapeutic approach to carotid sacrifice and most of them had good surgical outcomes.

Brain↗