Australine, a pyrrolizidine alkaloid that inhibits amyloglucosidase and glycoprotein processing

Tropea, Joseph E.; Molyneux, Russell J.; Kaushal, Gur P.; Pan, Yuan; Mitchell, Mark B.; Elbein, Alan D.

doi:10.1021/bi00431a010

Cited by 107 publications

(66 citation statements)

References 54 publications

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“…Pyrrolizidine alkaloids such as australine and others such as swainsonine are known to affect glycosylation in the Golgi (42,64). Thus another explanation for the ability of MCTP to cause accumulations of diverse Golgi tethers, SNAREs, and SNAPs and a subsequent block in protein trafficking would be if the functional state of the Golgi was affected due to compromised activity of one or more enzyme(s) acting on the N-linked glycosylation pathway in the Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The observations that pyrrolizidine alkaloids such as australine and indolizidine alkaloids such as swainsonine target specific Golgi-resident glycosidases (42,64) suggested the possibility that MCT might also target specific glycosidases in the Golgi. The report that swainsonine caused PH and right ventricular hypertrophy in calves (17) was intriguing.…”

Section: Discussionmentioning

confidence: 99%

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Dysfunction of Golgi tethers, SNAREs, and SNAPs in monocrotaline-induced pulmonary hypertension

Sehgal¹,

Mukhopadhyay²,

Xu³

et al. 2007

American Journal of Physiology-Lung Cellular and Molecular Phys

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Monocrotaline (MCT)-induced pulmonary hypertension (PH) in the rat is a widely used experimental model. We have previously shown that MCT pyrrole (MCTP) produces loss of caveolin-1 (cav-1) and endothelial nitric oxide synthase from plasma membrane raft microdomains in pulmonary arterial endothelial cells (PAEC) with the trapping of these proteins in the Golgi organelle (the Golgi blockade hypothesis). In the present study, we investigated the mechanisms underlying this intracellular trafficking block in experiments in cell culture and in the MCT-treated rat. In cell culture, PAEC showed trapping of cav-1 in Golgi membranes as early as 6 h after exposure to MCTP. Phenotypic megalocytosis and a reduction in anterograde trafficking (assayed in terms of the secretion of horseradish peroxidase derived from exogenously transfected expression constructs) were evident within 12 h after MCTP. Cell fractionation and immunofluorescence techniques revealed the marked accumulation of diverse Golgi tethers, soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein receptors (SNAREs), and soluble NSF attachment proteins (SNAPs), which mediate membrane fusion during vesicular trafficking (GM130, p115, giantin, golgin 84, clathrin heavy chain, syntaxin-4, -6, Vti1a, Vti1b, GS15, GS27, GS28, SNAP23, and ␣-SNAP) in the enlarged/ circumnuclear Golgi in MCTP-treated PAEC and A549 lung epithelial cells. Moreover, NSF, an ATPase required for the "disassembly" of SNARE complexes subsequent to membrane fusion, was increasingly sequestered in non-Golgi membranes. Immunofluorescence studies of lung tissue from MCT-treated rats confirmed enlargement of perinuclear Golgi elements in lung arterial endothelial and parenchymal cells as early as 4 days after MCT. Thus MCTinduced PH represents a disease state characterized by dysfunction of Golgi tethers, SNAREs, and SNAPs and of intracellular vesicular trafficking.soluble N-ethylmaleimide-sensitive factor attachment protein receptors; endothelium; intracellular membrane trafficking; Golgi blockade PULMONARY HYPERTENSION (PH) is a progressive disease with high morbidity and mortality (10). As the clinical manifestations of PH typically occur long after the initial injury, experimental models provide an opportunity to investigate the initiating mechanism at the cellular and biochemical levels (45). Among experimental models of PH, administration of the pyrrolizidine alkaloid monocrotaline (MCT) to the juvenile male rat has and continues to be used extensively (21,29). In this model, progressive PH develops 10 -14 days after a single injection of MCT. The injected MCT is converted to its active pyrrolic derivative [MCT pyrrole (MCTP)] by the cytochrome P-450 system in the liver (36). The bioactive MCTP, which has a short half-life (ϳ3 s in aqueous medium), affects the first vascular bed it encounters: the pulmonary arterial system. The major cellular targets of MCT in the rat lung include the pulmonary arterial endothelial cells (PAEC), pulmonary arterial smooth muscle cells (PASMC), and ...

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Dysfunction of Golgi tethers, SNAREs, and SNAPs in monocrotaline-induced pulmonary hypertension

Sehgal¹,

Mukhopadhyay²,

Xu³

et al. 2007

American Journal of Physiology-Lung Cellular and Molecular Phys

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“…The mixture was then filtered through a sintered glass frit and rinsed with methanol. 17 (ddd,1H,J 10.5,7.0,4.0 Hz,3.02 (ddd,1H,J 9.0,6.5,4.0 Hz,2.93 (ddd,1H,J 10.5,9.5,6.5 Hz,2.04 (ddt,1H,J 13.5,6.5,4.0 Hz,1.96 (dddd,1H,J 13.5,9.5,7.0,5. Hz, H-7), 5.06 (ddd, 1H, J 7.8, 4.8, 3.9 Hz, H-1), 4.59 (s, 2H, Ar*CH 2 ), 4.36 (s, 2H, ArCH 2 ), 4.15 (dd,1H,J 6.6,3.9 Hz,3.93 (dd,1H,J 6.3,4.2 Hz, …”

Section: Fourmentioning

confidence: 99%

“…5 These interesting biological properties coupled with the polyfunctional and stereochemically rich nature of these compounds have attracted the attention of synthetic chemists resulting in the total synthesis of alexine, 6 and its epimers, 6,7 australine, 8 and its epimers, [7][8][9][10][11] and casuarine. We demonstrated the viability of this synthestic methodology with the asymmetric synthesis of (-)-7-epiaustaline and (+) -1,7-diepiaustraline.…”

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confidence: 99%

Asymmetric synthesis of (+)-1-epiaustraline and attempted synthesis of australine

Tang

Pyne

2004

Tetrahedron

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A diastereoselective synthesis of the pyrrolizidine alkaloid, (+)-1-epiaustraline has been achieved via a diastereoselective syn-dihydroxylation of a pyrrolo[1,2-c]oxazol-3-one precursor that was readily prepared by a RCM reaction. Attempts to extend this methodology to the synthesis of australine were not successful since the final pyrrolidine ring closure to produce the desired pyrrolizidine of the target molecule was not productive.

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“…We performed a reconstitution assay where CD45 immunoprecipitates from BW cells were stripped of endogenously bound GII. To these immunoprecipitates, we added BW/T200 Ϫ lysates pretreated with either dNM, a GII inhibitor (28), or australine, a glucosidase I-specific inhibitor (29). When dNM-treated lysates were added to CD45 immunoprecipitates devoid of GII, the ability of GII from that lysate to bind CD45 was inhibited (Fig.…”

Section: Only a Higher Molecular Weight Isoform Of Gii␣ Is Capable Ofmentioning

confidence: 99%

Specific Isoforms of the Resident Endoplasmic Reticulum Protein Glucosidase II Associate with the CD45 Protein-tyrosine Phosphatase via a Lectin-like Interaction

Baldwin

Gogela-Spehar

Ostergaard

2000

Journal of Biological Chemistry

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We have previously demonstrated that CD45 physically associates with the endoplasmic reticulum processing enzyme glucosidase II (GII). GII consists of the catalytic ␣-chain and an associated ␤-chain. To gain insight into the basis of the association between CD45 and GII, we examined the biochemical requirements for the interaction. We show that the ␣-subunit is essential for the interaction. Interestingly, only a higher molecular weight form of GII␣ is capable of associating with CD45 in a competitive situation where multiple GII␣ isoforms are expressed. Further, transfection studies demonstrate that only isoforms containing the alternatively spliced sequence Box A1 are capable of binding CD45, although all isoforms are catalytically active. The interaction between CD45 and GII is dependent on the active site of GII, is mediated through the carbohydrate on CD45, and can be inhibited with mannose. Taken together, these results suggest that GII␣ acts as a lectin and binds to CD45 in an exon-dependent manner. This lectin activity of GII may be a novel mechanism for the regulation of CD45 biology and play a role in immune function, possibly by regulating CD45 glycosylation.CD45 is a highly abundant, transmembrane, protein-tyrosine phosphatase expressed on all cells of hematopoietic origin (1). The cytoplasmic phosphatase activity of CD45 has been shown to be essential for the early signal transduction events leading to both thymocyte maturation and T cell activation (1). There is substantial evidence to suggest that CD45 regulates the tyrosine phosphorylation of Src family kinases (2, 3). The external domain of CD45 is extremely heterogeneous with respect to size and carbohydrate content primarily because of three alternatively spliced exons that encode for potential Olinked glycosylations (4). The usage of these exons appears to be developmentally regulated (4). As well, the extracellular domain encodes attachment sites for numerous N-linked glycans, and these glycosylations appear to be important for cell surface expression and protein stability of CD45 (5). Finally, although CD45 is a cell surface protein, no specific ligand for the extracellular domain has been definitively identified. Perhaps relevant to the present study, there have been studies suggesting that some lectins such as CD22 (6, 7), galectin-1 (8, 9), and the mannan-binding protein (10) are able to bind to CD45 carbohydrate, although the biological significance of these interactions are largely not understood.Recently, our laboratory has demonstrated that the carbohydrate processing enzyme ␣-glucosidase II (GII) 1 physically interacts with CD45 (11). GII is found within the ER and catalyzes the hydrolysis of the inner two ␣1,3-linked glucose residues present on all N-linked immature oligosaccharides (12, 13). This processing of glucose in the ER has been shown to be intimately involved in protein folding by regulating the interaction between the nascent polypeptide and the lectin chaperones calnexin and calreticulin. More specifically, removal of t...

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Australine, a pyrrolizidine alkaloid that inhibits amyloglucosidase and glycoprotein processing

Cited by 107 publications

References 54 publications

Dysfunction of Golgi tethers, SNAREs, and SNAPs in monocrotaline-induced pulmonary hypertension

Dysfunction of Golgi tethers, SNAREs, and SNAPs in monocrotaline-induced pulmonary hypertension

Asymmetric synthesis of (+)-1-epiaustraline and attempted synthesis of australine

Specific Isoforms of the Resident Endoplasmic Reticulum Protein Glucosidase II Associate with the CD45 Protein-tyrosine Phosphatase via a Lectin-like Interaction

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