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Dive into the research topics where Neil Emans is active.

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Featured researches published by Neil Emans.


Nature | 2005

Auxin inhibits endocytosis and promotes its own efflux from cells.

Tomasz Paciorek; Eva Zazimalova; Nadia Ruthardt; Jan Petrášek; York-Dieter Stierhof; Jürgen Kleine-Vehn; David A. Morris; Neil Emans; Gerd Jürgens; Niko Geldner; Jiri Friml

One of the mechanisms by which signalling molecules regulate cellular behaviour is modulating subcellular protein translocation. This mode of regulation is often based on specialized vesicle trafficking, termed constitutive cycling, which consists of repeated internalization and recycling of proteins to and from the plasma membrane. No such mechanism of hormone action has been shown in plants although several proteins, including the PIN auxin efflux facilitators, exhibit constitutive cycling. Here we show that a major regulator of plant development, auxin, inhibits endocytosis. This effect is specific to biologically active auxins and requires activity of the Calossin-like protein BIG. By inhibiting the internalization step of PIN constitutive cycling, auxin increases levels of PINs at the plasma membrane. Concomitantly, auxin promotes its own efflux from cells by a vesicle-trafficking-dependent mechanism. Furthermore, asymmetric auxin translocation during gravitropism is correlated with decreased PIN internalization. Our data imply a previously undescribed mode of plant hormone action: by modulating PIN protein trafficking, auxin regulates PIN abundance and activity at the cell surface, providing a mechanism for the feedback regulation of auxin transport.


Transgenic Research | 2000

Molecular farming of pharmaceutical proteins.

Rainer Fischer; Neil Emans

Molecular farming is the production of pharmaceutically important and commercially valuable proteins in plants. Its purpose is to provide a safe and inexpensive means for the mass production of recombinant pharmaceutical proteins. Complex mammalian proteins can be produced in transformed plants or transformed plant suspension cells. Plants are suitable for the production of pharmaceutical proteins on a field scale because the expressed proteins are functional and almost indistinguishable from their mammalian counterparts. The breadth of therapeutic proteins produced by plants range from interleukins to recombinant antibodies. Molecular farming in plants has the potential to provide virtually unlimited quantities of recombinant proteins for use as diagnostic and therapeutic tools in health care and the life sciences. Plants produce a large amount of biomass and protein production can be increased using plant suspension cell culture in fermenters, or by the propagation of stably transformed plant lines in the field. Transgenic plants can also produce organs rich in a recombinant protein for its long-term storage. This demonstrates the promise of using transgenic plants as bioreactors for the molecular farming of recombinant therapeutics, including vaccines, diagnostics, such as recombinant antibodies, plasma proteins, cytokines and growth factors.


Biological Chemistry | 1999

Molecular farming of recombinant antibodies in plants.

Rainer Fischer; Y.-C. Liao; K. Hoffmann; Stefan Schillberg; Neil Emans

Abstract ‘Molecular farming’ is the production of recombinant proteins in plants. It is intended to harness the power of agriculture to cultivate and harvest transgenic plants producing recombinant therapeutics. Molecular farming has the potential to rovide virtually unlimited quantities of recombinant antibodies for use as diagnostic and therapeutic tools in both health care and the life sciences. Importantly, recombinant antibody expression can be used to modify the inherent properties of plants, for example by using expressed antipathogen antibodies to increase disease resistance. Plant transformation is technically straightforward for model plant species and some cereals, and the functional expression of recombinant proteins can be rapidly analyzed using transient expression systems in intact or virally infected plants. Protein production can then be increased using plant suspension cell production in fermenters, or by the propagation of stably transformed plant lines in the field. Transgenic plants can be exploited to produce organs rich in a recombinant protein for its long-term storage. This demonstrates the promise of using transgenic plants as bioreactors for the ‘molecular farming’ of recombinant therapeutics, blood substitutes and diagnostics, such as recombinant antibodies.


Biotechnology and Applied Biochemistry | 1999

Towards molecular farming in the future: transient protein expression in plants

Rainer Fischer; Carmen Vaquero‐Martin; Markus Sack; Jürgen Drossard; Neil Emans; Ulrich Commandeur

Molecular farming in plants can be achieved by stable or transient expression of a recombinant protein. Transient expression of recombinant proteins in plants can rapidly provide large amounts of the proteins for detailed characterization. It is fast, flexible and can be carried out at field scale using viral vectors, but it lacks the increases in production volume that can be achieved easily with stable transgenic crops. This review article focuses on discussing the applications of transient expression using viral vectors, biolistic methods or agroinfiltration.


Cellular and Molecular Life Sciences | 2003

Molecular farming of recombinant antibodies in plants

Stefan Schillberg; Rainer Fischer; Neil Emans

Abstract: Antibodies represent a large proportion of therapeutic drugs currently in development. In most cases, they are produced in mammalian cell lines or transgenic animals because these have been shown to fold and assemble the proteins correctly and generate authentic glycosylation patterns. However, such expression systems are expensive, difficult to scale up and there are safety concerns due to potential contamination with pathogenic organisms or oncogenic DNA sequences. Plants represent an inexpensive, efficient and safe alternative for the production of recombinant antibodies. Research over the last 10 years has shown that plants can produce a variety of functional antibodies and there is now intense interest in scaling up production to commercial levels. In this review, we discuss the advantages of plants over traditional expression systems, describe how antibody expression in plants is achieved and optimized and then consider the practical issues concerning large-scale molecular farming in plants. The first plant-produced therapeutic antibodies are already in clinical trials, and, given the economic benefits of this production system, we are likely to see many more recombinant antibodies produced in this manner in the future.


Biotechnology and Applied Biochemistry | 1999

Towards molecular farming in the future: using plant-cell-suspension cultures as bioreactors

Rainer Fischer; Neil Emans; Flora Schuster; Stephan Hellwig; Jürgen Drossard

Plant‐suspension cells are an in vitro system that can be used for recombinant protein production under carefully controlled certified conditions. Plant‐suspension cells can be grown in shake flasks or fermenters to produce secondary metabolites, like vincristine and vinblastine, and to produce recombinant proteins after transformation. This review article focuses on discussing the generation of transformed suspension‐cell lines expressing recombinant proteins, like antibodies, and recombinant‐protein downstream processing and purification.


Biotechnology and Applied Biochemistry | 1999

Towards molecular farming in the future: moving from diagnostic protein and antibody production in microbes to plants.

Rainer Fischer; Jürgen Drossard; Ulrich Commandeur; Stefan Schillberg; Neil Emans

Molecular farming of pharmaceuticals in plants has the potential to provide almost unlimited amounts of recombinant proteins for use in disease diagnosis and therapy. Transgenic plants are attracting interest as bioreactors for the inexpensive production of large amounts of safe, functional, recombinant macromolecules, such as blood substitutes, vaccines and antibodies. In some cases, the function of expressed recombinant proteins can be rapidly analysed by expression in microbes or by transient expression in intact or virally infected plants. Protein production can be increased by upscaling production in fermenters, using yeast‐ or plant‐suspension cells or by using transient‐expression systems. Stable transgenic plants can be used to produce leaves or seeds rich in the recombinant protein for long‐term storage or direct processing. This demonstrates the promise for using plants as bioreactors for the molecular farming of recombinant therapeutics, diagnostics, blood substitutes and antibodies. We anticipate that this technology has the potential to greatly benefit human health by making safe recombinant pharmaceuticals widely available.


Proceedings of the National Academy of Sciences of the United States of America | 2003

An unusual internal ribosomal entry site of inverted symmetry directs expression of a potato leafroll polerovirus replication-associated protein

Hannah Miriam Jaag; L. M. Kawchuk; Wolfgang Rohde; Rainer Fischer; Neil Emans; Dirk Prüfer

Potato leafroll polerovirus (PLRV) genomic RNA acts as a polycistronic mRNA for the production of proteins P0, P1, and P2 translated from the 5′-proximal half of the genome. Within the P1 coding region we identified a 5-kDa replication-associated protein 1 (Rap1) essential for viral multiplication. An internal ribosome entry site (IRES) with unusual structure and location was identified that regulates Rap1 translation. Core structural elements for internal ribosome entry include a conserved AUG codon and a downstream GGAGAGAGAGG motif with inverted symmetry. Reporter gene expression in potato protoplasts confirmed the internal ribosome entry function. Unlike known IRES motifs, the PLRV IRES is located completely within the coding region of Rap1 at the center of the PLRV genome.


Biotechnology and Applied Biochemistry | 1999

Towards molecular farming in the future: Pichia pastoris‐based production of single‐chain antibody fragments

Rainer Fischer; Jürgen Drossard; Neil Emans; Ulrich Commandeur; Stephan Hellwig

This review article focuses on the use of the methylotrophic yeast Pichia pastoris as a recombinant protein‐expression system. P. pastoris is a useful system for the expression of milligram‐to‐gram quantities of a protein, which can be scaled up to fermentation to meet greater demands. Compared with mammalian cells, Pichia do not require a complex growth medium or culture conditions, they are as easy to manipulate genetically as Escherichia coli and have a eukaryotic protein‐synthesis pathway. They seem suited to laboratory‐scale production of recombinant proteins for in‐house use or, in some cases, molecular farming of recombinant products. This review article focuses on the use of P. pastoris, describes a fermentation production run of a single‐chain antibody fragment and includes a discussion of fermentation as a production strategy.


Plant Physiology | 2002

Targeting Tryptophan Decarboxylase to Selected Subcellular Compartments of Tobacco Plants Affects Enzyme Stability and in Vivo Function and Leads to a Lesion-Mimic Phenotype

Stefano Di Fiore; Qr Li; Mark J. Leech; Flora Schuster; Neil Emans; Rainer Fischer; Stefan Schillberg

Tryptophan decarboxylase (TDC) is a cytosolic enzyme that catalyzes an early step of the terpenoid indole alkaloid biosynthetic pathway by decarboxylation of l-tryptophan to produce the protoalkaloid tryptamine. In the present study, recombinant TDC was targeted to the chloroplast, cytosol, and endoplasmic reticulum (ER) of tobacco (Nicotiana tabacum) plants to evaluate the effects of subcellular compartmentation on the accumulation of functional enzyme and its corresponding enzymatic product. TDC accumulation and in vivo function was significantly affected by the subcellular localization. Immunoblot analysis demonstrated that chloroplast-targeted TDC had improved accumulation and/or stability when compared with the cytosolic enzyme. Because ER-targeted TDC was not detectable by immunoblot analysis and tryptamine levels found in transient expression studies and in transgenic plants were low, it was concluded that the recombinant TDC was most likely unstable if ER retained. Targeting TDC to the chloroplast stroma resulted in the highest accumulation level of tryptamine so far reported in the literature for studies on heterologous TDC expression in tobacco. However, plants accumulating high levels of functional TDC in the chloroplast developed a lesion-mimic phenotype that was probably triggered by the relatively high accumulation of tryptamine in this compartment. We demonstrate that subcellular targeting may provide a useful strategy for enhancing accumulation and/or stability of enzymes involved in secondary metabolism and to divert metabolic flux toward desired end products. However, metabolic engineering of plants is a very demanding task because unexpected, and possibly unwanted, effects may be observed on plant metabolism and/or phenotype.

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Markus Sack

RWTH Aachen University

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Yu-Cai Liao

RWTH Aachen University

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L. M. Kawchuk

Agriculture and Agri-Food Canada

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