Download Moss – An Innovative Tool for Protein Production

GREEN BIOTECHNOLOGY
Fig. 1: The moss Physcomitrella patens
The complete sequencing of the human
genome has significantly increased the
number of pharmaceutically important
proteins (“biopharmaceuticals”) to be
produced at large scale. As this tendency
is expected to continue, production capacity of biopharmaceuticals has become
a strategic issue for the pharmaceutical
industry.
Mammalian cells such as those of baby
hamster kidney and Chinese hamster
ovary have been used for more than two
decades. However, these systems require
major investments in production facilities
and running costs of production are very
high. Among other technologies, e. g.
yeasts and transgenic animals, plants are
an alternative for the production of recombinant proteins [1]. So far seed plants
like tobacco, corn, and Alfalfa, have been
tested for molecular farming. We here will
focus on a moss, Physcomitrella patens,
as an innovative tool. Physcomitrella has
a moderately small genome of 511 Mbp
[2]. Mosses are higher multicellular eukaryotes and therefore perform extensive
posttranslational processing of proteins
including the formation of disulfide
bridges and complex glycosylation. Their
major developmental stage is the haploid
gametophyte (Fig. 1). In contrast, the
dominating developmental stage of seed
plants is the diploid or polyploid sporophyte [3]. Moss is unique among all
multicellular plants analyzed to date in
exhibiting a very effective homologous
recombination in its nuclear DNA. This
allows targeted knockouts of genes [4, 5],
which is a highly attractive tool for production strain design. Thus, the manipulation of the glycosylation pathway is
2 • BIOforum Europe 2/2003
Moss – An Innovative Tool
for Protein Production
Eva L. Decker, Gilbert Gorr, Ralf Reski
GREEN BIOTECHNOLOGY
Keywords
biotechnology, homologous recombination,
moss, Physcomitrella patens, recombinant
proteins
feasible in moss, as opposed to seed
plants. Xylose and fucose residues linked
to the core structure are characteristic
for plant glycans. These plant-specific
residues are associated with allergenic
risk and thus because of drug safety reasons their removal is essential for production of biopharmaceuticals [1].
Physcomitrella is grown under photoautotrophic conditions in a simple
medium essentially consisting of water
and minerals. Light and carbon dioxide
serve as the only energy and carbon
sources. Furthermore, cultivation in glass
bioreactors is well established (Fig. 2)
[6]. As compared to animal cell systems
requirements for extensive process
technology are reduced significantly.
Physcomitrella grows under broad pH
and temperature ranges.
Our production system is based on the
secretion of recombinant proteins into the
medium. As newly synthesized extracellular proteins have to pass the endoplasmic
reticulum and the Golgi apparatus where
posttranslational modifications including
glycosylation and disulfide bonding occur,
secreted proteins are completely posttranslationally processed. Additionally,
secretion into such simple medium has
major advantages for protein purification
in greatly reducing the costs for downstream processing. Proof of concept has
been achieved by expression and secretion of biologically active human vascular
endothelial growth factor (VEGF) using
the human leader peptide for targeting
the recombinant protein to the secretion
pathway of the moss cells [7].
Above that Physcomitrella has an
excellent safety profile as a production
system for biopharmaceuticals. As in all
plant-based production systems the risk
of contamination with human or animal
pathogens is minimized. As a contained
system the moss bioreactor is not related
to environmental release of transgenic
plants and therefore allows production in
an environmentally responsible manner.
In conclusion, the moss Physcomitrella
patens offers a paramount of important
features that make it highly attractive not
only as a model organism for the scientific community but also as an organism
for the production of biopharmaceuticals.
Literature
Fig. 2: Photoautotrophic cultivation of
moss in the bioreactor
[1] W. L. Larrick, D. W. Thomas: Current Opinion
in Biotechnology 12, 411–418 (2001)
[2] G. Schween, G. Gorr, A. Hohe, R. Reski: Plant
Biology, in press
[3] R. Reski: Planta 208, 301–309 (1999)
[4] T. Girke, H. Schmidt, U. Zähringer, R. Reski,
E. Heinz: Plant J.15, 39–48 (1998)
[5] A. Koprivova, A. J. Meyer, G. Schween, C.
Herschbach, R. Reski, S. Kopriva: J. Biol.
Chem. 277, 32195–32201 (2002)
[6] A. Hohe, E. L. Decker, G. Gorr, G. Schween, R.
Reski: Plant Cell Rep. 20, 1135–1140 (2002)
[7] G. Gorr, E. Decker, M. Kietzmann, R. Reski:
Naunyn-Schmiedeberg’s Arch. Pharmacol.
363(4) Suppl.,R 85 (2001)
Dr Eva Decker
was appointed Assistant
Professor at the Chair
Plant Biotechnology,
Albert-Ludwigs-University of Freiburg (Germany) in 2000. She received her PhD in 1999
for her work on the
transcriptional regulation of human cytokine
gene expression at the
Bernhard Nocht Institute for Tropical Medicine in Hamburg (Germany). Before that, she studied
biology at the universities of Bielefeld and Hamburg.
Prof Dr Ralf Reski
was appointed Full Professor (C4) and head of
the newly founded Chair
Plant Biotechnology at
Albert-Ludwigs-University Freiburg (Germany)
in 1999. He was Assistant Professor at Hamburg University and received his Habilitation in
“General Botany”. For
his pioneering work on
moss genetics he was
awarded a Heisenberg-Fellowship by the Deutsche
Forschungsgemeinschaft in 1996. He is co-inventor of
the moss bioreactor and co-founder of greenovation
Biotech GmbH. Since 2002 Prof Reski serves this company as chairman of the advisory board.
Albert-Ludwigs-University
Plant Biotechnology
Schänzlestrasse 1
79104 Freiburg, Germany
[email protected]
www.plant-biotech.net
Dr. Gilbert Gorr
was nominated CSO on
June 19th, 2002. Dr. Gorr
is co-inventor of the
moss bioreactor. He
joined greenovation
Biotech GmbH in October 2000 as Senior Scientist. He has studied
biology and chemistry
and received his PhD
from Hamburg University for his pioneering
work on the use of a
moss for the expression of human VEGF. Before coming
to greenovation Biotech GmbH he worked as scientist
at the Institute for Pharmacology, Toxicology, and Pharmacy, School of Veterinary Medicine, Hannover.
greenovation Biotech GmbH
Boetzingerstrasse 29b
79112 Freiburg, Germany
www.greenovation.com
BIOforum Europe 2/2003 • 3