|
Institut Curie/CNRS Joint
Press Release
Because they are able to recognize
a particular cell marker — a protein — antibodies are generally
used to identify abnormal cells in the body. As such, they play a key
role in diagnosis, treatment and basic research.
At the Institut Curie, CNRS research scientists have recently prepared
a new type of antibody which for the first time combines several crucial
features: it can be produced in a few days, it can be expressed directly
in cells, and it is, moreover, sensitive to the shape of proteins. The
latter property is particularly important as the activity of proteins
depends on their shape. Thus certain cancers or illnesses such as Creutzfeldt-Jakob
disease are due to a protein that has assumed an abnormal shape.
This study, which constitutes a technological advance both for basic research
and diagnosis, is published in the 9 May 2003 issue of Science.
All stages in the life of a cell are controlled
by the activity of proteins. Proteins enable cells to produce energy,
to reproduce and to interact with their environment. All these processes
must be closely monitored to avoid pathological dysfunction.
To enhance understanding of the normal and pathological function of cells,
it is therefore necessary to monitor gene expression, but also to analyze
the behavior of the proteins themselves. This is where antibodies prove
valuable.
In research, scientists conventionally track proteins using antibodies
coupled to fluorescent molecules or to metal microbeads. In medicine,
antibodies are routinely used in diagnosis to detect tumor markers in
biopsied material and so to determine the nature of a tumor or to identify
the origin of a metastasis.
We are rapidly acquiring knowledge of proteins and their roles (proteomics)
in diseases like cancer. To study these proteins and to transfer rapidly
the resulting knowledge to medical practice, we need to optimize the identification
of new, highly selective antibodies.
The quality of the antibodies depends on their specificity for proteins.
The capacity of antibodies to detect proteins inside cells is also an
advantage. We are now able to prepare and then humanize1 antibodies,
but the task now is to hasten their identification, which currently takes
several months, and to ameliorate their selectivity so that they are capable
of recognizing fine differences between proteins.
Proteins as "biological switches"
Many proteins regulate their activity and hence
their function by altering shape (conformation). In this way some act
as biological switches: they switch from an "inactive" to an
"active" position, thus enabling them to interact with other
proteins. By distinguishing between these two forms we can provide additional
information for scientists studying cell function, but also for physicians
making diagnoses.
When a protein with a key role in cell function is blocked in one conformation,
the cell becomes uncontrolled and in particular this may trigger the formation
of a tumor. For example, mutations in the Ras gene, which are found in
30 to 60% of human cancers, give rise to a constitutively active form
of the protein, leading to severe disruption of signal transmission within
the cells. In general, proteins are more active in tumor tissues and may
therefore serve as markers.
Accelerated production of "intelligent"
antibodies
Using a library of several billion human antibodies2
, the group of Franck Perez, in Bruno
Goud's team at the Institut Curie3 , has succeeded in just
a few weeks in preparing in vitro antibodies against the active form of
the intracellular protein Rab64 .
The antibody library also indicated which gene
codes for this antibody. Perez and colleagues were therefore able to introduce
this gene into the cells where its expression led to production of the
antibody.
This is the first production of synthetic antibodies of human origin that
are both sensitive to protein conformation and can also be expressed directly
in living cells. This enables Rab6 to be tracked in real time and solely
in its active form inside cells.
This wholly in vitro technique of producing antibodies also has the advantage
of being inexpensive and applicable to many other proteins, or even to
complexes of proteins.
By combining for the first time in the same
antibody sensitivity to protein conformation, rapid identification and
expression in living cells, Perez and colleagues have taken a new step
forward in what can be considered as an innovative diagnostic approach.
It may prove possible to use such antibodies to detect the pathological
forms of proteins, such as the prion5 in Creutzfeldt-Jakob
disease, or a protein blocked in a particular form, as in the case of
Ras protein in certain cancers.
Reference
Recombinant antibodies to the small GTPase Rab6 as conformation sensors.
Clément Nizak1, Solange Monier1, Elaine del
Nery1, Sandrine Moutel2, Bruno Goud1,
Franck Perez1
Science, 9 May 2003, vol. 300, n° 5621
1 - UMR 144 CNRS/Institut Curie, France
2 - Translational Department, Institut Curie, France
1 - The antibodies are produced in animals
(mice, rats). The parts common to all the antibodies are then replaced
by human sequences, thus minimizing rejection. Several months are needed
to identify and produce these antibodies.
2 - The antibody library was provided by G. Winter of the Medical Research
Council (Cambridge, UK).
3 - Franck Perez is a CNRS research scientist in the "Molecular mechanisms
of intracellular transport " team headed by Bruno Goud, in the CNRS/Institut
Curie Joint Research Unit "Subcellular structure and cellular dynamics".
4 - Rab6: This protein participates in an intracellular transport pathway
(between the Golgi apparatus and the endoplasmic reticulum). A recent
study (Nature, 415, pp. 530-537) has shown that Rab6 is associated
with a poor prognosis in certain breast cancers. These antibodies directed
specifically against the active form should enhance understanding of the
role of Rab6 in this type of cancer.
5 - The brain contains a normal form of the same protein which is naturally
degraded by proteases. The abnormal form, on the other hand, is resistant
to these proteases and therefore accumulates in the brain.
Institut Curie Press Relations
Catherine Goupillon
Phone 01 44 32 40 63
service.presse@curie.fr
www.curie.fr
Céline Giustranti
Phone 01 44 32 40 64
Artwork
Cécile Charré
Phone 01 44 32 40 51
CNRS Press Office
Martine Hasler
Phone 01 44 96 46 35
martine.hasler@cnrs-dir.fr
|