![]() |
6th ESACP Congress, Heidelberg, April 7-11, 1999 |
A157
ErbB2, a transmembrane tyrosine kinase, forms both homo- and heterodimers
with other members of the erbB family. Previously we found evidence for
the existence of membrane regions in breast cancer cells where the
homoassociation of erbB2 is anomalously high. In our current work we set
out to characterize the dimensions and the possible physiological importance
of these regions. We used a scanning near-field optical microscope to
visualize erbB2 clustering in fluorescent antibody-labeled cells. Quiescent
MDA453 and SKBR3 breast tumor cells showed a conspicuously uneven distribution
of erbB2 with a cluster diameter of 450 nm. A single cluster contains about
1000-2000 erbB2 proteins in unstimulated SKBR3 cells. To correlate the
activation state of erbB2 with the diameter of clusters, we used three
different agents to stimulate SKBR3 cells: EGF and heregulin treatment, and
incubation at 37 oC with the 4D5 antibody known to be a partial agonist.
Each of these treatments increased the size of erbB2 clusters, although they
exert their activation effect differently. The EGF-induced effect could be
blocked with an EGF-receptor specific receptor tyrosine kinase inhibitor. Our
results imply that erbB2 is concentrated in protein clusters in an activation
dependent manner. In addition to the acknowledged short scale association of
erbB proteins (e.g. dimers), the clustering of several hundreds of proteins
may also be significant in signal transduction by ensuring a high local
concentration of signaling proteins.
SMALL AND LARGE SCALE CLUSTERING OF THE ERBB2 RECEPTOR TYROSINE KINASE
ON QUIESCENT AND STIMULATED CELLS DETECTED BY SCANNING NEAR-FIELD OPTICAL
MICROSCOPY
Nagy P, Jenei A, Kirsch AK, Szollosi J, Damjanovich S
Dept.Biophysics and Cell Biology, University Medical School
Debrecen, Hungary, Max Planck Institut für Biophysikalische
Chemie, Göttingen, Germany
This work was supported by OTKA research grants F020102, F022725, T019372
from the Hungarian Academy of Sciences. AJ was supported by a long-term
EMBO fellowship.