Barzilay E, Ben-Califa N, Supino-Rosin L, Kashman Y, Hirschberg
K, Elazar Z, Neumann D.Geldanamycin associated inhibition of
intracellular trafficking is attributed to a co-purified
activity.
J Biol Chem. 2004 Feb 20;279(8):6847-52. Epub 2003 Dec 01.
Department of Cell and Developmental Biology, Sackler Faculty
of Medicine, Tel-Aviv University, Ramat-Aviv, Israel.
Geldanamycin, an ansamycin antibiotic that specifically
inhibits heat-shock protein-90 (HSP90) and its endoplasmic
reticulum homologue, glucose-regulated protein-94 (GRP94),
accelerates the degradation of selected cellular proteins. We
showed previously that geldanamycin inhibits maturation and
transport of the epidermal growth factor receptor in addition to
accelerating its degradation (Supino-Rosin, L., Yoshimura, A.,
Yarden, Y., Elazar, Z., and Neumann, D. (2000) J. Biol. Chem.
275, 21850-21855).
Here we demonstrate that the additional activities of
geldanamycin on intracellular transport and protein maturation
are related to its supply source. By combining chemical
separation of Streptomyces hygroscopicus var. geldanus extracts
and biological screens, we show that the geldanamycin-associated
effects on intracellular transport and protein maturation are
not mediated by geldanamycin itself but are due to the presence
of an additional component(s. Chromatography of S. hygroscopicus
var. geldanus extracts on a silica-gel column allowed separation
between the inhibition of intracellular trafficking and
geldanamycin-mediated degradation. One fraction that was devoid
of geldanamycin blocked secretion of a soluble form of the
erythropoietin receptor, retarded maturation of the epidermal
growth factor receptor without enhancing its degradation, and
blocked anterograde transport of a temperature-sensitive mutant
of the vesicular stomatitis virus G protein (VSVGtsO45) from the
early Golgi cisternae. This fraction was enriched (>95%) in
17-demethylgeldanamycin. However, as synthetically derived
17-demethylgeldanamycin did not inhibit intracellular
trafficking, we concluded that 17-demethylgeldanamycin is not
the active component. We thus propose that a compound(s) that
co-purifies with benzoquinone ansamycins inhibits intracellular
transport. Taken together, our data demonstrate that the
inhibitory effects on protein maturation and intracellular
trafficking, previously attributed to geldanamycin, are mediated
by another distinct moiety.
PMID: 14660597
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