Hj. Wang et al., THE AMF-R TUBULE IS A SMOOTH ILIMAQUINONE-SENSITIVE SUBDOMAIN OF THE ENDOPLASMIC-RETICULUM, Journal of Cell Science, 110, 1997, pp. 3043-3053
Autocrine motility factor receptor (AMF-R) is a marker for a distinct
smooth membranous tubule, Ilimaquinone (IQ) is a sea sponge metabolite
which induces the complete vesiculation of the Golgi apparatus and we
show here that the addition of IQ to MDCK cells also results in the d
isruption of the AM[F-R tubule. By immunofluorescence microscopy, the
resultant punctate AMF-R label resembles the products of IQ-mediated v
esiculation of the trans-Golgi network, however, the two labels can be
distinguished by confocal microscopy, AMF-R tubule fragmentation occu
rs after nocodazole or taxol treatment of the cells demonstrating that
the action of IQ on AMF-R tubules is not related to the ability of IQ
to depolymerize microtubules, IQ activity is therefore not Golgi-spec
ific, Electron microscopy of IQ-treated cells reveals that AMF-R is di
stributed to fenestrated networks of narrow interconnected tubules whi
ch are distinguishable from the uniform Golgi-derived vesicles and mor
phologically equivalent to smooth ER, Distinct fenestrations are visib
le in incompletely fragmented tubules which may represent intermediate
s in the fragmentation ]process. Smooth AMF-R labeled tubules exhibit
continuity with rough ER cisternae and IQ selectively targets smooth a
nd not rough ER, AMF-R tubules can be distinguished from the intermedi
ate compartment labeled for ERGIC-53 by confocal microscopy and thus c
onstitute a distinct IQ-sensitive subdomain of the smooth ER.