Yc. Qian et al., COINCIDENT EXPRESSION OF MENKES GENE WITH COPPER EFFLUX IN HUMAN PLACENTAL CELLS, American journal of physiology. Cell physiology, 39(6), 1996, pp. 1880-1884
BeWo cells, a human choriocarcinoma cell line, have a high-affinity sy
stem for transporting copper ions into the cell (K-m, = 0.21 mu M) but
are sluggish in releasing copper back into the medium from preloaded
cells. The slow efflux rate has recently been shown to correlate with
a failure of BeWo cells to express the Menkes transcript [Y. Qian, E.
Tiffany-Castiglioni, and E. D. Harris. Am. J. Physiol. 271 (Cell Physi
ol. 40). In press]. We have now determined that only when BeWo cells w
ere grown on plastic surfaces such as petri dishes or flasks did they
display negligible release and enhanced retention of Cu-67. Reverse tr
anscriptase-polymerase chain reaction with the use of primers selectiv
e for the Menkes gene failed to show any evidence of a Menkes transcri
pt in cells cultured on plastic surfaces. In contrast, cells grown on
porous filters previously shown to allow apical and basolateral surfac
es to develop did display the transcript and showed significant copper
release with normal retention. Release of copper from filter-grown ce
lls was blocked with p-chloromercuribenzoate, thus confirming sulfhydr
yl group involvement. Absorption of the Cu-67, either as a free ion or
bound to ceruloplasmin, was unaffected by the different culture condi
tions. The data link the Menkes gene product with the ability of cells
to release copper ions. They also suggest that the expression of the
Menkes gene may be regulated by the development-of polarized cell memb
ranes.