rGDNF HEK-293

[apaden]

Hi,

I have inherited some stabley-transfected HEK 293 cells that produce
GDNF, a neurotrohic factor. Supposedly they have been transfected,
selected and are currently clonal. I successfully purified GDNF from
these cells via metal-affinity chromatography.

There are two problems.

1. The expression of recombinant protein seems to rapidly decrease
(ca. one to two weeks.) This has been verified by anti-His tag
Western blot of the 1X supernatant and by anti-His tag Western blot
after purification of the supernatant.

2. The His-tag Western blot itself often produces no results. There
is much non-specific protein but no recombinant protein. I am suspect
that if I loaded the full 25uL onto the gel instead of the 10uL I
currently load, I might get a signal.

Can anyone offer suggestions? Is it really possible for a clonal cell
line to loose expression that quickly?

Thanks so much,
Andrew