XXII. BIOCHEMICKÝ ZJAZD - Jesseniova lekárska fakulta

Posters
121.
OVEREXPRESSION OF P-GLYCOPROTEIN IN L1210/VCR CELLS IS
ASSOCIATED WITH CHANGES IN SEVEraL ENDOPLASMIC RETICULUM
PROTEINS
Mário Šereš, Eva Poláková, Oľga Križanová, Zdena Sulová and Albert Breier
Institute of Molecular Physiology and Genetics SAS Bratislava
Multidrug resistant cells R, which express membrane drug efflux transporter – P-glycoprotein
(P-gp, a member of ABC transporter family), was found to be also less sensitive to thapsigargin,
inhibitor of sarco(endo)plasmic reticulum calcium pump (SERCA), in contrast
to parental drug-sensitive cells L1210 (S). R cells was obtained from S cells by selection
with vincristine (VCR). We have studied differences among S and R cells in expression
of endoplasmic reticulum proteins involved in the regulation of calcium homeostasis
and calcium-dependent processes. Amounts of mRNA encoding RyR and IP 3
-receptor
channels were found to be at similar in S and R cells. However, mRNAs encoding IP 3
R1
or 2 were decreased in resistant cells cultivated in the presence of VCR, while mRNA
encoding RyR remained unchanged. The amount of mRNA encoding SERCA2 was lower
in R cells as in S cells. This decrease was more pronounced when R cells were cultivated
in the presence of VCR. Calnexin was believed to be active in P-gp maturation, but surprisingly,
calnexin was found to be less expressed at the protein level in R as in S cells.
We have also studied thapsigargin effect on expression of some endoplasmic reticulum
proteins and P-glycoprotein. P-gp expression was decreased in presence of thapsigargin.
Thus, S and R cells differ in the expression of endoplasmic reticulum proteins involved
in the control of intracellular calcium homeostasis or calcium-dependent processes.
Acknowledgement: This work was supported by: VVCE-0064-07, APVV-0084-07 and
VEGA 2/0123/10, 2/0155/09.
246 XXII. Biochemistry Congress, Martin