IP6K1 over-expression rescues TNP inhibition of InsP7
synthesis. A, HPLC of InsP6 and InsP7 from
HeLa cells overexpressing GFP-IP6K1 labeled with [3H]inositol.
Cells were stimulated with DMSO (filled circles) or TNP at 100
nm (open circles); 1 μm (open
triangles), and 10 μm (closed triangles) for 2 h
at 37 °C. The soluble inositol phosphates were extracted and separated as
explained under “Experimental Procedures.” B, decrease in
InsP7 from HeLa cells overexpressing GFP (filled circles)
or GFP-IP6K1 (open circles) as a function of TNP concentration. Data
are the average of triplicate experiments, and error bars represent
the S.D. of the data. Curve fitting to the InsP7 data was done
using the Sigma Plot software, and IC50 calculations were carried
out from the equation used to fit the curve.