Fig. 2. Expression of IGF-IR and IR and IGF-IR kinase activity.
A, nonmalignant and malignant mammary cell lines growing
in complete growth medium were lysed with RIPA buffer. Five hundred
µg of lysate protein were immunoprecipitated (IP) with
anti-IGF-IR, resolved by 10% SDS-PAGE, and immunoblotted
(IB) with anti-IGF-IR. B, cells were
grown to confluence, serum-starved for 16 h, and incubated for 10
min with or without IGF-I. Cell lysates were prepared with RIPA buffer,
and 500 µg of each lysate were immunoprecipitated with anti-IGF-IR.
Immunoprecipitates were subjected to in vitro kinase
assay and analyzed as described in "Materials and Methods."
C, 20 µg of cell lysate from A was
resolved by SDS-PAGE and immunoblotted with anti-IR. The positions of
the molecular weight markers are indicated. *, nonmalignant.