Journal of the American Chemical Society
Article
pathways. Anisomycin has been reported to activate both JNK
and p38 MAPK pathways,46 and EGF was reported to induce
ERK and to a lesser extent the JNK pathway.47
cell lysates in vitro at neutral aqueous conditions using
chemometric analysis. In this manner, a new pattern
recognition approach was derived to target this class of analyte.
The ability of this sensing ensemble to differentiate cells that
have been induced with different stimulants increases our
expectation for the ability of this array to differentiate between
different types of cells, such as cells from diseased and
nondiseased tissues or even cells from different organs.
Before array analysis, Western blot (WB) on lysates was
performed to confirm the anticipated changes in these kinases
(see Figure S12 Supporting Information). The WBs showed an
increased activation/phosphorylation of JNK and p38 in the
cells that were stimulated with anisomycin if compared to the
untreated ones (control cells). Further, the ERK activation/
phosphorylation pathway was confirmed to be increased in cells
stimulated with EGF when compared to the control. Two other
sets of lysates contained HEK293T cells that have ERK1-WT
overexpressed, while one of them was also stimulated with
EGF. WB analysis showed that overexpressed ERK-1 was
partially phosphorylated. However, induction of the cells with
EGF significantly increased its phosphorylation.
Cell lysate expression, purification, and activation, are
described in the Supporting Information. HEK293T cell lysates
were prepared in CytoBuster Protein Extraction Reagent
(EMD-Biosciences) after washing in PBS (Invitrogen). The
lysates were cleared by centrifugation, and ATP was washed
away using Amicon Ultra 0.5 mL Centrifugal Filters. Bradford
analysis (Bio-Rad) was used to measure the protein
concentration. Discrimination of cell lysates was obtained at
total protein concentration according to Supporting Informa-
tion, Table S4. For the detection, 6 μL of cell lysate was added
to the same sensing ensemble and same data analysis was
followed.
The LDA score plot (Figure 6A) of the fluorescence data
showed excellent differentiation between the cells overexpress-
ing ERK-1 (ERK-), cells overexpressing ERK-1 and induced by
EGF (ERK+), and control cells along the F1 and F2 axes, and
good clustering of the replicates. This result suggests that the
variation of the responses is dependent on protein and
phospho-protein identity. Furthermore, the LDA score plot
(Figure 6C) of the fluorescence data also showed excellent
discrimination of the cells that have ERK induced by EGF
(EGF), which are separated along the second principal
component (F2) from the cells that have JNK/p38 induced
by anisomycin, and separated from the control cells along the
first principal component (F1). This differentiation suggests
that the sensing array is able to detect subtle changes in
phosphoproteins when cells are stimulated with different
activators. These cell extracts are classified into respective sets
with 100% accuracy according to a jack-knife analysis. Another
general trend was found (Figure 6A,C), where the induced
and/or overexpressed cell lysates are located on the right side
of the score plot and the control lysates are located on the left
side.
ASSOCIATED CONTENT
* Supporting Information
■
S
Detail synthetic procedures, product characterization, and
experimental details. This material is available free of charge
AUTHOR INFORMATION
Corresponding Author
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by NSF Grant CHE-1212971 and the
Welch Foundation (F-1151) to Dr. Eric V. Anslyn. We also
acknowledge CONACYT fellowship 212537 to Diana Zamora-
Olivares. Tamer S. Kaoud is supported by a postdoctoral
trainee fellowship from Cancer Prevention Research Institute of
Texas (CPRIT). This research was also supported by the grants
from the Welch Foundation (F-1390) and NIH (GM059802
and CA167505) to Dr. Kevin Dalby.
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