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Western blot analysis of extracts from 293 cells, transfected with 100 nM SignalSilence® Control siRNA (Unconjugated) #6568 (-), SignalSilence® p38α MAPK siRNA I (+) or SignalSilence® p38α MAPK siRNA II #6277 (+), using p38α MAPK Antibody #9218 (upper) or α-Tubulin (11H10) Rabbit mAb #2125 (lower). The p38α MAPK Antibody confirms silencing of p38α MAPK expression, while the α-Tubulin (11H10) Rabbit mAb is used as a loading control.

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Product Usage Information

CST recommends transfection with 100 nM p38α MAPK siRNA I 48 to 72 hours prior to cell lysis. For transfection procedure, follow protocol provided by the transfection reagent manufacturer. Please feel free to contact CST with any questions on use.

Each vial contains the equivalent of 100 transfections, which corresponds to a final siRNA concentration of 100 nM per transfection in a 24-well plate with a total volume of 300 μl per well.


Storage: SignalSilence® siRNA is supplied in RNAse-free water. Aliquot and store at -20ºC.

Product Description

SignalSilence® p38α MAPK siRNA I from Cell Signaling Technology (CST) allows the researcher to specifically inhibit p38α MAPK expression using RNA interference, a method whereby gene expression can be selectively silenced through the delivery of double stranded RNA molecules into the cell. All SignalSilence® siRNA products from CST are rigorously tested in-house and have been shown to reduce target protein expression by western analysis.


Quality Control

Oligonucleotide synthesis is monitored base by base through trityl analysis to ensure appropriate coupling efficiency. The oligo is subsequently purified by affinity-solid phase extraction. The annealed RNA duplex is further analyzed by mass spectrometry to verify the exact composition of the duplex. Each lot is compared to the previous lot by mass spectrometry to ensure maximum lot-to-lot consistency.

p38 MAP kinase (MAPK), also called RK (1) or CSBP (2), is the mammalian orthologue of the yeast HOG kinase that participates in a signaling cascade controlling cellular responses to cytokines and stress (1-4). Four isoforms of p38 MAPK, p38α, β, γ (also known as Erk6 or SAPK3), and δ (also known as SAPK4) have been identified. Similar to the SAPK/JNK pathway, p38 MAPK is activated by a variety of cellular stresses including osmotic shock, inflammatory cytokines, lipopolysaccharide (LPS), UV light, and growth factors (1-5). MKK3, MKK6, and SEK activate p38 MAPK by phosphorylation at Thr180 and Tyr182. Activated p38 MAPK has been shown to phosphorylate and activate MAPKAP kinase 2 (3) and to phosphorylate the transcription factors ATF-2 (5), Max (6), and MEF2 (5-8).

SB203580 (4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-imidazole) is a selective inhibitor of p38 MAPK. This compound inhibits the activation of MAPKAPK-2 by p38 MAPK and subsequent phosphorylation of HSP27 (9). SB203580 inhibits p38 MAPK catalytic activity by binding to the ATP-binding pocket, but does not inhibit phosphorylation of p38 MAPK by upstream kinases (10).


1.  Han, J. et al. (1994) Science 265, 808-11.

2.  Raingeaud, J. et al. (1995) J. Biol. Chem. 270, 7420-7426.

3.  Rouse, J. et al. (1994) Cell 78, 1027-1037.

4.  Lee, J.C. et al. (1994) Nature 372, 739-46.

5.  Freshney, N.W. et al. (1994) Cell 78, 1039-49.

6.  Zervos, A.S. et al. (1995) Proc Natl Acad Sci U S A 92, 10531-4.

7.  Zhao, M. et al. (1999) Mol Cell Biol 19, 21-30.

8.  Yang, S.H. et al. (1999) Mol Cell Biol 19, 4028-38.

9.  Cuenda, A. et al. (1995) FEBS Lett 364, 229-33.

10.  Kumar, S. et al. (1999) Biochem Biophys Res Commun 263, 825-31.


Entrez-Gene Id 1432
Swiss-Prot Acc. Q16539


For Research Use Only. Not For Use In Diagnostic Procedures.
Cell Signaling Technology® is a trademark of Cell Signaling Technology, Inc.
SignalSilence® is a trademark of Cell Signaling Technology, Inc.