The tyrosine kinase CSK associates with FLT3 and c-Kit receptors and regulates downstream signaling.

Julhash U. Kazi, Marica Vaapil, Shruti Agarwal, Enrico Bracco, Sven Påhlman, Lars Rönnstrand

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Type III receptor tyrosine kinases (RTKs), FLT3 and c-Kit play important roles in a variety of cellular processes. A number of SH2-domain containing proteins interact with FLT3 and c-Kit and regulate downstream signaling. The SH2-domain containing non-receptor protein tyrosine kinase CSK is mainly studied in context of regulating Src family kinases. Here we present an addition role of this kinase in RTK signaling. We show that CSK interacts with FLT3 and c-Kit in a phosphorylation dependent manner. This interaction is facilitated through the SH2-domain of CSK. Under basal conditions CSK is mainly localized throughout the cytosolic compartment but upon ligand stimulation it is recruited to the inner side of cell membrane. CSK association did not alter receptor ubiquitination or phosphorylation but disrupted downstream signaling. Selective depletion of CSK using siRNA, or inhibition with CSK inhibitor, led to increased phosphorylation of Akt and Erk, but not p38, upon FLT3 ligand (FL) stimulation. Stem cell factor (SCF)-mediated Akt and Erk activation was also elevated by CSK inhibition. However, siRNA mediated CSK knockdown increased SCF stimulated Akt phosphorylation but decreased Erk phosphorylation. CSK depletion also significantly increased both FL- and SCF-induced SHC, Gab2 and SHP2 phosphorylation. Furthermore, CSK depletion contributed to oncogenic FLT3- and c-Kit-mediated cell proliferation, but not to cell survival. Thus, the results indicate that CSK association with type III RTKs, FLT3 and c-Kit can have differential impact on receptor downstream signaling.
Original languageEnglish
Pages (from-to)1852-1860
JournalCellular Signalling
Issue number9
Publication statusPublished - 2013

Bibliographical note

The information about affiliations in this record was updated in December 2015.
The record was previously connected to the following departments: Molecular Medicine (013031200), Experimental Clinical Chemistry (013016010)

Subject classification (UKÄ)

  • Microbiology


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