Src-Like Adaptor Protein (SLAP) Binds to the Receptor Tyrosine Kinase Flt3 and Modulates Receptor Stability

Fms-like tyrosine kinase 3 (Flt3) is an important growth factor receptor in hematopoiesis. Gain-of-function mutations of the receptor contribute to the transformation of acute myeloid leukemia (AML). Src-like adaptor protein (SLAP) is an interaction partner of the E3 ubiquitin ligase Cbl that can regulate receptor tyrosine kinases-mediated signal transduction. In this study, we analyzed the role of SLAP in signal transduction downstream of the type III receptor tyrosine kinase Flt3. The results show that upon ligand stimulation SLAP stably associates with Flt3 through multiple phosphotyrosine residues in Flt3. SLAP constitutively interacts with oncogenic Flt3-ITD and co-localizes with Flt3 near the cell membrane. This association initiates Cbl-dependent receptor ubiquitination and degradation. Depletion of SLAP expression by shRNA in Flt3-transfected Ba/F3 cells resulted in a weaker activation of FL-induced PI3K-Akt and MAPK signaling. Meta-analysis of microarray data from patient samples suggests that SLAP mRNA is differentially expressed in different cancers and its expression was significantly increased in patients carrying the Flt3-ITD mutation. Thus, our data suggest a novel role of SLAP in different cancers and in modulation of receptor tyrosine kinase signaling apart from its conventional role in regulation of receptor stability. Citation: Kazi JU, Rönnstrand L (2012) Src-Like Adaptor Protein (SLAP) Binds to the Receptor Tyrosine Kinase Flt3 and Modulates Receptor Stability and Downstream Signaling. PLoS ONE 7(12): e53509. doi:10.1371/journal.pone.0053509 Editor: Jon C.D. Houtman, University of Iowa, United States of America Received September 17, 2012; Accepted November 29, 2012; Published December 31, 2012 Copyright: 2012 Kazi, Rönnstrand. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This research was funded by the Swedish Cancer Society, the Swedish Children’s Cancer Organization, the Swedish Research Council, and an ALF governmental clinical grant. J.U. Kazi was supported by Wenner-Gren Foundations. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: [email protected]