title: Anchoring of FLT3 in the endoplasmic reticulum alters signaling quality.
abstract: The mechanism of cell transformation by Fms-like tyrosine kinase 3 (FLT3) in acute myeloid leukemia (AML) is incompletely understood. The most prevalent activated mutant FLT3 ITD exhibits an altered signaling quality, including strong activation of the STAT5 transcription factor. FLT3 ITD has also been found partially retained as a high-mannose precursor in an intracellular compartment. To analyze the role of intracellular retention of FLT3 for transformation, we have generated FLT3 versions that are anchored in the perinuclear endoplasmic reticulum (ER) by appending an ER retention sequence containing a RRR (R3) motif. ER retention of R3, but not of corresponding A3 FLT3 versions, is shown by biochemical, fluorescence-activated cell sorting, and immunocytochemical analyses. ER anchoring reduced global autophosphorylation and diminished constitutive activation of ERK1/2 and AKT of the constitutively active FLT3 versions. ER anchoring was, however, associated with elevated signaling to STAT3. Transforming activity of the FLT3 D835Y mutant was suppressed by ER anchoring. In contrast, ER-anchored FLT3 ITD retained STAT5-activating capacity and was transforming in vitro and in vivo. The findings highlight another aspect of the different signaling quality of FLT3 ITD: It can transform cells from an intracellular location.
authors.affiliation: Institute of Molecular Cell Biology, Center for Molecular Biomedicine, Friedrich Schiller University Jena, Jena, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Schmidt-Arras
authors.forename: Sylvia-Annette
authors.initials: SA
authors.lastname: Böhmer
authors.forename: Sina
authors.initials: S
authors.lastname: Koch
authors.forename: Jörg P
authors.initials: JP
authors.lastname: Müller
authors.forename: Lutz
authors.initials: L
authors.lastname: Blei
authors.forename: Hauke
authors.initials: H
authors.lastname: Cornils
authors.forename: Reinhard
authors.initials: R
authors.lastname: Bauer
authors.forename: Sridhar
authors.initials: S
authors.lastname: Korasikha
authors.forename: Christian
authors.initials: C
authors.lastname: Thiede
authors.forename: Frank-D
authors.initials: FD
authors.lastname: Böhmer
mesh_terms: D000818:Animals; D002455:Cell Division / Q000502:physiology; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D020440:Gene Duplication; D006801:Humans; D007668:Kidney / Q000166:cytology; D015470:Leukemia, Myeloid, Acute / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D016296:Mutagenesis; D050796:STAT3 Transcription Factor / Q000378:metabolism; D050799:STAT5 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D051941:fms-Like Tyrosine Kinase 3 / Q000235:genetics* / Q000378:metabolism*
chemical_list: D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D050799:STAT5 Transcription Factor; C497970:FLT3 protein, human; D051941:fms-Like Tyrosine Kinase 3