Point mutations in the juxtamembrane domain of FLT3 define a new class of activating mutations in AML.

Abstract

In acute myeloid leukemia (AML), two clusters of activating mutations are known in the FMS-like tyrosine kinase-3 (FLT3) gene: FLT3-internal tandem duplications (FLT3-ITDs) in the juxtamembrane (JM) domain in 20% to 25% of patients, and FLT3 point mutations in the tyrosine-kinase domain (FLT3-TKD) in 7% to 10% of patients, respectively. Here, we have characterized a new class of activating point mutations (PMs) that cluster in a 16-amino acid stretch of the juxtamembrane domain of FLT3 (FLT3-JM-PMs). Expression of 4 FLT3-JM-PMs in interleukin-3 (IL-3)-dependent Ba/F3 cells led to factor-independent growth, hyperresponsiveness to FLT3 ligand, and resistance to apoptotic cell death. FLT3-JM-PM receptors were autophosphorylated and showed a higher constitutive dimerization rate compared with the FLT3-wild-type (WT) receptor. As a molecular mechanism, we could show activation of STAT5 and up-regulation of Bcl-x(L) by all FLT3-JM-PMs. The FLT3 inhibitor PKC412 abrogated the factor-independent growth of FLT3-JM-PM-expressing cells. Compared with FLT3-ITD and FLT3-TKD mutants, the FLT3-JM-PMs showed a weaker transforming potential related to lower autophosphorylation of the receptor and its downstream target STAT5. Mapping of the FLT3-JM-PMs on the crystal structure of FLT3 showed that these mutations reduce the stability of the autoinhibitory JM domain, and provides a structural basis for the transforming capacity of this new class of gain-of-function mutations of FLT3.

• Authors: Carola Reindl, Ksenia Bagrintseva, Sridhar Vempati, Susanne Schnittger, Joachim W Ellwart, Katja Wenig, Karl-Peter Hopfner, Wolfgang Hiddemann, Karsten Spiekermann
• Journal: Blood (Blood) Vol. 107 Issue 9 Pg. 3700-7 (May 01 2006) ISSN: 0006-4971 [Print] United States
• PMID: 16410449 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• DNA, Neoplasm
• Interleukin-3
• Recombinant Proteins
• STAT5 Transcription Factor
• Tyrosine
• FLT3 protein, human
• fms-Like Tyrosine Kinase 3
• Staurosporine
• midostaurin

Topics

• Amino Acid Sequence
• Animals
• Apoptosis
• Base Sequence
• Cell Line
• DNA, Neoplasm (genetics)
• Enzyme Activation (genetics)
• Humans
• In Vitro Techniques
• Interleukin-3 (pharmacology)
• Leukemia, Myeloid, Acute (enzymology, genetics)
• Mice
• Models, Molecular
• Molecular Sequence Data
• Mutagenesis, Site-Directed
• Phosphorylation
• Point Mutation
• Protein Structure, Tertiary
• Recombinant Proteins (chemistry, genetics, metabolism)
• STAT5 Transcription Factor (metabolism)
• Staurosporine (analogs & derivatives, pharmacology)
• Tyrosine (chemistry)
• fms-Like Tyrosine Kinase 3 (chemistry, genetics, metabolism)