The Role of the Juxtamembrane Domain of FLT3-ITDs in Acute Myeloid Leukemia
Beschreibung
vor 17 Jahren
Activating mutations in the juxtamembrane domain of FLT3
(FLT3-internal tandem duplications, FLT3-ITDs) represent the most
frequent genetic alterations in acute myeloid leukemia (AML).
FLT3-internal tandem duplications (FLT3-ITDs) are a heterogenous
group of mutations in patients with acute leukemias that are
prognostically important. To characterize the mechanism of
transformation by FLT3-ITDs, we sequenced the juxtamembrane region
(JM) of FLT3 from 284 patients with acute leukemias. The length of
FLT3-ITDs varied from 2 to 42 amino acids (AA) with a median of 17
AA. The analysis of duplicated AAs showed that in the majority of
patients, the duplications localize between AA 591 to 599
(YVDFREYEY). Arginine 595 (R595) within this region is duplicated
in 77% of patients. Single duplication of R595 in FLT3 conferred
factor-independent growth to Ba/F3 cells and activated STAT5.
Moreover, deletion or substitution of the duplicated R595 in two
FLT3-ITD constructs as well as the deletion of wildtype-R595 in
FLT3-ITD substantially reduced the transforming potential, pointing
to a critical role of the positive charge of R595 in stabilizing
the active confirmation of FLT3-ITDs. Deletion of R595 in the
FLT3-WT inhibited the growth of cells upon FL stimulation and the
STAT5 activation. In this study we could also show that the
tyrosine residues 589 and 591 of the FLT3-ITDs could be important
phosphorylation sites and are very crucial for the activation of
FLT3- ITDs. Simultaneous substitution of these two tyrosine
residues with phenyalanine showed complete inhibition of the
transforming potential of FLT3-ITDs and STAT5 activation. The
substitution of tyrosine residues 597 and 599 did not show any
effect on the transforming potential of FLT3-ITDs, supporting the
previous hypothesis that these tyrosines may be only important to
maintain the integrity of FLT3-WT in its inactive state. Our data
provide important insights into the role of the juxtamembrane
domain in the mechanism of transformation by FLT3-ITDs.
(FLT3-internal tandem duplications, FLT3-ITDs) represent the most
frequent genetic alterations in acute myeloid leukemia (AML).
FLT3-internal tandem duplications (FLT3-ITDs) are a heterogenous
group of mutations in patients with acute leukemias that are
prognostically important. To characterize the mechanism of
transformation by FLT3-ITDs, we sequenced the juxtamembrane region
(JM) of FLT3 from 284 patients with acute leukemias. The length of
FLT3-ITDs varied from 2 to 42 amino acids (AA) with a median of 17
AA. The analysis of duplicated AAs showed that in the majority of
patients, the duplications localize between AA 591 to 599
(YVDFREYEY). Arginine 595 (R595) within this region is duplicated
in 77% of patients. Single duplication of R595 in FLT3 conferred
factor-independent growth to Ba/F3 cells and activated STAT5.
Moreover, deletion or substitution of the duplicated R595 in two
FLT3-ITD constructs as well as the deletion of wildtype-R595 in
FLT3-ITD substantially reduced the transforming potential, pointing
to a critical role of the positive charge of R595 in stabilizing
the active confirmation of FLT3-ITDs. Deletion of R595 in the
FLT3-WT inhibited the growth of cells upon FL stimulation and the
STAT5 activation. In this study we could also show that the
tyrosine residues 589 and 591 of the FLT3-ITDs could be important
phosphorylation sites and are very crucial for the activation of
FLT3- ITDs. Simultaneous substitution of these two tyrosine
residues with phenyalanine showed complete inhibition of the
transforming potential of FLT3-ITDs and STAT5 activation. The
substitution of tyrosine residues 597 and 599 did not show any
effect on the transforming potential of FLT3-ITDs, supporting the
previous hypothesis that these tyrosines may be only important to
maintain the integrity of FLT3-WT in its inactive state. Our data
provide important insights into the role of the juxtamembrane
domain in the mechanism of transformation by FLT3-ITDs.
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