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Myeloproliferative disease induced by TEL-PDGFRB displays dynamic range sensitivity to Stat5 gene dosage.

ABSTRACT: Expression of the constitutively activated TEL/PDGFbetaR fusion protein is associated with the t(5;12)(q33;p13) chromosomal translocation found in a subset of patients with chronic myelomonocytic leukemia. TEL/PDGFbetaR activates multiple signal transduction pathways in cell-culture systems, and expression of the TEL-PDGFRB fusion gene induces myeloproliferative disease (MPD) in mice. We used gene-targeted mice to characterize the contribution of signal transducer and activator of transcription (Stat) and Src family genes to TEL-PDGFRB-mediated transformation in methylcellulose colony and murine bone marrow transduction/transplantation assays. Fetal liver hematopoietic stem and progenitor cells harboring targeted deletion of both Stat5a and Stat5b (Stat5ab(null/null)) genes were refractory to transformation by TEL-PDGFRB in methylcellulose colony assays. Notably, these cell populations were maintained in Stat5ab(null/null) fetal livers and succumbed to transformation by c-Myc. Surprisingly, targeted disruption of either Stat5a or Stat5b alone also impaired TEL-PDGFRB-mediated transformation. Survival of TPiGFP-->Stat5a(-/-) and TPiGFP-->Stat5a(+/-) mice was significantly prolonged, demonstrating significant sensitivity of TEL-PDGFRB-induced MPD to the dosage of Stat5a. TEL-PDGFRB-mediated MPD was incompletely penetrant in TPiGFP-->Stat5b(-/-) mice. In contrast, Src family kinases Lyn, Hck, and Fgr and the Stat family member Stat1 were dispensable for TEL-PDGFRB disease. Together, these data demonstrate that Stat5a and Stat5b are dose-limiting mediators of TEL-PDGFRB-induced myeloproliferation.

SUBMITTER: Cain JA

PROVIDER: S-EPMC1874559 | biostudies-literature | 2007 May

REPOSITORIES: biostudies-literature

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Myeloproliferative disease induced by TEL-PDGFRB displays dynamic range sensitivity to Stat5 gene dosage.

Cain Jennifer A JA Xiang Zhifu Z O'Neal Julie J Kreisel Friederike F Colson AnnaLynn A Luo Hui H Hennighausen Lothar L Tomasson Michael H MH

Blood 20070111 9

Expression of the constitutively activated TEL/PDGFbetaR fusion protein is associated with the t(5;12)(q33;p13) chromosomal translocation found in a subset of patients with chronic myelomonocytic leukemia. TEL/PDGFbetaR activates multiple signal transduction pathways in cell-culture systems, and expression of the TEL-PDGFRB fusion gene induces myeloproliferative disease (MPD) in mice. We used gene-targeted mice to characterize the contribution of signal transducer and activator of transcription ...[more]

PMID: 17218386

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Project description:AimsA key event in the regulation of cardiac contraction and relaxation is the phosphorylation of phospholamban (PLN) that relieves the inhibition of the sarco/endoplasmic reticulum (SR) Ca2+-ATPase (SERCA2a). PLN exists in an equilibrium between monomers and pentamers. While only monomers can inhibit SERCA2a by direct interaction, the functional role of pentamers is still unclear. This study investigates the functional consequences of PLN pentamerization.Methods and resultsWe generated transgenic mouse models expressing either a PLN mutant that cannot form pentamers (TgAFA-PLN) or wild-type PLN (TgPLN) in a PLN-deficient background. TgAFA-PLN hearts demonstrated three-fold stronger phosphorylation of monomeric PLN, accelerated Ca2+ cycling of cardiomyocytes, and enhanced contraction and relaxation of sarcomeres and whole hearts in vivo. All of these effects were observed under baseline conditions and abrogated upon inhibition of protein kinase A (PKA). Mechanistically, far western kinase assays revealed that PLN pentamers are phosphorylated by PKA directly and independent of any subunit exchange for free monomers. In vitro phosphorylation of synthetic PLN demonstrated that pentamers even provide a preferred PKA substrate and compete with monomers for the kinase, thereby reducing monomer phosphorylation and maximizing SERCA2a inhibition. However, β-adrenergic stimulation induced strong PLN monomer phosphorylation in TgPLN hearts and sharp acceleration of cardiomyocyte Ca2+ cycling and haemodynamic values that now were indistinguishable from TgAFA-PLN and PLN-KO hearts. The pathophysiological relevance of PLN pentamerization was evaluated using transverse aortic constriction (TAC) to induce left ventricular pressure overload. Compared to TgPLN, TgAFA-PLN mice demonstrated reduced survival after TAC, impaired cardiac haemodynamics, failure to respond to adrenergic stimulation, higher heart weight, and increased myocardial fibrosis.ConclusionsThe findings show that PLN pentamerization greatly impacts on SERCA2a activity as it mediates the full range of PLN effects from maximum inhibition to full release of SERCA2a function. This regulation is important for myocardial adaptation to sustained pressure overload.

Dataset Information

Myeloproliferative disease induced by TEL-PDGFRB displays dynamic range sensitivity to Stat5 gene dosage.

Publications

Myeloproliferative disease induced by TEL-PDGFRB displays dynamic range sensitivity to Stat5 gene dosage.

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