25 research outputs found
Expression and regulation of type 2A protein phosphatases and alpha4 signalling in cardiac health and hypertrophy
Abstract Cardiac physiology and hypertrophy are regulated
by the phosphorylation status of many proteins, which
is partly controlled by a poorly defined type 2A protein
phosphatase-alpha4 intracellular signalling axis. Quantitative
PCR analysis revealed that mRNA levels of the type
2A catalytic subunits were differentially expressed in H9c2
cardiomyocytes (PP2ACb[PP2ACa[PP4C[PP6C),
NRVM (PP2ACb[PP2ACa = PP4C = PP6C), and
adult rat ventricular myocytes (PP2ACa[
PP2ACb[PP6C[PP4C). Western analysis confirmed
that all type 2A catalytic subunits were expressed in H9c2
cardiomyocytes; however, PP4C protein was absent in
adult myocytes and only detectable following 26S proteasome
inhibition. Short-term knockdown of alpha4 protein
expression attenuated expression of all type 2A catalytic
subunits. Pressure overload-induced left ventricular (LV)
hypertrophy was associated with an increase in both
PP2AC and alpha4 protein expression. Although PP6C
expression was unchanged, expression of PP6C regulatory
subunits (1) Sit4-associated protein 1 (SAP1) and (2)
ankyrin repeat domain (ANKRD) 28 and 44 proteins was
elevated, whereas SAP2 expression was reduced in
hypertrophied LV tissue. Co-immunoprecipitation studies
demonstrated that the interaction between alpha4 and
PP2AC or PP6C subunits was either unchanged or reduced
in hypertrophied LV tissue, respectively. Phosphorylation
status of phospholemman (Ser63 and Ser68) was significantly
increased by knockdown of PP2ACa, PP2ACb, or
PP4C protein expression. DNA damage assessed by histone
H2A.X phosphorylation (cH2A.X) in hypertrophied tissue
remained unchanged. However, exposure of cardiomyocytes
to H2O2 increased levels of cH2A.X which was
unaffected by knockdown of PP6C expression, but was
abolished by the short-term knockdown of alpha4 expression.
This study illustrates the significance and altered
activity of the type 2A protein phosphatase-alpha4 complex
in healthy and hypertrophied myocardium
Doxorubicin plus dacarbazine, doxorubicin plus ifosfamide, or doxorubicin alone as a firstâline treatment for advanced leiomyosarcoma: A propensity score matching analysis from the European Organization for Research and Treatment of Cancer Soft Tissue and Bone Sarcoma Group
Background
The optimal treatment for advanced leiomyosarcoma is still debated. Given histotypeâspecific prospective controlled data lacking, this study retrospectively evaluated doxorubicin plus dacarbazine, doxorubicin plus ifosfamide, and doxorubicin alone as firstâline treatments for advanced/metastatic leiomyosarcoma treated at European Organization for Research and Treatment of Cancer Soft Tissue and Bone Sarcoma Group (EORTCâSTBSG) sites.
Methods
The inclusion criteria were a confirmed histological diagnosis, treatment between January 2010 and December 2015, measurable disease (Response Evaluation Criteria in Solid Tumors 1.1), an Eastern Cooperative Oncology Group performance status â€2, and an age â„ 18 years. The endpoints were progressionâfree survival (PFS), overall survival (OS), and overall response rate (ORR). PFS was analyzed with methods for intervalâcensored data. Patients were matched according to their propensity scores, which were estimated with a logistic regression model accounting for histology, grade, age, sex, performance status, tumor site, and tumor extent.
Results
Three hundred three patients from 18 EORTCâSTBSG sites were identified. One hundred seventeen (39%) received doxorubicin plus dacarbazine, 71 (23%) received doxorubicin plus ifosfamide, and 115 (38%) received doxorubicin. In the 2:1:2 propensity scoreâmatched population (205 patients), the estimated median PFS was 9.2 months (95% confidence interval [CI], 5.2â9.7 months), 8.2 months (95% CI, 5.2â10.1 months), and 4.8 months (95% CI, 2.3â6.0 months) with ORRs of 30.9%, 19.5%, and 25.6% for doxorubicin plus dacarbazine, doxorubicin plus ifosfamide, and doxorubicin alone, respectively. PFS was significantly longer with doxorubicin plus dacarbazine versus doxorubicin (hazard ratio [HR], 0.72; 95% CI, 0.52â0.99). Doxorubicin plus dacarbazine was associated with longer OS (median, 36.8 months; 95% CI, 27.9â47.2 months) in comparison with both doxorubicin plus ifosfamide (median, 21.9 months; 95% CI, 16.7â33.4 months; HR, 0.65; 95% CI, 0.40â1.06) and doxorubicin (median, 30.3 months; 95% CI, 21.0â36.3 months; HR, 0.66; 95% CI, 0.43â0.99). Adjusted analyses retained an effect for PFS but not for OS. None of the factors selected for multivariate analysis had a significant interaction with the received treatment for both PFS and OS.
Conclusions
This is the largest retrospective study of firstâline treatment for advanced leiomyosarcoma. In the propensity scoreâmatched population, doxorubicin and dacarbazine showed favorable activity in terms of both ORR and PFS and warrants further evaluation in prospective trials
Stalk cell phenotype depends on integration of Notch and Smad1/5 signaling cascades.
Gradients of vascular endothelial growth factor (VEGF) induce single endothelial cells to become leading tip cells of emerging angiogenic sprouts. Tip cells then suppress tip-cell features in adjacent stalk cells via Dll4/Notch-mediated lateral inhibition. We report here that Smad1/Smad5-mediated BMP signaling synergizes with Notch signaling during selection of tip and stalk cells. Endothelium-specific inactivation of Smad1/Smad5 in mouse embryos results in impaired Dll4/Notch signaling and increased numbers of tip-cell-like cells at the expense of stalk cells. Smad1/5 downregulation in cultured endothelial cells reduced the expression of several target genes of Notch and of other stalk-cell-enriched transcripts (Hes1, Hey1, Jagged1, VEGFR1, and Id1-3). Moreover, Id proteins act as competence factors for stalk cells and form complexes with Hes1, which augment Hes1 levels in the endothelium. Our findings provide in vivo evidence for a regulatory loop between BMP/TGFÎČ-Smad1/5 and Notch signaling that orchestrates tip- versus stalk-cell selection and vessel plasticity
Mice lacking phosphatase PP2A subunit PR61/BâÎŽ (Ppp2r5d) develop spatially restricted tauopathy by deregulation of CDK5 and GSK3ÎČ
Functional diversity of protein phosphatase 2A (PP2A) enzymes mainly results from their association with distinct regulatory subunits. To analyze the functions of one such holoenzyme in vivo, we generated mice lacking PR61/BâÎŽ (B56ÎŽ), a subunit highly expressed in neural tissues. In PR61/BâÎŽ-null mice the microtubule-associated protein tau becomes progressively phosphorylated at pathological epitopes in restricted brain areas, with marked immunoreactivity for the misfolded MC1-conformation but without neurofibrillary tangle formation. Behavioral tests indicated impaired sensorimotor but normal cognitive functions. These phenotypical characteristics were further underscored in PR61/BâÎŽ-null mice mildly overexpressing human tau. PR61/BâÎŽ-containing PP2A (PP2AT61ÎŽ) poorly dephosphorylates tau in vitro, arguing against a direct dephosphorylation defect. Rather, the activity of glycogen synthase kinase-3ÎČ, a major tau kinase, was found increased, with decreased phosphorylation of Ser-9, a putative cyclin-dependent kinase 5 (CDK5) target. Accordingly, CDK5 activity is decreased, and its cellular activator p35, strikingly absent in the affected brain areas. As opposed to tau, p35 is an excellent PP2AT61ÎŽ substrate. Our data imply a nonredundant function for PR61/BâÎŽ in phospho-tau homeostasis via an unexpected spatially restricted mechanism preventing p35 hyperphosphorylation and its subsequent degradation