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Answer added in T Cell Biology13 How can we block IL-6 signal transduction in CD8 T cells in functional assays without the use of blocking mAb against IL-6 or IL-6 receptor?Knockdown (siRNA, shRNA) of the cognate IL6-R is of course the most specific. But as an alternative, you could use a cocktail of a MEK, a PI3K and a ... [more]
Publications (113) View all
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Article: Angiopoietin-2 differentially regulates angiogenesis through TIE2 and integrin signaling.
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ABSTRACT: Angiopoietin-2 (ANG-2) is a key regulator of angiogenesis that exerts context-dependent effects on ECs. ANG-2 binds the endothelial-specific receptor tyrosine kinase 2 (TIE2) and acts as a negative regulator of ANG-1/TIE2 signaling during angiogenesis, thereby controlling the responsiveness of ECs to exogenous cytokines. Recent data from tumors indicate that under certain conditions ANG-2 can also promote angiogenesis. However, the molecular mechanisms of dual ANG-2 functions are poorly understood. Here, we identify a model for the opposing roles of ANG-2 in angiogenesis. We found that angiogenesis-activated endothelium harbored a subpopulation of TIE2-negative ECs (TIE2lo). TIE2 expression was downregulated in angiogenic ECs, which abundantly expressed several integrins. ANG-2 bound to these integrins in TIE2lo ECs, subsequently inducing, in a TIE2-independent manner, phosphorylation of the integrin adaptor protein FAK, resulting in RAC1 activation, migration, and sprouting angiogenesis. Correspondingly, in vivo ANG-2 blockade interfered with integrin signaling and inhibited FAK phosphorylation and sprouting angiogenesis of TIE2lo ECs. These data establish a contextual model whereby differential TIE2 and integrin expression, binding, and activation control the role of ANG-2 in angiogenesis. The results of this study have immediate translational implications for the therapeutic exploitation of angiopoietin signaling.The Journal of clinical investigation 05/2012; 122(6):1991-2005. · 15.39 Impact Factor -
Article: A novel player in cellular hypertrophy: Giβγ/PI3K-dependent activation of the RacGEF TIAM-1 is required for α₁-adrenoceptor induced hypertrophy in neonatal rat cardiomyocytes.
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ABSTRACT: Activation of α(1)-adrenoceptors (α(1)-AR) by high catecholamine levels, e.g. in heart failure, is thought to be a driving force of cardiac hypertrophy. In this context several downstream mediators and cascades have been identified to potentially play a role in cardiomyocyte hypertrophy. One of these proteins is the monomeric G protein Rac1. However, until now it is unclear how this essential G protein is activated by α(1)-AR agonists and what are the downstream targets inducing cellular growth. By using protein-based as well as pharmacological inhibitors and the shRNA technique, we demonstrate that in neonatal rat cardiomyocytes (NRCM) Rac1 is activated via a cascade involving the α(1A)-AR subtype, G(i)βγ, the phosphoinositide-3'-kinase and the guanine nucleotide exchange factor Tiam1. We further demonstrate that this signaling induces an increase in protein synthesis, cell size and atrial natriuretic peptide expression. We identified the p21-activated kinase 2 (PAK2) as a downstream effector of Rac1 and were able to link this cascade to the activation of the pro-hypertrophic kinases ERK1/2 and p90RSK. Our data thus reveal a prominent role of the α(1A)-AR/G(i)βγ/Tiam1-mediated activation of Rac1 and its effector PAK2 in the induction of hypertrophy in NRCM.Journal of Molecular and Cellular Cardiology 05/2012; 53(2):165-75. · 5.17 Impact Factor -
Article: Role of RyR2 phosphorylation at S2814 during heart failure progression.
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ABSTRACT: Increased activity of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is thought to promote heart failure (HF) progression. However, the importance of CaMKII phosphorylation of ryanodine receptors (RyR2) in HF development and associated diastolic sarcoplasmic reticulum Ca(2+) leak is unclear. Determine the role of CaMKII phosphorylation of RyR2 in patients and mice with nonischemic and ischemic forms of HF. Phosphorylation of the primary CaMKII site S2814 on RyR2 was increased in patients with nonischemic, but not with ischemic, HF. Knock-in mice with an inactivated S2814 phosphorylation site were relatively protected from HF development after transverse aortic constriction compared with wild-type littermates. After transverse aortic constriction, S2814A mice did not exhibit pulmonary congestion and had reduced levels of atrial natriuretic factor. Cardiomyocytes from S2814A mice exhibited significantly lower sarcoplasmic reticulum Ca(2+) leak and improved sarcoplasmic reticulum Ca(2+) loading compared with wild-type mice after transverse aortic constriction. Interestingly, these protective effects on cardiac contractility were not observed in S2814A mice after experimental myocardial infarction. Our results suggest that increased CaMKII phosphorylation of RyR2 plays a role in the development of pathological sarcoplasmic reticulum Ca(2+) leak and HF development in nonischemic forms of HF such as transverse aortic constriction in mice.Circulation Research 04/2012; 110(11):1474-83. · 9.49 Impact Factor -
Article: LARG links histamine-H1-receptor-activated Gq to Rho-GTPase-dependent signaling pathways.
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ABSTRACT: Activation of heterotrimeric G proteins, such as G(12/13) and G(q), by cell surface receptors is coupled to the regulation of numerous cellular functions controlled by activated Rho GTPases. Previous studies have implicated the Rho guanine nucleotide exchange factor (RhoGEF) leukemia-associated RhoGEF (LARG) as a regulatory protein receiving stimulatory inputs from activated Gα(12/13) and Gα(q). However, the molecular mechanisms of the Gα(q)-mediated LARG activation are not fully understood and the structural elements of LARG involved in this process have remained unclear. In the present work, the specific coupling of the histamine H1 receptor (HRH1) exogenously expressed in COS-7 cells to G(q), but not to G(12/13), was used to conduct a detailed analysis of receptor- and Gα(q)-mediated LARG activation and to define its structural requirements. The results show that HRH1-mediated activation of the strictly Rho-dependent transcriptional activity of serum response factor requires the PDZ domain of LARG and can be mimicked by activated Gα(q)(Q209L). The functional interaction between activated Gα(q) and LARG requires no more than the catalytic DH-PH tandem of LARG, and is independent of PLCβ activation and distinct from the mechanisms of Gα(q)-mediated p63RhoGEF and PLCβ(3) activation. Activated Gα(q) physically interacts with the relevant portions of LARG in COS-7 cells and histamine causes activation of LARG in native HeLa cells endogenously expressing HRH1, G(q), and LARG. This work is the first positive demonstration of a stimulatory effect of LARG on the ability of a strictly G(q)-coupled receptor to cause activation of a Rho-GTPase-dependent signaling pathway.Cellular signalling 11/2011; 24(3):652-63. · 4.09 Impact Factor -
Article: A critical evaluation of biochemical activities reported for the nucleoside diphosphate kinase/Nm23/Awd family proteins: opportunities and missteps in understanding their biological functions.
Archiv für Experimentelle Pathologie und Pharmakologie 05/2011; 384(4-5):331-9. · 2.65 Impact Factor
