Farshi P.,Institute for Physiological Chemistry and Pathobiochemistry |
Ohlig S.,Institute for Physiological Chemistry and Pathobiochemistry |
Pickhinke U.,Institute for Physiological Chemistry and Pathobiochemistry |
Hoing S.,Max Planck Institute for Molecular Biomedicine |
And 4 more authors.
Journal of Biological Chemistry | Year: 2011
The fly morphogen Hedgehog (Hh) and its mammalian orthologs, Sonic, Indian, and Desert hedgehog, are secreted signaling molecules that mediate tissue patterning during embryogenesis and function in tissue homeostasis and regeneration in the adult. The function of all Hh family members is regulated at the levels of morphogen multimerization on the surface of producing cells, multimer release, multimer diffusion to target cells, and signal reception. These mechanisms are all known to depend on interactions of positively charged Hh amino acids (the Cardin-Weintraub (CW) motif) with negatively charged heparan sulfate (HS) glycosaminoglycan chains. However, a precise mechanistic understanding of these interactions is still lacking. In this work, we characterized ionic HS interactions of multimeric Sonic hedgehog (called ShhNp) as well as mutant forms lacking one or more CW residues. We found that deletion of all five CW residues as well as site-directed mutagenesis of CW residues Lys 33, Arg 35, and Lys 39 (mouse nomenclature) abolished HS binding. In contrast, CW residues Arg 34 and Lys 38 did not contribute to HS binding. Analysis and validation of Shh crystal lattice contacts provided an explanation for this finding. We demonstrate that CW residues Arg 34 and Lys 38 make contact with an acidic groove on the adjacent molecule in the multimer, suggesting a new function of these residues in ShhNp multimerization rather than HS binding. Therefore, the recombinant monomeric morphogen (called ShhN) differs in CW-dependent HS binding and biological activity from physiologically relevant ShhNp multimers, providing new explanations for functional differences observed between ShhN and ShhNp. © 2011 by The American Society for Biochemistry and Molecular Biology, Inc. Source
Pick K.S.,Ludwig Maximilians University of Munich |
Philippe H.,University of Montreal |
Schreiber F.,University of Gottingen |
Erpenbeck D.,Ludwig Maximilians University of Munich |
And 7 more authors.
Molecular Biology and Evolution | Year: 2010
Despite expanding data sets and advances in phylogenomic methods, deep-level metazoan relationships remain highly controversial. Recent phylogenomic analyses depart from classical concepts in recovering ctenophores as the earliest branching metazoan taxon and propose a sister-group relationship between sponges and cnidarians (e.g., Dunn CW, Hejnol A, Matus DQ, et al. (18 co-authors). 2008. Broad phylogenomic sampling improves resolution of the animal tree of life. Nature 452:745-749). Here, we argue that these results are artifacts stemming from insufficient taxon sampling and long-branch attraction (LBA). By increasing taxon sampling from previously unsampled nonbilaterians and using an identical gene set to that reported by Dunn et al., we recover monophyletic Porifera as the sister group to all other Metazoa. This suggests that the basal position of the fast-evolving Ctenophora proposed by Dunn et al. was due to LBA and that broad taxon sampling is of fundamental importance to metazoan phylogenomic analyses. Additionally, saturation in the Dunn et al. character set is comparatively high, possibly contributing to the poor support for some nonbilaterian nodes. © 2010 The Author. Source
Awwad K.,Goethe University Frankfurt |
Hu J.,Goethe University Frankfurt |
Shi L.,Goethe University Frankfurt |
Mangels N.,Goethe University Frankfurt |
And 7 more authors.
Cardiovascular Research | Year: 2015
Aims Secreted modular calcium-binding protein 1 (SMOC1) is a matricellular protein that potentially interferes with growth factor receptor signalling. The aim of this study was to determine how its expression is regulated in endothelial cells and its role in the regulation of endothelial cell function. Methods and results SMOC1 was expressed by native murine endothelial cells as well as by cultured human, porcine, and murine endothelial cells. SMOC1 expression in cultured cells was increased by hypoxia via the down-regulation of miR-223, and SMOC1 expression was increased in lungs from miR-223-deficient mice. Silencing SMOC1 (small interfering RNA) attenuated endothelial cell proliferation, migration, and sprouting in in vitro angiogenesis assays. Similarly endothelial cell sprouting from aortic rings ex vivo as well as postnatal retinal angiogenesis in vivo was attenuated in SMOC1+/- mice. In endothelial cells, transforming growth factor (TGF)-β signalling via activin-like kinase (ALK) 5 leads to quiescence, whereas TGF-β signalling via ALK1 results in endothelial cell activation. SMOC1 acted as a negative regulator of ALK5/SMAD2 signalling, resulting in altered α2 integrin levels. Mechanistically, SMOC1 associated (immunohistochemistry, proximity ligation assay, and co-immunoprecipitation) with endoglin; an endothelium-specific type III auxiliary receptor for the TGF-β super family and the effects of SMOC1 down-regulation on SMAD2 phosphorylation were abolished by the down-regulation of endoglin. Conclusion These results indicate that SMOC1 is an ALK5 antagonist produced by endothelial cells that tips TGF-β signalling towards ALK1 activation, thus promoting endothelial cell proliferation and angiogenesis. © 2015 Published on behalf of the European Society of Cardiology. All rights reserved. Source