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Charton K.,French National Center for Scientific Research | Daniele N.,French National Center for Scientific Research | Vihola A.,University of Helsinki | Roudaut C.,French National Center for Scientific Research | And 7 more authors.
Human Molecular Genetics | Year: 2010

The dominant tibial muscular dystrophy (TMD) and recessive limb-girdle muscular dystrophy 2J are allelic disorders caused by mutations in the C-terminus of titin, a giant sarcomeric protein. Both clinical presentations were initially identified in a large Finnish family and linked to a founder mutation (FINmaj). To further understand the physiopathology of these two diseases, we generated a mouse model carrying the FINmaj mutation. In heterozygous mice, dystrophic myopathology appears late at 9 months of age in few distal muscles. In homozygous (HO) mice, the first signs appear in the Soleus at 1 month of age and extend to most muscles at 6 months of age. Interestingly, the heart is also severely affected in HO mice. The mutation leads to the loss of the very C-terminal end of titin and to a secondary deficiency of calpain 3, a partner of titin. By crossing the FINmaj model with a calpain 3-deficient model, the TMD phenotype was corrected, demonstrating a participation of calpain 3 in the pathogenesis of this disease. © The Author 2010. Published by Oxford University Press. All rights reserved. Source

Clement M.-J.,CAS Research Center for Eco Environmental Sciences | Tissot B.,CNRS Laboratory for Analysis and Modelling for Biology and Environment | Tissot B.,CNRS Structure and Activity of Normal and Pathological Biomolecules | Chevolot L.,Imperial College London | And 5 more authors.
Glycobiology | Year: 2010

Fucoidan is a potent inhibitor of the human complement system whose activity is mediated through interactions with certain proteins belonging to the classical pathway, particularly the protein C4. Branched fucoidan oligosaccharides displayed a higher anticomplementary activity as compared to linear structures. Nuclear magnetic resonance (NMR) characterization of the branched oligosaccharides and saturation transfer difference-NMR experiment of the interaction with the protein C4 allowed the identification of the glycan residues in close contact with the target protein. Transferred nuclear Overhauser effect spectroscopy experiment and molecular modeling of fucoidan oligosaccharides indicated that the presence of side chains reduces the flexibility of the oligosaccharide backbone, which thus adopts a conformation which is very close to the one recognized by the protein C4. Together, these results suggest that branching of fucoidan oligosaccharides, determining their conformational state, has a major impact on their anticomplementary activity. © The Author 2010. Published by Oxford University Press. All rights reserved. Source

Saidi Brikci-Nigassa A.,CNRS Structure and Activity of Normal and Pathological Biomolecules | Saidi Brikci-Nigassa A.,Abou Bekr Belkaid University Tlemcen | Clement M.-J.,CNRS Structure and Activity of Normal and Pathological Biomolecules | Ha-Duong T.,University of Evry Val dEssonne | And 5 more authors.
Biochemistry | Year: 2012

Connexins are structurally related transmembrane proteins that assemble to form gap junction channels involved in the mediation of intercellular communication. It has been shown that the intracellular tail of connexin43 (Cx43) interacts with tubulin and microtubules with putative impacts on its own intracellular trafficking, its activity in channel communication, and its interference with specific growth factor signal transduction cascades. We demonstrate here that the microtubule binding of Cx43 is mainly driven by a short region of 26 amino acid residues located within the intracellular tail of Cx43. The nuclear magnetic resonance structural analysis of a peptide (K26D) corresponding to this region shows that this peptide is unstructured when free in solution and adopts a helix conformation upon binding with tubulin. In addition, the resulting K26D-tubulin molecular complex defines a new structural organization that could be shared by other microtubule partners. Interestingly, the K26D-tubulin interaction is prevented by the phosphorylation of K26D at a src kinase specific site. Altogether, the results elucidate the mechanism of the interaction of Cx43 with the microtubule cytoskeleton and propose a pathway for understanding the microtubule-dependent regulation of Cx43 gap junctional communications and the involvement of Cx43 in TGF-β signal transduction. © 2012 American Chemical Society. Source

Fassier C.,French Institute of Health and Medical Research | Tarrade A.,French Institute of Health and Medical Research | Tarrade A.,CNRS Structure and Activity of Normal and Pathological Biomolecules | Tarrade A.,CNRS Developmental Biology Laboratory | And 11 more authors.
DMM Disease Models and Mechanisms | Year: 2013

Mutations in SPG4, encoding the microtubule-severing protein spastin, are responsible for the most frequent form of hereditary spastic paraplegia (HSP), a heterogeneous group of genetic diseases characterized by degeneration of the corticospinal tracts. We previously reported that mice harboring a deletion in Spg4, generating a premature stop codon, develop progressive axonal degeneration characterized by focal axonal swellings associated with impaired axonal transport. To further characterize the molecular and cellular mechanisms underlying this mutant phenotype, we have assessed microtubule dynamics and axonal transport in primary cultures of cortical neurons from spastin-mutant mice. We show an early and marked impairment of microtubule dynamics all along the axons of spastin-deficient cortical neurons, which is likely to be responsible for the occurrence of axonal swellings and cargo stalling. Our analysis also reveals that a modulation of microtubule dynamics by microtubule-targeting drugs rescues the mutant phenotype of cortical neurons. Together, these results contribute to a better understanding of the pathogenesis of SPG4-linked HSP and ascertain the influence of microtubule-targeted drugs on the early axonal phenotype in a mouse model of the disease. © 2012. Published by The Company of Biologists Ltd. Source

Hamon L.,CNRS Structure and Activity of Normal and Pathological Biomolecules | Savarin P.,CNRS Structure and Activity of Normal and Pathological Biomolecules | Curmi P.A.,CNRS Structure and Activity of Normal and Pathological Biomolecules | Pastre D.,CNRS Structure and Activity of Normal and Pathological Biomolecules
Biophysical Journal | Year: 2011

Microtubules (MTs) are cylindrical cytoskeleton polymers composed of α-β tubulin heterodimers whose dynamic properties are essential to fulfill their numerous cellular functions. In response to spatial confinement, dynamic MTs, even in the absence of protein partners, were shown to self-organize into higher order structures (spindle or striped structures) which lead to interesting dynamical properties (MT oscillations). In this study, we considered the assembly and sensitivity of dynamic MTs when in bundles. To perform this study, spermine, a natural tetravalent polyamine present at high concentrations in all eukaryote cells, was used to trigger MT bundling while preserving MT dynamics. Interestingly, we first show that, near physiological ionic strengths, spermine promotes the bundling of MTs whereas it does not lead to aggregation of free tubulin, which would have been detrimental to MT polymerization. Experimental and theoretical results also indicate that, to obtain a high rate of bundle assembly, bundling should take place at the beginning of assembly when rapid rotational movements of short and newly nucleated MTs are still possible. On the other hand, the bundling process is significantly slowed down for long MTs. Finally, we found that short MT bundles exhibit a higher sensitivity to cold exposure than do isolated MTs. To account for this phenomenon, we suggest that a collective behavior takes place within MT bundles because an MT entering into a phase of shortening could increase the probability of the other MTs in the same bundle to enter into shortening phase due to their close proximity. We then elaborate on some putative applications of our findings to in vivo conditions including neurons. © 2011 Biophysical Society. Source

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