TY  - JOUR
A1  - Atak, Sinem
A1  - Langlhofer, Georg
A1  - Schaefer, Natascha
A1  - Kessler, Denise
A1  - Meiselbach, Heike
A1  - Delto, Carolyn
A1  - Schindelin, Hermann
A1  - Villmann, Carmen
T1  - Disturbances of ligand potency and enhanced degradation of the human glycine receptor at affected positions G160 and T162 originally identified in patients suffering from hyperekplexia
JF  - Frontiers in Molecular Neuroscience
N2  - Ligand-binding of Cys-loop receptors is determined by N-terminal extracellular loop structures from the plus as well as from the minus side of two adjacent subunits in the pentameric receptor complex. An aromatic residue in loop B of the glycine receptor (GIyR) undergoes direct interaction with the incoming ligand via a cation-π interaction. Recently, we showed that mutated residues in loop B identified from human patients suffering from hyperekplexia disturb ligand-binding. Here, we exchanged the affected human residues by amino acids found in related members of the Cys-loop receptor family to determine the effects of side chain volume for ion channel properties. GIyR variants were characterized in vitro following transfection into cell lines in order to analyze protein expression, trafficking, degradation and ion channel function. GIyR α1 G160 mutations significantly decrease glycine potency arguing for a positional effect on neighboring aromatic residues and consequently glycine-binding within the ligand-binding pocket. Disturbed glycinergic inhibition due to T162 α1 mutations is an additive effect of affected biogenesis and structural changes within the ligand-binding site. Protein trafficking from the ER toward the ER-Golgi intermediate compartment, the secretory Golgi pathways and finally the cell surface is largely diminished, but still sufficient to deliver ion channels that are functional at least at high glycine concentrations. The majority of T162 mutant protein accumulates in the ER and is delivered to ER-associated proteasomal degradation. Hence, G160 is an important determinant during glycine binding. In contrast, 1162 affects primarily receptor biogenesis whereas exchanges in functionality are secondary effects thereof.
KW  - mutations
KW  - trafficking
KW  - domain
KW  - hyperekplexia
KW  - loop B
KW  - side chain properties
KW  - ligand potencies
KW  - Cys-loop receptor
KW  - glycine receptor
KW  - site
KW  - activation
KW  - binding
KW  - channel
KW  - mechanisms
KW  - dominant
KW  - startle
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-144818
VL  - 8
IS  - 79
ER  - 
TY  - JOUR
A1  - Doppler, Kathrin
A1  - Appeltshauser, Luise
A1  - Krämer, Heidrun H.
A1  - King Man Ng, Judy
A1  - Meinl, Edgar
A1  - Villmann, Carmen
A1  - Brophy, Peter
A1  - Dib-Hajj, Sulayman D.
A1  - Waxman, Stephen G.
A1  - Weishaupt, Andreas
A1  - Sommer, Claudia
T1  - Contactin-1 and Neurofascin-155/-186 Are Not Targets of Auto-Antibodies in Multifocal Motor Neuropathy
JF  - PLoS One
N2  - Multifocal motor neuropathy is an immune mediated disease presenting with multifocal muscle weakness and conduction block. IgM auto-antibodies against the ganglioside GM1 are detectable in about 50% of the patients. Auto-antibodies against the paranodal proteins contactin-1 and neurofascin-155 and the nodal protein neurofascin-186 have been detected in subgroups of patients with chronic inflammatory demyelinating polyneuropathy. Recently, auto-antibodies against neurofascin-186 and gliomedin were described in more than 60% of patients with multifocal motor neuropathy. In the current study, we aimed to validate this finding, using a combination of different assays for auto-antibody detection. In addition we intended to detect further auto-antibodies against paranodal proteins, specifically contactin-1 and neurofascin-155 in multifocal motor neuropathy patients’ sera. We analyzed sera of 33 patients with well-characterized multifocal motor neuropathy for IgM or IgG anti-contactin-1, anti-neurofascin-155 or -186 antibodies using enzyme-linked immunosorbent assay, binding assays with transfected human embryonic kidney 293 cells and murine teased fibers. We did not detect any IgM or IgG auto-antibodies against contactin-1, neurofascin-155 or -186 in any of our multifocal motor neuropathy patients. We conclude that auto-antibodies against contactin-1, neurofascin-155 and -186 do not play a relevant role in the pathogenesis in this cohort with multifocal motor neuropathy.
KW  - motor proteins
KW  - enzyme-linked immunoassays
KW  - binding analysis
KW  - neuropathy
KW  - nerve fibers
KW  - cell binding assay
KW  - antibodies
KW  - enzyme assays
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-126156
VL  - 10
IS  - 7
ER  -