TY - JOUR A1 - Jandke, Solveig A1 - Garz, Cornelia A1 - Schwanke, Daniel A1 - Sendtner, Michael A1 - Heinze, Hans-Jochen A1 - Carare, Roxana O. A1 - Schreiber, Stefanie T1 - The association between hypertensive arteriopathy and cerebral amyloid angiopathy in spontaneously hypertensive stroke-prone rats JF - Brain Pathology N2 - We aimed to test the hypothesis that in spontaneously hypertensive stroke-prone rats (SHRSP), non-amyloid cerebral small vessel disease/hypertensive arteriopathy (HA) results in vessel wall injury that may promote cerebral amyloid angiopathy (CAA). Our study comprised 21 male SHRSP (age 17–44 weeks) and 10 age- and sex-matched Wistar control rats, that underwent two-photon (2PM) imaging of the arterioles in the parietal cortex using Methoxy-X04, Dextran and cerebral blood flow (CBF) measurements. Our data suggest that HA in SHRSP progresses in a temporal and age-dependent manner, starting from small vessel wall damage (stage 1A), proceeding to CBF reduction (stage 1B), non-occlusive (stage 2), and finally, occlusive thrombi (stage 3). Wistar animals also demonstrated small vessel wall damage, but were free of any of the later HA stages. Nearly half of all SHRSP additionally displayed vascular Methoxy-X04 positivity indicative of cortical CAA. Vascular β-amyloid deposits were found in small vessels characterized by thrombotic occlusions (stage 2 or 3). Post-mortem analysis of the rat brains confirmed the findings derived from intravital 2PM microscopy. Our data thus overall suggest that advanced HA may play a role in CAA development with the two small vessel disease entities might be related to the same pathological spectrum of the aging brain. KW - cerebral amyloid angiopathy KW - cerebral small vessel disease KW - hypertensive arteriopathy KW - intravital imaging KW - spontaneously hypertensive stroke-prone rat Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-323279 VL - 28 ER - TY - JOUR A1 - Breitinger, Ulrike A1 - Bahnassawy, Lamiaa M. A1 - Janzen, Dieter A1 - Römer, Vera A1 - Becker, Cord-Michael A1 - Villmann, Carmen A1 - Breitinger, Hans-Georg T1 - PKA and PKC modulators affect ion channel function and internalization of recombinant alpha1 and alpha1-beta glycine receptors JF - Frontiers in Molecular Neurosience N2 - Glycine receptors (GlyRs) are important mediators of fast inhibitory neurotransmission in the mammalian central nervous system. Their function is controlled by multiple cellular mechanisms, including intracellular regulatory processes. Modulation of GlyR function by protein kinases has been reported for many cell types, involving different techniques, and often yielding contradictory results. Here, we studied the effects of protein kinase C (PKC) and cAMP-dependent protein kinase A (PKA) on glycine induced currents in HEK293 cells expressing human homomeric \(\alpha\)1 and heteromeric \(\alpha\)1-\(\beta\) GlyRs using whole-cell patch clamp techniques as well as internalization assays. In whole-cell patch-clamp measurements, modulators were applied in the intracellular buffer at concentrations between 0.1 \(\mu\)M and 0.5 \(\mu\)M. EC50 of glycine increased upon application of the protein kinase activators Forskolin and phorbol-12-myristate-13-acetate (PMA) but decreased in the presence of the PKC inhibitor Staurosporine aglycon and the PKA inhibitor H-89. Desensitization of recombinant \(\alpha\)1 receptors was significantly increased in the presence of Forskolin. Staurosporine aglycon, on the other hand decreased desensitization of heteromeric \(\alpha\)1-\(\beta\) GlyRs. The time course of receptor activation was determined for homomeric \(\alpha\)1 receptors and revealed two simultaneous effects: cells showed a decrease of EC50 after 3-6 min of establishing whole-cell configuration. This effect was independent of protein kinase modulators. All modulators of PKA and PKC, however, produced an additional shift of EC50, which overlay and eventually exceeded the cells intrinsic variation of EC50. The effect of kinase activators was abolished if the corresponding inhibitors were co-applied, consistent with PKA and PKC directly mediating the modulation of GlyR function. Direct effects of PKA-and PKC-modulators on receptor expression on transfected HEK cells were monitored within 15 min of drug application, showing a significant increase of receptor internalization with PKA and PKC activators, while the corresponding inhibitors had no significant effect on receptor surface expression or internalization. Our results confirm the observation that phosphorylation via PKA and PKC has a direct effect on the GlyR ion channel complex and plays an important role in the fine-tuning of glycinergic signaling. KW - glycine receptor KW - PKA KW - PKC KW - activators/inhibitors of phosphorylation KW - whole-cell currents KW - modulation kinetics KW - receptor internalization Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-220401 VL - 11 ER - TY - JOUR A1 - Schaefer, Natascha A1 - Roemer, Vera A1 - Janzen, Dieter A1 - Villmann, Carmen T1 - Impaired Glycine Receptor Trafficking in Neurological Diseases JF - Frontiers in Molecular Neuroscience N2 - Ionotropic glycine receptors (GlyRs) enable fast synaptic neurotransmission in the adult spinal cord and brainstem. The inhibitory GlyR is a transmembrane glycinegated chloride channel. The immature GlyR protein undergoes various processing steps, e.g., folding, assembly, and maturation while traveling from the endoplasmic reticulum to and through the Golgi apparatus, where post-translational modifications, e.g., glycosylation occur. The mature receptors are forward transported via microtubules to the cellular surface and inserted into neuronal membranes followed by synaptic clustering. The normal life cycle of a receptor protein includes further processes like internalization, recycling, and degradation. Defects in GlyR life cycle, e.g., impaired protein maturation and degradation have been demonstrated to underlie pathological mechanisms of various neurological diseases. The neurological disorder startle disease is caused by glycinergic dysfunction mainly due to missense mutations in genes encoding GlyR subunits (GLRA1 and GLRB). In vitro studies have shown that most recessive forms of startle disease are associated with impaired receptor biogenesis. Another neurological disease with a phenotype similar to startle disease is a special form of stiff-person syndrome (SPS), which is most probably due to the development of GlyR autoantibodies. Binding of GlyR autoantibodies leads to enhanced receptor internalization. Here we focus on the normal life cycle of GlyRs concentrating on assembly and maturation, receptor trafficking, post-synaptic integration and clustering, and GlyR internalization/recycling/degradation. Furthermore, this review highlights findings on impairment of these processes under disease conditions such as disturbed neuronal ER-Golgi trafficking as the major pathomechanism for recessive forms of human startle disease. In SPS, enhanced receptor internalization upon autoantibody binding to the GlyR has been shown to underlie the human pathology. In addition, we discuss how the existing mouse models of startle disease increased our current knowledge of GlyR trafficking routes and function. This review further illuminates receptor trafficking of GlyR variants originally identified in startle disease patients and explains changes in the life cycle of GlyRs in patients with SPS with respect to structural and functional consequences at the receptor level. KW - glycine receptor KW - startle disease KW - autoimmune antibodies KW - protein maturation KW - trafficking pathways Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-227531 VL - 11 IS - 291 ER - TY - JOUR A1 - Schaefer, Natascha A1 - Zheng, Fang A1 - van Brederode, Johannes A1 - Berger, Alexandra A1 - Leacock, Sophie A1 - Hirata, Hiromi A1 - Paige, Christopher J. A1 - Harvey, Robert J. A1 - Alzheimer, Christian A1 - Villmann, Carmen T1 - Functional Consequences of the Postnatal Switch From Neonatal to Mutant Adult Glycine Receptor α1 Subunits in the Shaky Mouse Model of Startle Disease JF - Frontiers in Molecular Neuroscience N2 - Mutations in GlyR α1 or β subunit genes in humans and rodents lead to severe startle disease characterized by rigidity, massive stiffness and excessive startle responses upon unexpected tactile or acoustic stimuli. The recently characterized startle disease mouse mutant shaky carries a missense mutation (Q177K) in the β8-β9 loop within the large extracellular N-terminal domain of the GlyR α1 subunit. This results in a disrupted hydrogen bond network around K177 and faster GlyR decay times. Symptoms in mice start at postnatal day 14 and increase until premature death of homozygous shaky mice around 4–6 weeks after birth. Here we investigate the in vivo functional effects of the Q177K mutation using behavioral analysis coupled to protein biochemistry and functional assays. Western blot analysis revealed GlyR α1 subunit expression in wild-type and shaky animals around postnatal day 7, a week before symptoms in mutant mice become obvious. Before 2 weeks of age, homozygous shaky mice appeared healthy and showed no changes in body weight. However, analysis of gait and hind-limb clasping revealed that motor coordination was already impaired. Motor coordination and the activity pattern at P28 improved significantly upon diazepam treatment, a pharmacotherapy used in human startle disease. To investigate whether functional deficits in glycinergic neurotransmission are present prior to phenotypic onset, we performed whole-cell recordings from hypoglossal motoneurons (HMs) in brain stem slices from wild-type and shaky mice at different postnatal stages. Shaky homozygotes showed a decline in mIPSC amplitude and frequency at P9-P13, progressing to significant reductions in mIPSC amplitude and decay time at P18-24 compared to wild-type littermates. Extrasynaptic GlyRs recorded by bath-application of glycine also revealed reduced current amplitudes in shaky mice compared to wild-type neurons, suggesting that presynaptic GlyR function is also impaired. Thus, a distinct, but behaviorally ineffective impairment of glycinergic synapses precedes the symptoms onset in shaky mice. These findings extend our current knowledge on startle disease in the shaky mouse model in that they demonstrate how the progression of GlyR dysfunction causes, with a delay of about 1 week, the appearance of disease symptoms. KW - glycine receptor KW - startle disease KW - β8-β9 loop KW - mouse model KW - fast decay Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-196056 SN - 1662-5099 VL - 11 IS - 167 ER -