Protein phase separation hotspots at the presynapse

Fundamental discoveries have shaped our molecular understanding of presynaptic processes, such as neurotransmitter release, active zone organization and mechanisms of synaptic vesicle (SV) recycling. However, certain regulatory steps still remain incompletely understood. Protein liquid-liquid phase separation (LLPS) and its role in SV clustering and active zone regulation now introduce a new perception of how the presynapse and its different compartments are organized. This article highlights the newly emerging concept of LLPS at the synapse, providing a systematic overview on LLPS tendencies of over 500 presynaptic proteins, spotlighting individual proteins and discussing recent progress in the field. Newly discovered LLPS systems like ELKS/liprin-alpha and Eps15/FCho are put into context, and further LLPS candidate proteins, including epsin1, dynamin, synaptojanin, complexin and rabphilin-3A, are highlighted.

Intramitochondrial proteostasis is directly coupled to α-synuclein and amyloid β1-42 pathologies

Mitochondrial dysfunction has long been implicated in the neurodegenerative disorder Parkinson's disease (PD); however, it is unclear how mitochondrial impairment and α-synuclein pathology are coupled. Using specific mitochondrial inhibitors, EM analysis, and biochemical assays, we report here that intramitochondrial protein homeostasis plays a major role in α-synuclein aggregation. We found that interference with intramitochondrial proteases, such as HtrA2 and Lon protease, and mitochondrial protein import significantly aggravates α-synuclein seeding. In contrast, direct inhibition of mitochondrial complex I, an increase in intracellular calcium concentration, or formation of reactive oxygen species, all of which have been associated with mitochondrial stress, did not affect α-synuclein pathology. We further demonstrate that similar mechanisms are involved in amyloid-β 1-42 (Aβ42) aggregation. Our results suggest that, in addition to other protein quality control pathways, such as the ubiquitin-proteasome system, mitochondria per se can influence protein homeostasis of cytosolic aggregation-prone proteins. We propose that approaches that seek to maintain mitochondrial fitness, rather than target downstream mitochondrial dysfunction, may aid in the search for therapeutic strategies to manage PD and related neuropathologies.

An Easy-to-Implement Protocol for Preparing Postnatal Ventral Mesencephalic Cultures

Postnatally derived cultures of ventral mesencephalic neurons offer several crucial advantages over embryonic ventral mesencephalic cultures, including a higher content of TH-positive cells and the ability to derive cells from the substantia nigra, which contains the neurons most vulnerable to Parkinson's disease. On the other hand, these cultures are more challenging to produce consistently. Here, we provide an easy-to-implement protocol for culturing postnatal ventral mesencephalic cells from the substantia nigra (SN) and the ventral tegmental area using commercially available media, dishes, and general lab equipment, avoiding extensive material and equipment purchases. The protocol can be completed in about 5 h and provides ventral midbrain neuron cultures on cortex glia feeder layers in three weeks' time. The protocol uses an optimized protease digestion, tissue storage in Hibernate A during dissection and purification of neurons on an OptiPrep density gradient.

C-terminal calcium binding of α-synuclein modulates synaptic vesicle interaction

Alpha-synuclein is known to bind to small unilamellar vesicles (SUVs) via its N terminus, which forms an amphipathic alpha-helix upon membrane interaction. Here we show that calcium binds to the C terminus of alpha-synuclein, therewith increasing its lipid-binding capacity. Using CEST-NMR, we reveal that alpha-synuclein interacts with isolated synaptic vesicles with two regions, the N terminus, already known from studies on SUVs, and additionally via its C terminus, which is regulated by the binding of calcium. Indeed, dSTORM on synaptosomes shows that calcium mediates the localization of alpha-synuclein at the pre-synaptic terminal, and an imbalance in calcium or alpha-synuclein can cause synaptic vesicle clustering, as seen ex vivo and in vitro. This study provides a new view on the binding of alpha-synuclein to synaptic vesicles, which might also affect our understanding of synucleinopathies.

Novel computer vision algorithm for the reliable analysis of organelle morphology in whole cell 3D images--A pilot study for the quantitative evaluation of mitochondrial fragmentation in amyotrophic lateral sclerosis

The function of intact organelles, whether mitochondria, Golgi apparatus or endoplasmic reticulum (ER), relies on their proper morphological organization. It is recognized that disturbances of organelle morphology are early events in disease manifestation, but reliable and quantitative detection of organelle morphology is difficult and time-consuming. Here we present a novel computer vision algorithm for the assessment of organelle morphology in whole cell 3D images. The algorithm allows the numerical and quantitative description of organelle structures, including total number and length of segments, cell and nucleus area/volume as well as novel texture parameters like lacunarity and fractal dimension. Applying the algorithm we performed a pilot study in cultured motor neurons from transgenic G93A hSOD1 mice, a model of human familial amyotrophic lateral sclerosis. In the presence of the mutated SOD1 and upon excitotoxic treatment with kainate we demonstrate a clear fragmentation of the mitochondrial network, with an increase in the number of mitochondrial segments and a reduction in the length of mitochondria. Histogram analyses show a reduced number of tubular mitochondria and an increased number of small mitochondrial segments. The computer vision algorithm for the evaluation of organelle morphology allows an objective assessment of disease-related organelle phenotypes with greatly reduced examiner bias and will aid the evaluation of novel therapeutic strategies on a cellular level.

Endoplasmic reticulum stress is accompanied by activation of NF-κB in amyotrophic lateral sclerosis

BACKGROUND

Recent studies have indicated that endoplasmic reticulum (ER) stress is involved in the pathogenesis of amyotrophic lateral sclerosis (ALS). ER stress occurs when the ER-mitochondria calcium cycle is disturbed and misfolded proteins accumulate in the ER. To cope with ER stress, cells activate the unfolded protein response (UPR). Accumulating evidence from non-neuronal cell models suggests that there is extensive cross-talk between the UPR and the NF-κB pathway.

METHODS

Here we investigated the expression of NF-κB and the main UPR markers X-box binding protein 1 (XBP1), basic leucine-zipper transcription factor 6 (ATF6) and phosphorylated eukaryotic initiation factor-2α (p-eIF2) in mutated SOD1(G93A) cell models of ALS, as well as their modulation by lipopolysaccharide and ER-stressing (tunicamycin) stimuli.

RESULTS

Expression of NF-κB was enhanced in the presence of SOD1(G93A). Lipopolysaccharide did not induce the UPR in NSC34 cells and motor neurons in a mixed motor neuron-glia coculture system. The induction of the UPR by tunicamycin was accompanied by activation of NF-κB in NSC34 cells and motor neurons.

CONCLUSION

Our data linked two important pathogenic mechanisms of ALS, ER stress and NF-κB signalling, in motor neurons.

Proteome analysis of body fluids for amyotrophic lateral sclerosis biomarker discovery

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder of motor neurons leading to death of the patients, mostly within 2-5 years after disease onset. The pathomechanism of motor neuron degeneration is only partially understood and therapeutic strategies based on mechanistic insights are largely ineffective. The discovery of reliable biomarkers of disease diagnosis and progression is the sine qua non of both the revelation of insights into the ALS pathomechanism and the assessment of treatment efficacies. Proteomic approaches are an important pillar in ALS biomarker discovery. Cerebrospinal fluid is the most promising body fluid for differential proteome analyses, followed by blood (serum, plasma), and even urine and saliva. The present study provides an overview about reported peptide/protein biomarker candidates that showed significantly altered levels in certain body fluids of ALS patients. These findings have to be discussed according to proposed pathomechanisms to identify modifiers of disease progression and to pave the way for the development of potential therapeutic strategies. Furthermore, limitations and advantages of proteomic approaches for ALS biomarker discovery in different body fluids and reliable validation of biomarker candidates have been addressed.

Overexpression of human mutated G93A SOD1 changes dynamics of the ER mitochondria calcium cycle specifically in mouse embryonic motor neurons

Motor neurons vulnerable to the rapidly progressive deadly neurodegenerative disease amyotrophic lateral sclerosis (ALS) inherently express low amounts of calcium binding proteins (CaBP), likely to allow physiological motor neuron firing frequency modulation. At the same time motor neurons are susceptible to AMPA receptor mediated excitotoxicity and internal calcium deregulation which is not fully understood. We analysed ER mitochondria calcium cycle (ERMCC) dynamics with subsecond resolution in G93A hSOD1 overexpressing motor neurons as a model of ALS using fluorescent calcium imaging. When comparing vulnerable motor neurons and non-motor neurons from G93A hSOD1 mice and their non-transgenic littermates, we found a decelerated cytosolic calcium clearance in the presence of G93A hSOD1. While both non-transgenic as well as G93A hSOD1 motor neurons displayed large mitochondrial calcium uptake by the mitochondrial uniporter (mUP), the mitochondrial calcium extrusion system was altered in the presence of G93A hSOD1. In addition, ER calcium uptake by the sarco-/endoplasmic reticulum ATPase (SERCA) was increased in G93A hSOD1 motor neurons. In survival assays, blocking the mitochondrial sodium calcium exchanger (mNCE) by CGP37157 as well as inhibiting SERCA by cyclopiazonic acid showed protective effects against kainate induced excitotoxicity. Thus, our study shows for the first time that the functional consequence of G93A hSOD1 overexpression in intact motor neurons is indeed a disturbance of the ER mitochondria calcium cycle, and identified two promising targets for therapeutic intervention in the pathology of ALS.

Short-term treatment of primary fibromyalgia with the 5-HT3-receptor antagonist tropisetron. Results of a randomized, double-blind, placebo-controlled multicenter trial in 418 patients

We investigated the efficacy and tolerability of short-term treatment with tropisetron, a selective, competitive 5-HT3-receptor antagonist in fibromyalgia. The trial was designed as a prospective, multicenter, double-blind, parallel-group, dose-finding study. We randomly assigned 418 patients suffering from primary fibromyalgia to receive either placebo, 5 mg, 10 mg or 15 mg tropisetron once daily for 10 days. Clinical response was measured by changes in pain score, visual analog scale, tender point count and ancillary symptoms. Responders were prospectively defined as patients showing a 35% or higher reduction in pain score. Treatment with 5 mg tropisetron resulted in a significantly higher response rate (39.2%) than placebo (26.2%) (p < 0.05). In the visual analog scale, the group administered 5 mg tropisetron showed a significant improvement (p < 0.05) and the group administered 10 mg tropisetron showed a nonsignificant clinical benefit. The number of painful tender points was significantly reduced (p = 0.002) in the 5 mg tropisetron group. Regarding ancillary symptoms, the 5 mg tropisetron group showed a significant improvement (p < 0.05) in sleep and dizziness. The patients' overall assessment of efficacy was significantly higher for 5 mg (p = 0.016) and 10 mg (p = 0.002) tropisetron than for placebo. The safety and tolerability of tropisetron was good; gastrointestinal tract symptoms were the most frequently reported adverse events. Short-term treatment of fibromyalgia patients with 5 mg tropisetron for 10 days proved to be efficacious and well tolerated. In this study a bell-shaped dose-response curve was seen.

Present state of medication therapy in fibromyalgia syndrome

For the treatment of primary fibromyalgia syndrome (FMS) the low dose application of tri- and tetracyclic antidepressive drugs was often studied. Up to now from all those drugs the effects of amitriptyline (AMI) are best documented. Because of its sedative properties it doesn't only influence pain but also improves the often disturbed sleep. Its use in patients with FMS is limited by the occurrence of side effects and the lack of response in a substantial number of patients. Serotonin reuptake inhibitors alone seem to be of little value. Nevertheless there is evidence that they may improve pain in combination with other antidepressive agents. Regarding pain moclobemide a reversible inhibitor of monoamine oxidase seems to be inferior to AMI. In controlled studies corticosteroids and non-steroidal anti-inflammatory drugs (NSAIDs) also failed to improve FMS. The combination of NSAIDs with benzodiazepines gave inconsistent results. Although often used, we have only small information about the effectiveness of opioids. No beneficial effect could be attributed to the muscle relaxant chlormezanone. In conclusion, although only about 1/3 of the patients respond, AMI remains the drug of first choice in the conventional medication treatment of FMS.

Efficacy and tolerability of tropisetron in primary fibromyalgia--a highly selective and competitive 5-HT3 receptor antagonist. German Fibromyalgia Study Group

OBJECTIVE

Based on a potential role for serotonin receptors in fibromyalgia, we investigated the efficacy and tolerability of treatment with tropisetron, a highly selective, competitive inhibitor of the 5-HT3 receptor.

METHODS

In this prospective, multicenter, double-blind, parallel-group, dose-finding study, 418 patients suffering from primary fibromyalgia (ACR criteria) were randomly assigned to receive either placebo, 5 mg, 10 mg or 15 mg tropisetron once daily, respectively. The duration of treatment was 10 days. The clinical response was measured by changes in pain-score, visual analog scale (VAS), and the number of painful tender-points.

RESULTS

Treatment with 5 mg tropisetron resulted in a significantly higher response rate (39.2%) when compared with placebo (26.2%) (p=0.033). The absolute reduction in pain-score was -13.5% for 5 mg tropisetron, -13.0% for 10 mg tropisetron, and -6.3% for placebo (p<0.05). The effects of 15 mg tropisetron were similar to placebo, thus suggesting a bell-shaped dose-response curve. Compared with placebo, treatment with 5 mg tropisetron led to a significant improvement (p<0.05) in VAS, while a clear trend in terms of clinical benefit was seen with 10 mg tropisetron. The number of painful tender-points was also reduced significantly (p=0.002) in the 5 mg tropisetron group. Of interest, during the 12-month follow-up period, pain intensity of responders on 5 mg and 10 mg tropisetron was still markedly below baseline. The treatment was well tolerated, with gastro-intestinal complaints being the most frequently reported side effects, in keeping with the known safety profile for 5-HT3 receptor antagonists.

CONCLUSIONS

This study demonstrates the efficacy of short-term treatment with 5 mg tropisetron once daily in primary fibromyalgia. Treatment was well tolerated and prolonged clinical benefits were seen.

[Comparative evaluation of a German version of the Health Assessment Questionnaire and the Hannover Functional Capacity Questionnaire]

OBJECTIVE

To translate the Health Assessment Questionnaire Disability Index (HAQ) into a German version, to validate and to compare its properties with two different versions of the Hannover Functional Ability Questionnaire (HFAQ) in a German speaking population.

METHODS

The test-retest reliability was tested by Pearson correlation in 32 outpatients of the Department of Rheumatology of the Medizinische Hochschule Hannover. For retesting, the questionnaire was mailed to them 1 week later. To validate the questionnaire it was administered to 110 inpatients in three different hospitals. All patients fulfilled the American College of Rheumatology 1987 revised criteria of rheumatoid arthritis (RA) or the Rome criteria of definitive inactive RA. The internal consistency was measured by Cronbach's coefficient alpha (CCA). To assess criterion validity we compared the HAQ and the two versions of the HFAQ with Keitel's test (KT) and the modified Steinbrocker classification (mSC). Construct validity was assessed by comparing these instruments with different clinical and laboratory variables. A multivariate analysis was used to identify the most important factors that are influencing the HAQ- and HFAQ-scores.

RESULTS

Test-retest reliability of the HAQ was r = 0.94. CCA was 0.91 (HAQ), 0.90 (HFAQ-P) and 0.93 (HFAQ-PR). The KT Pearson correlation coefficients reached r = -0.73 (HAQ), r = +0.74 (HFAQ-P) and r = +0.71 (HFAQ-PR). The mSC correlated r = +0.75 (HAQ), r = -0.72 (HFAQ-P) and r = -0.70 (HFAQ-PR). The correlation coefficients of HAQ/HFAQ-P was r = -0.87 and of HAQ/HFAQ-PR r = -0.88. The correlations between other clinical and laboratory variables reached from r = +/-0.58 (pain/HAQ) to r = +/-0.11 (number of swollen joints/HFAQ-PR). In backward multiple regression analysis 59-64% of the variance of disability measured by the questionnaires was explained predominantly by pain (32-33%) and by range of motion (16-21%).

CONCLUSION

The German version of the HAQ presented here and the two versions of the HFAQ are reliable and valid instruments for measuring functional disability in a German-speaking population with RA. The construct measured by the HAQ and both versions of the HFAQ showed a high degree of correspondence.

[Acupuncture in treatment of inflammatory rheumatic diseases]

Seventeen studies were examined with regard to efficacy and scientific quality of acupuncture in rheumatoid arthritis, spondarthropathy, lupus erythematosus, local and progressive systemic scleroderma. Acupuncture cannot be recommended for treatment of these diseases. By far, the most studies examined failed to show sufficient quality.

[Generalized tendomyopathy. I: Clinical aspects, follow-up and differential diagnosis]

Generalized tendomyopathy (GTM), or fibromyalgia, is a disorder characterized by diffuse pain in the musculoskeletal apparatus which usually begins at a single site, e.g., as low-back pain or cervical syndrome, and develops into generalized pain over months or years. It is accompanied by increased tenderness at characteristic tender points, although the pain threshold on the whole is reduced. In addition to the main symptoms (pain in the musculoskeletal system, tenderness at the tender points), autonomic and functional symptoms are almost invariably present and are often accompanied by pathological psychological findings such as neuroses and depression. To date, no reliable laboratory parameters or pathognomonic histological findings have been identified. The disorder affects primarily women, beginning around the age of 35 and reaching its peak during or after the menopause. It also affects young people and those over age 60, although it is much less common in these cases. Secondary forms are observed particularly in rheumatoid arthritis. The differential diagnosis must first distinguish primary GTM from the secondary forms. There must also be further differentiation between internal and psychiatric disorders and primary GTM. This can be achieved in many cases by careful clinical diagnosis, although a more complete examination is sometimes required.

[Generalized tendomyopathy. II: Pathogenesis and therapy]

Many factors are known to play a role in the pathogenesis of generalized tendomyopathy (GTM), or fibromyalgia. While the secondary forms develop along with known diseases, particularly rheumatoid arthritis, the cause of primary GTM is often not well understood. The fact that this disorder usually appears first at a single site, e.g., as low-back pain or cervical syndrome in which poor posture or malformation of the spine can be observed, gives rise to the theory that local changes in the spine or the joints are particular underlying causes of the initial manifestation. As the disorder becomes generalized, however, psychological causes predominate. Psychosocial factors in particular seem to further the process of generalization. Therapy can take many forms. Above all, it calls for an understanding attitude on the part of the managing physician and, whenever, possible, elimination of likely causal factors. Analgesics and antiinflammatories are often inadequate; antidepressants and neuroleptics provide more effective relief. Moreover, intensive physiotherapy and psychotherapy are necessary. GTM in many cases is resistant to treatment despite intensive management, although it often subsides naturally after age 60. Recognizing GTM is of great importance in order to initiate appropriate treatment promptly, avoid incorrect diagnoses and their consequences, e.g., repeat surgery, and to prevent premature disability.

[Hyaluronic acid and N-terminal procollagen-III-peptide in the urine in inflammatory and degenerative joint diseases]

In a cross-sectional study of 130 patients (main diagnosis: rheumatoid arthritis, n = 41, osteoarthritis, n = 39; ankylosing spondylitis, n = 28) we measured the concentrations of hyaluronan (HA) and the N-terminal propeptide of type-III collagen (NP III P) in urine and evaluated the relationship with their serum levels. Increased HA levels in serum correlated with increased urinary excretion (r = 0.69 for patients with active rheumatoid arthritis). Only patients with rheumatoid arthritis showed significantly elevated HA concentrations in urine (mean = 1,493 micrograms/mmol creatinine). Because of relatively wide fluctuations in urinary HA in normals (mean = 944, standard deviation 818 micrograms/mmol creatinine) and only modest differences between groups, the diagnostic accuracy of urinary HA measurements is inferior to serum determinations. NP III P showed no significant differences between patients and controls (means 10.5 to 15 micrograms/mmol creatinine). Obviously, renal excretion is of minor importance in the metabolism of HA and NP III P. The possible diagnostic usefulness of determinations of these parameters in serum is not enhanced by measurements in urine.

[Localized pressure pain in the diagnosis of generalized tendomyopathy (fibromyalgia)]

56 tender points were examined in 100 patients and 50 age- and sex-matched healthy volunteers using a dolorimeter. 24 of the 56 points were especially selected according to ability of discrimination, best possible distribution on the body, and easy localization. All 56 points as well as the 24 specially selected points were examined as to their sensitivity and specificity in the diagnosis of generalized tendomyopathy. The sensitivity and the specificity for both point-combinations were acceptable. The sensitivity and specificity of the 24 points were superior to the 56 points in the case of discrimination ability. A 100% sensitivity and specificity could not, however, be achieved. It remains to be considered if functional and vegetative symptoms must still be used to support the diagnosis of generalized tendomyopathy (fibromyalgia).

[Measuring pressure pain of tendons and muscles in healthy probands and patients with generalized tendomyopathy (fibromyalgia syndrome)]

A newly developed dolorimeter was tested by repeated measurements in 25 healthy volunteers to demonstrate its reliability. Repeated measurements at 12 different points demonstrated good correlation. Measurements at these points gave a highly significant difference between 100 patients with generalized tendomyopathy (fibrositis-syndrome/fibromyalgia) and a group of 50 age- and sex-matched healthy volunteers.

[Serum hyaluronic acid and aminoterminal procollagen III peptide in inflammatory and degenerative joint diseases]

Serum levels of hyaluronic acid (HA) and the amino-terminal type III procollagen peptide (NP-III-P) were determined simultaneously by specific immunoassays in patients with rheumatoid arthritis (n = 41), osteoarthritis (n = 43), ankylosing spondylitis (n = 7), psoriatic arthritis (n = 6), and reactive arthritis (n = 6). Increased serum levels of both HA and NP-III-P, were found in rheumatoid arthritis and - although less pronounced - in osteoarthritis, differing significantly from age- and sex-matched controls (n = 77). Furthermore, patients suffering from active rheumatoid arthritis showed higher serum levels of both antigens than patients with inactive disease, and significant correlations were found in rheumatoid arthritis between acute phase plasma proteins, HA and NP-III-P, respectively. In contrast, determination of low molecular weight fractions of NP-III-P by Fab- assay proved not to be useful in regard to clinical application. No significant effects of anti-inflammatory treatment were evident in any of the parameters. In rheumatoid patients, the serum concentrations of HA were found to correlate positively with the serum reactivity of NP-III-P related antigens (r = 0.692) and with the excretion of urinary pyridinoline (r = 0.455). Thus, both parameters seem to reflect similar mechanisms of connective tissue activation and may be related to inflammatory activity in joint diseases.

[Accident during local anesthesia in a patient with antiarrhythmic therapy]

A side reaction of antiarrhythmic treatment in a 18-year-old patient with congestive cardiomyopathy is reported. During treatment with high doses of aprindine cerebral convulsions occurred. After ceasing the medication temporarily, a pacemaker revision was done in local anesthesia. Cerebral convulsions reappeared after injection of the local anesthetic. The patient died due to cardiac arrest. It is discussed that some amount of the local anesthetic agent (mepivacaine) was absorbed from the tissue elevating the blood level of local anesthetic drugs (aprindine and mepivacine) into the toxic range, thus producing cerebral convulsions, augmenting the stimulation threshold and depressing the automaticity of the heart. It is urged that antiarrhythmic treatment should be stopped before local anesthesia will be performed.