BAX inhibitor-1 is a Ca(2+) channel critically important for immune cell function and survival.

The endoplasmic reticulum (ER) serves as the major intracellular Ca(2+) store and has a role in the synthesis and folding of proteins. BAX (BCL2-associated X protein) inhibitor-1 (BI-1) is a Ca(2+) leak channel also implicated in the response against protein misfolding, thereby connecting the Ca(2+) store and protein-folding functions of the ER. We found that BI-1-deficient mice suffer from leukopenia and erythrocytosis, have an increased number of splenic marginal zone B cells and higher abundance and nuclear translocation of NF-κB (nuclear factor-κ light-chain enhancer of activated B cells) proteins, correlating with increased cytosolic and ER Ca(2+) levels. When put into culture, purified knockout T cells and even more so B cells die spontaneously. This is preceded by increased activity of the mitochondrial initiator caspase-9 and correlated with a significant surge in mitochondrial Ca(2+) levels, suggesting an exhausted mitochondrial Ca(2+) buffer capacity as the underlying cause for cell death in vitro. In vivo, T-cell-dependent experimental autoimmune encephalomyelitis and B-cell-dependent antibody production are attenuated, corroborating the ex vivo results. These results suggest that BI-1 has a major role in the functioning of the adaptive immune system by regulating intracellular Ca(2+) homeostasis in lymphocytes.

The plasma membrane channel ORAI1 mediates detrimental calcium influx caused by endogenous oxidative stress.

The mouse hippocampal cell line HT22 is an excellent model for studying the consequences of endogenous oxidative stress. Addition of extracellular glutamate depletes the cells of glutathione (GSH) by blocking the glutamate-cystine antiporter system x(c)(-). GSH is the main antioxidant in neurons and its depletion induces a well-defined program of cell death called oxytosis, which is probably synonymous with the iron-dependent form of non-apoptotic cell death termed ferroptosis. Oxytosis is characterized by an increase of reactive oxygen species and a strong calcium influx preceding cell death. We found a significant reduction in store-operated calcium entry (SOCE) in glutamate-resistant HT22 cells caused by downregulation of the Ca(2+) channel ORAI1, but not the Ca(2+) sensors STIM1 or STIM2. Pharmacological inhibition of SOCE mimicked this protection similarly to knockdown of ORAI1 by small interfering RNAs. Long-term calcium live-cell imaging after induction of the cell death program showed a specific reduction in Ca(2+)-positive cells by ORAI1 knockdown. These results suggest that dysregulated Ca(2+) entry through ORAI1 mediates the detrimental Ca(2+) entry in programmed cell death induced by GSH depletion. As this detrimental Ca(2+) influx occurs late in the course of the cell death program, it might be amenable to therapeutic intervention in diseases caused by oxidative stress.

A case of relapsing-remitting neuroborreliosis? Challenges in the differential diagnosis of recurrent myelitis.

We report the case of a 31-year-old woman with 4 episodes of myelitis with pleocytosis, a positive Borrelia burgdorferi serology with positive antibody indices, and full recovery each time after antibiotic and steroid treatment, suggesting neuroborreliosis. We nevertheless believe that recurrent neuroborreliosis is improbable based on the levels of the chemokine CXCL13 in cerebrospinal fluid and favor the diagnosis of post-infectious autoimmune-mediated transverse myelitis possibly triggered by an initial neuroborreliosis as the cause of the relapses observed in our patient. We demonstrate the diagnostic steps and procedures which were important in the differential diagnosis of this unusual and challenging case.

Degeneration of retinal layers in multiple sclerosis subtypes quantified by optical coherence tomography.

BACKGROUND: Optical coherence tomography can be used to assess retinal degeneration in multiple sclerosis (MS). Thinning of the retinal nerve fibre layer and macular thickness have been well characterized, but newer devices allow quantification of all retinal layers. OBJECTIVES: The objective of this study was to evaluate the thickness of the paramacular retina, peripapillary retinal nerve fibre layer, and deeper paramacular layers in MS patient subgroups, using state-of-the-art optical coherence tomography. METHODS: Using a Heidelberg Engineering Spectralis device, we performed paramacular volumetric retinal scans and circular peripapillary fibre-layer scans, manually segmenting different retinal layers into single horizontal foveal scans in 95 patients with definite MS (42 relapsing-remitting, 41 secondary progressive, 12 primary progressive), plus 91 age- and sex-matched controls. RESULTS: Even without a history of optic neuritis, all MS subgroups had significant thinning of the peripapillary retinal nerve fibre layer, the paramacular retinal thickness and the retinal ganglion cell- and inner plexiform layer. Only in primary progressive MS was the inner nuclear layer significantly reduced. CONCLUSIONS: Our findings indicate a primary retinal pathology involving the inner nuclear layer in primary progressive MS. Results in eyes without history of optic neuritis suggest possible subclinical episodes of optic neuritis or retrograde trans-synaptic degeneration of retinal ganglion cells and their axons.

Mutation of ATF4 mediates resistance of neuronal cell lines against oxidative stress by inducing xCT expression.

Selecting neuronal cell lines for resistance against oxidative stress might recapitulate some adaptive processes in neurodegenerative diseases where oxidative stress is involved like Parkinson's disease. We recently reported that in hippocampal HT22 cells selected for resistance against oxidative glutamate toxicity, the cystine/glutamate antiporter system x(c)(-), which imports cystine for synthesis of the antioxidant glutathione, and its specific subunit, xCT, are upregulated. (Lewerenz et al., J Neurochem 98(3):916-25). Here, we show that in these glutamate-resistant HT22 cells upregulation of xCT mediates glutamate resistance, and xCT expression is induced by upregulation of the transcription factor ATF4. The mechanism of ATF4 upregulation consists of a 13 bp deletion in the upstream open reading frame (uORF2) overlapping the ATF4 open reading frame. The resulting uORF2-ATF4 fusion protein is efficiently translated even at a low phosphorylation levels of the translation initiation factor eIF2α, a condition under which ATF4 translation is normally suppressed. A similar ATF4 mutation associated with prominent upregulation of xCT expression was identified in PC12 cells selected for resistance against amyloid ß-peptide. Our data indicate that ATF4 has a central role in regulating xCT expression and resistance against oxidative stress. ATF4 mutations might have broader significance as upregulation of xCT is found in tumor cells and associated with anticancer drug resistance.

[POEMS syndrome. An interdisciplinary clinical challenge]. / POEMS-Syndrom. Eine interdisziplinäre klinische Herausforderung.

POEMS syndrome is a rare paraneoplastic syndrome due to a plasma cell dyscrasia, which includes peripheral neuropathy, organomegaly, endocrinopathy, monoclonal plasma cell proliferation and skin changes. Elevated levels of VEGF (vascular endothelial growth factor) in the serum of patients are suggested to play a pivotal role in the pathophysiology. A 60-year-old male presented with POEMS syndrome and painful edema, skin thickening of the distal extremities and livid-erythematous discoloration. The sclerotic changes resulted in a severe limitation of joint flexibility. Furthermore, the patient showed clubbing, white nails and a facial lipoatrophy. In addition to the skin changes, the patient was diagnosed with polyneuropathy, monoclonal gammopathy (type lambda), high elevated VEGF-levels, hepatomegaly, lymphadenopathy, hypothyreosis, hypogonadism and thrombocytosis in the course of POEMS syndrome. Treatment with 4 cycles of bortezomib and dexamethasone resulted in improvement of symptoms.

Multiple vascular abnormalities and a paradoxical combination of vitamin B12 deficiency and thrombocytosis in a case with POEMS syndrome.

POEMS/Crow-Fukase syndrome is a rare multisystem disorder associated with elevated vascular endothelial growth factor (VEGF), which clinically presents with polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes. We report a case of POEMS syndrome due to a gammopathy of undetermined significance with thrombocytosis, vitamin B(12) deficiency, highly elevated VEGF and in addition to glomeruloid angiomas two previously undescribed proliferative vascular lesions: a spinal arteriovenous fistula and a plexogenic pulmonary arteriopathy, which ultimately resulted in lethal pulmonary hypertension. We assume that the high VEGF levels caused the vascular abnormalities observed in our patient.

Human septin 3 on chromosome 22q13.2 is upregulated by neuronal differentiation.

An expression sequence tag identified in a screen for genes upregulated by retinoic acid induced neuronal differentiation of the human teratocarcinoma cell line Ntera2/D1 was found in close genomic proximity to a region of high sequence homology to the septin subfamily of GTPase genes. We could show that the tag corresponds to the 3' untranslated region of this novel gene named septin 3 and cloned three isoforms A (2191 bp), B (4378 bp), and C (1896 bp) from human Ntera2/D1 cDNA. We present the genomic localization and organization on chromosome 22q13.2, a chromosomal hot spot for translocations implicated in leukemia. Interestingly, MSF the closest paralog of septin 3 is a fusion partner in a therapy-related acute myeloid leukemia. Quantitative PCR confirmed the upregulation of the putative septin by neuronal differentiation and northern blotting showed only one band corresponding to sep3B with a neurospecific expression pattern in adult human tissues.

Identification of genes up-regulated by retinoic-acid-induced differentiation of the human neuronal precursor cell line NTERA-2 cl.D1.

The human teratocarcinoma cell line NTERA-2 cl.D1 (NT2 cells) can be induced with retinoic acid and cell aggregation to yield postmitotic neurones. This seems to model the in vivo situation, as high concentrations of retinoic acid, retinoic acid binding proteins, and receptors have been detected in the embryonic CNS and the developing spinal cord suggesting a role for retinoic acid in neurogenesis. Suppression subtractive hybridization was used to detect genes up-regulated by this paradigm of neuronal differentiation. Microfibril-associated glycoprotein 2 was found to be drastically up-regulated and has not been implicated in neuronal differentiation before. Suppression subtractive hybridization also identified DYRK4, a homologue of the Drosophila gene minibrain. Minibrain mutations result in specific defects in the development of the fly central nervous system. In adult rats, DYRK4 is only expressed in testis, but our results suggest an additional role for DYRK4 in neuronal differentiation. We have shown that suppression subtractive hybridization in conjunction with an efficient screening procedure is a valuable tool to produce a repertoire of differentially expressed genes and propose a new physiological role for several identified genes and expressed sequence tags.

Identification of a novel seven-transmembrane receptor with homology to glycoprotein receptors and its expression in the adult and developing mouse.

Using a PCR-based cloning strategy we have isolated a cDNA from mouse brain and named it fex, because it codes for a novel putative G protein-coupled receptor expressed in follicles. The deduced amino acid sequence shows a higher degree of homology to the family of glycoprotein receptors, namely those for FSH, LH, and TSH, than to other G protein-coupled receptors. With 18 leucine-rich repeats FEX exhibits features in its N-terminal portion characterizing it as unique within the glycoprotein receptor family. In the adult mouse fex expression was detected in the male and female gonads, the adrenal medulla, and the olfactory bulb of the brain. During embryonic development fex transcripts were detected transiently in various tissues, particularly in selected regions of the central nervous system, the developing face, the intervertebral discs anlagen, and the limb buds. Because fex was expressed during periods of active morphogenesis, it may be an important receptor for signals controlling growth and differentiation of specific embryonic tissues.

Unique expression pattern of a novel mosaic receptor in the developing cerebral cortex.

Recently, a new type of transmembrane protein with a unique combination of protein domains was characterized from human, rabbit and chicken. This protein exhibits features of the low-density lipoprotein receptor family and shows homology to the receptor of the neuropeptide head activator isolated from hydra. To study the temporal and spatial pattern of expression of this unusual new receptor we have isolated a murine homolog and, in accordance with its human counterpart, named it mSorLA. Northern blot analysis revealed the highest abundance of mSorLA transcripts in the adult brain, lower levels in a variety of other organs and expression during embryogenesis. In situ hybridization showed predominant localization in neurons of the cortex, the hippocampus and the cerebellum. During embryonic development mSorLA displayed a unique pattern of expression in the cerebral cortex, where a subpopulation of neurons was labeled before final differentiation. Transcripts of mSorLA were also detected outside the central nervous system in regions active in morphogenesis.

A novel G protein-coupled receptor with homology to neuropeptide and chemoattractant receptors expressed during bone development.

A novel G protein-coupled receptor was isolated from a cDNA derived from the cell line NH15-CA2 and a cDNA library from adult mouse brain using a PCR cloning strategy. The amino acid sequence of the candidate receptor DEZ showed homology to neuropeptide and chemoattractant receptors. Highest overall homology was found with the orphan receptor GPR-1 (65%), the angiotensin II receptor (62%), and the C5a anaphylatoxin receptor (60%). Northern blot analysis of dez revealed a predominant 2.6 kb mRNA species in NH15-CA2 cells. In situ hybridization experiments showed that dez is differentially regulated during development, with a prominent expression in developing osseous and cartilaginous tissue. It was also detectable in the adult parathyroid glands, hinting at a possible function in bone metabolism.