The synaptic vesicle-associated protein amphiphysin is the 128-kD autoantigen of Stiff-Man syndrome with breast cancer

Amphiphysin I but not dynamin I nor synaptojanin mRNA expression increased after repeated methamphetamine administration in the rat cerebrum and cerebellum

Dopamine increases/decreases synaptic vesicle recycling and in schizophrenia the proteins/mRNA is decreased. We isolated cDNA clone, similar to amphiphysin 1 (vesicle protein) mRNA from the neocortex of rats injected repeatedly with methamphetamine using polymerase chain reaction (PCR) differential display. This clone is highly homologous to the 3' region of the human amphiphysin gene. PCR extension study using a primer specific for the rat amphiphysin 1 gene and a primer located within the clone revealed that it is the 3' UTR region of the rat amphiphysin 1 gene. Furthermore, in situ hybridization revealed that amphiphysin 1 mRNA is expressed in the cerebrum, medial thalamus, hippocampus and cerebellum. In the cerebellum, amphiphysin mRNA expression was confined to upper granule cell layer. Repeated methamphetamine administration increased amphiphysin I mRNA expression in both anterior part of the cerebrum, and the cerebellum. However, the repeated administration did not alter mRNA expression of the other vesicle proteins, synaptotagmin I, synapsin I, synaptojanin and dynamin I, we conclude that the repeated administration selectively increased amphiphysin 1 mRNA expression. Thus, amphiphysin 1 does not work as synaptic recycling, but it is suggested, as a part of pathogenesis of brain tissue injury (under Ca²⁺ and Mg²⁺ devoid environment) in repeated methamphetamine-injected states, the gene regulate actin-asssembly, learning, cell stress signaling and cell polarity.

Lower extremity predominant stiff-person syndrome and limbic encephalitis with amphiphysin antibodies in breast cancer

A 54-year-old woman presented with several weeks of psychiatric symptoms, partial-onset seizures, and painful spasms of the lower extremities. On examination, she exhibited severe stiffness and intermittent extensor spasms of the lower extremities. Magnetic resonance imaging of the brain showed T2 hyperintensity in the left temporal lobe with enhancement after gadolinium administration on T1-weighted images. Amphiphysin antibodies were present in the serum. Radiographic screening for malignancy disclosed a metastatic breast cancer. The case is a unique example of amphiphysin autoimmunity, illustrating the possibility of paraneoplastic stiff-person syndrome and limbic encephalitis coexisting in a patient with a "classical" presentation of stiff-person syndrome confined to the lower extremities.

Paraneoplastic and non-paraneoplastic autoimmunity to neurons in the central nervous system

Autoimmune central nervous system (CNS) inflammation occurs both in a paraneoplastic and non-paraneoplastic context. In a widening spectrum of clinical disorders, the underlying adaptive (auto) immune response targets neurons with a divergent role for cellular and humoral disease mechanisms: (1) in encephalitis associated with antibodies to intracellular neuronal antigens, neuronal antigen-specific CD8⁺ T cells seemingly account for irreversible progressive neuronal cell death and neurological decline with poor response to immunotherapy. However, a pathogenic effect of humoral immune mechanisms is also debated. (2) In encephalitis associated with antibodies to synaptic and extrasynaptic neuronal cell surface antigens, potentially reversible antibody-mediated disturbance of synaptic transmission and neuronal excitability occurs in the absence of excessive neuronal damage and accounts for a good response to immunotherapy. However, a pathogenic effect of cellular immune mechanisms is also debated. We provide an overview of entities, clinical hallmarks, imaging features, characteristic laboratory, electrophysiological, cerebrospinal fluid and neuropathological findings, cellular and molecular disease mechanisms as well as therapeutic options in these two broad categories of inflammatory CNS disorders.

Autoimmune stiff person syndrome and related myelopathies: understanding of electrophysiological and immunological processes

Stiff person syndrome (SPS) is a disabling autoimmune central nervous system disorder characterized by progressive muscle rigidity and gait impairment with superimposed painful spasms that involve axial and limb musculature, triggered by heightened sensitivity to external stimuli. Impaired synaptic GABAergic inhibition resulting from intrathecal B-cell-mediated clonal synthesis of autoantibodies against various presynaptic and synaptic proteins in the inhibitory neurons of the brain and spinal cord is believed to be an underlying pathogenic mechanism. SPS is most often idiopathic, but it can occur as a paraneoplastic condition. Despite evidence that anti-GAD and related autoantibodies impair GABA synthesis, the exact pathogenic mechanism of SPS is not fully elucidated. The strong association with several MHC-II alleles and improvement of symptoms with immune-modulating therapies support an autoimmune etiology of SPS. In this review, we discuss the clinical spectrum, neurophysiological mechanisms, and therapeutic options, including a rationale for agents that modulate B-cell function in SPS.

Barfly: sculpting membranes at the Drosophila neuromuscular junction

The ability of a cell to change the shape of its membranes is intrinsic to many cellular functions. Proteins that can alter or recognize curved membrane structures and those that can act to recruit other proteins which stabilize the membrane curvature are likely to be essential in cell functions. The BAR (Bin, amphiphysin, RVS167 homology) domain is a protein domain that can either induce lipidic membranes to curve or can sense curved membranes. BAR domains are found in several proteins at neuronal synapses. We will review BAR domain structure and the role that BAR domain containing proteins play in regulating the morphology and function of the Drosophila neuromuscular junction. In flies the BAR domain containing proteins, endophilin and syndapin affect synaptic vesicle endocytosis, whereas CIP4, dRich, nervous wreck and syndapin affect synaptic morphology. We will review the growing evidence implicating mutations in BAR domain containing proteins being the cause of human pathologies.

Defective membrane remodeling in neuromuscular diseases: insights from animal models

Proteins involved in membrane remodeling play an essential role in a plethora of cell functions including endocytosis and intracellular transport. Defects in several of them lead to human diseases. Myotubularins, amphiphysins, and dynamins are all proteins implicated in membrane trafficking and/or remodeling. Mutations in myotubularin, amphiphysin 2 (BIN1), and dynamin 2 lead to different forms of centronuclear myopathy, while mutations in myotubularin-related proteins cause Charcot-Marie-Tooth neuropathies. In addition to centronuclear myopathy, dynamin 2 is also mutated in a dominant form of Charcot-Marie-Tooth neuropathy. While several proteins from these different families are implicated in similar diseases, mutations in close homologues or in the same protein in the case of dynamin 2 lead to diseases affecting different tissues. This suggests (1) a common molecular pathway underlying these different neuromuscular diseases, and (2) tissue-specific regulation of these proteins. This review discusses the pathophysiology of the related neuromuscular diseases on the basis of animal models developed for proteins of the myotubularin, amphiphysin, and dynamin families. A better understanding of the common mechanisms between these neuromuscular disorders will lead to more specific health care and therapeutic approaches.

Paraneoplastic encephalomyelopathies: pathology and mechanisms

The last three decades have seen major advances in the understanding of paraneoplastic and idiopathic autoimmune disorders affecting the central nervous system (CNS). Neural-specific autoantibodies and their target antigens have been discovered, immunopathology and neuroimaging patterns recognized and pathogenic mechanisms elucidated. Disorders accompanied by autoantibody markers of neural peptide-specific cytotoxic effector T cells [such as anti-neuronal nuclear antibody type 1 (ANNA-1, aka anti-Hu), Purkinje cell antibody type 1 (PCA-1, aka anti-Yo) and CRMP-5 IgG] are generally poorly responsive to immunotherapy. Disorders accompanied by neural plasma membrane-reactive autoantibodies [the effectors of synaptic disorders, which include antibodies targeting voltage-gated potassium channel (VGKC) complex proteins, NMDA and GABA-B receptors] generally respond well to early immunotherapy. Here we describe in detail the neuropathological findings and pathophysiology of paraneoplastic CNS disorders with reference to antigen-specific serology and neurological and oncological contexts.

Stiff person syndrome: advances in pathogenesis and therapeutic interventions

Stiff person syndrome (SPS) varies from mild to severe, but if untreated it can be progressive and disabling. Although progress has been made in understanding and treating SPS, the disease remains underdiagnosed, delaying treatment. Antibodies against glutamic acid decarboxylase provide an excellent diagnostic marker, but their role in disease pathogenesis is uncertain. Research focused on identifying new autoantigens has provided evidence that gamma-aminobutyric acid (GABA)(A) receptor-associated protein (GABARAP), a 14-kD protein localized at the postsynaptic regions of GABAergic synapses, is an antigenic target. Circulating anti-GABARAP antibodies that inhibit GABA(A) receptor expression on GABAergic neurons have been found in up to 65% of SPS patients. The impairment of GABAergic pathways and reduction of brain GABA results in clinical manifestations of stiffness, spasms, and phobias. Increased awareness of SPS among practicing physicians is necessary to recognize the disease early and prevent permanent disability. Most patients with SPS respond to GABA-enhancing drugs, but the high doses required cause unacceptable adverse effects. The disease clearly responds to intravenous immunoglobulin, but repeated infusions are needed to maintain response. New immunomodulating agents are being explored to treat difficult cases and to induce long-lasting remissions.

Stiff-person syndrome (SPS) and anti-GAD-related CNS degenerations: protean additions to the autoimmune central neuropathies

Stiff Person Syndrome (SPS) is a rare autoimmune neurological disease attributable to autoantibodies to glutamic acid decarboxylase (anti-GAD) more usually associated with the islet beta cell destruction of autoimmune type 1 diabetes (T1D). SPS is characterized by interference in neurons with the synthesis/activity of the inhibitory neurotransmitter gamma amino butyric acid (GABA) resulting in the prototypic progressive spasmodic muscular rigidity of SPS, or diverse neurological syndromes, cerebellar ataxia, intractable epilepsy, myoclonus and several others. Remarkably, a single autoantibody, anti-GAD, can be common to widely different disease expressions, i.e. T1D and SPS. One explanation for these data is the differences in epitope engagement between the anti-GAD reactivity in SPS and T1D: in both diseases, anti-GAD antibody reactivity is predominantly to a conformational epitope region in the PLP- and C-terminal domains of the 65 kDa isoform but, additionally in SPS, there is reactivity to conformational epitope(s) on GAD67, and short linear epitopes in the C-terminal region and at the N-terminus of GAD65. Another explanation for disease expressions in SPS includes ready access of anti-GAD to antigen sites due to immune responsiveness within the CNS itself according to intrathecal anti-GAD-specific B cells and autoantibody. Closer study of the mysterious stiff-person syndrome should enhance the understanding of this disease itself, and autoimmunity in general.

Paraneoplastic neurological disorders

The article provides an overview on the diagnosis and pathogenesis of paraneoplastic neurological disorders (PNDs), and subsequently the current therapeutic strategies in these patients. PNDs are nervous system dysfunctions in cancer patients, which are not due to a local effect of the tumor or its metastases. Most of these clinically defined syndromes in adults are associated with lung cancer, especially small-cell lung cancer, lymphoma and gynecological tumors. In a part of the PND, an overlapping of different clinical syndromes can be observed. Highly specific autoantibodies directed against onconeuronal antigens led to the current hypothesis of an autoimmune pathophysiology. Whereas the most central nervous PNDs are more T-cell-mediated, limbic encephalitis can be caused by pathogenic receptor autoantibodies. The PND of the neuromuscular junction and paraneoplastic autonomic neuropathy are mainly associated with receptor or ion channel autoantibodies. The childhood opsoclonus-myoclonus syndrome and the PNDs associated with receptor/ion channel autoantibodies often respond to immunosuppressive therapies, plasmapheresis and intravenous immunoglobulins. By contrast, most CNS PNDs associated with defined antineuronal antibodies directed against intracellular antigens only stabilize after tumor treatment.

Stiff-person syndrome: a case report and review of the literature

We report a case of stiff-person syndrome associated with several autoimmune diseases. A 49-year-old male with type 1 diabetes presented with a 6-month history of muscle rigidity and spasms of his upper and lower extremities. Anti-glutamic acid decarboxylase 65 antibody was elevated at 609 nmol/L. Electromyography revealed continuous motor unit activity in agonist and antagonist muscles. He responded favorably to diazepam, baclofen, and intravenous immunoglobulin infusions. This case report describes stiff-person syndrome in association with pernicious anemia and diabetes mellitus. A review of the literature discusses the diagnosis and treatment of this rare entity.

Autoimmune limbic encephalitis

Limbic encephalitis (LE) was first described in 1960 by Brierley et al. and was defined by an acute or subacute temporal lobe epilepsy, memory loss and psychiatric disturbances. Corsellis et al. then demonstrated that LE was associated with small-cell lung cancer and a paraneoplastic origin of LE was suggested. In the 1980s, onconeuronal antibodies specific to paraneoplastic neurological syndromes were described and some of them, such as Hu-Ab, were clearly associated with LE. In the last 20 years, other onconeuronal antibodies targeting intracellular antigens were subsequently identified and LE was considered as a rare paraneoplastic neurological syndrome with a poor outcome and as mainly being associated with Hu-Ab, Ma2-Ab or CV2/CRMP5-Ab. The concept of LE has dramatically evolved since 2004, with the description of LE becoming associated with novel autoantibodies that target neuronal surface rather than intracellular antigens. In these cases, LE was not always paraneoplastic. Interestingly, these newly described LE cases offer a much better prognosis than the previous ones. At present, LE is considered to be an autoimmune disorder that can be paraneoplastic or not and could be more frequent than previously suspected. The associated antibodies lead to the classification of different subtypes of LE and are used as prognostic markers. Those that are directed against cell surface antigens could play a direct role in the neurological symptoms of LE.

A critical update on the immunopathogenesis of Stiff Person Syndrome

BACKGROUND

Stiff Person Syndrome (SPS) is a relatively rare but often overlooked autoimmune neurological disorder that targets antigens within the brain's inhibitory pathways resulting in incapacitating stiffness and spasms that impact on the patients' quality of life. Although a number of immunomodulating therapies significantly improve the patients' symptoms, the exact pathogenic mechanisms remain unclear.

MATERIALS AND METHODS

The current literature on SPS was reviewed and combined with the authors' experience with many patients and various laboratory studies. The majority of the patients have high-titre anti-GAD (Glutamic Acid Decarboxylase) antibodies in the sera and CSF suggesting dysfunction of the GABAergic neurotransmission. These antibodies are excellent disease markers but their pathogenic role remains uncertain.

CONCLUSIONS

This review provides a critical assessment on the immunobiology of SPS, describes the identification of anti-GABARAP antibodies as a new antigenic target in the GABAergic synapse and identifies the areas for future research.

Dissecting BAR domain function in the yeast Amphiphysins Rvs161 and Rvs167 during endocytosis

BAR domains are protein modules that bind to membranes and promote membrane curvature. One type of BAR domain, the N-BAR domain, contains an additional N-terminal amphipathic helix, which contributes to membrane-binding and bending activities. The only known N-BAR-domain proteins in the budding yeast Saccharomyces cerevisiae, Rvs161 and Rvs167, are required for endocytosis. We have explored the mechanism of N-BAR-domain function in the endocytosis process using a combined biochemical and genetic approach. We show that the purified Rvs161-Rvs167 complex binds to liposomes in a curvature-independent manner and promotes tubule formation in vitro. Consistent with the known role of BAR domain polymerization in membrane bending, we found that Rvs167 BAR domains interact with each other at cortical actin patches in vivo. To characterize N-BAR-domain function in endocytosis, we constructed yeast strains harboring changes in conserved residues in the Rvs161 and Rvs167 N-BAR domains. In vivo analysis of the rvs endocytosis mutants suggests that Rvs proteins are initially recruited to sites of endocytosis through their membrane-binding ability. We show that inappropriate regulation of complex sphingolipid and phosphoinositide levels in the membrane can impinge on Rvs function, highlighting the relationship between membrane components and N-BAR-domain proteins in vivo.

An AP-3-dependent mechanism drives synaptic-like microvesicle biogenesis in pancreatic islet beta-cells

Pancreatic islet beta-cells contain synaptic-like microvesicles (SLMVs). The origin, trafficking, and role of these SLMVs are poorly understood. In neurons, synaptic vesicle (SV) biogenesis is mediated by two different cytosolic adaptor protein complexes, a ubiquitous AP-2 complex and the neuron-specific AP-3B complex. Mice lacking AP-3B subunits exhibit impaired GABAergic (inhibitory) neurotransmission and reduced neuronal vesicular GABA transporter (VGAT) content. Since beta-cell maturation and exocytotic function seem to parallel that of the inhibitory synapse, we predicted that AP-3B-associated vesicles would be present in beta-cells. Here, we test the hypothesis that AP-3B is expressed in islets and mediates beta-cell SLMV biogenesis. A secondary aim was to test whether the sedimentation properties of INS-1 beta-cell microvesicles are identical to those of bona fide SLMVs isolated from PC12 cells. Our results show that the two neuron-specific AP-3 subunits beta3B and mu3B are expressed in beta-cells, the first time these proteins have been found to be expressed outside the nervous system. We found that beta-cell SLMVs share the same sedimentation properties as PC12 SLMVs and contain SV proteins that sort specifically to AP-3B-associated vesicles in the brain. Brefeldin A, a drug that interferes with AP-3-mediated SV biogenesis, inhibits the delivery of AP-3 cargoes to beta-cell SLMVs. Consistent with a role for AP-3 in the biogenesis of GABAergic SLMV in beta-cells, INS-1 cell VGAT content decreases upon inhibition of AP-3 delta-subunit expression. Our findings suggest that beta-cells and neurons share molecules and mechanisms important for mediating the neuron-specific membrane trafficking pathways that underlie synaptic vesicle formation.

Update on paraneoplastic neurologic disorders

When patients with cancer develop neurologic symptoms, common causes include metastasis, infections, coagulopathy, metabolic or nutritional disturbances, and neurotoxicity from treatments. A thorough clinical history, temporal association with cancer therapies, and results of ancillary tests usually reveal one of these mechanisms as the etiology. When no etiology is identified, the diagnosis considered is often that of a paraneoplastic neurologic disorder (PND). With the recognition that PNDs are more frequent than previously thought, the availability of diagnostic tests, and the fact that, for some PNDs, treatment helps, PNDs should no longer be considered diagnostic zebras, and when appropriate should be included in the differential diagnosis early in the evaluation.

Successful treatment with rituximab in a patient with stiff-person syndrome complicated by dysthyroid ophthalmopathy

We report a patient with stiff-person syndrome and insulin-dependent diabetes mellitus with anti-glutamic acid decarboxylase (GAD) antibody, who suddenly complained of diplopia due to dysthyroid ophthalmopathy. Therapeutic efficacy of plasmapheresis and high-dose intravenous immunoglobulin was transient. After starting administration of rituximab, the patient showed obvious improvement of muscle spasms due to stiff-person syndrome and ophthalmoplegia following quick depletion of CD20-positive cells in peripheral blood. The anti-GAD and anti-thyroid antibodies decreased slowly. This drug might be a potent therapeutic option for refractory patients with stiff-person syndrome, particularly in those associated with dysthyroid ophthalmopathy.

Stiff person syndrome associated anti-amphiphysin antibodies reduce GABA associated [Ca(2+)]i rise in embryonic motoneurons

Autoantibodies to the synaptic protein amphiphysin play a crucial pathogenic role in paraneoplastic stiff-person syndrome. Impairment of GABAergic inhibition is the presumed pathophysiological mechanism by which these autoantibodies become pathogenic. Here we used calcium imaging on rat embryonic motor neurons to investigate whether antibodies to amphiphysin directly hinder GABAergic signaling. We found that the immunoglobulin G fraction from a patient with stiff-person syndrome, containing high titer antibodies to amphiphysin and inducing stiffness in rats upon passive transfer, reduced GABA-induced calcium influx in embryonic motor neurons. Depletion of the anti-amphiphysin fraction from the patient's IgG by selective affinity chromatography abolished this effect, showing its specificity for amphiphysin. Quantification of the surface expression of the Na(+)/K(+)/2Cl(2-) cotransporter revealed a reduction after incubation with anti-amphiphysin IgG, which is concordant with a lower intracellular chloride concentration and thus impairment of GABA mediated calcium influx. Thus, anti-amphiphysin antibodies exert a direct effect on GABA signaling, which is likely to contribute to the pathogenesis of SPS.

Dynamic interaction of amphiphysin with N-WASP regulates actin assembly

Amphiphysin 1, an endocytic adaptor concentrated at synapses that couples clathrin-mediated endocytosis to dynamin-dependent fission, was also shown to have a regulatory role in actin dynamics. Here, we report that amphiphysin 1 interacts with N-WASP and stimulates N-WASP- and Arp2/3-dependent actin polymerization. Both the Src homology 3 and the N-BAR domains are required for this stimulation. Acidic liposome-triggered, N-WASP-dependent actin polymerization is strongly impaired in brain cytosol of amphiphysin 1 knock-out mice. FRET-FLIM analysis of Sertoli cells, where endogenously expressed amphiphysin 1 co-localizes with N-WASP in peripheral ruffles, confirmed the association between the two proteins in vivo. This association undergoes regulation and is enhanced by stimulating phosphatidylserine receptors on the cell surface with phosphatidylserine-containing liposomes that trigger ruffle formation. These results indicate that actin regulation is a key function of amphiphysin 1 and that such function cooperates with the endocytic adaptor role and membrane shaping/curvature sensing properties of the protein during the endocytic reaction.

Protective and detrimental immunity: lessons from stiff person syndrome and multiple sclerosis

BACKGROUND

The immune system may attack the brain and cause inflammatory disorders like multiple sclerosis (MS). On the other hand, the immune system may protect and support neurons.

METHODS

There are two obstacles to study this paradox in humans. First, the target antigens in many human central nervous system (CNS) disorders are unknown. Second, it is often difficult to separate pathogenic from protective events, as well as primary from secondary phenomena. Idiopathic stiff person syndrome (SPS) circumvents the first obstacle, because most patients secrete antibodies against glutamic acid decarboxylase (GAD) 65. The immune response against glatiramer acetate (GA) may circumvent the second obstacle. Migration of activated T helper cells to the intrathecal compartment could be a common denominator in GA treatment and SPS.

RESULTS

We here discuss recent results on T cells in MS and SPS, showing that GAD65-specific and GA-reactive lymphocytes in the cerebrospinal fluid are not a simple reflection of those in blood.

CONCLUSION

The rules and mechanisms governing T cell selection and maintenance in the CNS may provide a key to the understanding of protective and detrimental aspects of CNS immunity.

Paraneoplastic movement disorders

Neurologic paraneoplastic syndromes (NPSs) result from damage to the nervous system due to the remote effects of cancer not related to metastasis, infection, or metabolic derangements. NPSs are rare, affecting 1 in 10,000 patients with cancer. Pathogenesis is likely related to the immune mechanisms: normal neural tissue is mistakenly attacked due to the similarity in the onconeural antigens expressed by the tumor cells. Among the various "classic" and other NPSs, this review focuses on paraneoplastic movement disorders, including ataxia due to cerebellar degeneration, stiff-person syndrome, opsoclonus-myoclonus syndrome, chorea, parkinsonism, and tremor. The recently described syndrome of paraneoplastic anti-N-methyl-D-aspartate receptor encephalitis is also included, given that these patients have complex movements such as stereotypies and dyskinesias in addition to psychiatric symptoms, altered sensorium, and other neurologic signs. Although variable, treatment and prognosis of NPSs rely heavily on treatment of the underlying malignancy and immunotherapy.

Stiff-person syndrome with amphiphysin antibodies: distinctive features of a rare disease

BACKGROUND

Stiff-person syndrome (SPS), formerly Stiff-man syndrome, is a rare autoimmune disease usually exhibiting severe spasms and thoracolumbar stiffness, with very elevated glutamic acid decarboxylase antibodies (GAD Ab). A paraneoplastic variant, less well characterized, is associated with amphiphysin antibodies (amphiphysin Ab). The objective of this study was to identify distinctive clinical features of amphiphysin Ab-associated SPS.

METHODS

Records associated with 845 sera tested in the Yale SPS project were examined, and 621 patients with clinically suspected SPS were included in the study. Clinical characteristics were assessed with correction for multiple comparisons.

RESULTS

In all, 116 patients had GAD antibodies and 11 patients had amphiphysin Ab; some clinical information was available for 112 and 11 of these patients, respectively. Patients with amphiphysin Ab-associated SPS were exclusively female; mean age was 60. All except one had breast cancer; none had diabetes. Compared to patients with GAD Ab-associated SPS, those with amphiphysin Ab were older (p = 0.02) and showed a dramatically different stiffness pattern (p < 0.0000001) with cervical involvement more likely, p < or = 0.001. Electromyography showed continuous motor unit activity or was reported positive in eight. Benzodiazepines at high dose (average 50 mg/day diazepam) were partially effective. Four patients were steroid responsive and tumor excision with chemotherapy produced marked clinical improvement in three of five patients.

CONCLUSIONS

Amphiphysin Ab-associated stiff-person syndrome is strongly associated with cervical region stiffness, female sex, breast cancer, advanced age, EMG abnormalities, and benzodiazepine responsiveness. The condition may respond to steroids and can dramatically improve with cancer treatment.

BAR the door: cancer suppression by amphiphysin-like genes

The evolutionarily conserved amphiphysin-like genes Bin1 and Bin3 function in membrane and actin dynamics, cell polarity, and stress signaling. Recent genetic studies in mice discriminate non-essential roles in endocytic processes commonly ascribed to amphiphysins from essential roles in cancer suppression. Bin1 acts in default pathways of apoptosis and senescence that are triggered by the Myc and Raf oncogenes in primary cells, and Bin1 gene products display a 'moonlighting function' in the nucleus where a variety of other 'endocytic' proteins are also found. Together, genetic investigations in yeast, flies, and mice suggest that amphiphysin-like adapter proteins may suppress cancer by helping integrate cell polarity signals generated by actin and vesicle dynamics with central regulators of cell cycle arrest, apoptosis, and immune surveillance.

Advances in the pathogenesis and treatment of patients with stiff person syndrome

Advances in the clinical diagnosis, prognosis, pathogenesis, and therapies for stiff person syndrome (SPS), based on observations in more than 50 consecutive patients, are presented. The syndrome varies from mild to severe, but if untreated it can be progressive and disabling. SPS remains a largely underdiagnosed condition. Anti-glutamic acid decarboxylase (GAD) antibodies provide an excellent diagnostic marker, but their role in disease pathogenesis is uncertain. Research focused on identifying new autoantigens has provided evidence that gamma-aminobutyric acid (GABA)(A) receptor-associated protein (GABARAP), a 14-kD protein localized at the postsynaptic regions of GABAergic synapses, is a new antigenic target. In up to 65% of SPS patients, there are circulating anti-GABARAP antibodies that inhibit the GABA(A) receptor expression on GABAergic neurons. This review examines the diagnostic criteria for SPS, SPS variants, common errors in diagnosis, and a step-by-step therapeutic approach, including new advances in therapy.

Quantification of antineural antibodies in autoimmune neurological disorders

More than 50 different neurological pathologies have a confirmed or suspected autoimmune etiology affecting an estimated number of 75 million people worldwide. Autoantibodies are a useful diagnostic marker for most autoimmune diseases even though their pathological role is not evident, and several tests for their detection are commercially available. However, for autoimmune diseases involving the nervous system, lack of clear information on the identity of antineural antibody targets and the presence of many rare diseases have hampered the development of specific diagnostic assays. This review focuses on the actual knowledge on confirmed and suspected autoimmune diseases that target the CNS and the diagnostic relevance of corresponding antineural autoantibodies.

Paraneoplastic neurological syndromes and onconeural antibodies: clinical and immunological aspects

Paraneoplastic neurological syndromes (PNS) are infrequent disorders that are associated with cancer. The syndromes are highly heterogeneous and often affect several areas of the nervous system. Among the most well-known syndromes are paraneoplastic encephalomyelitis, cerebellar degeneration, sensory neuronopathy, and Lambert-Eaton myastenic syndrome. There are various associated tumors, in particular small cell lung cancer, cancer of the breast and ovary, and thymoma. The onset of neurological symptoms often precedes the cancer diagnosis, and the recognition of a paraneoplastic syndrome should lead to immediate search for cancer. The etiology of the paraneoplastic syndromes is believed to be autoimmune. Antibodies to onconeural antigens, expressed in the tumor of the affected individual and in normal neurons, are found in many of the patients. These antibodies are useful markers for paraneoplastic etiology. The pathogenesis of the PNS is uncertain, but cellular immune responses are thought to be the main effector mechanism. The cornerstone of therapy is the identification and treatment of the underlying malignancy. In some of the disorders, immunosuppressive therapy is of additional benefit. The prognosis of the different PNS varies depending on the level of affection and the degree of neuronal death.

Antigen-specific oligoclonal bands in cerebrospinal fluid and serum from patients with anti-amphiphysin- and anti-CV2/CRMP5 associated paraneoplastic neurological syndromes

Using isoelectric focusing and affinity blotting employing paraneoplastic recombinant antigens, we investigated cerebrospinal fluid (CSF) and sera from three patients with positive anti-CV2/CRMP5- and one patient with positive anti-amphiphysin serology. CSF and sera were previously adjusted to total IgG concentrations of 20 mg/l. All patients suffered from paraneoplastic neurological syndromes (PNS) with predominant involvement of the central nervous system (CNS). Using affinity blot preloaded with paraneoplastic antigen, we detected in three of four patients more or stronger specific oligoclonal bands (OCB) in the CSF than in the corresponding serum, providing qualitative evidence of antigen specific intrathecal antibody synthesis. These results are in line with previous studies demonstrating specific OCB predominantly in CSF from patients with anti-Hu-, anti-Yo- and anti-Ri-associated PNS, supporting the hypothesis of autoimmunity in the pathogenesis of PNS. One patient harboured extensive anti-amphiphysin specific OCB, although OCB of total IgG could not be detected, indicating a higher sensitivity for detection of intrathecal antibody synthesis of the affinity blot preloaded with the paraneoplastic antigen, compared with investigation of total IgG OCB. These results could have implications concerning pathophysiological autoimmune aspects in other inflammatory diseases of CNS associated with total IgG OCB, provided that the target antigen is known.

Major Cdk5-dependent phosphorylation sites of amphiphysin 1 are implicated in the regulation of the membrane binding and endocytosis

Amphiphysin 1 (amph 1) is an endocytic protein enriched in the nerve terminals that functions in the clathrin-mediated endocytosis. It acts as membrane curvature sensor, a linker of clathrin coat proteins, and an enhancer of dynamin Guanosine Triphosphatase (GTPase) activity. Amph 1 undergoes phosphorylation by cyclin-dependent kinase 5 (Cdk5), at five phosphorylation sites, serine 262, 272, 276, 285, and threonine 310, as determined by mass spectrometry (MS). We show here that Cdk5-dependent phosphorylation of amph 1 is enhanced in the presence of lipid membranes. Analysis by tandem liquid chromatograph MS revealed that the phosphorylation occurs at two phosphorylation sites. The phosphorylation was markedly decreased by mutation either Ser276 or Ser285 of amph 1 to alanine (S276A and S285A). Furthermore, mutation of both sites (S276, 285A) completely eliminated the phosphorylation. Functional studies indicated that binding of amph 1 to lipid membrane was attenuated by Cdk5-dependent phosphorylation of wild type amph 1, but not of the S276, 285A form. Interestingly, endocytosis was increased in rat pheochromocytoma cells expressing amph 1 S276, 285A in comparison with wild type. These results suggest that Ser276 and Ser285 are regulatory Cdk5 phosphorylation sites of amph 1 in the lipid-bound state. Phosphorylation at these sites alters binding of amph 1 to lipid membranes, and may be an important regulatory aspect in the regulation of synaptic vesicle endocytosis.

Rigidity and spasms from autoimmune encephalomyelopathies: stiff-person syndrome

Stiff-person syndrome (SPS) is a disorder characterized by progressive muscle rigidity with superimposed painful muscle spasms and gait impairment due to continuous motor activity. Evidence has accumulated in favor of SPS representing an autoimmune, predominantly encephalomyelopathic disorder resulting from B-cell-mediated clonal production of autoantibodies against presynaptic inhibitory epitopes on the enzyme glutamic acid decarboxylase (GAD) and the synaptic membrane protein amphiphysin. Recognition of the clinical spectrum of SPS is important, particularly the upper-limb, cervical, and cranial nerve involvement that occurs in paraneoplastic variants. The correlation between antibody levels and severity of disease offers evidence for a pathogenic role for the anti-GAD and anti-amphiphysin autoantibodies. The scarcity of neuropathological correlates stand in sharp contrast with the severity of the disability in affected individuals and suggests that functional impairment of inhibitory circuits without structural damage is sufficient to develop the full clinical spectrum of SPS. The rarity of this condition limits the feasibility of controlled clinical trials in the treatment of SPS, but the available evidence suggest that drugs that increase cortical and spinal inhibition such as benzodiazepines and drugs that provide immune modulation such as intravenous immunoglobulin, plasmapheresis, and prednisone are effective treatments.

Cell biology of membrane trafficking in human disease

Understanding the molecular and cellular mechanisms underlying membrane traffic pathways is crucial to the treatment and cure of human disease. Various human diseases caused by changes in cellular homeostasis arise through a single gene mutation(s) resulting in compromised membrane trafficking. Many pathogenic agents such as viruses, bacteria, or parasites have evolved mechanisms to subvert the host cell response to infection, or have hijacked cellular mechanisms to proliferate and ensure pathogen survival. Understanding the consequence of genetic mutations or pathogenic infection on membrane traffic has also enabled greater understanding of the interactions between organisms and the surrounding environment. This review focuses on human genetic defects and molecular mechanisms that underlie eukaryote exocytosis and endocytosis and current and future prospects for alleviation of a variety of human diseases.

Antiamphiphysin-positive stiff-person syndrome associated with small cell lung cancer

The paraneoplastic amphiphysin(+) stiff-person syndrome (SPS) has so far only been described in women with breast adenocarcinoma. Here, we describe the rare case of a female patient with antiamphiphysin(+) SPS due to small cell cancer of the lung.

The BAR domain proteins: molding membranes in fission, fusion, and phagy

The Bin1/amphiphysin/Rvs167 (BAR) domain proteins are a ubiquitous protein family. Genes encoding members of this family have not yet been found in the genomes of prokaryotes, but within eukaryotes, BAR domain proteins are found universally from unicellular eukaryotes such as yeast through to plants, insects, and vertebrates. BAR domain proteins share an N-terminal BAR domain with a high propensity to adopt alpha-helical structure and engage in coiled-coil interactions with other proteins. BAR domain proteins are implicated in processes as fundamental and diverse as fission of synaptic vesicles, cell polarity, endocytosis, regulation of the actin cytoskeleton, transcriptional repression, cell-cell fusion, signal transduction, apoptosis, secretory vesicle fusion, excitation-contraction coupling, learning and memory, tissue differentiation, ion flux across membranes, and tumor suppression. What has been lacking is a molecular understanding of the role of the BAR domain protein in each process. The three-dimensional structure of the BAR domain has now been determined and valuable insight has been gained in understanding the interactions of BAR domains with membranes. The cellular roles of BAR domain proteins, characterized over the past decade in cells as distinct as yeasts, neurons, and myocytes, can now be understood in terms of a fundamental molecular function of all BAR domain proteins: to sense membrane curvature, to bind GTPases, and to mold a diversity of cellular membranes.

Current therapies for neuromuscular manifestations of paraneoplastic syndromes

The neuromuscular manifestations of paraneoplastic disorders result in diverse syndromes that may also occur in patients without cancer. In general, treatment of these disorders is the same whether or not there is an underlying malignancy. However, when the disorder is believed to be paraneoplastic, the main concern should be prompt detection and treatment of the tumor, as this has been shown to offer the best chance for neurologic stabilization or improvement. The paraneoplastic neuromuscular disorders can be divided into two main categories: those that are directly mediated by antibodies and those that are believed to result from other immune-mediated mechanisms, including cytotoxic T-cell responses with or without association with specific antibodies. For disorders in which the antibodies are pathogenic, therapy is aimed at removing the antibodies. For the other disorders, adjuvant therapies are for the most part empiric and include a variety of immunosuppressant and immunomodulatory agents.

A novel link between a rab GTPase and Rvs proteins: the yeast amphiphysin homologues

The BAR proteins are a well-conserved family of proteins including Rvsp in yeast, amphiphysins and Bin proteins in mammals. In yeast, as in mammals, BAR proteins are known to be implicated in vesicular traffic. The Gyp5p (Ypl249p) and Ymr192p proteins interact in two-hybrid tests with both Rvs161p and Rvs167p. Gyp5p is a Ypt/Rab-specific GAP and Ymr192p is highly similar to Gyp5p. To specify the interaction between Rvsp and Gyp5p, we used two-hybrid tests to determine the domains necessary for these interactions. The specific SH3 domain of Rvs167p interacted with the N-terminal domain of Gyp5p. Moreover, Gyp5p could form a homodimer. Fus2 protein is a specific partner of Rvs161p in two-hybrid tests. To characterize the functional relationships between these five proteins, we have studied cellular phenotypes in single, double and triple mutant strains for which rvs mutants present defects, such as polarity, cell fusion and meiosis. Phenotypic analysis showed that Gyp5p, Ymr192p and Fus2p were involved in bipolar budding pattern and in meiosis. Specific epistasis or suppressive phenomena were found between the five mutations. Finally, The Gyp5p-GFP fusion protein was localized at the bud tip during apical growth and at the mother-bud neck during cytokinesis. Moreover, Rvs167p and Rvs161p were shown to be essential for the correct localization of Gyp5p. Altogether, these data support the hypothesis that both Rvsp proteins act in vesicular traffic through physical and functional interactions with Ypt/Rab regulators.

Amphiphysin autoimmunity: paraneoplastic accompaniments

Amphiphysin-IgG was identified in 71 patients among 120,000 evaluated serologically for paraneoplastic autoantibodies. Clinical information was available for 63 patients. Cancer was detected in 50 (mostly limited), proven histologically in 46, and was imaged intrathoracically in 4 patients (lung, small-cell [27] and non-small cell [1]), breast [16] and melanoma [2]). Neurological accompaniments included (decreasing frequency): neuropathy, encephalopathy, myelopathy, stiff-man phenomena, and cerebellar syndrome. In a case examined neuropathologically, parenchymal T-lymphocyte infiltration (predominantly CD8(+)) was prominent in lower brainstem, spinal cord, and dorsal root ganglion. Coexisting paraneoplastic autoantibodies, identified in 74% of patients, predicted a common neoplasm and indicated other neuronal autoantigen targets that plausibly explained several neurological manifestations; for example, P/Q-type Ca(2+)-channel antibody with Lambert-Eaton syndrome (n = 5), anti-neuronal nuclear antibody type 1 with sensory neuronopathy (n = 7), K(+)-channel antibody with limbic encephalitis (n = 1) or neuromyotonia (n = 1), and collapsin response-mediator protein-5-IgG with optic neuritis (n = 3). Patients with isolated amphiphysin-IgG (n = 19) were more likely to be women (with breast cancer, p < 0.05) and to have myelopathy or stiff-man phenomena (p < 0.01). Overall, a minority of women (39%) and men (12%) had stiff-man phenomena. Only 10% of women (some with lung carcinoma) and 4% of men fulfilled diagnostic criteria for stiff-man syndrome.

Graves’ Disease and Stiff-Person (Stiff-Man) Syndrome: Case Report and Literature Review

OBJECTIVE

To report an association between two autoimmune conditions, Graves' disease and stiff-person (stiff-man) syndrome, and discuss the relevant literature.

METHODS

We present a case of a 52-year-old white woman with stiff-person syndrome who also had Graves' disease, discuss her management, and review the related literature. Pertinent published reports from 1950 through 2004 were researched with use of MEDLINE and PubMed, and cross-references to other articles were reviewed.

RESULTS

A 52-year-old white woman presented with symptoms of hyperthyroidism due to Graves' disease. Laboratory data were as follows: thyrotropin <0.005 m IU/mL, thyroxine 11.1 microg/dL, free thyroxine index (FTI) 10.7, and triiodothyronine 170 ng/dL. Thyroid-stimulating immunoglobulins (TSI) and thyrotropin-binding inhibitory immunoglobulins (TBII) were positive at 1,986% and 82.5 U/L, respectively. The hyperthyroidism was treated with propranolol. She had a long-standing history of musculoskeletal complaints and was ultimately diagnosed with stiff-person syndrome. During her thyroid evaluation, she had severe neurologic deterioration that necessitated hospitalization and treatment with clonazepam, baclofen, intravenous immunoglobulin, and subsequently prednisone and azathioprine for appreciable symptomatic relief. The aggressive immunosuppression had a profound effect on her symptoms of hyperthyroidism, results of thyroid function tests, and thyrotropin receptor antibodies (TRABs). Thyrotropin was 0.52 microIU/mL, thyroxine was 6.9 microg/dL, and FTI was 5.7. The TSI decreased from 1,986% to 248%, and her TBII normalized from 82.5 U/L to <5 U/L. She was clinically and biochemically euthyroid at last follow-up in May 2004.

CONCLUSION

This case illustrates the association between TRAB-positive Graves' disease and stiff-person syndrome and the improvement of Graves' disease with immunosuppressive therapy.

Neuroimmunology of the paraneoplastic neurological degenerations

The paraneoplastic neurological degenerations (PNDs) are remarkable examples of naturally occurring tumor immunity in humans. In PND patients, common tumors such as breast, ovarian and lung tumors express proteins normally made exclusively in the brain, eliciting an immune response that successfully suppresses growth of the tumor. This successful anti-tumor response would be expected to go clinically unnoticed by the patient, but the immune cells mediating the response somehow cross into the brain, resulting in an autoimmune attack on neurons and neurological symptoms. Pieces of the mystery of this tumor immune response and neuronal autoimmunity have been assembled, but much more needs to be learned.

The pathobiology of the septin gene family

Septins are an evolutionarily conserved group of GTP-binding and filament-forming proteins that belong to the large superclass of P-loop GTPases. While originally discovered in yeast as cell division cycle mutants with cytokinesis defects, they are now known to have diverse cellular roles which include polarity determination, cytoskeletal reorganization, membrane dynamics, vesicle trafficking, and exocytosis. Septin proteins form homo- and hetero-oligomeric polymers which can assemble into higher-order filaments. They are also known to interact with components of the cytoskeleton, ie actin and tubulin. The precise role of GTP binding is not clear but a current model suggests that it is associated with conformational changes which alter binding to other proteins. There are at least 12 human septin genes, and although information on expression patterns is limited, most undergo complex alternative splicing with some degree of tissue specificity. Nevertheless, an increasing body of data implicates the septin family in the pathogenesis of diverse disease states including neoplasia, neurodegenerative conditions, and infections. Here the known biochemical properties of mammalian septins are reviewed in the light of the data from yeast and other model organisms. The data implicating septins in human disease are considered and a model linking these data is proposed. It is posited that septins can act as regulatable scaffolds where the stoichiometry of septin associations, modifications, GTP status, and the interactions with other proteins allow the regulation of key cellular processes including polarity determination. Derangements of such septin scaffolds thus explain the role of septins in disease states.

Reduction in levels of amphiphysin 1 mRNA in the hippocampus of aged rats subjected to repeated variable stress

Various neurobiological studies of aging indicate that elevated levels of circulating glucocorticoids lead to hippocampal vulnerability to stress, though little is known about the molecular mechanism underlying stress vulnerability in the elderly. We have compared the gene expression profiles in the hippocampus of aged (20 months) and adult (3 months) rats in response to repeated variable stress (RVS) for 4 days, using a cDNA array technique and real-time quantitative PCR, to identify putative genes involved in the mechanism of stress vulnerability in the elderly. We found a significant decrease in the levels of amphiphysin 1 mRNA in aged rats subjected to RVS compared with treated and untreated adult rats or to untreated aged rats. Similarly, we found a significant decrease in hippocampal levels of amphiphysin 1 mRNA in aged rats subjected to RVS for 8 days, but not in those subjected to a single VS. These findings suggest that the decrease in the hippocampal levels of amphiphysin 1 mRNA in response to repeated stress may be involved in the stress vulnerability in the elderly, and may lead to the disturbance of learning and memory under stressful conditions in the elderly.

Autoantibody testing

Recent advances in neuroimmunology have led to improvements in the pathogenesis, diagnosis, prognosis, and treatment of many neuromuscular disorders. The value of autoantibody testing is increasing steadily in neurologic practice. Not all antibodies have a high yield in diagnosis. In some disorders, such as generalized adult onset of myasthenia gravis, Lambert-Eaton myasthenic syndrome,Miller Fisher syndrome, and multifocal motor neuropathy,autoantibody tests provide accurate diagnosis and can be considered biologic markers of these disorders.

Two distinct interaction motifs in amphiphysin bind two independent sites on the clathrin terminal domain β-propeller

During the assembly of clathrin-coated vesicles, many peripheral membrane proteins, including the amphiphysins, use LLDLD-type clathrin-box motifs to interact with the N-terminal beta-propeller domain (TD) of clathrin. The 2.3 A-resolution structure of the clathrin TD in complex with a TLPWDLWTT peptide from amphiphysin 1 delineates a second clathrin-binding motif, PWXXW (the W box), that binds at a site on the TD remote from the clathrin box-binding site. The presence of both sequence motifs within the unstructured region of the amphiphysins allows them to bind more tightly to free TDs than do other endocytic proteins that contain only clathrin-box motifs. This property, along with the propensity of the N-terminal BAR domain to bind curved membranes, will preferentially localize amphiphysin and its partner, dynamin, to the periphery of invaginated clathrin lattices.

Rhabdomyolysis and paraneoplastic stiff-man syndrome with amphiphysin autoimmunity

Stiff-Man syndrome (SMS) is a rare disease of the central nervous system characterized by chronic muscle rigidity and autoimmunity directed against synaptic antigens. In a subset of patients, generally positive for antiamphiphysin autoantibodies, SMS has an autoimmune paraneoplastic origin. Amphiphysin isoforms are expressed at high levels in brain and skeletal muscle and often are overexpressed in breast cancer. We report here the occurrence of rhabdomyolysis in a patient with SMS, breast cancer, and antibodies that recognize both brain and muscle amphiphysin isoforms. Immunotherapy induced a remission of both rhabdomyolysis and SMS symptoms. Autoimmune rhabdomyolysis may represent a paraneoplastic complication of cancer patients with amphiphysin autoimmunity.