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R B Darnell

Publications and source records attributed to R B Darnell.

14 recordsLinked to original sources
PubMed1996

Onconeural antigens and the paraneoplastic neurologic disorders: at the intersection of cancer, immunity, and the brain.

Paraneoplastic neurologic disorders (PNDs) are believed to be autoimmune neuronal degenerations that develop in some patients with systemic cancer. A series of genes encoding previously undiscovered neuronal proteins have been cloned using antiserum from PND patients. Identification of these onconeural antigens suggests a reclassification of the disorders into four groups: those in which neuromuscular junction proteins, nerve terminal/vesicle-associated proteins, neuronal RNA binding proteins, or neuronal signal-transduction proteins serve as target antigens. This review considers insights into basic neurobiology, tumor immunology, and autoimmune neuronal degeneration offered by the characterization of the onconeural antigens.

Antigens, Neoplasm↗
PubMed1996

The onconeural antigen Nova-1 is a neuron-specific RNA-binding protein, the activity of which is inhibited by paraneoplastic antibodies.

Nova-1, a protein expressed in tumors and neurons, is a target antigen in a human paraneoplastic motor disorder [paraneoplastic opsoclonus-myoclonus ataxia (POMA)]. We evaluated the relationship between the function of Nova-1 and its role as a disease antigen. We show that Nova-1 is a neuron-specific RNA-binding protein with sequence and functional similarities to FMR-1. Nova-1 mRNA is restricted to the subcortical nervous system, and the protein binds to RNA with high affinity. Nova-1 KH domains mediate this RNA binding, and point mutations within them abrogate binding. POMA disease antisera (6/6) recognize the third KH domain but not an inactive point mutant, and affinity-purified antibody blocks Nova-1 RNA binding. Thus, a cardinal feature of POMA is the production of antibodies that inhibit Nova-1-RNA interactions, suggesting such inhibition may cause the neurological disease.

Amino Acid Sequence↗
PubMed1996

A novel adaptor-related protein complex.

Coat proteins are required for the budding of the transport vesicles that mediate membrane traffic pathways, but for many pathways such proteins pathways, but for many pathways such proteins have not yet been identified. We have raised antibodies against p47, a homologue of the medium chains of the adaptor complexes of clathrin-coated vesicles (Pevsner, J., W. Volknandt, B.R. Wong, and R.H. Scheller. 1994. Gene (Amst.). 146:279-283), to determine whether this protein might be a component of a new type of coat. p47 coimmunoprecipitates with three other proteins: two unknown proteins of 160 and 25 kD, and beta-NAP, a homologue of the beta/beta'-adaptins, indicating that it is a subunit of an adaptor-like heterotetrameric complex. However, p47 is not enriched in preparations of clathrin-coated vesicles. Recruitment of the p47-containing complex onto cell membranes is stimulated by GTP gamma S and blocked by brefeldin A, indicating that, like other coat proteins, its membrane association is regulated by an ARF. The newly recruited complex is localized to non-clathrin-coated buds and vesicles associated with the TGN. Endogenous complex in primary cultures of neuronal cells is also localized to the TGN, and in addition, some complex is associated with the plasma membrane. These results indicate that the complex is a component of a novel type of coat that facilitates the budding of vesicles from the TGN, possibly for transporting newly synthesized proteins to the plasma membrane.

Adaptor Protein Complex 3↗
PubMed1995

Beta-NAP, a cerebellar degeneration antigen, is a neuron-specific vesicle coat protein.

We have identified a target antigen in autoimmune cerebellar degeneration, beta-NAP, that is closely related to the beta-adaptin and beta-COP coat proteins. Beta-NAP is a nonclathrin-associated phosphoprotein expressed exclusively in neurons, from E12 through adulthood. Beta-NAP is present in the neuronal soma and nerve terminal as soluble and membrane-bound pools and is associated with a discrete set of nerve-terminal vesicles. These results establish beta-NAP as a neuron-specific vesicle coat protein. We propose a model in which beta-NAP mediates vesicle transport between the soma and the axon terminus and suggest that beta-NAP may represent a general class of coat proteins that mediates apical transport in polarized cells.

Adaptor Protein Complex 3↗
PubMed1993

The neuronal nuclear antigen recognized by the human anti-Ri autoantibody is expressed in central but not peripheral nervous system neurons.

Anti-Ri is a human autoantibody that recognizes a neuronal nuclear antigen (Ri). Biotinylated IgG from serum of two patients with high titers of anti-Ri antibodies was used to study the distribution of the Ri antigen in a panel of normal human tissues. the expression of the Ri antigen was evaluated by an avidin-biotin peroxidase technique and confirmed by immunoblotting. The Ri antigen was restricted to the neurons of the central nervous system (CNS) and some pituitary cells. Most neurons in dorsal root, Gasserian and sympathetic ganglia, and myenteric plexus were negative or, a few of them, very weakly positive. The functional implication of the different expression of the Ri antigen between neurons of the central and peripheral nervous system is presently unknown.

Antigens↗
PubMed1993

Regression of small-cell lung carcinoma in patients with paraneoplastic neuronal antibodies.

We describe three patients with known or suspected small-cell lung cancer (SCLC), paraneoplastic neurological syndromes, and antineuronal antibodies who had unusually benign clinical courses. One patient survived 8 years free of disease and was positive for the anti-Hu antibody. A second patient survived 6 years after spontaneous tumour regression and had an atypical antineuronal antibody. A third patient with both the anti-Hu and atypical antineuronal antibody had spontaneous regression of a lung mass. All three patients had a subacute sensory neuropathy. Since paraneoplastic antineuronal antibodies also bind to tumour cells, these cases suggest that some (paraneoplastic) neurological syndromes without identifiable tumour may result from immune-mediated eradication of tumour cells.

Aged↗
PubMed1993

Nova, the paraneoplastic Ri antigen, is homologous to an RNA-binding protein and is specifically expressed in the developing motor system.

Paraneoplastic opsoclonus-ataxia, a disorder of motor control, develops in breast or lung cancer patients who harbor an antibody (Ri) that recognizes their tumors and a nuclear neuronal protein of 55 kd. We have characterized a gene, Nova, encoding an antigen recognized by the Ri antibody. Nova encodes a novel, highly conserved protein, homologous to the RNA-binding protein hnRNP K, the yeast splicing protein MER1, and a motif in several retroviral proteases. Northern blot analysis detects Nova transcripts only in brain, and several alternatively spliced forms are present in brain and tumor cells. Nova expression is restricted to the ventral brain stem and spinal cord in E18 mice. Since Nova encodes a target antigen in the motor disorder paraneoplastic opsoclonus-ataxia that is expressed in the developing subcortical motor system, it is a likely participant in both the pathogenesis of paraneoplastic opsoclonus-ataxia and the developmental biology of the motor system. The homology between Nova and hnRNP K suggests that Nova regulates RNA splicing or metabolism in a specific subset of developing neurons.

Amino Acid Sequence↗
PubMed1993

A novel antineuronal antibody in stiff-man syndrome.

Two-thirds of stiff-man syndrome (SMS) patients harbor an autoantibody specific for a 64-kD species of glutamic acid decarboxylase (GAD), the rate-limiting enzyme in GABA synthesis. We assayed SMS antisera from two patients with SMS for the presence of anti-GAD antibodies using Western blot, immunohistochemical, and enzymatic analyses. Both SMS antisera recognized an 80-kD antigen present in human and rat neuronal extracts, and failed to recognize the 64-kD GAD species. Immunohistochemistry demonstrated neuronal binding identical to that reported with anti-GAD antibodies. Both sera depleted GAD activity from brain extracts. Our analysis indicates that these SMS antisera differ from previously reported SMS antisera by recognizing a novel 80-kD antigen, and suggests that they contain antibodies directed against either a species of GAD different in size from the 64-kD enzyme, or a protein that co-immunoprecipitates with GAD.

Adult↗
PubMed1993

Reversible diencephalic dysfunction: episodic hyperhidrosis due to a trapped third ventricle.

We present a patient with episodic hyperhidrosis (EH) who had 15 attacks per day for 3 years following placement of a lateral ventricular shunt. MRI revealed that she had an isolated third ventricle. Stereotactic shunting of the third ventricle resulted in immediate and complete resolution of her symptoms. We suggest that this patient had periodic rises in third ventricular pressure resulting in episodic diencephalic dysfunction and EH.

Aged↗
PubMed1991

Antiserum from a patient with cerebellar degeneration identifies a novel protein in Purkinje cells, cortical neurons, and neuroectodermal tumors.

The serum and cerebrospinal fluid of a patient (NB) with subacute cerebellar degeneration were found to contain a novel antineuronal autoantibody (anti-Nb). Using this antibody, we have identified and characterized antigens present in a subset of neurons in the CNS and in some neuroectodermal tumor lines. Anti-Nb antibody bound to antigens of Mr 150, 120, and 65 kDa in Western blots using extracts of human cerebellar Purkinje cells or human cerebral cortical neurons. Immunohistochemistry demonstrated relatively specific binding of anti-Nb IgG to Purkinje cells in sections of human cerebellum and to some neocortical neurons, especially those in layer VI. Because of the association of cerebellar degeneration with occult malignancies, we screened a number of tumor cell lines for immunoreactivity to anti-Nb antibody; only tumor lines of neuroectodermal origin (melanoma, small-cell lung cancer, and neuroblastoma) expressed the Nb antigen. Anti-Nb antibody thus identifies neuronal and tumor cell antigens that appear to be unique in size and distribution of expression.

Adult↗
PubMed1985

Differential expression of the human gonadotropin alpha gene in ectopic and eutopic cells.

We have analyzed the regulation of the alpha gonadotropin gene in eutopic placental cells and ectopic tumor cells by constructing a series of plasmid vectors containing alpha genomic 5' flanking DNA placed upstream of the gene encoding the bacterial enzyme chloramphenicol acetyltransferase (CAT). These plasmid DNAs were transfected into a eutopic (JAr) and an ectopic (HeLa) cell line. Both cell types expressed the CAT gene from plasmid constructs containing as much as 1,500 base pairs (bp) and as little as 140 bp of alpha 5' flanking DNA; JAr cells were considerably more efficient than HeLa cells. Ectopic and eutopic cells differed qualitatively in their expression from these alpha-CAT constructs when cells were treated with cAMP or butyrate. Butyrate induced alpha expression in HeLa cells but not in JAr cells, while cAMP induced expression in JAr cells. These results are consistent with and extend previous observations suggesting that there are cell-specific differences in the regulation of alpha gene expression in ectopic and eutopic cells. However, by using deletion constructs of the alpha-CAT gene, we found that the basal expression and cell-specific induction of the alpha gene in ectopic and eutopic cells were dependent on the same 140 bp of alpha 5' flanking DNA. These 140 bp were sequenced and found to contain a 9-bp stretch of DNA homologous with the consensus viral enhancer sequence. Such features of alpha expression common to both ectopic and eutopic cells may be involved in the coordinate expression of the alpha gene and the tumorigenic phenotype observed in each cell type.

Acetyltransferases↗
PubMed1984

Independent regulation by sodium butyrate of gonadotropin alpha gene expression and cell cycle progression in HeLa cells.

Sodium butyrate alters the growth and gene expression of a variety of differentiating and neoplastic cell types. For example, addition of 5 mM butyrate to HeLa cells is reported to both induce gonadotropin alpha subunit biosynthesis and block cell cycling in G1. We have studied these two actions of butyrate on HeLa cells and found that they are regulated in distinct ways. The induction of alpha subunit synthesis was due to an increase in the rate of transcription of the alpha gene. Using synchronized populations of HeLa cells, we determined that butyrate stimulates alpha transcription throughout the cell cycle. In contrast, treated cells arrest in G1 only if exposed to butyrate for a discrete period during the previous S phase. We conclude that butyrate inhibits DNA synthesis through a cell cycle-specific action that is independent from its direct action to stimulate transcription of the gonadotropin alpha gene.

Butyrates↗