Retrograde transport of dopamine beta-hydroxylase antibodies in sympathetic neurons: effects of drugs modifying noradrenergic transmission

Interactions of noncanonical motifs with hnRNP A2 promote activity-dependent RNA transport in neurons

Ca²⁺-dependent RNA–protein interactions enable activity-inducible RNA transport in dendrites.

A key determinant of neuronal functionality and plasticity is the targeted delivery of select ribonucleic acids (RNAs) to synaptodendritic sites of protein synthesis. In this paper, we ask how dendritic RNA transport can be regulated in a manner that is informed by the cell’s activity status. We describe a molecular mechanism in which inducible interactions of noncanonical RNA motif structures with targeting factor heterogeneous nuclear ribonucleoprotein (hnRNP) A2 form the basis for activity-dependent dendritic RNA targeting. High-affinity interactions between hnRNP A2 and conditional GA-type RNA targeting motifs are critically dependent on elevated Ca²⁺ levels in a narrow concentration range. Dendritic transport of messenger RNAs that carry such GA motifs is inducible by influx of Ca²⁺ through voltage-dependent calcium channels upon β-adrenergic receptor activation. The combined data establish a functional correspondence between Ca²⁺-dependent RNA–protein interactions and activity-inducible RNA transport in dendrites. They also indicate a role of genomic retroposition in the phylogenetic development of RNA targeting competence.

Presence of GAD65 autoantibodies in the serum of children with autism or ADHD

Antibodies against glutamic acid decarboxylase 65 (GAD65) have been detected in the serum of patients with several neurological disorders. The presence of antibodies against GAD65 has not yet been examined in the serum of patients with neurodevelopmental disorders such as autism or attention-deficit/hyperactivity disorder (ADHD). In this study, GAD65 antibodies and total IgG were assayed in the serum of normal subjects and patients diagnosed with autism or ADHD. GAD65 antibodies were detected in the serum of 15% of children with autism (N = 20), 27% of children with ADHD (N = 15) and of none of the controls (N = 14). The serum of 60% of autistic and 53% of ADHD patients reacted with Purkinje neurons in mouse cerebellum. Serum from 20% of ADHD patients reacted also with the cells in the molecular and granule cell layers and cells in the vicinity of the Purkinje neurons. No association was found between the titer of GAD65 antibodies and total IgG levels, and presence of seizures or mental retardation. None of the ADHD patients were diagnosed with mental retardation. Serum anti-GAD65 antibodies may be a common marker of subgroups of patients with autism and ADHD. Reactions of serum antibodies with the cells in the cerebellum in these patients suggest direct effects on brain function. The subgroup of children with autism and ADHD that tests positive for GAD65 antibodies needs further characterization in a larger study.

An immunological basis of hyperphagia driven by GABAergic dysfunction in Prader-Willi Syndrome

Impaired immune function is increasingly seen as a core element of various neurological, psychiatric, and developmental disorders but has not yet been investigated in subjects with Prader-Willi Syndrome. We hypothesize that the emergence and the progression of PWS may be regulated by immune dysfunction involving auto-antibodies and miRNA driven by GABAergic dysfunction. Future research testing this hypothesis is discussed.

Retrograde Axonal Transport of Dopamine Beta Hydroxylase Antibodies by Neurons in the Trigeminal Ganglion

In this study we describe a population of neurons in the adult rat trigeminal ganglion (TG) that express dopamine beta-hydroxylase (DBH) and tyrosine hydroxylase (TH), and transport anti-DBH from their terminals. We have used NGF and NT3 labeled with biotin and anti-p75NTR labeled with FITC to examine the transport of neurotrophins and their receptors by these cells. In both the superior cervical ganglion (SCG) and the TG all neurons that transported anti-DBH transported NGF. While 100% of the DBH positive neurons in the TG also transported NT3, approximately 25% of these neurons in the SCG failed to transport NT3. In the SCG virtually all the neurons transported anti-p75NTR with the neurotrophins while in the TG more than 25% of these neurons failed to transport anti-p75NTR with the neurotrophins. These findings suggest that DBH positive neurons in the TG depend upon target-derived NGF and NT3 for their noradrenergic phenotype.

The immunological impairment of arcuate neuropeptide Y neurons by ricin A chain produces persistent decrease of food intake and body weight

Neuropeptide Y is demonstrated as a potent orexigenic peptide when injected into the rat hypothalamic paraventricular nuclei. The neuropeptide Y innervation of paraventricular nuclei originates from both hypothalamic arcuate nuclei and brainstem neurons, whose specific role in the control of food intake is still under discussion. To assess the role of the arcuate neuropeptide Y in the regulation of food intake, we propose a new method for immunologically impairing the neuronal secretion of neuropeptide Y from a unique brain site. The monoclonal antibody to the neuropeptide Y precursor epitope, the C-flanking peptide, was microinjected with two cellular toxins (the ricin A chain and the monensin) into the hypothalamic arcuate nuclei or paraventricular nuclei. One microinjection into the arcuate nuclei reduced the food intake and body weight gain for 10 days. It prevented the food intake stimulation usually induced by a 12 h food deprivation. This decrease of food intake was not due to the aversive properties of monoclonal antibody or cellular toxins, or the immunoneutralization of the biologically active neuropeptide Y, because (i) the acute effect of the microinjection into the arcuate nuclei promoted a transient increase of the food intake likely induced by a strong release of neuropeptide Y from the arcuate neurons which were immunologically damaged, and (ii) the C-flanking peptide monoclonal antibody binds neither neuropeptide Y nor its receptors. The microinjection was inefficient when C-flanking peptide monoclonal antibody was replaced by non-specific rat immunoglobulins or when the C-flanking peptide monoclonal antibody/toxins mixture was injected into the paraventricular nuclei. The data bring further arguments in two domains.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of the retrograde axonal transport of dopamine-beta-hydroxylase antibodies by the calcium ionophore A23187

High levels of calcium, as well as calcium ionophores, have been reported to inhibit the anterograde transport of proteins. The effect of the calcium ionophore, A23187, on the retrograde axonal transport of proteins was therefore investigated. The uptake of antibodies to dopamine-beta-hydroxylase (anti-D beta H) by sympathetic nerve terminals in the iris and their subsequent accumulation in the superior cervical ganglion was inhibited by up to 65% by A23187 (6 nmol, i.o.). At this dose, catecholamine fluorescence in the iris was reduced, indicating a high rate of exocytosis, but tyrosine hydroxylase levels and the capacity of the treated irides to take up noradrenaline were unaffected. Higher amounts of A23187 (28 nmol, i.o.) did not cause a greater degree of inhibition of retrograde transport. However, this dose was toxic to the neurons, as shown by a 68% decrease in the ability of the nerve terminals in the iris to take up [3H]noradrenaline. This loss of function occurred gradually over a 12-h period. On the other hand, tyrosine hydroxylase levels were unaffected by 28 nmol A23187. The toxicity of A23187 may be a consequence of a build up in intracellular calcium, but such toxicity did not lead to any apparent loss of nerve terminals within a 3-day period.