Light-Activatable, Cell-Type Specific Labeling of the Nascent Proteome.

Elucidating the mechanisms by which protein synthesis contributes to complex biological processes has remained a challenging endeavor. This is particularly true in the field of neuroscience, where multiple, tightly regulated periods of new protein synthesis in different cell-types are thought to facilitate intricate neurological functions, such as memory formation. Current methods for labeling the de novo proteome have lacked the spatial and temporal resolution to accurately discriminate these overlapping and often competing windows of mRNA translation. To address this technological limitation, here we describe a novel, light-inducible specific method for labeling newly synthesized proteins within a targeted cell-type.By developing Opto-ANL, a photocaged version of the nonendogenous amino acid azidonorleucine (ANL), we can selectively label newly synthesized proteins in specific cell-types through the targeted expression of a mutant methionyl-tRNA synthetase (L274G-MetRS). We demonstrate that Opto-ANL can be rapidly uncaged by UV light treatment in both cell culture and mouse brain slices, with Opto-ANL labeled proteins being able to be visualized via fluorescent noncanonical amino acid tagging. We also reveal that pretreatment with Opto-ANL not only allows for the period of de novo proteomic labeling to be tightly controlled, but also improves labeling efficiency compared to regular ANL. To demonstrate the potential applications of this novel technique, we use Opto-ANL to detect insulin-induced increases in protein synthesis and to label the excitatory neuronal de novo proteome in mouse brain slices. We believe that this application of photopharmacology will allow researchers to generate novel insights into how the translational landscape is altered across cell-types during complex neurological phenomena such as memory formation.

A Photoactivated Protein Degrader for Optical Control of Synaptic Function.

Hundreds of proteins determine the function of synapses, and synapses define the neuronal circuits that subserve myriad brain, cognitive, and behavioral functions. It is thus necessary to precisely manipulate specific proteins at specific sub-cellular locations and times to elucidate the roles of particular proteins and synapses in brain function. We developed PHOtochemically TArgeting Chimeras (PHOTACs) as a strategy to optically degrade specific proteins with high spatial and temporal precision. PHOTACs are small molecules that, upon wavelength-selective illumination, catalyze ubiquitylation and degradation of target proteins through endogenous proteasomes. Here we describe the design and chemical properties of a PHOTAC that targets Ca 2+ /calmodulin-dependent protein kinase II alpha (CaMKIIα), which is abundant and crucial for baseline synaptic function of excitatory neurons. We validate the PHOTAC strategy, showing that the CaMKIIα-PHOTAC is effective in mouse brain tissue. Light activation of CaMKIIα-PHOTAC removed CaMKIIα from regions of the mouse hippocampus only within 25 µm of the illuminated brain surface. The optically-controlled degradation decreases synaptic function within minutes of light activation, measured by the light-initiated attenuation of evoked field excitatory postsynaptic potential (fEPSP) responses to physiological stimulation. The PHOTACs methodology should be broadly applicable to other key proteins implicated in synaptic function, especially for evaluating their precise roles in the maintenance of long-term potentiation and memory within subcellular dendritic domains.

Restoring Light Sensitivity in Blind Retinae Using a Photochromic AMPA Receptor Agonist.

Retinal degenerative diseases can have many possible causes and are currently difficult to treat. As an alternative to therapies that require genetic manipulation or the implantation of electronic devices, photopharmacology has emerged as a viable approach to restore visual responses. Here, we present a new photopharmacological strategy that relies on a photoswitchable excitatory amino acid, ATA. This freely diffusible molecule selectively activates AMPA receptors in a light-dependent fashion. It primarily acts on amacrine and retinal ganglion cells, although a minor effect on bipolar cells has been observed. As such, it complements previous pharmacological approaches based on photochromic channel blockers and increases the potential of photopharmacology in vision restoration.

A red-shifted photochromic sulfonylurea for the remote control of pancreatic beta cell function.

Azobenzene photoresponsive elements can be installed on sulfonylureas, yielding optical control over pancreatic beta cell function and insulin release. An obstacle to such photopharmacological approaches remains the use of ultraviolet-blue illumination. Herein, we synthesize and test a novel yellow light-activated sulfonylurea based on a heterocyclic azobenzene bearing a push-pull system.

Correlations of glutathione peroxidase activity with memory impairment in adults with Down syndrome.

BACKGROUND: Down syndrome (DS) is a genetic disorder (trisomy 21 in 96% of cases), associated with an excess of a key enzyme involved with free radical metabolism (FRM), superoxide dismutase-1 (SOD-1), that is encoded by a gene on chromosome 21. Consequently, SOD-1 activity is elevated in DS, which also occurs in conditions of oxidative stress, and is associated with a compensatory increase in glutathione peroxidase activity (GSHPx). METHODS: This study examined the relationship of memory function with erythrocyte SOD-1, GSHPx and catalase (CAT) activity in 22-51 year old adults with DS. RESULTS: Mean erythrocyte SOD-1 (p < .02) and GSHPx (p < .01), but not CAT (p = .76), activities were significantly greater in the DS group than the controls. In the DS group, erythrocyte GSHPx, but not SOD-1 or CAT activities, was significantly correlated with memory function (r = .625, p < .025, df = 13 for savings score, r = .631, p < .01, df = 14 for intrusion errors) but not with intelligence quotients. CONCLUSIONS: These observations suggest a possible relationship between altered FRM with memory deficits among adults with DS within the age-range in that an age-related increase in the prevalence for Alzheimer's neuropathology is known to be robust before reaching a plateau of 100%.

Olivopontocerebellar atrophy with dementia, blindness, and chorea. Response to baclofen.

Olivopontocerebellar atrophy is a hereditary disorder that has variable clinical manifestations. Five types have been described, as well as a sixth that contains sporadic cases. This report describes a family with three affected members who demonstrate a composite of types III and V. Their features include progressive spasticity, ataxia, dementia, visual loss with retinal pigmentation, dysarthria, ophthalmoplegia, and chorea. This family might represent an additional category of the disease. In the two family members who developed chorea, baclofen resulted in marked improvement with abolition of the choreiform movements. Response has been sustained for several years in the mother and for eight months in the daughter. Neither has experienced any return of chorea while receiving treatment. When attempts were made to discontinue baclofen, choreiform movements returned promptly and with their original severity. Baclofen, a gamma-aminobutyric acid analogue, may be useful in the treatment of other forms of chorea as well.

Detection of urea cycle enzymopathies in childhood.

Inborn errors of ureagenesis must be considered in the differential diagnosis of recurrent vomiting and lethargy in childhood. Elevations of liver enzyme levels are often present during these episodes and may lead to an erroneous diagnosis of hepatic encephalopathy. We studied two cases of urea cycle defects.

EEG correlations with biochemical abnormalities in Reye syndrome.

A patient with Reye syndrome was studied throughout the course of the illness with continuous EEG monitoring, and these patterns were correlated with serial determinations of serum ammonia and short-chain fatty acid concentrations. There was high correlation between degree of EEG abnormality, clinical symptoms, and elevations of the short-chain fatty acids, while serum ammonia concentrations correlated poorly with the EEG and with the clinical state.

Neurophysiologic studies of the peripheral nervous system in nephropathic cystinosis.

Cystinosis is an autosomal recessive metabolic disorder in which nonprotein cystine accumulates within most body tissues due to a defect in lysosomal cystine transport. Neurologic declarations are only recently being recognized. We studied 13 cystinotic subjects (aged 5 to 21 years old), determining median motor and sensory nerve conduction velocities, F waves, peroneal motor nerve conduction velocities, sural sensory nerve conduction velocities, median sympathetic skin response, electrocardiogram R-to-R variability, and blink reflex analysis. The results were normal. We conclude that neurophysiologic testing suggests relative sparing of the peripheral nervous system in nephropathic cystinosis.

Medium-chain triglyceride (MCT) diet in intractable seizure disorders.

Seventeen patients with intractable seizures have been treated with the medium-chain triglyceride (MCT) diet. All had frequent (often daily) seizures despite multiple medications. Age range was 12 months to 13 years. Types of seizures included myoclonic, akinetic, focal motor, atypical absence, generalized tonic, and tonic-clonic. Five patients achieved total seizure control, and anticonvulsants were decreased or stopped. Five others had some improvement in seizure control. No change was seen in two. In two cases, parents could not deal with the diet, even though total control had been achieved in one case. The diet had to be discontinued in three others because of side effects (diarrhea, vomiting, irritability). Intractable seizures of all types may respond to treatment with the MCT diet. This mode of therapy has few side effects, is tolerated well in most instances, and can result in reduction or discontinuation of anticonvulsant medications.

Short chain fatty acid-induced central hyperventilation in rabbits.

The short chain fatty acid sodium octanoate was infused into rabbits as an 0.2 M solution over 4 hours, resulting in blood and brain levels of 200 to 700 mumoles per liter. During the infusion, animals exhibited marked hyperventilation, resulting in a mild respiratory alkalosis. Octanoate infusion also resulted in significant hyperammonemia and lactic acidemia. Saline-treated control animals demonstrated no clinical or chemical abnormalities. Several short chain fatty acids, including octanoate, are increased in the plasma of patients with hepatic encephalopathies and Reye syndrome. The present study suggests that short chain fatty acids may be endogenous toxins in these clinical disorders. In particular, the central hyperventilation in these conditions may be due to the neurotoxic effect of short chain fatty acids.

Inhibition of fatty acid beta oxidation by influenza B virus and salicylic acid in mice: implications for Reye's syndrome.

Injection of concentrated influenza B/Lee/40 virus into 4-week-old Balb C mice resulted in 60% inhibition of 14C-palmitate oxidation in isolated hepatic mitochondria. Oral feeding of carnitine to infected mice prevented the inhibition of fatty acid oxidation. High concentrations of salicylic acid given orally also inhibited 14C-palmitate oxidation. Serum free fatty acid concentrations of infected mice and of those fed salicylic acid were significantly higher than in control mice. A combination of low-dose virus and low-dose salicylic acid inhibited palmitate oxidation, suggesting an additive effect on the metabolic derangement when the two agents were present simultaneously.

Short-chain organic acidemia and Reye's syndrome.

Short-chain fatty acids were determined prior to therapy in seven patients with Reye's syndrome. Elevated concentrations of propionate, butyrate, and isobutyrate were found in all patients. Isovalerate concentrations were high in three patients. In view of the fact that the administration of certain short-chain fatty acids to experimental animals results in coma, electroencephalographic changes, and fatty accumulation in the viscera, the elevations of short-chain fatty acid concentrations observed in the present study suggest that these fatty acids may play a role in the clinical manifestations of Reye's syndrome.

Cognitive impairment in adults with Down's syndrome: similarities to early cognitive changes in Alzheimer's disease.

Postmortem studies of brains from adults with Down's syndrome (DS) reveal a dramatic age-dependent increase in the incidence of neuropathology associated with Alzheimer's disease (AD). By the age of 40 years, virtually all DS individuals have AD neuropathology. Documentation of cognitive correlates of this phenomenon has been difficult, partly because of the preexisting mental retardation in DS. In the current study, we compared a group of adults with DS, 22 to 51 years old, with a matched control group on various behavioral measures such as savings scores, which are known to be sensitive in detecting early dementia in AD patients. By using the short delayed savings score from the California Verbal Learning Test (a test of verbal memory), a subgroup of DS adults was identified as memory-impaired. This group demonstrated a decline in performance on various other cognitive tests with advancing age, whereas another group identified as having non-memory-impaired DS, and the non-DS controls, showed no evidence of decline with age. These results provide evidence for the presence of early dementia among adults with DS within an age range in which neuropathologic manifestations of AD are predicted to be developing.

The development of drawing in children with congenital focal brain injury: evidence for limited functional recovery.

Children with pre- or perinatal injury to right hemisphere (RH) brain regions show impairment of spatial integrative functions similar to that observed among adults with comparable injury. Unlike adults, children show considerable improvement with development on a range of spatial construction tasks which require spatial integration. Such gains could reflect true recovery of spatial integrative abilities. Alternatively, the improvement could be more limited in scope, reflecting the development of compensatory strategies which are task specific and allow the children to circumvent, rather than overcome, their primary spatial disorders. The studies presented here examined this distinction within the context of drawing tasks in which the child was first asked to draw a house and then an impossible house. The impossible house task was designed to examine the extent to which children rely on graphic formulas in generating organized drawings. The results showed that while all of the children with RH injury make considerable progress in free drawing into the school age period, they are very reliant on the use of graphic formulas. When given a task which requires them to alter their drawings, they did not change the spatial configuration of the depicted object. Rather they found alternate ways to render the object 'impossible'.

Affective facial expression in infants with focal brain damage.

Children are fluent affective communicators by their first birthday. The development of affective facial expression in infants with focal brain damage thus provides a promising context in which to investigate the developing neural substrates of emotions. We examined both positive and negative affective expression in 12 infants (6-24 months) with pre- or perinatal unilateral focal brain damage (6RHD and 6LHD) and their age- and gender-matched controls. Infants were videotaped in free and semi-structured tasks. Interactions were microanalytically coded, including the use of FACS. Both normal and babies with posterior LHD exhibited the full range of appropriate affective expressions. In contrast, infants with posterior RHD showed marked affective impairment to positive, but not to negative simulation.

Reye's syndrome in infancy.

Reye's syndrome in infancy is not a well-defined entity and is infrequently diagnosed. Eight infants 6 months of age or younger had a prodromal viral illness followed by the rapid onset of lethargy, seizures, and coma, resulting in the diagnosis of Reye's syndrome. All had abnormal results of liver function tests including elevations of blood ammonia level. Three patients had pathological studies that confirmed fatty visceral infiltration. The data on these patients, as well as a review of the literature, indicate that the most prominent clinical findings in Reye's syndrome in infancy include marked respiratory abnormalities with tachypnea and apneic episodes; frequent occurrence of seizures in the early stages of the illness; and hypoglycemia in most cases. A strong socioeconomic bias was noted in these patients, with the infants coming primarily from lower socioeconomic, urban environments, while older children with Reye's syndrome have been observed to be predominantly middle-class and from suburban or rural areas.

Accumulation of aluminum in a nondialyzed uremic child receiving aluminum hydroxide.

A child with renal insufficiency was treated with the oral phosphate binder aluminum hydroxide from age 6 to 31 months. The prescribed dose of elemental aluminum varied from 31 to 108 mg/kg/d. Concurrently the patient developed vitamin D-resistant osteomalacia which failed to improve with parathyroidectomy. Encephalopathy with myoclonic seizures, loss of speech, and motor impairment also occurred. Serum and bone aluminum levels were elevated at 334 micrograms/L (normal 7 +/- 3 micrograms/L) and 156 mg/kg (normal 3.3 +/- 2.9 mg/kg), respectively. This case demonstrates that aluminum may accumulate in tissue of children receiving oral aluminum hydroxide. The accumulation of aluminum may have contributed to the vitamin D-resistant osteomalacia and the encephalopathy in this patient. Children receiving aluminum-containing antacids as phosphate binders should be monitored for aluminum accumulation and signs of aluminum intoxication.

Global intellectual deficits in cystinosis.

Fourteen families of children with infantile nephropathic cystinosis were evaluated using the Stanford-Binet Intelligence Scale, Fourth Edition [Thorndike et al., 1986: Stanford-Binet Intelligence Scale, Fourth Ed.]. The IQs of 15 children with cystinosis, their 23 sibs and 24 parents were compared in order to evaluate a potential effect of cystinosis on intelligence. Children with cystinosis had a significantly lower mean IQ than their sibs and their parents (P = .001). Thus, even though the mean IQ of the children with cystinosis (94.4 +/- 10) was within the average range, there is evidence that these children have a mild global intellectual deficit relative to their expected IQ based upon the IQs of other relatives. In addition, to a subset of the subjects we administered a measure of scholastic ability, the Wide Range Achievement Test-Revised [Jastak and Wilkinson, 1984: The Wide Range Achievement Test-Revised], which consists of spelling, reading, and arithmetic subtests. The 11 cystinosis subjects scored significantly lower (P = .01) than their 16 sibs and their 14 parents in the area of spelling, whereas they did not significantly differ in their performance in the areas of reading and arithmetic.

Academic achievement in individuals with infantile nephropathic cystinosis.

The present study examined academic skills in children and young adults with infantile nephropathic cystinosis. Cystinosis is a genetic metabolic disorder in which the amino acid cystine accumulates in various tissues and organs, including the kidney, cornea, thyroid, and brain. Individuals with cystinosis have normal intelligence but subtle visual processing impairments. Subjects were 19 children and young adults with cystinosis and 19 age-, sex-, and IQ-matched controls. All subjects had IQs within the normal range. On a test of academic achievement, mean standard scores for cystinosis and control subjects, respectively, were as follows: arithmetic 89.95 +/- 13.77 vs. 102.16 +/- 9.62; spelling 90.68 +/- 18.81 vs. 98.00 +/- 10.96; reading 97.47 +/- 15.59 vs. 98.58 +/- 12.41. Multivariate analysis of variance revealed a significant main effect for Group (P = .009); there was no main effect for Sex, nor was there a Group x Sex interaction. Univariate follow-up tests indicated that the cystinosis group performed significantly more poorly than did controls on the arithmetic subtest (P = .001) and that there was a trend (P = .085) toward poorer performance by the cystinosis group on the spelling subtest. Regression analyses revealed no evidence of a developmental lag or deterioration of function with age. The visual processing deficits previously identified in these individuals may underlie the academic difficulties observed here. It is possible that both visual processing and academic difficulties may reflect a common mechanism of selective cortical damage by this genetic defect.