Selective effects of LSD and hyperthermia on the synthesis of synaptic proteins and glycoproteins

Heat shock response and homeostatic plasticity

Heat shock response and homeostatic plasticity are mechanisms that afford functional stability to cells in the face of stress. Each mechanism has been investigated independently, but the link between the two has not been extensively explored. We explore this link. The heat shock response enables cells to adapt to stresses such as high temperature, metabolic stress and reduced oxygen levels. This mechanism results from the production of heat shock proteins (HSPs) which maintain normal cellular functions by counteracting the misfolding of cellular proteins. Homeostatic plasticity enables neurons and their target cells to maintain their activity levels around their respective set points in the face of stress or disturbances. This mechanism results from the recruitment of adaptations at synaptic inputs, or at voltage-gated ion channels. In this perspective, we argue that heat shock triggers homeostatic plasticity through the production of HSPs. We also suggest that homeostatic plasticity is a form of neuroprotection.

Effects of the 5-HT2A antagonist mirtazapine in rat models of thermoregulation

Thermoregulation is a complex intercommunicative function requiring coordination between core body temperature (CBT), the central nervous system, and peripheral vasculature. In menopausal women, dysregulation of thermoregulatory mechanisms leads to hot flushes and night sweats. A previous study in ovariectomized (OVX) rats has suggested that mirtazapine can alleviate thermoregulatory dysfunction by blocking 5-HT(2A) receptor signaling. This is in opposition to other work in which 5-HT(2A) receptor blockade appeared to exacerbate thermoregulatory dysfunction in OVX rats. Thus, the goals of the present study were to reexamine the effects of mirtazapine on temperature regulation in OVX rat models and explore further the role of 5-HT(2A) receptor blockade. Mirtazapine exhibited potent functional antagonism (EC(50)=0.62 nM) at the cloned human 5-HT(2A) receptor. In the morphine-dependent model of thermoregulatory dysfunction, mirtazapine (10 mg/kg, i.p.) induced an increase in tail-skin temperature (TST) prior to naloxone administration. In the telemetry model, mirtazapine (0.3-3 mg/kg, i.p.) caused an increase in TST. However, at the highest dose tested (10 mg/kg, i.p.), mirtazapine induced a small but significant decrease in TST followed by an increase in TST. To examine this finding further, mirtazapine's effect on CBT was determined. Administration of mirtazapine (1-3 mg/kg, i.p.) resulted in a slight decrease in CBT but at the 10 mg/kg dose a dramatic decrease (-3.6 degrees C) in CBT was observed. These data support the concept that 5-HT(2A) receptors play a role in temperature regulation but that functional blockade of these receptors by mirtazapine is not a likely mechanism for restoring thermoregulatory processes in OVX rats.

Serotonin 2A receptors modulate tail-skin temperature in two rodent models of estrogen deficiency-related thermoregulatory dysfunction

Menopause-associated thermoregulatory dysfunction, including hot flushes and night sweats, is effectively treated by hormonal therapies that include estrogens. Evidence suggests that estrogen regulates serotonin 2A (5-HT(2A)) receptor expression and that 5-HT(2A) receptors are involved in thermoregulation. Therefore, the role of 5-HT(2A) receptors in thermoregulation was assessed in two rat models of ovariectomy-induced thermoregulatory dysfunction. The first model is based on measurement of the tail-skin temperature (TST) increase following naloxone-induced withdrawal in morphine-dependent ovariectomized (OVX) rats (MD model), while the second model relies on telemetric assessment of diurnal TST changes in ovariectomized rats (telemetry model). Treatment with a 5-HT(2A/2C) receptor agonist, (-)-2,5-dimethoxy-4-iodoamphetamine hydrochloride (DOI), prevented the naloxone-induced TST increase in the MD model and restored normal active-phase TST in the telemetry model. The selective 5-HT(2A) receptor antagonist, MDL-100907, had no effect on the naloxone-induced flush when administered alone in the MD model, but it decreased DOI's ability to abate the flush. In the telemetry model, MDL-100907 attenuated the DOI-induced decrease in active-phase TST. Interestingly, MDL-100907 increased TST in both models when given alone, with the TST increase occurring prior to the naloxone-induced flush in the MD model. To evaluate the role of central nervous system (CNS) 5-HT(2A) receptors in TST regulation, DOI was administered in combination with a known peripheral 5-HT(2A/2C) receptor antagonist, xylamidine, in the MD model. Xylamidine had no effect on DOI's ability to abate the naloxone-induced flush. These results indicate that activation of central 5-HT(2A) receptors restores temperature regulation in two rodent models of ovariectomy-induced thermoregulatory dysfunction.

Stress proteins as molecular markers of neurotoxicity

In response to many environmental and pathophysiologic stressful stimuli, cells undergo a stress response characterized by induction of a variety of proteins, including the heat shock protein family. The inducible heat shock protein 70 (hsp70) is believed to participate in an array of cellular activities, including cytoprotection. Normal brain cells have little detectable hsp70 RNA or protein. However, following a stressful condition hsp70 mRNA and protein are induced in different cell types depending on the severity and the nature of the stimulus. The induction of hsp70 protein correlates with the regional and cellular vulnerability to a particular injury as identified by standard histologic methods. The pattern of hsp70 expression differs in response to various neurotoxic stimuli, including hyperthermia, ischemia, seizures, hemorrhage, and N-methyl-D-aspartate receptor antagonist administration. Hsp70 expression is a useful marker of cellular injury and may help to identify previously unrecognized areas of vulnerability in the nervous system after a neurotoxic stimulus. Hsp70 may also play a neuroprotective role in the brain.

Neuroprotection at Drosophila synapses conferred by prior heat shock

Synapses are critical sites of information transfer in the nervous system, and it is important that their functionality be maintained under stressful conditions to prevent communication breakdown. Here we show that synaptic transmission at the Drosophila larval neuromuscular junction is protected by prior exposure to heat shock that strongly induces expression of heat shock proteins, in particular hsp70. Using a macropatch electrode to record synaptic activity at individual, visualized boutons, we found that prior heat shock sustains synaptic performance at high test temperatures through pre- and postsynaptic alterations. After heat shock, nerve impulses release more quantal units at high temperatures and exhibit fewer failures of release (presynaptic modification), whereas the amplitude of quantal currents remains more constant than does that in nonheat-shocked controls (postsynaptic modification). The time course of these physiological changes is similar to that of elevated hsp70. Thus, stress-induced neuroprotective mechanisms maintain function at synapses by modifying their properties.

Differential expression of heat shock 70 proteins in primary cultures from rat cerebellum

While a number of studies have described the heat shock response in established cell lines and in primary cultures of cells derived from the nervous system, there has been no systematic analysis comparing expression and localization of the inducible heat shock 70 (hsp70) proteins and the constitutively synthesized members of the family (hsc70) in neurons and glia. In the present communication, we utilized specific probes to compare the expression of hsp70 and hsc70 mRNAs and proteins in two types of primary cultures, astroglial and neuro-astroglial, from postnatal rat cerebellum. Conditions were adjusted to maintain physiological numbers of microglia in both types of culture, and cultures were analyzed at a number of different time points following a precisely defined heat shock. The northern, in situ hybridization and immunohistochemical analyses resulted in a number of novel observations concerning the nature of the heat shock response in these neuronal and glial cells. In postnatal day 4-5 cultures, hsp70 mRNA levels were elevated for at least 10 h in both types of culture, but in situ hybridization analysis showed no evidence for hsp70 mRNAs in neurons. Microglia were the only cell type in which hsp70 was detected in non-stressed cultures and this cell type contained the highest concentrations of hsp70 proteins in stressed cultures. Hsc70 mRNA levels were also increased after heat shock, but the increase was more transient. Hsc70 mRNAs and proteins were present in all cell types, again with the highest concentrations being present in microglia. Hsc70 mRNAs and proteins were localized in the cytoplasm at all time points examined, with hsc70 protein also being localized in nucleoli. Hsp70 mRNAs and proteins were diffusely localized over nuclei of astrocytes, as well as of most microglia. Hsp70, but not hsc70, was localized on chromosomes in glia once they had resumed cell division after heat shock, suggesting a role for hsp70 either in targeting damaged chromosomal proteins or in cell division. Some cytoplasmic hsp70 was observed in astrocytes of the mixed neuro-astroglial cultures and a delayed hsp70 immunoreactivity was observed in granule neurons in these cultures, suggesting either that translation of low levels of hsp70 mRNAs was more efficient in neurons, or that glial-neuronal translocation of hsp70 proteins had taken place. These results suggest that metabolism and functions of different heat shock protein family members may not always be identical and that care must be taken in extrapolation of results from one cell type to another.

Neuronal differentiation in PC12 cells is accompanied by diminished inducibility of Hsp70 and Hsp60 in response to heat and ethanol

The stress response of PC12 cells was characterized by evaluating the production of heat shock proteins of the 70 kDa (Hsp70), 60 kDa (Hsp60) and 90 kDa (Hsp90) families by western blot analysis. Induction of Hsp synthesis was elicited by brief exposure to elevated temperatures or by addition of ethanol to the cultures. Normal PC12 cells responded to stress with rapid up-regulation of Hsp70 and Hsp60 production. However, fully differentiated PC12 cells (induced by nerve growth factor, NGF) failed to produce Hsp70 or Hsp60 in response to heat or ethanol treatment. The disappearance of the heat shock response of the cells was directly related to the extent of neuronal differentiation. The cellular levels of the constitutive proteins, Hsc70 and Hsp90, were not altered by differentiation of the cells. Production of Hsps was restored in the differentiated cells by removal of NGF which coincided with the loss of neurite expression and retraction of processes.

D-lysergic acid reduces microtubule-associated tau protein in SH-SY5Y human neuroblastoma cells

1. SH-SY5Y, an adrenergic human neuroblastoma cell line, was used to examine the hypothesis that D-lysergic acid (LSD) affects the metabolism of microtubule-associated tau protein, thus affecting microtubule assembly and the transport of neurotransmitters. 2. After 48 hr treatment LSD (10(-5) and 10(-7) M) decreased 50 kDa tau protein in the membrane (pellet) fraction. The drug (10(-5) M) also decreased in the cytoplasmic (supernatant) fraction. 3. This reduction in tau protein was accompanied by a 65% increase (P < 0.05) in total protein after LSD (10(-7) M) in the cytoplasmic fraction.

Differential expression of heat shock proteins by human glial cells

Heat shock proteins (HSP) have been implicated in the interactions between the gamma delta T lymphocyte population and target tissues. gamma delta T cells are found in increased numbers in multiple sclerosis (MS) plaques compared to their proportion in peripheral blood, co-localizing with oligodendrocytes (OGC) expressing HSP. We have demonstrated that such gamma delta T cells can induce in vitro lysis of human adult-derived OGC. Using immunohistochemical and flow cytometry techniques, we examined the constitutive and/or inducible expression of HSP in or on adult human-derived glial cell cultures in vitro. HSP70 was expressed in OGC maintained at basal temperature, but the expression of the inducible HSP70 protein was upregulated by a prior 43 degrees C heat exposure. HSP70 could not be detected within astrocytes (GFAP+ cells), whether heat stress was applied or not. Constitutive expression of HSP60 could be discerned on the surface of all OGC under non-stressed culture conditions. Only some astrocytes demonstrated minor punctate surface HSP60 staining, whereas the remainder did not express HSP60 constitutively. These observations raise the possibility that OGC, by virtue of their differential expression of HSP compared to other glial cells, may be particularly prone to interaction with HSP-reactive gamma delta T cells. Such findings may further implicate gamma delta T cells in the pathogenesis of MS, a putative autoimmune disease in which immune-mediated injury is directed specifically against the oligodendrocyte-myelin unit within the central nervous system.

The stress protein response in cultured neurons: characterization and evidence for a protective role in excitotoxicity

We used purified cultures of cerebellar granule cells to investigate the possible protective role of stress proteins in an in vitro model of excitotoxicity. Initial experiments used one- and two-dimensional polyacrylamide gel electrophoresis to confirm the induction of typical stress protein size classes by heat shock, sodium arsenite, and the calcium ionophore A23187. Immunoblot analysis and immunocytochemistry verified the expression of the highly inducible 72 kd heat shock protein (HSP72). Granule cell cultures exposed to glutamate showed evidence of cellular injury that was prevented by the noncompetitive NMDA antagonist MK-801, yet glutamate did not induce a detectable stress protein response. Nonetheless, preinduction of heat shock proteins was associated with protection from toxic concentrations of glutamate. These results imply that the HSP72 expression observed in in vivo models of excitotoxicity may not be directly related to the effects of excitatory amino acids. However, the ability of stress protein induction to protect against injury from glutamate may offer a novel approach toward ameliorating damage from excitotoxins.

Cerebrovascular and metabolic effects on the rat brain of focal Nd:YAG laser irradiation

To investigate the effects of focal neodymium:yttrium-aluminum-garnet (Nd:YAG) laser irradiation (lambda = 1060 nm) on regional cerebral blood flow, cerebral protein synthesis, and blood-brain barrier permeability, the parietal brain surface of 44 rats was irradiated with a focused laser beam at a constant output energy of 30 J. Survival times ranged from 5 minutes to 48 hours. Laser irradiation immediately caused well-defined cortical coagulation necrosis. Within 5 minutes after unilateral irradiation, 14C-iodoantipyrine autoradiographs demonstrated severely reduced blood flow to the irradiation site and perilesional neocortex, but a distinct reactive hyperemia in all other areas of the forebrain. Apart from a persistent ischemic focus in the vicinity of the cortical coagulation necrosis, blood flow alterations in remote areas of the brain subsided within 3 hours after irradiation. Autoradiographic assessment of 3H-tyrosine incorporation into brain proteins revealed rapid onset and prolonged duration of protein synthesis inhibition in perifocal morphologically intact cortical and subcortical structures. Impairment of amino acid incorporation proved to be completely reversible within 48 hours. Immunoautoradiographic visualization of extravasated plasma proteins using 3H-labeled rabbit anti-rat immunoglobulins-showed that, up to 1 hour after irradiation, immunoreactive proteins were confined to the neocortex at the irradiation site. At 4 hours, vasogenic edema was present in the vicinity of the irradiation site and the subcortical white matter, and, at later stages (16 to 36 hours), also extended into the contralateral hemisphere. Although this was followed by a gradual decrease in labeling intensity, resolution of edema was still not complete after 48 hours. Analysis of sequential functional changes in conjunction with morphological alterations indicates that the evolution of morphological damage after laser irradiation does not correlate with the time course and spatial distribution of protein synthesis inhibition or vasogenic edema. Although the central coagulation necrosis represents a direct effect of radiation, the final size of the laser-induced lesion is determined by a delayed colliquation necrosis due to persistent perifocal ischemia. Extent and severity of ischemia in a zone with initial preservation of neuroglial cells can be explained by the optical properties of the Nd:YAG laser; extensive scattering of light within brain parenchyma associated with a high blood-to-brain absorption ratio selectively affects blood vessels outside the irradiation focus.

Induction of heat shock (stress) genes in the mammalian brain by hyperthermia and other traumatic events: a current perspective

Is the heat shock response physiologically relevant? For example, following hyperthermia or ischemia, what neural cell types show induction of heat shock genes and what is the time course of the effect? Initial experiments in this area demonstrated the prominent induction of a 70 kDa heat shock protein (hsp70) when labeled brain proteins isolated from hyperthermic animals were analyzed. Recently, in situ hybridization and immunocytochemistry have been utilized to map out the pattern of expression of both constitutively expressed and stress-inducible members of the hsp70 multigene family. Different types of neural trauma have been found to induce characteristic cellular responses in the mammalian brain with regard to the type of brain cell that responds by inducing hsp70 and the timing of the induction response. Fever-like temperature causes a dramatic induction of hsp70 mRNA within 1 hr in fiber tracts of the forebrain and cerebellum, a pattern consistent with a strong glial response to heat shock. Tissue injury, namely, a small surgical cut in the cerebral cortex, induces a rapid and highly localized induction of hsp70 mRNA in cells proximal to the injury site. Using an immunocytochemical approach, a neuronal pattern of induction of hsp70 has been demonstrated following ischemia or kainic acid-induced seizures. It is apparent that the pattern of induction of hsp70 may be a useful early marker of cellular injury and may identify previously unrecognized areas of vulnerability in the nervous system.

Heat stress increases delivery of a unique sub-population of proteins conveyed by fast axonal transport

The effect of heat stress on protein synthesis and fast axonal transport was examined in vitro in bullfrog dorsal root ganglion (DRG) and associated spinal/sciatic nerve. Qualitative and quantitative changes of individual 35S-methionine-labelled proteins were determined following DRG labelling and fast transport in respective nerves via two-dimensional gel electrophoresis/autoradiography. Elevation of temperature from 18 degrees C to 33 degrees C for up to 6 hr resulted in a marked increase in synthesis of five individual DRG species of approximately 74,000 daltons that comigrate with heat shock proteins (HSPs). A quantitative comparison of species within this subset revealed two subgroups differentially affected by stress. The three most basic proteins were induced to approximately 1300% of unstressed controls after 6 hr of stress, while the two most acidic species demonstrated an increase to only 300% of controls over the same period. The relative abundance of 25 additional DRG proteins were uneffected by heat stress. Of 70 35S-labelled fast-transported proteins similarly analyzed, 15, comprising 5 families, were consistently transported at greater than 150% of controls following up to 6 hr of heat stress. Over this period all 15 proteins shared a similar profile of abundance relative to non-induced proteins. Transport was elevated to the greatest extent after 2 hr of stress, declined after 3 hr, and tended to rebound at later times. The remaining 55 fast-transported protein spots analyzed were unaffected. An increased delivery of this unique sub-population of 15 fast-transported proteins suggests a possible involvement in early cellular events that mediate heat stress in the nervous system.

Heat stress induces changes in protein synthesis and fast axonal transport in bullfrog sensory neurons

The effects of heat stress on protein synthesis and fast axonal transport were examined in an in vitro bullfrog primary afferent neuron preparation. The magnitude of effect was determined for individual [35S]methionine-labelled protein species separated via two-dimensional gel electrophoresis. Elevation of temperature of the preparation from 18 degrees C to 33 degrees C caused a transient inhibition of synthesis of non-heat-shock proteins, whereas the synthesis of a 74,000-dalton protein increased to 927% of controls after 4 h. Similar prolonged stress conditions had no effect on the relative abundance of 36 individual, newly synthesized proteins undergoing fast axonal transport. A dramatic exception was represented by a 55,000-dalton glycoprotein whose fast transport was increased to 291% of control. The increase in transport of this protein during a time when synthesis and transport of other non-heat-shock proteins were not enhanced suggests that it may play a unique role in the early cellular events that mediate survival or thermotolerance in the neuron.

Characterization of a translational inhibitor isolated from rabbit brain following intravenous administration of d-lysergic acid diethylamide

Intravenous administration of d-lysergic acid diethylamide (LSD) to rabbits results in a transient inhibition of brain protein synthesis in vivo and in vitro. A translational inhibitor that appears in the postribosomal supernatant fraction of cerebral hemispheres following LSD administration was partially purified by gel filtration on Sephadex G-150 and precipitation with 60% ammonium sulfate. This inhibitor, which was proteinaceous, reduced the translational capacity of an initiating cell-free protein synthesis system derived from brain. It also inhibited a messenger RNA-dependent reticulocyte lysate programmed with brain polysomes and a globin-synthesizing reticulocyte lysate system. Addition of the partially purified inhibitor to a brain cell-free protein synthesis system resulted in the decreased formation of ternary complexes as well as 40 and 80S initiation complexes, suggesting that the inhibitor affects an early step in the initiation of protein synthesis in brain.

Induction of a heat shock protein in the isolated mammalian retina

The effects of elevated ambient temperature and addition of the psychotropic drug LSD on protein synthesis in the isolated rabbit retina were investigated. Two dimensional gel electrophoresis followed by fluorography of proteins synthesized in vitro demonstrated that synthesis of a heat shock protein of molecular weight 74,000 (74K) was induced by the elevation of temperature and not by the addition of LSD. The appearance of this heat shock protein was shown to be dependent upon the synthesis of new RNA as shown by the addition of actinomycin-D to the incubation medium. The newly synthesized heat shock protein was associated with both nuclear and cytoplasmic fractions.

Heat shock response of the rat lens

The sequence relationship between the small heat shock proteins and the eye lens protein alpha-crystallin (Ingolia, T. D., and E. E. Craig, 1982, Proc. Natl. Acad. Sci. USA, 79: 2360-2364) prompted us to subject rat lenses in organ culture to heat shock and other forms of stress. The effects on protein synthesis were followed by labeling with [35S]methionine and analysis by one- and two-dimensional gel electrophoresis and fluorography. Heat shock gave a pronounced induction of a protein that could be characterized as the stress protein SP71. This protein probably corresponds to the major mammalian heat shock protein hsp70. Also two minor proteins of 16 and 85 kD were induced, while the synthesis of a constitutive heat shock-related protein, P73, was considerably increased. The synthesis of SP71 started between 30 and 60 min after heat shock, reached its highest level after 3 h, and had stopped again after 8 h. In rat lenses that were preconditioned by an initial mild heat shock, a subsequent shock did not cause renewed synthesis of SP71. This effect resembles the thermotolerance phenomenon observed in cultured cells. The proline analogue azetidine-2-carboxylic acid, zinc chloride, ethanol, and calcium chloride did not, under the conditions used, induce stress proteins in the rat lens. Sodium arsenite, however, had very much the same effects as heat shock. Calcium ionophore A23187 specifically and effectively induced the synthesis of the glucose-regulated protein GRP78. No special response to stress on crystallin synthesis was noticed.

Axonal transport of a heat shock protein in the rabbit visual system

Intraocular injection of [35S]methionine was used to demonstrate the pronounced induction of a 74-kDa heat shock protein in the rabbit retina after a 3 degrees C increase in body temperature was generated by intravenous administration of D-lysergic acid diethylamide. Two-dimensional polyacrylamide gel electrophoresis and fluorography revealed that the induced heat shock protein underwent axonal transport from retinal ganglion cells into the optic nerve and subsequently down the contralateral optic tract to synaptic termini in the visual projection area. Since the heat shock protein took more than 8 days to move down the optic nerve to the superior colliculus, it is transported by slow rather than by fast axonal transport.

Effect of intravenous administration of D-lysergic acid diethylamide on initiation of protein synthesis in a cell-free system derived from brain

An initiating cell-free protein synthesis system derived from brain was utilized to demonstrate that the intravenous injection of D-lysergic acid diethylamide (LSD) to rabbits resulted in a lesion at the initiation stage of brain protein synthesis. Three inhibitors of initiation, edeine, poly(I), and aurintricarboxylic acid were used to demonstrate a reduction in initiation-dependent amino acid incorporation in the brain cell-free system. One hour after LSD injection, there was also a measurable decrease in the formation of 40S and 80S initiation complexes in vitro, using either [35S]methionine or [35S]Met-tRNAf. Analysis of the methionine pool size after LSD administration indicated there was no change in methionine levels. Analysis of the formation of initiation complexes in the brain cell-free protein synthesis system prepared 6 h after LSD administration indicated that there was a return to control levels at this time. The effects of LSD on steps in the initiation process are thus reversible.

Induction of a ‘stress’ protein in intact mammalian organs after the intravenous administration of sodium arsenite

The profile of nascent proteins synthesized in various rabbit organs after the intravenous injection of sodium arsenite was analyzed by the cell-free translation of purified polysomes. Examination of the translation products of polysomes isolated 1 hr after injection of sodium arsenite revealed a marked induction of synthesis of a protein of molecular weight 74,000 (74K) in the kidney, heart and liver which was similar to a 'heat shock' protein which was induced in these organs after elevation of body temperature by 2.5 to 3 degrees C. Synthesis of the 74K protein was not detected in the translation products of brain polysomes isolated 1 hr after sodium arsenite injection.

Heat shock protein in mammalian brain and other organs after a physiologically relevant increase in body temperature induced by D-lysergic acid diethylamide

A physiologically relevant increase in body temperature from 39.7 to 42.5 degrees C, which was generated after the intravenous injection of D-lysergic acid diethylamide (LSD), caused the induction of synthesis of a 74,000-dalton heat shock protein in the brain, heart, and kidney of the young adult rabbit. A marked increase in the relative labeling of a 74,000-dalton protein was noted after analysis of both in vivo labeled proteins and cell-free translation products of isolated polysomes. A temporal decrease in the synthesis of this protein was noted as LSD-induced hyperthermia subsided. The 74,000-dalton protein, which is induced in various organs of the intact animal at a body temperature similar to that attained during fever reactions, may play a role in homeostatic control mechanisms.

Biochemical and morphological comparison of postsynaptic densities prepared from rat, hamster, and monkey brains by phase partitioning

A new procedure for the preparation of postsynaptic densities (PSDs) is described. A synaptic membrane fraction was homogenized in an aqueous two-phase polymer system containing Poly(ethylene glycol) 6000 (5% wt/wt) and Dextran T500 (6% wt/wt) containing 1% 1-o-n-octyl-beta-D-glucoside. Following a brief centrifugation to separate the phases, highly purified PSDs banded at the interface of the two phases. Using this procedure PSDs have been isolated from rat and hamster cerebral cortex and from the frontal cortex, cerebral cortex, hippocampus, and pooled caudate/putamen regions of Macaca mulatta Rhesus monkeys. The isolated PSDs appeared as curved bars when sectioned or as discs when viewed en face in the electron microscope. The hamster PSDs were associated with large numbers of small rod-like structures 4.5 nm thick and 28 nm long. Similar structures were present, although in fewer numbers, in the rat and monkey preparations. Polyacrylamide gel electrophoresis showed that the PSDs contained a complex population of proteins with major components having molecular weights of 180,000, 130,000, 110,000, 94,000, 65,000, 60,000, and 51,000. Reaction of polyacrylamide gels with 125I-concanavalin A (Con A) identified two major (apparent Mr 180,000 and 130,000) and three minor (apparent Mr 230,000, 145,000, and 110,000) Con A-binding glycoproteins in the PSD fractions. Although some quantitative variation between species and brain regions was apparent, the overall protein and glycoprotein composition was similar for all fractions studied.

Concanavalin A receptors associated with rat brain synaptic junctions are high mannose-type oligosaccharides

Glycoproteins were isolated from a rat brain synaptic junction fraction by affinity chromatography on Concanavalin A-agarose. The isolated glycoproteins were digested with pronase and radiolabeled with 125I-Bolton Hunter reagent, and 125I-Concanavalin A-binding glycopeptides were isolated by chromatography on Concanavalin A-agarose. Treatment of the 125I-Concanavalin A-binding glycopeptides with either alpha-mannosidase or endo-beta-N-acetylglucosaminidase-C11 abolished their interaction with Concanavalin A. The pronase digest was reacted with endo-beta-N-acetylglucosaminidase-C11 and released oligosaccharides were reduced with NaB3H4. Following affinity chromatography on Concanavalin A-agarose, Concanavalin A-binding [3H]oligosaccharides were chromatographed on Biogel P4. Two major oligosaccharides corresponding to standard carbohydrates containing eight and five mannose residues were identified. Treatment of these oligosaccharides with alpha-mannosidase converted them to smaller saccharides having a mobility on Biogel P4 columns equal to the standard disaccharide mannose-beta-1-4-N'-acetylglucosamine. These results demonstrate that the Concanavalin A receptor activity associated with CNS synaptic junctions resides in asparagine-linked oligosaccharides of the high-mannose type.

Translation of mRNA associated with monosomes and residual polysomes following disaggregation of brain polysomes by LSD and hyperthermia

Intravenous administration of LSD to young adult rabbits induces a transient disaggregation of brain polysomes and a relocalization of mRNA from polysomes to monosomes. To analyze the spectrum of mRNA molecules which were associated with either the residual polysomes or the translationally inactive monosome complex, these two fractions were isolated on sucrose gradients and translated in a reticulocyte cell-free system. Analysis of [35S]methionine labeled translation products by one and two dimensional gel electrophoresis revealed that a full spectrum of mRNA molecules was relocalized from polysomes to monosomes following drug induced polysome disaggregation. The only exception was the mRNA coding for the LSD-induced 74K protein which was associated with the residual polysome fraction and not with the monosome complex. This brain protein is similar in molecular weight to one of the major 'heat shock' proteins which are induced in tissue culture cells following elevation of ambient temperature and disaggregation of existing polysomes. The mRNA coding for the 74K brain protein was not observed in polysomes isolated following blockage of LSD-induced hyperthermia but it was noted when hyperthermia was induced by elevation of ambient temperature. The mRNA species coding for the 74K protein was polyadenylated.

Trauma-induced protein in rat tissues: a physiological role for a "heat shock" protein?

Hyperthermic shock induces the synthesis of a novel protein (P71) in many rat tissues in vivo. In incubated rat tissue slices P71 is the major protein synthesized even though it is undetectable in the tissues of a normal, unstressed rat. P71 is "heat shock" protein, and it may be induced in vivo by stimuli other than hyperthermia. These results indicate that caution must be used in studies of protein synthesis in tissue explants, since the pattern of proteins synthesized by rat tissue slices is characteristic of stressed tissue.

Cell-free translation of free and membrane-bound polysomes and polyadenylated mRNA from rabbit brain following administration of d-lysergic acid diethylamide in vivo

Free and membrane-bound polysomes and polyadenylated mRNA isolated from rabbit brain were translated in an mRNA-dependent rabbit reticulocyte lysate system. Electrophoretic analysis of the cell-free translation products demonstrated that although most of the nascent proteins were common to both free and membrane-bound brain polysomes, qualitative and quantitative differences were observed. Compared with the results obtained with purified polyadenylated mRNA, the addition of intact polysomes to the cell-free translation assay was more efficient and produced higher molecular weight products. Analysis of the translation products of free and membrane-bound polysomes revealed the appearance of 74K protein following neither LSD administration or hyperthermia induced by elevated temperature treatment. The presence of this 74K protein was verified by analysis of the translation products by two-dimensional gel electrophoresis.

Characterization of an initiating cell-free protein synthesis system derived from rabbit brain

Protein synthesis in the brain is known to be affected by a wide range of treatments. The detailed analysis of the mechanisms that are involved would be facilitated by the development of cell-free translation systems derived from brain tissue. To date, brain cell-free systems have not been fully characterized to demonstrate a capacity for initiation of translation. The following criteria were utilized to demonstrate that a cell-free protein synthesis system derived from rabbit brain was capable of initiation in vitro: (a) sensitivity of cell-free translation to the initiation inhibitor aurintricarboxylic acid (ATA); (b) binding of [35S]Met-tRNAf to 40S and 80S initiation complexes; (c) incorporation of labeled initiation methionine into high-molecular-weight proteins; and (d) the association of labeled exogenous mRNA with polysomes. The optimum conditions for amino acid incorporation in this system were 4 mM-Mg2+, 140 mM-K+, and pH 7.55. Incorporation was dependent on the addition of ATP, GTP, and an energy-generating system. Cell-free protein synthesis reflected the normal process, since a similar spectrum of proteins was synthesized in vitro and in vivo. This initiating cell-free translation system should have wide application in the analysis of the mechanisms whereby various treatments affect protein synthesis in the brain.

Effect of intravenous administration of d-lysergic acid diethylamide on subsequent protein synthesis in a cell-free system derived from brain

An initiating cell-free protein synthesis system derived from brain was utilized to demonstrate that the intravenous injection of d-lysergic acid diethylamide (LSD) to rabbits induced a transient inhibition of translation following a brief stimulatory period. Subfractionation of the brain cell-free system into postribosomal supernatant (PRS) and microsome fractions demonstrated that LSD in vivo induced alterations in both of these fractions. In addition to the overall inhibition of translation in the cell-free system, differential effects were noted, i.e., greater than average relative decreases in in vitro labeling of certain brain proteins and relative increases in others. The brain proteins of molecular weights 75K and 95K, which were increased in relative labeling under conditions of LSD-induced hyperthermia, are similar in molecular weight to two of the major "heat shock" proteins reported in tissue culture systems. Injection of LSD to rabbits at 4 degrees C prevented LSD-induced hyperthermia but behavioral effects of the drug were still apparent. The overall decrease in cell-free translation was still observed but the differential labeling effects were not. LSD appeared to influence cell-free translation in the brain at two dissociable levels: (a) an overall decrease in translation that was observed even in the absence of LSD-induced hyperthermia and (b) differential labeling effects on particular proteins that were dependent on LSD-induced hyperthermia.

Comparison of the effect of intravenous administration of d-lysergic acid diethylamide on free and membrane-bound polysomes in the rabbit brain

The intravenous administration of LSD to young adult rabbits resulted in the disaggregation of both free and membrane-bound classes of brain polysomes. Based on the analysis of LSD dosage and the time course of the LSD-induced brain polysome shift, it was found that free polysomes were more sensitive to the drug than the membrane-bound polysome fraction. LSD-induced hyperthermia may be involved in the disaggregation of free and membrane-bound polysomes, since a correlation was found between the extent of LSD-induced hyperthermia and the degree of brain polysome shift. Prevention of LSD-induced hyperthermia by maintaining the animal at 4 degrees C blocked the disaggregation of both polysome classes. Induction of hyperthermia by elevation of ambient temperature also resulted in a shift in free and membrane-bound polysomes. In all cases the disaggregation of polysomes to monosomes was not caused by RNase activation. During polysome disaggregation, polyadenylated mRNA associated with both free and membrane-bound polysomes was not degraded but was relocalized from polysomes to monosomes.