Slow axonal transport of the cytosolic chaperonin CCT with Hsc73 and actin in motor neurons

An updated reappraisal of synapsins: structure, function and role in neurological and psychiatric disorders

Synapsins (Syns) are phosphoproteins strongly involved in neuronal development and neurotransmitter release. Three distinct genes SYN1, SYN2 and SYN3, with elevated evolutionary conservation, have been described to encode for Synapsin I, Synapsin II and Synapsin III, respectively. Syns display a series of common features, but also exhibit distinctive localization, expression pattern, post-translational modifications (PTM). These characteristics enable their interaction with other synaptic proteins, membranes and cytoskeletal components, which is essential for the proper execution of their multiple functions in neuronal cells. These include the control of synapse formation and growth, neuron maturation and renewal, as well as synaptic vesicle mobilization, docking, fusion, recycling. Perturbations in the balanced expression of Syns, alterations of their PTM, mutations and polymorphisms of their encoding genes induce severe dysregulations in brain networks functions leading to the onset of psychiatric or neurological disorders. This review presents what we have learned since the discovery of Syn I in 1977, providing the state of the art on Syns structure, function, physiology and involvement in central nervous system disorders.

The Molecular Chaperone CCT/TRiC: An Essential Component of Proteostasis and a Potential Modulator of Protein Aggregation

Chaperonin containing tailless complex polypeptide 1 (CCT) or tailless complex polypeptide 1 ring complex (TRiC) is an essential eukaryotic molecular chaperone. It is a multi-subunit oligomer of two rings of eight individual protein subunits. When assembled, each of the eight CCT subunits occupies a specific position within each chaperonin ring. Thus a geometrically defined binding interface is formed from the divergent sequences within the CCT subunit substrate binding domains. CCT is required for the folding of the abundant cytoskeletal proteins actin and tubulin, which in turn form assemblies of microfilaments and microtubules. CCT is also involved in the folding of some additional protein substrates and some CCT subunits have been shown to have functions when monomeric. Since observations were made in worms over a decade ago using an RNAi screen, which connected CCT subunits to the aggregation of polyglutamine tracts, a role for CCT as a potential modulator of protein aggregation has started to emerge. Here there will be a focus on how mechanistically CCT may be able to achieve this and if this potential function of CCT provides any insights and directions for developing future treatments for protein aggregation driven neurodegenerative diseases generally, many of which are associated with aging.

Knockdown of BmTCP-1β Delays BmNPV Infection in vitro

The molecular mechanism of silkworm resistance to Bombyx mori nucleopolyhedrovirus (BmNPV) infection remains unclear. The chaperonin containing t-complex polypeptide 1 (TCP-1) is essential for the folding of tubulin and actin to produce stable and functional competent protein conformation. However, little is known about this protein in silkworm. In the present study, a gene encoding the TCP-1β protein in silkworm was characterized, which has an open reading fragment of 1,611 bp encoding a predicted 536 amino acid residue-protein with a molecular weight of approximately 57.6 kDa containing a Cpn60_TCP1 functional domain. The sequence conservation is 81.52%. The highest level of BmTCP-1β mRNA expression was found in the midgut, while the lowest was in the hemolymph. To further study the function of BmTCP-1β, expression was knocked down with siRNA in vitro, resulting in significant downregulation of the selected cytoskeletal-related genes, actin and tubulin, which was also confirmed by overexpression of BmTCP-1β in BmN cells using the pIZT/V5-His-mCherry insect vector. Moreover, knockdown of BmTCP-1β significantly prolonged the infection process of BmNPV in BmN cells, which was also verified by overexpression of BmTCP-1β in BmN cells. Based on the results of the present study, we concluded that BmTCP-1β plays a vital role in BmNPV infection by regulating the expression of tubulin and actin. Taken together, our work provides valuable data for the clarification of the molecular mechanism of silkworm resistance to BmNPV infection.

Miles to go (mtgo) encodes FNDC3 proteins that interact with the chaperonin subunit CCT3 and are required for NMJ branching and growth in Drosophila

Analysis of mutants that affect formation and function of the Drosophila larval neuromuscular junction (NMJ) has provided valuable insight into genes required for neuronal branching and synaptic growth. We report that NMJ development in Drosophila requires both the Drosophila ortholog of FNDC3 genes; CG42389 (herein referred to as miles to go; mtgo), and CCT3, which encodes a chaperonin complex subunit. Loss of mtgo function causes late pupal lethality with most animals unable to escape the pupal case, while rare escapers exhibit an ataxic gait and reduced lifespan. NMJs in mtgo mutant larvae have dramatically reduced branching and growth and fewer synaptic boutons compared with control animals. Mutant larvae show normal locomotion but display an abnormal self-righting response and chemosensory deficits that suggest additional functions of mtgo within the nervous system. The pharate lethality in mtgo mutants can be rescued by both low-level pan- and neuronal-, but not muscle-specific expression of a mtgo transgene, supporting a neuronal-intrinsic requirement for mtgo in NMJ development. Mtgo encodes three similar proteins whose domain structure is most closely related to the vertebrate intracellular cytosolic membrane-anchored fibronectin type-III domain-containing protein 3 (FNDC3) protein family. Mtgo physically and genetically interacts with Drosophila CCT3, which encodes a subunit of the TRiC/CCT chaperonin complex required for maturation of actin, tubulin and other substrates. Drosophila larvae heterozygous for a mutation in CCT3 that reduces binding between CCT3 and MTGO also show abnormal NMJ development similar to that observed in mtgo null mutants. Hence, the intracellular FNDC3-ortholog MTGO and CCT3 can form a macromolecular complex, and are both required for NMJ development in Drosophila.

Acute Heat Stress Changes Protein Expression in the Testes of a Broiler-Type Strain of Taiwan Country Chickens

Heat stress leads to decreased fertility in roosters. This study investigated the global protein expression in response to acute heat stress in the testes of a broiler-type strain of Taiwan country chickens (TCCs). Twelve 45-week-old roosters were randomly allocated to the control group maintained at 25°C, and three groups subjected to acute heat stress at 38°C for 4 h, with 0, 2, and 6 h of recovery, respectively. Testis samples were collected for hematoxylin and eosin staining, apoptosis assay, and protein analysis. The results revealed 101 protein spots that differed significantly from the control following exposure to acute heat stress. The proteins that were differentially expressed participated mainly in protein metabolism and other metabolic processes, responses to stimuli, apoptosis, cellular organization, and spermatogenesis. Proteins that negatively regulate apoptosis were downregulated and proteins involved in autophagy and major heat shock proteins (HSP90α, HSPA5, and HSPA8) were upregulated in the testes of heat-stressed chickens. In conclusion, acute heat stress causes a change in protein expression in the testes of broiler-type B strain TCCs and may thus impair cell morphology, spermatogenesis, and apoptosis. The expression of heat shock proteins increased to attenuate the testicular injury induced by acute heat stress.

Hsc70 chaperone activity is required for the cytosolic slow axonal transport of synapsin

Soluble cytosolic proteins vital to axonal and presynaptic function are synthesized in the neuronal soma and conveyed via slow axonal transport. Our previous studies suggest that the overall slow transport of synapsin is mediated by dynamic assembly/disassembly of cargo complexes followed by short-range vectorial transit (the "dynamic recruitment" model). However, neither the composition of these complexes nor the mechanistic basis for the dynamic behavior is understood. In this study, we first examined putative cargo complexes associated with synapsin using coimmunoprecipitation and multidimensional protein identification technology mass spectrometry (MS). MS data indicate that synapsin is part of a multiprotein complex enriched in chaperones/cochaperones including Hsc70. Axonal synapsin-Hsc70 coclusters are also visualized by two-color superresolution microscopy. Inhibition of Hsc70 ATPase activity blocked the slow transport of synapsin, disrupted axonal synapsin organization, and attenuated Hsc70-synapsin associations, advocating a model where Hsc70 activity dynamically clusters cytosolic proteins into cargo complexes, allowing transport. Collectively, our study offers insight into the molecular organization of cytosolic transport complexes and identifies a novel regulator of slow transport.

Drag of the cytosol as a transport mechanism in neurons

Axonal transport is typically divided into two components, which can be distinguished by their mean velocity. The fast component includes steady trafficking of different organelles and vesicles actively transported by motor proteins. The slow component comprises nonmembranous materials that undergo infrequent bidirectional motion. The underlying mechanism of slow axonal transport has been under debate during the past three decades. We propose a simple displacement mechanism that may be central for the distribution of molecules not carried by vesicles. It relies on the cytoplasmic drag induced by organelle movement and readily accounts for key experimental observations pertaining to slow-component transport. The induced cytoplasmic drag is predicted to depend mainly on the distribution of microtubules in the axon and the organelle transport rate.

Fast vesicle transport is required for the slow axonal transport of synapsin

Although it is known that cytosolic/soluble proteins synthesized in cell bodies are transported at much lower overall velocities than vesicles in fast axonal transport, the fundamental basis for this slow movement is unknown. Recently, we found that cytosolic proteins in axons of mouse cultured neurons are conveyed in a manner that superficially resembles diffusion, but with a slow anterograde bias that is energy- and motor-dependent (Scott et al., 2011). Here we show that slow axonal transport of synapsin, a prototypical member of this rate class, is dependent upon fast vesicle transport. Despite the distinct overall dynamics of slow and fast transport, experimentally induced and intrinsic variations in vesicle transport have analogous effects on slow transport of synapsin as well. Dynamic cotransport of vesicles and synapsin particles is also seen in axons, consistent with a model where higher-order assemblies of synapsin are conveyed by transient and probabilistic associations with vesicles moving in fast axonal transport. We posit that such dynamic associations generate the slow overall anterogradely biased flow of the population ("dynamic-recruitment model"). Our studies uncover the underlying kinetic basis for a classic cytosolic/soluble protein moving in slow axonal transport and reveal previously unknown links between slow and fast transport, offering a clearer conceptual picture of this curious phenomenon.

Proteomic analysis of the effect of acupuncture on the suppression of kainic Acid-induced neuronal destruction in mouse hippocampus

Kainic acid (KA) is a neurotoxin that induces epileptic seizures and excitotoxicity in the hippocampus. Acupuncture is frequently used as an alternative therapy for epilepsy, and it has been known to protect hippocampal neurons against KA toxicity. Using proteomic analysis, we investigated protein expression changes in the hippocampus following acupuncture stimulation at HT8. Eight-week-old male C57BL/6 mice (20-25 g) received acupuncture treatment at HT8 acupoint bilaterally once a day for 3 days and were then administered KA (30 mg/kg) intraperitoneally. Twenty-four hours after KA injection, neuronal survival and astrocyte activation in the hippocampus were measured, and protein expression in the hippocampus was identified by 2-dimensional electrophoresis. Acupuncture stimulation at HT8 suppressed KA-induced neuronal death and astrocyte activation in the hippocampus. We identified the changes in the expression of 11 proteins by KA or acupuncture stimulation at HT8 and found that acupuncture stimulation at HT8 normalized the expression of dihydropyrimidinase-related protein 2 and upregulated the expression of transcriptional activator protein pur-alpha, serine/threonine-protein phosphatase 5, and T-complex protein 1 subunit alpha, which are related to the survival of neurons. These results suggest that acupuncture stimulation at HT8 changes protein expression profiles in the hippocampus in favor of neuronal survival in KA-treated mice.

Application of 2D BN/SDS-PAGE coupled with mass spectrometry for identification of VDAC-associated protein complexes related to mitochondrial binding sites for type I brain hexokinase

Two types of binding sites for hexokinase, designated as Type A or Type B sites, have been shown to coexist on brain mitochondria. The ratio of these sites varies between species. HK1 attaches by reversibly binding to the voltage dependent anion channel (VDAC). Regarding the nature of hexokinase binding sites, we investigated if it was linked to distinct VDAC interactomes. We approached this question by 2D BN/SDS-PAGE of mitochondria, followed by mass spectrometry. Our results are consistent with the possibility that the ratio of Type A/Type B sites is due to differential VDAC interactions in bovine and rat neuronal cells.

Kinesin-1/Hsc70-dependent mechanism of slow axonal transport and its relation to fast axonal transport

Cytoplasmic protein transport in axons ('slow axonal transport') is essential for neuronal homeostasis, and involves Kinesin-1, the same motor for membranous organelle transport ('fast axonal transport'). However, both molecular mechanisms of slow axonal transport and difference in usage of Kinesin-1 between slow and fast axonal transport have been elusive. Here, we show that slow axonal transport depends on the interaction between the DnaJ-like domain of the kinesin light chain in the Kinesin-1 motor complex and Hsc70, scaffolding between cytoplasmic proteins and Kinesin-1. The domain is within the tetratricopeptide repeat, which can bind to membranous organelles, and competitive perturbation of the domain in squid giant axons disrupted cytoplasmic protein transport and reinforced membranous organelle transport, indicating that this domain might have a function as a switchover system between slow and fast transport by Hsc70. Transgenic mice overexpressing a dominant-negative form of the domain showed delayed slow transport, accelerated fast transport and optic axonopathy. These findings provide a basis for the regulatory mechanism of intracellular transport and its intriguing implication in neuronal dysfunction.

Off-target effects of psychoactive drugs revealed by genome-wide assays in yeast

To better understand off-target effects of widely prescribed psychoactive drugs, we performed a comprehensive series of chemogenomic screens using the budding yeast Saccharomyces cerevisiae as a model system. Because the known human targets of these drugs do not exist in yeast, we could employ the yeast gene deletion collections and parallel fitness profiling to explore potential off-target effects in a genome-wide manner. Among 214 tested, documented psychoactive drugs, we identified 81 compounds that inhibited wild-type yeast growth and were thus selected for genome-wide fitness profiling. Many of these drugs had a propensity to affect multiple cellular functions. The sensitivity profiles of half of the analyzed drugs were enriched for core cellular processes such as secretion, protein folding, RNA processing, and chromatin structure. Interestingly, fluoxetine (Prozac) interfered with establishment of cell polarity, cyproheptadine (Periactin) targeted essential genes with chromatin-remodeling roles, while paroxetine (Paxil) interfered with essential RNA metabolism genes, suggesting potential secondary drug targets. We also found that the more recently developed atypical antipsychotic clozapine (Clozaril) had no fewer off-target effects in yeast than the typical antipsychotics haloperidol (Haldol) and pimozide (Orap). Our results suggest that model organism pharmacogenetic studies provide a rational foundation for understanding the off-target effects of clinically important psychoactive agents and suggest a rational means both for devising compound derivatives with fewer side effects and for tailoring drug treatment to individual patient genotypes.

Cytoskeletal requirements in axonal transport of slow component-b

Slow component-b (SCb) translocates approximately 200 diverse proteins from the cell body to the axon and axon tip at average rates of approximately 2-8 mm/d. Several studies suggest that SCb proteins are cotransported as one or more macromolecular complexes, but the basis for this cotransport is unknown. The identification of actin and myosin in SCb led to the proposal that actin filaments function as a scaffold for the binding of other SCb proteins and that transport of these complexes is powered by myosin: the "microfilament-complex" model. Later, several SCb proteins were also found to bind F-actin, supporting the idea, but despite this, the model has never been directly tested. Here, we test this model by disrupting the cytoskeleton in a live-cell model system wherein we directly visualize transport of SCb cargoes. We focused on three SCb proteins that we previously showed were cotransported in our system: alpha-synuclein, synapsin-I, and glyceraldehyde-3-phosphate dehydrogenase. Disruption of actin filaments with latrunculin had no effect on the velocity or frequency of transport of these three proteins. Furthermore, cotransport of these three SCb proteins continued in actin-depleted axons. We conclude that actin filaments do not function as a scaffold to organize and transport these and possibly other SCb proteins. In contrast, depletion of microtubules led to a dramatic inhibition of vectorial transport of SCb cargoes. These findings do not support the microfilament-complex model, but instead indicate that the transport of protein complexes in SCb is powered by microtubule motors.

Autoantibody profiling of Chinese patients with autoimmune hepatitis using immunoproteomic analysis

In the present study, immunoproteomic analysis was utilized to systemically characterize global autoantibody profiles in autoimmune hepatitis (AIH). Sera from 21 patients with AIH and 15 healthy controls were analyzed for the antibody reactivity against the protein antigens of HepG2, a human hepatoma cell line. The lysates of HepG2 cells were separated by two-dimensional electrophoresis and then immunoblotted with each serum sample. Matrix-assisted laser desorption/ionization mass spectrometry or/and nanoelectrospray ionization MS/MS were then used to identify antigens, among which a bifunctional enzyme in mitochondrial, fumarate hydratase (FH), was further analyzed by ELISA using recombinant FH as a coating antigen. A total of 18 immunoreactive spots were identified as 13 proteins, 8 of which have not been reported in AIH. Immune reactivity to FH was detected in 66.67% of patients with AIH, 19.35% of patients with primary biliary cirrhosis (PBC), 12.31% of patients with chronic hepatitis B (CHB), 6.35% of patients with chronic hepatitis C (CHC), 11.32% of patients with systemic lupus erythematosus (SLE), and 3.57% of normal individuals. The differences of prevalence between AIH patients and healthy controls as well as other diseases were of statistical significance (P<0.001). These data demonstrate the serological heterogeneity in AIH and suggest the diversity of the mechanisms underlying AIH. FH, recognized mainly in AIH rather than in viral hepatitis and other autoimmune diseases, may have utility in improved diagnosis of AIH.

Mouse olfactory sensory neurons express 10,000 genes

Olfactory epithelial cells from olfactory marker protein-green fluorescent protein (OMP-GFP) mice were separated by fluorescence-activated cell sorting into a GFP+ sample enriched in mature olfactory sensory neurons (OSNs) and a GFP- sample enriched in all other cells. GeneChip expression profiling of these samples provided a predictive measure of expression in OSNs. Validation tests comparing the ratio of GFP+/GFP- signal intensity against expression patterns from in situ hybridization for 189 mRNAs proved statistically significant and provided probabilities of expression in OSNs scaled according to the signal intensity ratios. These probabilities predict that, among 11,596 mRNAs detected in the GFP+ sample, more than 10,000 are expressed in OSNs. Transcripts and overrepresented categories of mRNAs detected in the GFP+ sample agreed with known properties of OSNs and predict additional properties. For example, ciliogenesis and spermatogenesis were overrepresented, consistent with similarities between OSN cilia and sperm flagella. Chromatin assembly mRNAs were expressed throughout the OSN cell lineage, consistent with the hypothesis that chromatin remodeling plays a role in OSN differentiation. We detected numerous signaling proteins and receptors, such as 30 nonchemosensory G-protein-coupled receptors, including the presynaptic glutamate receptor mGlur4 and the Wnt receptor Fzd3. The largest group of mRNAs, however, was the hundreds of transcriptional regulators that presumably determine the OSN phenotype. The absence of OMP protein in OMP-GFP mice had no detectable effect on mRNA abundance. Within limits prescribed by the nature of microarray data and the in situ hybridization validation, these data should be useful in directing further experiments on OSN function.

Rapid and intermittent cotransport of slow component-b proteins

After synthesis in neuronal perikarya, proteins destined for synapses and other distant axonal sites are transported in three major groups that differ in average velocity and protein composition: fast component (FC), slow component-a (SCa), and slow component-b (SCb). The FC transports mainly vesicular cargoes at average rates of approximately 200-400 mm/d. SCa transports microtubules and neurofilaments at average rates of approximately 0.2-1 mm/d, whereas SCb translocates approximately 200 diverse proteins critical for axonal growth, regeneration, and synaptic function at average rates of approximately 2-8 mm/d. Several neurodegenerative diseases are characterized by abnormalities in one or more SCb proteins, but little is known about mechanisms underlying SCb compared with FC and SCa. Here, we use live-cell imaging to visualize and quantify the axonal transport of three SCb proteins, alpha-synuclein, synapsin-I, and glyceraldehyde-3-phosphate dehydrogenase in cultured hippocampal neurons, and directly compare their transport to synaptophysin, a prototypical FC protein. All three SCb proteins move rapidly but infrequently with pauses during transit, unlike synaptophysin, which moves much more frequently and persistently. By simultaneously visualizing the transport of proteins at high temporal and spatial resolution, we show that the dynamics of alpha-synuclein transport are distinct from those of synaptophysin but similar to other SCb proteins. Our observations of the cotransport of multiple SCb proteins in single axons suggest that they move as multiprotein complexes. These studies offer novel mechanistic insights into SCb and provide tools for further investigating its role in disease processes.

Mutation in the epsilon subunit of the cytosolic chaperonin-containing t-complex peptide-1 (Cct5) gene causes autosomal recessive mutilating sensory neuropathy with spastic paraplegia

BACKGROUND

Mutilating sensory neuropathy with spastic paraplegia is a very rare disease with both autosomal dominant and recessive modes of inheritance. We previously mapped the locus of the autosomal recessive form to a 25 cM interval between markers D5S2048 and D5S648 on chromosome 5p. In this candidate interval, the Cct5 gene encoding the epsilon subunit of the cytosolic chaperonin-containing t-complex peptide-1 (CCT) was the most obvious candidate gene since mutation in the Cct4 gene encoding the CCT delta subunit has been reported to be associated with autosomal recessive mutilating sensory neuropathy in mutilated foot (mf) rat mutant.

METHODS

A consanguineous Moroccan family with four patients displaying mutilating sensory neuropathy associated with spastic paraplegia was investigated. To identify the disease causing gene, the 11 coding exons of the Cct5 gene were screened for mutations by direct sequencing in all family members including the four patients, parents, and six at risk relatives.

RESULTS

Sequence analysis of the Cct5 gene revealed a missense A492G mutation in exon 4 that results in the substitution of a highly conserved histidine for arginine amino acid 147. Interestingly, R147 was absent in 384 control matched chromosomes tested.

CONCLUSION

This is the first disease causing mutation that has been identified in the human CCT subunit genes; the mf rat mutant could serve as an animal model for studying these chaperonopathies.

Transcriptional changes during neuronal death and replacement in the olfactory epithelium

The olfactory epithelium has the unusual ability to replace its neurons. We forced replacement of mouse olfactory sensory neurons by bulbectomy. Microarray, bioinformatics, and in situ hybridization techniques detected a rapid shift in favor of pro-apoptotic proteins, a progressive immune response by macrophages and dendritic cells, and identified or predicted 439 mRNAs enriched in olfactory sensory neurons, including gene silencing factors and sperm flagellar proteins. Transcripts encoding cell cycle regulators, axonogenesis proteins, and transcription factors and signaling proteins that promote proliferation and differentiation were increased at 5--7 days after bulbectomy and were expressed by basal progenitor cells or immature neurons. The transcription factors included Nhlh 1, Hes 6, Lmyc 1, c-Myc, Mxd 4, Id 1, Nmyc 1, Cited 2, c-Myb, Mybl 1, Tead 2, Dp 1, Gata 2, Lmo 1, and Sox1 1. The data reveal significant similarities with embryonic neurogenesis and make several mechanistic predictions, including the roles of the transcription factors in the olfactory sensory neuron lineage.

A microarray study of MPP+-treated PC12 Cells: Mechanisms of toxicity (MOT) analysis using bioinformatics tools

Background

This paper describes a microarray study including data quality control, data analysis and the analysis of the mechanism of toxicity (MOT) induced by 1-methyl-4-phenylpyridinium (MPP⁺) in a rat adrenal pheochromocytoma cell line (PC12 cells) using bioinformatics tools. MPP⁺ depletes dopamine content and elicits cell death in PC12 cells. However, the mechanism of MPP⁺-induced neurotoxicity is still unclear.

Results

In this study, Agilent rat oligo 22K microarrays were used to examine alterations in gene expression of PC12 cells after 500 μM MPP⁺ treatment. Relative gene expression of control and treated cells represented by spot intensities on the array chips was analyzed using bioinformatics tools. Raw data from each array were input into the NCTR ArrayTrack database, and normalized using a Lowess normalization method. Data quality was monitored in ArrayTrack. The means of the averaged log ratio of the paired samples were used to identify the fold changes of gene expression in PC12 cells after MPP⁺ treatment. Our data showed that 106 genes and ESTs (Expressed Sequence Tags) were changed 2-fold and above with MPP⁺ treatment; among these, 75 genes had gene symbols and 59 genes had known functions according to the Agilent gene Refguide and ArrayTrack-linked gene library. The mechanism of MPP⁺-induced toxicity in PC12 cells was analyzed based on their genes functions, biological process, pathways and previous published literatures.

Conclusion

Multiple pathways were suggested to be involved in the mechanism of MPP⁺-induced toxicity, including oxidative stress, DNA and protein damage, cell cycling arrest, and apoptosis.

Cutaneous and sympathetic denervation in neonatal rats with a mutation in the delta subunit of the cytosolic chaperonin-containing t-complex peptide-1 gene

The mutilated-foot rat (mf rat) is an autosomal recessive mutant with characteristic digit deformities in adult animals, and this phenotype mimics many aspects of human sensory neuropathy. The genetics of mf rats was recently elucidated. To understand whether the genotype is responsible for cutaneous denervation before clinically overt mutilation in adult mf rats, we investigated skin innervation in postnatal day 7 (P7) mf rats and compared the patterns with P7 wild-type rats. The mf rat carries a G-->A mutation in the gene encoding the delta subunit of the cytosolic chaperonin-containing t-complex peptide-1 (Cct4). In the footpad skin of P7 mf rats, there was a >90% loss of epidermal nerves (0.7-7.9% of P7 wild-type rats) as indicated by neuronal markers including protein gene product 9.5 (PGP 9.5), growth-associated protein 43 (GAP43), calcitonin gene-related peptide (CGRP), and substance P (SP). The epidermis of hairy skin in hind feet was completely denervated in mf rats as well. Compared with an approximately 80% reduction in the size of dermal nerve fascicles and a parallel loss of nerve fibers, the nearly complete absence of epidermal innervation suggests further sensory nerve degeneration at the level of nerve terminals in the epidermis. In contrast, the loss of epidermal nerves in the abdominal skin of mf rats was less extensive than that in the footpad skin of mf rats; CGRP (+) and SP (+) fibers were moderately reduced (28.3-56.4% of levels of wild-type rats) with normal amounts of PGP 9.5 (+) and GAP43 (+) nerves. Sympathetic innervation as assessed by tyrosine hydroxylase immunoreactivity was absent from the footpad and abdominal skin of mf rats. In conclusion, there is regional skin denervation with diffuse sympathetic denervation in P7 mf rats. These results suggest that the mutation in Cct4 underlies cutaneous nerve degeneration in mf rats.

Stress-induced release of HSC70 from human tumors

In this study, we demonstrate that the pro-inflammatory cytokine interferon-gamma (IFN-gamma) induces the active release of the constitutive form of the 70-kDa heat shock protein (HSC70) from K562 erythroleukemic cells. Treatment of K562 cells with IFN-gamma induced the upregulation of the inducible form of the 70-kDa heat shock protein (HSP70), but not the constitutive form of HSC70 within the cytosol, in a proteasome-dependent manner. In addition, IFN-gamma induced the downregulation of surface-bound HSC70, but did not significantly alter surface-bound HSP70 expression. These findings indicate that HSC70 can be actively released from tumor cells and is indicative of a previously unknown mechanism by which immune modulators stimulate the release of intracellular HSC70. This mechanism may account for the potent chaperokine activity of heat shock proteins recently observed during heat shock protein-based immunotherapy against a variety of cancers.