Sorcin is an early marker of neurodegeneration, Ca2+ dysregulation and endoplasmic reticulum stress associated to neurodegenerative diseases.

Dysregulation of calcium signaling is emerging as a key feature in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD), and targeting this process may be therapeutically beneficial. Under this perspective, it is important to study proteins that regulate calcium homeostasis in the cell. Sorcin is one of the most expressed calcium-binding proteins in the human brain; its overexpression increases endoplasmic reticulum (ER) calcium concentration and decreases ER stress in the heart and in other cellular types. Sorcin has been hypothesized to be involved in neurodegenerative diseases, since it may counteract the increased cytosolic calcium levels associated with neurodegeneration. In the present work, we show that Sorcin expression levels are strongly increased in cellular, animal, and human models of AD, PD, and HD, vs. normal cells. Sorcin partially colocalizes with RyRs in neurons and microglia cells; functional experiments with microsomes containing high amounts of RyR2 and RyR3, respectively, show that Sorcin is able to regulate these ER calcium channels. The molecular basis of the interaction of Sorcin with RyR2 and RyR3 is demonstrated by SPR. Sorcin also interacts with other ER proteins as SERCA2 and Sigma-1 receptor in a calcium-dependent fashion. We also show that Sorcin regulates ER calcium transients: Sorcin increases the velocity of ER calcium uptake (increasing SERCA activity). The data presented here demonstrate that Sorcin may represent both a novel early marker of neurodegenerative diseases and a response to cellular stress dependent on neurodegeneration.

C-terminal tails mimicking bioactive intermediates cause different plasma degradation patterns and kinetics in neuropeptides γ-MSH, α-MSH, and neurotensin.

Peptides are attractive drugs because of their specificity and minimal off-target effects. Short half-lives are within their major drawbacks, limiting actual use in clinics. The golden standard in therapeutic peptide development implies identification of a minimal core sequence, then modified to increase stability through several strategies, including the introduction of nonnatural amino acids, cyclization, and lipidation. Here, we investigated plasma degradations of hormone sequences all composed of a minimal active core peptide and a C-terminal extension. We first investigated pro-opimelanocortin (POMC) γ2/γ3-MSH hormone behavior and extended our analysis to POMC-derived α-melanocyte stimulating hormone/adrenocorticotropic hormone signaling neuropeptides and neurotensin. We demonstrated that in all the three cases analyzed in this study, few additional residues mimicking the natural sequence alter both peptide stability and the mechanism(s) of degradation of the minimal conserved functional pattern. Our results suggest that the impact of extensions on the bioactivity of a peptide drug has to be carefully evaluated throughout the optimization process.

A split-GFP tool reveals differences in the sub-mitochondrial distribution of wt and mutant alpha-synuclein.

Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by dopaminergic neuronal loss that initiates in the substantia nigra pars compacta and by the formation of intracellular inclusions mainly constituted by aberrant α-synuclein (α-syn) deposits known as Lewy bodies. Most cases of PD are sporadic, but about 10% are familial, among them those caused by mutations in SNCA gene have an autosomal dominant transmission. SNCA encodes α-syn, a small 140-amino acids protein that, under physiological conditions, is mainly localized at the presynaptic terminals. It is prevalently cytosolic, but its presence has been reported in the nucleus, in the mitochondria and, more recently, in the mitochondria-associated ER membranes (MAMs). Whether different cellular localizations may reflect specific α-syn activities is presently unclear and its action at mitochondrial level is still a matter of debate. Mounting evidence supports a role for α-syn in several mitochondria-derived activities, among which maintenance of mitochondrial morphology and modulation of complex I and ATP synthase activity. α-syn has been proposed to localize at the outer membrane (OMM), in the intermembrane space (IMS), at the inner membrane (IMM) and in the mitochondrial matrix, but a clear and comparative analysis of the sub-mitochondrial localization of WT and mutant α-syn is missing. Furthermore, the reasons for this spread sub-mitochondrial localization under physiological and pathological circumstances remain elusive. In this context, we decided to selectively monitor the sub-mitochondrial distribution of the WT and PD-related α-syn mutants A53T and A30P by taking advantage from a bimolecular fluorescence complementation (BiFC) approach. We also investigated whether cell stress could trigger α-syn translocation within the different mitochondrial sub-compartments and whether PD-related mutations could impinge on it. Interestingly, the artificial targeting of α-syn WT (but not of the mutants) to the mitochondrial matrix impacts on ATP production, suggesting a potential role within this compartment.

Phenylboronic Acids Probing Molecular Recognition against Class A and Class C ß-lactamases.

Worldwide dissemination of pathogens resistant to almost all available antibiotics represent a real problem preventing efficient treatment of infectious diseases. Among antimicrobial used in therapy, ß-lactam antibiotics represent 40% thus playing a crucial role in the management of infections treatment. We report a small series of phenylboronic acids derivatives (BAs) active against class A carbapenemases KPC-2 and GES-5, and class C cephalosporinases AmpC. The inhibitory profile of our BAs against class A and C was investigated by means of molecular docking, enzyme kinetics and X-ray crystallography. We were interested in the mechanism of recognition among class A and class C to direct the design of broad serine ß-Lactamases (SBLs) inhibitors. Molecular modeling calculations vs GES-5 and crystallographic studies vs AmpC reasoned, respectively, the ortho derivative 2 and the meta derivative 3 binding affinity. The ability of our BAs to protect ß-lactams from BLs hydrolysis was determined in biological assays conducted against clinical strains: Fractional inhibitory concentration index (FICI) tests confirmed their ability to be synergic with ß-lactams thus restoring susceptibility to meropenem. Considering the obtained results and the lack of cytotoxicity, our derivatives represent validated probe for the design of SBLs inhibitors.

splitGFP Technology Reveals Dose-Dependent ER-Mitochondria Interface Modulation by α-Synuclein A53T and A30P Mutants.

Familial Parkinson's disease (PD) is associated with duplication or mutations of α-synuclein gene, whose product is a presynaptic cytosolic protein also found in mitochondria and in mitochondrial-associated ER membranes. We have originally shown the role of α-syn as a modulator of the ER-mitochondria interface and mitochondrial Ca2+ transients, suggesting that, at mild levels of expression, α-syn sustains cell metabolism. Here, we investigated the possibility that α-syn action on ER-mitochondria tethering could be compromised by the presence of PD-related mutations. The clarification of this aspect could contribute to elucidate key mechanisms underlying PD. The findings reported so far are not consistent, possibly because of the different methods used to evaluate ER-mitochondria connectivity. Here, the effects of the PD-related α-syn mutations A53T and A30P on ER-mitochondria relationship were investigated in respect to Ca2+ handling and mitochondrial function using a newly generated SPLICS sensor and aequorin-based Ca2+measurements. We provided evidence that A53T and A30P amino acid substitution does not affect the ability of α-syn to enhance ER/mitochondria tethering and mitochondrial Ca2+ transients, but that this action was lost as soon as a high amount of TAT-delivered A53T and A30P α-syn mutants caused the redistribution of α-syn from cytoplasm to foci. Our results suggest a loss of function mechanism and highlight a possible connection between α-syn and ER-mitochondria Ca2+ cross-talk impairment to the pathogenesis of PD.

Impaired Mitochondrial ATP Production Downregulates Wnt Signaling via ER Stress Induction.

Wnt signaling affects fundamental development pathways and, if aberrantly activated, promotes the development of cancers. Wnt signaling is modulated by different factors, but whether the mitochondrial energetic state affects Wnt signaling is unknown. Here, we show that sublethal concentrations of different compounds that decrease mitochondrial ATP production specifically downregulate Wnt/ß-catenin signaling in vitro in colon cancer cells and in vivo in zebrafish reporter lines. Accordingly, fibroblasts from a GRACILE syndrome patient and a generated zebrafish model lead to reduced Wnt signaling. We identify a mitochondria-Wnt signaling axis whereby a decrease in mitochondrial ATP reduces calcium uptake into the endoplasmic reticulum (ER), leading to endoplasmic reticulum stress and to impaired Wnt signaling. In turn, the recovery of the ATP level or the inhibition of endoplasmic reticulum stress restores Wnt activity. These findings reveal a mechanism that links mitochondrial energetic metabolism to the control of the Wnt pathway that may be beneficial against several pathologies.

A chloroplast-localized mitochondrial calcium uniporter transduces osmotic stress in Arabidopsis.

Chloroplasts are integral to sensing biotic and abiotic stress in plants, but their role in transducing Ca2+-mediated stress signals remains poorly understood1,2. Here we identify cMCU, a member of the mitochondrial calcium uniporter (MCU) family, as an ion channel mediating Ca2+ flux into chloroplasts in vivo. Using a toolkit of aequorin reporters targeted to chloroplast stroma and the cytosol in cMCU wild-type and knockout lines, we provide evidence that stress-stimulus-specific Ca2+ dynamics in the chloroplast stroma correlate with expression of the channel. Fast downstream signalling events triggered by osmotic stress, involving activation of the mitogen-activated protein kinases (MAPK) MAPK3 and MAPK6, and the transcription factors MYB60 and ethylene-response factor 6 (ERF6), are influenced by cMCU activity. Relative to wild-type plants, cMCU knockouts display increased resistance to long-term water deficit and improved recovery on rewatering. Modulation of stromal Ca2+ in specific processing of stress signals identifies cMCU as a component of plant environmental sensing.

Measuring Ca2+ Levels in Subcellular Compartments with Genetically Encoded GFP-Based Indicators.

Ca2+ homeostasis is crucial for the entire life of eukaryotic cells from the beginning to the end. Mishandling in Ca2+ homeostasis is indeed linked with a large number of pathological conditions. Thus, the possibility to specifically monitor cellular calcium fluxes in different subcellular compartments represents a key tool to deeply understand the mechanisms involved in cellular dysfunctions. To cope with this need, several Ca2+ indicators have been developed allowing to accurately measure both basal Ca2+ concentration and agonist-induced Ca2+ signals in a wide spectrum of organelles. Among these, the genetically encoded GFP-based indicators are routinely used to measure Ca2+ transients thanks to their ability to change their spectral properties in response to Ca2+ binding. In this chapter, we will describe a protocol that utilizes the GCaMP6f probe targeted to mitochondria (4mtGCaMP) to measure mitochondrial calcium levels in resting conditions in HeLa cells. This method allows to easily and quickly register alterations of mitochondrial Ca2+ homeostasis in different cell populations and experimental settings, representing a precious tool to unravel the pathological pathways leading to pathogenic conditions.

Tau localises within mitochondrial sub-compartments and its caspase cleavage affects ER-mitochondria interactions and cellular Ca2+ handling.

Intracellular neurofibrillary tangles (NFT) composed by tau and extracellular amyloid beta (Aß) plaques accumulate in Alzheimer's disease (AD) and contribute to neuronal dysfunction. Mitochondrial dysfunction and neurodegeneration are increasingly considered two faces of the same coin and an early pathological event in AD. Compelling evidence indicates that tau and mitochondria are closely linked and suggests that tau-dependent modulation of mitochondrial functions might be a trigger for the neurodegeneration process; however, whether this occurs either directly or indirectly is not clear. Furthermore, whether tau influences cellular Ca2+ handling and ER-mitochondria cross-talk is yet to be explored. Here, by focusing on wt tau, either full-length (2N4R) or the caspase 3-cleaved form truncated at the C-terminus (2N4RΔC20), we examined the above-mentioned aspects. Using new genetically encoded split-GFP-based tools and organelle-targeted aequorin probes, we assessed: i) tau distribution within the mitochondrial sub-compartments; ii) the effect of tau on the short- (8-10 nm) and the long- (40-50 nm) range ER-mitochondria interactions; and iii) the effect of tau on cytosolic, ER and mitochondrial Ca2+ homeostasis. Our results indicate that a fraction of tau is found at the outer mitochondrial membrane (OMM) and within the inner mitochondrial space (IMS), suggesting a potential tau-dependent regulation of mitochondrial functions. The ER Ca2+ content and the short-range ER-mitochondria interactions were selectively affected by the expression of the caspase 3-cleaved 2N4RΔC20 tau, indicating that Ca2+ mis-handling and defects in the ER-mitochondria communications might be an important pathological event in tau-related dysfunction and thereby contributing to neurodegeneration. Finally, our data provide new insights into the molecular mechanisms underlying tauopathies.

A Preclinical Model for the ATLL Lymphoma Subtype With Insights Into the Role of Microenvironment in HTLV-1-Mediated Lymphomagenesis.

Adult T cell Leukemia/Lymphoma (ATLL) is a mature T cell malignancy associated with Human T cell Leukemia Virus type 1 (HTLV-1) infection. Among its four main clinical subtypes, the prognosis of acute and lymphoma variants remains poor. The long latency (3-6 decades) and low incidence (3-5%) of ATLL imply the involvement of viral and host factors in full-blown malignancy. Despite multiple preclinical and clinical studies, the contribution of the stromal microenvironment in ATLL development is not yet completely unraveled. The aims of this study were to investigate the role of the host microenvironment, and specifically fibroblasts, in ATLL pathogenesis and to propose a murine model for the lymphoma subtype. Here we present evidence that the oncogenic capacity of HTLV-1-immortalized C91/PL cells is enhanced when they are xenotransplanted together with human foreskin fibroblasts (HFF) in immunocompromised BALB/c Rag2-/-γc-/- mice. Moreover, cell lines derived from a developed lymphoma and their subsequent in vivo passages acquired the stable property to induce aggressive T cell lymphomas. In particular, one of these cell lines, C91/III cells, consistently induced aggressive lymphomas also in NOD/SCID/IL2Rγc KO (NSG) mice. To dissect the mechanisms linked to this enhanced tumorigenic ability, we quantified 45 soluble factors released by these cell lines and found that 21 of them, mainly pro-inflammatory cytokines and chemokines, were significantly increased in C91/III cells compared to the parental C91/PL cells. Moreover, many of the increased factors were also released by human fibroblasts and belonged to the known secretory pattern of ATLL cells. C91/PL cells co-cultured with HFF showed features reminiscent of those observed in C91/III cells, including a similar secretory pattern and a more aggressive behavior in vivo. On the whole, our data provide evidence that fibroblasts, one of the major stromal components, might enhance tumorigenesis of HTLV-1-infected and immortalized T cells, thus throwing light on the role of microenvironment contribution in ATLL pathogenesis. We also propose that the lymphoma induced in NSG mice by injection with C91/III cells represents a new murine preclinical ATLL model that could be adopted to test novel therapeutic interventions for the aggressive lymphoma subtype.

The Close Encounter Between Alpha-Synuclein and Mitochondria.

The presynaptic protein alpha-synuclein (α-syn) is unequivocally linked to the development of Parkinson's disease (PD). Not only it is the major component of amyloid fibrils found in Lewy bodies but mutations and duplication/triplication in its gene are responsible for the onset of familial autosomal dominant forms of PD. Nevertheless, the precise mechanisms leading to neuronal degeneration are not fully understood. Several lines of evidence suggest that impaired autophagy clearance and mitochondrial dysfunctions such as bioenergetics and calcium handling defects and alteration in mitochondrial morphology might play a pivotal role in the etiology and progression of PD, and indicate the intriguing possibility that α-syn could be involved in the control of mitochondrial function both in physiological and pathological conditions. In favor of this, it has been shown that a fraction of cellular α-syn can selectively localize to mitochondrial sub-compartments upon specific stimuli, highlighting possible novel routes for α-syn action. A plethora of mitochondrial processes, including cytochrome c release, calcium homeostasis, control of mitochondrial membrane potential and ATP production, is directly influenced by α-syn. Eventually, α-syn localization within mitochondria may also account for its aggregation state, making the α-syn/mitochondria intimate relationship a potential key for the understanding of PD pathogenesis. Here, we will deeply survey the recent literature in the field by focusing our attention on the processes directly controlled by α-syn within mitochondrial sub-compartments and its potential partners providing possible hints for future therapeutic targets.

A V1143F mutation in the neuronal-enriched isoform 2 of the PMCA pump is linked with ataxia.

The fine regulation of intracellular calcium is fundamental for all eukaryotic cells. In neurons, Ca2+ oscillations govern the synaptic development, the release of neurotransmitters and the expression of several genes. Alterations of Ca2+ homeostasis were found to play a pivotal role in neurodegenerative progression. The maintenance of proper Ca2+ signaling in neurons demands the continuous activity of Ca2+ pumps and exchangers to guarantee physiological cytosolic concentration of the cation. The plasma membrane Ca2+ATPases (PMCA pumps) play a key role in the regulation of Ca2+ handling in selected sub-plasma membrane microdomains. Among the four basic PMCA pump isoforms existing in mammals, isoforms 2 and 3 are particularly enriched in the nervous system. In humans, genetic mutations in the PMCA2 gene in association with cadherin 23 mutations have been linked to hearing loss phenotypes, while those occurring in the PMCA3 gene were associated with X-linked congenital cerebellar ataxias. Here we describe a novel missense mutation (V1143F) in the calmodulin binding domain (CaM-BD) of the PMCA2 protein. The mutant pump was present in a patient showing congenital cerebellar ataxia but no overt signs of deafness, in line with the absence of mutations in the cadherin 23 gene. Biochemical and molecular dynamics studies on the mutated PMCA2 have revealed that the V1143F substitution alters the binding of calmodulin to the CaM-BD leading to impaired Ca2+ ejection.

Phenylboronic Acid Derivatives as Validated Leads Active in Clinical Strains Overexpressing KPC-2: A Step against Bacterial Resistance.

The emergence and dissemination of multidrug resistant (MDR) pathogens resistant to nearly all available antibiotics poses a significant threat in clinical therapy. Among them, Klebsiella pneumoniae clinical isolates overexpressing KPC-2 carbapenemase are the most worrisome, extending bacterial resistance to last-resort carbapenems. In this study, we investigate the molecular recognition requirements in the KPC-2 active site by small phenylboronic acid derivatives. Four new phenylboronic acid derivatives were designed and tested against KPC-2. For the most active, despite their simple chemical structures, nanomolar affinity was achieved. The new derivatives restored susceptibility to meropenem in clinical strains overexpressing KPC-2. Moreover, no cytotoxicity was detected in cell-viability assays, which further validated the designed leads. Two crystallographic binary complexes of the best inhibitors binding KPC-2 were obtained at high resolution. Kinetic descriptions of slow binding, time-dependent inhibition, and interaction geometries in KPC-2 were fully investigated. This study will ultimately lead toward the optimization and development of more-effective KPC-2 inhibitors.

SPLICS: a split green fluorescent protein-based contact site sensor for narrow and wide heterotypic organelle juxtaposition.

Contact sites are discrete areas of organelle proximity that coordinate essential physiological processes across membranes, including Ca2+ signaling, lipid biosynthesis, apoptosis, and autophagy. However, tools to easily image inter-organelle proximity over a range of distances in living cells and in vivo are lacking. Here we report a split-GFP-based contact site sensor (SPLICS) engineered to fluoresce when organelles are in proximity. Two SPLICS versions efficiently measured narrow (8-10 nm) and wide (40-50 nm) juxtapositions between endoplasmic reticulum and mitochondria, documenting the existence of at least two types of contact sites in human cells. Narrow and wide ER-mitochondria contact sites responded differently to starvation, ER stress, mitochondrial shape modifications, and changes in the levels of modulators of ER-mitochondria juxtaposition. SPLICS detected contact sites in soma and axons of D. rerio Rohon Beard (RB) sensory neurons in vivo, extending its use to analyses of organelle juxtaposition in the whole animal.

A novel PMCA3 mutation in an ataxic patient with hypomorphic phosphomannomutase 2 (PMM2) heterozygote mutations: Biochemical characterization of the pump defect.

The neuron-restricted isoform 3 of the plasma membrane Ca2+ ATPase plays a major role in the regulation of Ca2+ homeostasis in the brain, where the precise control of Ca2+ signaling is a necessity. Several function-affecting genetic mutations in the PMCA3 pump associated to X-linked congenital cerebellar ataxias have indeed been described. Interestingly, the presence of co-occurring mutations in additional genes suggest their synergistic action in generating the neurological phenotype as digenic modulators of the role of PMCA3 in the pathologies. Here we report a novel PMCA3 mutation (G733R substitution) in the catalytic P-domain of the pump in a patient affected by non-progressive ataxia, muscular hypotonia, dysmetria and nystagmus. Biochemical studies of the pump have revealed impaired ability to control cellular Ca2+ handling both under basal and under stimulated conditions. A combined analysis by homology modeling and molecular dynamics have revealed a role for the mutated residue in maintaining the correct 3D configuration of the local structure of the pump. Mutation analysis in the patient has revealed two additional function-impairing compound heterozygous missense mutations (R123Q and G214S substitution) in phosphomannomutase 2 (PMM2), a protein that catalyzes the isomerization of mannose 6-phosphate to mannose 1-phosphate. These mutations are known to be associated with Type Ia congenital disorder of glycosylation (PMM2-CDG), the most common group of disorders of N-glycosylation. The findings highlight the association of PMCA3 mutations to cerebellar ataxia and strengthen the possibility that PMCAs act as digenic modulators in Ca2+-linked pathologies.

Generation and validation of novel adeno-associated viral vectors for the analysis of Ca2+ homeostasis in motor neurons.

A finely tuned Ca2+ homeostasis in restricted cell domains is of fundamental importance for neurons, where transient Ca2+ oscillations direct the proper coordination of electro-chemical signals and overall neuronal metabolism. Once such a precise regulation is unbalanced, however, neuronal functions and viability are severely compromised. Accordingly, disturbed Ca2+ metabolism has often been claimed as a major contributor to different neurodegenerative disorders, such as amyotrophic lateral sclerosis that is characterised by selective motor neuron (MN) damage. This notion highlights the need for probes for the specific and precise analysis of local Ca2+ dynamics in MNs. Here, we generated and functionally validated adeno-associated viral vectors for the expression of gene-encoded fluorescent Ca2+ indicators targeted to different cell domains, under the transcriptional control of a MN-specific promoter. We demonstrated that the probes are specifically expressed, and allow reliable local Ca2+ measurements, in MNs from murine primary spinal cord cultures, and can also be expressed in spinal cord MNs in vivo, upon systemic administration to newborn mice. Preliminary analyses using these novel vectors have shown larger cytosolic Ca2+ responses following stimulation of AMPA receptors in the cytosol of primary cultured MNs from a murine genetic model of ALS compared to the healthy counterpart.

Recurrent Kaposi sarcoma associated with Koebner phenomenon in two HIV-seronegative patients: Two case reports and a review of the literature.

RATIONALE: Koebner phenomenon is occasionally reported in patients affected by classic Kaposi sarcoma (KS). PATIENT CONCERNS: Here, we report 2 cases of KS associated with Koebner phenomenon and the correlation of human herpesvirus 8 molecular analysis with the clinical outcome. INTERVENTIONS: In the first case, a patient with a history of sporadic cutaneous KS developed a recurrent lesion at the laryngeal tract, the site of a previous nodulectomy. In our second case, immunodeficiency induced by chemotherapy triggered the development of KS and Koebner phenomenon was limited to the skin at the site of safenectomy. LESSONS: Our observations suggest that careful planning of surgical treatment is required in immunocompetent and immunocompromised patients with a medical history of KS. Moreover, mucosal sites (both respiratory and in the gastrointestinal tract) should be considered as potential sites for KS development.

A novel prion protein-tyrosine hydroxylase interaction.

The prion protein (PrP) is currently one of the most studied molecules in the neurosciences. It is the main cause of a group of neurological diseases collectively called transmissible spongiform encephalopathies that severely affect both humans and a variety of mammals. Much effort has been directed to understanding the molecular basis of PrP activity, both in physiological and pathological terms. In this context, identification of neuronally-relevant interactors of PrP may play a crucial role. We recently discovered a specific, high-affinity (nanomolar KD) interaction with tyrosine hydroxylase (TH), a enzyme catalyzing the rate-limiting step in the synthesis of the neurotransmitter dopamine. Using molecular biological, biochemical and biophysical techniques we identified the C-terminal structured domain of PrP and the Nterminal regulatory domain of TH as interacting domains between these two proteins. This interaction does not affect TH activity in vitro, although co-expression experiments in HeLa and Chinese hamster ovary cells revealed that PrP is able to internalize TH. Moreover, TH modulated the level of expression of PrP and its localization at the plasma membrane. This novel interaction between two proteins of central importance in nervous system function may shed new light on our understanding of PrP in neurological diseases.

The small heat shock protein HspB8: role in nervous system physiology and pathology.

The accumulation and aggregation of misfolded proteins can be highly cytotoxic and may underlie several human degenerative diseases characterized by neuronal inclusions such as Alzheimer's, Parkinson's, prion-like and polyglutamine repeat diseases. In this context small heat shock proteins, molecular chaperones known to be induced by cell stress, play a fundamental role by facilitating folding of nascent polypeptides, preventing aggregation of misfolded proteins and enhancing their degradation. A recently identified member of the small heat shock protein family, HspB8, is of particular interest in the field of neurological diseases since mutations in its sequence correlate with development of distal hereditary motor neuropathy and Charcot-Marie-Tooth disease. HspB8 expression has been detected in neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, Huntington disease and spinocerebellar ataxia type 3. In the latter, HspB8 appears to be involved in protecting the cell from accumulation of insoluble aggregates either by preventing aggregation or by promoting degradation of improperly folded proteins. These data propose that HspB8 may be a major player in the neuroprotective response and a promising target for the development of therapeutic strategies.

The role of phosphorylation in synucleinopathies: focus on Parkinson's disease.

Synuclein is a soluble, natively unfolded protein that is highly enriched in the presynaptic terminals of neurons in the central nervous system. Interest in -synuclein has increased markedly following the discovery of a relationship between its dysfunction and several neurodegenerative diseases, including Parkinson's disease. The physiological functions of -synuclein remain to be fully defined, although recent data suggest a role in regulating membrane stability and neuronal plasticity. In addition, there is increasing evidence pointing to phosphorylation as playing an important role in the oligomerization, fibrillogenesis, Lewy body formation, and neurotoxicity of -syncline in Parkinson's disease. Immunohistochemical and biochemical studies reveal that the majority of -synuclein within inclusions from patients with Parkinson's disease and other synucleinopathies is phosphorylated at Ser129. -Synuclein can be phosphorylated in vitro also at Ser87, and three C-terminal tyrosine residues (Tyr125, Tyr 133, and Tyr136). Tyrosine 125 phosphorylation diminishes during the normal aging process in both humans and flies. Notably, cortical tissue from patients with Parkinson's disease-related synucleinopathy dementia with Lewy bodies showed less phosphorylation at Tyr125. While phosphorylation at Ser87 is enhanced in synucleinopathies, it inhibits -synuclein oligomerization, and influences synuclein-membrane interactions. The possibility that -synuclein neurotoxicity in Parkinson's disease and related synucleinopathies may result from an imbalance between the detrimental, oligomer-promoting effect of Ser129 phosphorylation and a neuroprotective action of Ser87/Tyr125 phosphorylation that inhibits toxic oligomer formation merits consideration, as will be discussed in this article.