Variation in heat-shock proteins among species of desert fishes (Poeciliidae, Poeciliopsis)

Analysis of the heat-shock proteins (hsps) of six closely related species of Poeciliopsis demonstrated the existence of biochemical diversity in the hsp100, hsp70, hsp60, and hsp30 protein families among species. Each species expressed five to seven hsp70-related isoforms. Constitutive 70-kD isoforms were identical among species, but four different patterns of heat-inducible isoforms were seen in these six species. Members of the hsp70 family of molecular chaperones are included among the most highly conserved proteins known, and the possibility of variation in hsp70 among closely related species has rarely been addressed. The hsp30 family is known to be less conserved than the hsp70 family, and, as expected, the Poeciliopsis hsp30 patterns showed more variation. Most of the hsp30 isoforms characteristic of a particular species were unique to that species. Hsp100 and hsp60 were identical in five of the species, but alternate isoforms were found in P. monacha. The small size and limited geographical distribution of the P. monacha population have probably contributed to the uniqueness of the monacha pattern. Two of the species were shown to acquire thermotolerance, the ability to withstand normally lethal temperatures when subjected to a gradual temperature increase. Rapid-heating protocols commonly used to establish critical thermal maxima of organisms do not include this inducible component of thermoresistance and therefore do not adequately assess an organism's capacity to withstand thermal stress.      

Suicidal ideation and reported suicide attempts in Greece during the economic crisis

The financial crisis in Greece is largely impinging on the health and mental health of the population, raising concerns about a potential rise in suicide rates. The aim of this study was to explore changes in suicidal ideation and reported suicide attempts between 2009 and 2011 in a representative sample of the population and in several population subgroups. The socio‐economic predictors of suicidal ideation and suicide attempts in 2011 were also investigated. Two nationwide cross‐sectional telephone surveys were conducted in 2009 and 2011 using the same methodology. A random and representative sample of 2192 and 2256 people, respectively, took part in the surveys. Between 2009 and 2011, there was a substantial increase in the prevalence of suicidal ideation and reported suicide attempts. People suffering from depression, men, married individuals, people experiencing financial strain, people with low interpersonal trust, and individuals with a history of suicide attempts were particularly vulnerable.     

Synuclein-1 is selectively up-regulated in response to nerve growth factor treatment in PC12 cells

Mutations in the alpha-synuclein gene have recently been identified in families with inherited Parkinson's disease and the protein product of this gene is a component of Lewy bodies, indicating that alpha-synuclein is involved in Parkinson's disease pathogenesis. A role for normal alpha-synuclein in synaptic function, apoptosis or plasticity responses has been suggested. We show here that in rat pheochromocytoma PC12 cells synuclein-1, the rat homolog of human alpha-synuclein, is highly and selectively up-regulated at the mRNA and protein levels after 7 days of nerve growth factor treatment. Synuclein-1 expression appears neither sufficient nor necessary for the neuritic sprouting that occurs within 1-2 days of nerve growth factor treatment. Rather, it likely represents a component of a late neuronal maturational response. Synuclein-1 redistributes diffusely within the cell soma and the neuritic processes in nerve growth factor-treated PC12 cells. Cultured neonatal rat sympathetic neurones express high levels of synuclein-1, with a diffuse intracellular distribution, similar to neuronal PC12 cells. These results suggest that levels of synuclein-1 may be regulated by neurotrophic factors in the nervous system and reinforce a role for alpha-synuclein in plasticity-maturational responses. In contrast, there is no correlation between synuclein expression and apoptotic death following trophic deprivation.     

Increase in ceramide level alters the lysosomal targeting of cathepsin D prior to onset of apoptosis in HT-29 colon cancer cells

Ceramide has been suggested as an important mediator of apoptosis. In HT-29 colorectal cancer cells increased ceramide levels, induced by exogenous N-acetylsphingosine (NAS, also known as C2-ceramide) or by 1-phenyl-2-(decanoylamino)-3-morpholino-1-propanol (PDMP), inhibited the transport and processing of cathepsin D (CD), a lysosomal protease implicated in apoptosis of tumour cells. C2-dihydroceramide (DH-C2), an inactive analogue of NAS, had no effect on CD transport and maturation. The treatment with either NAS or PDMP was revealed to be cytotoxic for HT-29 cells and led to cell death with classical features of apoptosis. Morphological signs of apoptosis and DNA fragmentation became apparent only between 24 and 48 h of incubation and poly(ADP ribose)-polymerase cleavage, a hallmark of caspase 3 activity, occurred no earlier than 8 h from incubation. Secretion of proCD was almost abolished and the formation of double-chain mature CD was reduced and delayed by NAS, whereas PDMP largely inhibited the lysosomal targeting and maturation of proCD. NAS- and PDMP-induced alteration of proCD transport and maturation were apparent already 2 h after incubation with the drugs, which is much earlier than when classical biochemical and morphological evidence of apoptosis could be detected. These data indicate that alteration of CD (and possibly of other glycoproteins) transport along the secretory pathway due to increased levels of cell-associated ceramide is an early event in cells undergoing apoptosis.     

Improving the clinical assessment of consciousness with advances in electrophysiological and neuroimaging techniques

In clinical neurology, a comprehensive understanding of consciousness has been regarded as an abstract concept - best left to philosophers. However, times are changing and the need to clinically assess consciousness is increasingly becoming a real-world, practical challenge. Current methods for evaluating altered levels of consciousness are highly reliant on either behavioural measures or anatomical imaging. While these methods have some utility, estimates of misdiagnosis are worrisome (as high as 43%) - clearly this is a major clinical problem. The solution must involve objective, physiologically based measures that do not rely on behaviour. This paper reviews recent advances in physiologically based measures that enable better evaluation of consciousness states (coma, vegetative state, minimally conscious state, and locked in syndrome). Based on the evidence to-date, electroencephalographic and neuroimaging based assessments of consciousness provide valuable information for evaluation of residual function, formation of differential diagnoses, and estimation of prognosis.     

alpha-synuclein is required for the fibrillar nature of ubiquitinated inclusions induced by proteasomal inhibition in primary neurons

Proteasomal dysfunction may underlie certain neuro-degenerative conditions such as Parkinson disease. We have shown that pharmacological inhibition of the proteasome in cultured neuronal cells leads to apoptotic death and formation of cytoplasmic ubiquitinated inclusions. These inclusions stain for alpha-synuclein and assume a fibrillar structure, as assessed by thioflavine S staining, and therefore resemble Lewy bodies. alpha-Synuclein is thought to be a central component of Lewy bodies. Whether alpha-synuclein is required for inclusion formation or apoptotic death has not been formally assessed. The present study examines whether alpha-synuclein deficiency in neurons alters their sensitivity to proteasomal inhibition-induced apoptosis or inclusion formation. Cortical neurons derived from alpha-synuclein-null mice showed a similar sensitivity to death induced by the proteasomal inhibitor lactacystin compared with neurons derived from wild-type mice. Furthermore, the absence of alpha-synuclein did not influence the percentage of lactacystin-treated neurons harboring cytoplasmic ubiquitinated inclusions or alter the solubility of such inclusions. In contrast, however, ubiquitinated inclusions in alpha-synuclein-deficient neurons lacked amyloid-like fibrillization, as determined by thioflavine S staining. This indicates that although alpha-synuclein deficiency does not affect the formation of ubiquitinated inclusions, it does significantly alter their structure. The lack of effect on survival in alpha-synuclein knock-out cultures further suggests that the fibrillar nature of the inclusions does not contribute to neuronal degeneration in this model.     

RAIDD is required for apoptosis of PC12 cells and sympathetic neurons induced by trophic factor withdrawal

Caspase 2 has been implicated in trophic deprivation-induced neuronal death. We have shown that overexpression of the caspase 2-binding protein RAIDD induces neuronal apoptosis, acting synergistically with trophic deprivation. Currently, we examine the role of endogenous RAIDD in apoptosis of PC12 cells and sympathetic neurons. Expression of a truncated caspase recruitment domain-only form of caspase 2, which presumably disrupts the RAIDD interaction with endogenous caspase 2, attenuated trophic deprivation-induced apoptosis. Furthermore, downregulation of RAIDD by small interfering RNA led to inhibition of trophic deprivation-induced death, whereas death induced by DNA damage, which is not caspase 2-mediated, was not inhibited. Therefore, RAIDD, likely through interaction with caspase 2, is involved in trophic deprivation-induced neuronal apoptosis. This is the first demonstration of the involvement of RAIDD in apoptosis, and provides further support for the idea that apoptotic pathways in the same system may differ depending on the initiating stimulus.     

The Neurobiology of LRRK2 and its Role in the Pathogenesis of Parkinson’s Disease

Leucine-rich repeat kinase 2 (LRRK2) is a large, widely expressed protein of largely unknown function. Mutations in the gene encoding LRRK2 have been linked to multiple diseases, including a prominent association with familial and sporadic Parkinson’s disease (PD), as well as inflammatory bowel disorders such as Crohn’s disease. The LRRK2 protein possesses both kinase and GTPase signaling domains, as well as multiple protein interaction domains. Experimental studies in both cellular and in vivo models of mutant LRRK2-induced neurodegeneration have given clues to potential function(s) of LRRK2, yet much remains unknown. For example, while it is known that intact kinase and GTPase activity are required for mutant forms of the protein to trigger cell death, the specific targets of these enzymatic activities that mediate the death of neurons are not known. In this review, we discuss the evidence linking LRRK2 to various cellular/neuronal activities such as extrinsic death and inflammatory signaling, lysosomal protein degradation, the cytoskeletal system and neurite outgrowth, vesicle trafficking, mitochondrial dysfunction, as well as multiple points of interaction with several other genes linked to the pathogenesis of PD. In order for more effective therapeutic strategies to be envisioned and implemented, the mechanisms underlying LRRK2-mediated neurodegeneration need to be better characterized. Furthermore, insights into LRRK2-associated PD pathogenesis can potentially advance our understanding of the more common sporadic forms of PD.