Gabriella Sconzo

Hsp70 and Its Molecular Role in Nervous System Diseases

Heat shock proteins (HSPs) are induced in response to many injuries including stroke, neurodegenerative disease, epilepsy, and trauma. The overexpression of one HSP in particular, Hsp70, serves a protective role in several different models of nervous system injury, but has also been linked to a deleterious role in some diseases. Hsp70 functions as a chaperone and protects neurons from protein aggregation and toxicity (Parkinson disease, Alzheimer disease, polyglutamine diseases, and amyotrophic lateral sclerosis), protects cells from apoptosis (Parkinson disease), is a stress marker (temporal lobe epilepsy), protects cells from inflammation (cerebral ischemic injury), has an adjuvant role in antigen presentation and is involved in the immune response in autoimmune disease (multiple sclerosis). The worldwide incidence of neurodegenerative diseases is high. As neurodegenerative diseases disproportionately affect older individuals, disease-related morbidity has increased along with the general increase in longevity. An understanding of the underlying mechanisms that lead to neurodegeneration is key to identifying methods of prevention and treatment. Investigators have observed protective effects of HSPs induced by preconditioning, overexpression, or drugs in a variety of models of brain disease. Experimental data suggest that manipulation of the cellular stress response may offer strategies to protect the brain during progression of neurodegenerative disease.

Extracellular membrane vesicles as a mechanism of cell-to-cell communication: advantages and disadvantages

Microvesicles represent a newly identified mechanism of intercellular communication. Two different types of microvesicles have been identified: membrane-derived vesicles (EVs) and exosomes. EVs originate by direct budding from the plasma membrane, while exosomes arise from ectocytosis of multivesicular bodies. Recent attention has focused on the capacity of EVs to alter the phenotype of neighboring cells to make them resemble EV-producing cells. Stem cells are an abundant source of EVs, and the interaction between stem cells and the microenvironment (i.e., stem cell niche) plays a critical role in determining stem cell phenotype. The stem cell niche hypothesis predicts that stem cell number is limited by the availability of niches releasing the necessary signals for self-renewal and survival, and the niche thus provides a mechanism for controlling and limiting stem cell numbers. EVs may play a fundamental role in this context by transferring genetic information between cells. EVs can transfer mRNA and microRNA to target cells, both of which may be involved in the change in target-cell phenotype towards that of EV-producing cells. The exchange of genetic information may be bidirectional, and EV-mediated transfer of genetic information after tissue damage may reprogram stem cells to acquire the phenotypic features of the injured tissue cells. In addition, stem cell-derived EVs may induce the de-differentiation of cells that survive injury by promoting their reentry into the cell cycle and subsequently increasing the possibility of tissue regeneration.

A constitutive 70 kDa heat-shock protein is localized on the fibres of spindles and asters at metaphase in an ATP-dependent manner: a new chaperone role is proposed.

In the present study, double immunofluorescence and immunoblot analysis have been used to show that centrosomes, isolated from Paracentrotus lividus sea urchin embryos at the first mitotic metaphase, contain the constitutive chaperone, heat-shock protein (HSP) 70. More specifically, we demonstrate that centrosomes contain only the HSP70-d isoform, which is one of the four isoforms identified in P. lividus. We also provide evidence that p34(cell division control kinase-2) and t complex polypeptide-1 (TCP-1) alpha, a subunit of the TCP-1 complex, are localized on the centrosomes. Furthermore, inhibition of TCP-1 in vivo, via microinjecting an anti-(TCP-1 alpha) antibody into P. lividus eggs before fertilization, either impaired mitosis or induced severe malformations in more than 50% of embryos. In addition, we have isolated the whole mitotic apparatus and shown that HSP70 localizes on the fibres of spindles and asters, and binds them in an ATP-dependent manner. These observations suggest that HSP70 has a chaperone role in assisting the TCP-1 complex in tubulin folding, when localized on centrosomes, and during the assembling and disassembling of the mitotic apparatus, when localized on the fibres of spindles and asters.

Protective role of heat shock proteins in Parkinson's disease.

Parkinson’s disease (PD) is the second most common neurodegenerative disease after Alzheimer’s disease. Despite a large amount of research, the pathogenetic mechanism of these diseases has not yet been clarified. Abnormal protein folding, oxidative stress, mitochondrial dysfunction, and apoptotic mechanisms have all been reported as causes of neurodegenerative diseases in association with neuroinflammatory mechanisms which, by generating deleterious molecules, could promote the cascade of events leading to neurodegeneration. Heat shock proteins (HSPs) play a central role in preventing protein misfolding and inhibiting apoptotic activity, and represent a class of proteins potentially involved in PD pathogenesis. The present review will focus on two HSPs, HSP70 and HSP90, with the aim of specifying their role in PD pathogenesis.

Studies on heat shock proteins in sea urchin development

Work on stress proteins in sea urchin embryos carried out over the last 20 years is reviewed and the following major results are described. Entire sea urchin embryos, if subjected to a rise in temperature at any postblastular stage undergo a wave of heat shock protein (hsp) synthesis and survive. If subjected to the same rise between fertilization and blastula formation, they are not yet able to synthesize hsp and die. Four clones coding for the major hsp, hsp70, have been isolated and sequenced; evidence for the existence of a heat shock factor has been provided, and a mechanism for the developmental regulation of hsp synthesis discussed. Intra‐ embryonic and intracellular hsp location has been described; and a mechanism for achievement of thermotolerance proposed. A chaperonine role for a constitutive mitochondrial hsp56 has been suggested, as well as a role for the constitutive hsp70 in cell division. Heat shock, if preceded by 12‐O‐tetradecanoylphorbol‐12‐acetate (TPA) treatment causes apoptosis.

Synthesis of ribosomal RNA in disaggregated cells of sea urchin embryos

Abstract The specific activity of the α-phosphate of the acid-soluble nucleotide pool has been found to remain constant for several hours after the dissociation into cells of embryos previously exposed to inorganic 32 P. The rate of incorporation of 32 P into 28-S rRNA of dissociated cells deriving from prelabeled embryos has been used as a measure of the rate of rRNA synthesis. The results strongly suggest that neither intercellular contact nor cell division, at least from the stage of hatching on, are needed for the activation of rRNA synthesis, characteristic of the normal development, to take place.

Synthesis of ribosomal RNA during sea urchin development: III. Evidence for an activation of transcription

Abstract Embryos of Paracentrotus lividus have been preloaded with 32P1 until the early blastula stage. The amount of the total acid-soluble nucleotide pool, as well as the specific activity of the α-phosphates of such nucleotides, were found to remain practically constant until at least the prism stage. The specific activity attained at different stages by the 28-S rRNA was calculated and referred to the total DNA content of the embryos. An activation of rRNA transcription following the swimming blastula stage has been demonstrated.

Parkinson's Disease and Cancer

Epidemiological evidence suggests a reduced incidence of many common types of cancers in individuals with Parkinsons disease (PD). Parkinsons disease and cancer are two diseases that result from an excessive signaling by one of two forces driving cells to opposite directions. PD results from the excessive death of dopaminergic neurons in the substantia nigra pars compacta (SNc) in the brain, while uncontrolled growth is the key property of cancer. Parkinsons disease is a complex disorder, probably due in most of the cases to the interaction of environment and genes. Many genes responsible for familial forms of PD are supposed to have a supportive role in regulating or maintaining the cell cycle, a fact that allows us to assume their interaction in tumorigenesis. Understanding the nature of these processes may help researchers find new and more efficacious therapeutic approaches for both diseases.

Studies on sea urchin oocytes II. Synthesis of RNA during oogenesis

Abstract Isolated oocytes of the sea urchin Paracentrotus lividus actively incorporate 3H-uridine into RNA. Labeled RNA was analysed by sucrose gradient and acrylamide gel electrophoresis following cell fractionation. Much of the radioactivity is incorporated at the nucleolar level in the form of rRNA precursors. The kinetics of maturation of these latter suggests that this occurs at a slower rate than during embryogenesis. Other non-nucleolar RNA classes are also actively labelled and retained in the nucleus for many hours. These results are confirmed by an autoradiographic investigation.

Studies on sea urchin oocytes: I. Purification and cell fractionation☆

Abstract A procedure is presented which permits a satisfactory purification in bulk of oocytes of Paracentrotus lividus at various stages in the growth period. Methods which allow a quantitative recovery of partially purified germinal vesicles or nucleoli are also reported.