Two special organelles found in Trypanosoma cruzi

We review here two unique organelles from Trypanosoma cruzi. One of them is the acidocalcisome, cytoplasmic vacuoles containing a very high Ca2+ concentration and a Ca2+ - H+ translocating ATPase activity, present in all trypanosomatids. The other organelle is the reservosome, site of accumulation of endocytosed macromolecules, very rich in cysteine proteinase, that is present only in epimastigote forms of trypanosomes belonging to the Schyzotrypanum sub-genus

INFRAESTRUCTURA EN ORO PARA PROTESIS METAL-CERÁMICAS OBTENIDAS MEDIANTE TÉCNICA DE ELETRODEPOSICIÓN

La electrodeposición es un proceso químico por el cual se realiza una deposición galvánica de oro del99% de pureza con el fin de obtener infraestructuras en prótesis metal-cerámicas. Las infraestructuraspresentan, en promedio, un espesor de 0,2 mm y un desajuste marginal inferior la 20 μm, posibilitandola utilización de un mayor espesor de cerámica si la comparamos a técnicas convencionales. Esta técnicaposibilita la disminución de la citotoxicidad, de las reacciones alérgicas y de la corrosión, determinandouna mayor duración de las restauraciones. La coloración dorada del material permite al ceramistaconseguir una estética más depurada, favoreciendo las tonalidades en la cerámica aplicada. Sin embargo,la necesidad de mano de obra calificada y de equipos modernos y de alto costo son factores que todavíahacen inviable la utilización de la electrodeposición de oro puro como práctica clínica habitual. El objetivo de este estudio es contribuir, a través de una revisión de la literatura, a la comparación en los siguientes factores: calidad del asentamiento marginal, durabilidad, biocompatibilidad, estética de las restauracionescuyas estructuras hayan sido obtenidos por la técnica de electrodepoisición frente a restauraciones realizadas con técnicas metal-cerámicas convencionales y sistemas cerámicos.ABSTRACT Electrodeposition is the galvanic deposition of 99% pure gold to obtain the framework for metal-ceramicprostheses. The framework is 0.2 mm thick, on average, with marginal maladjustment of less than 20μm, enabling the use of greater ceramic thickness than that of conventional techniques. This new technique reduces cytotoxicity, allergic reactions and corrosion, resulting in longer restoration longevity.The golden coloration of the material allows the ceramist to develop a more evolved esthetic, favoring thetonality of the ceramic applied. However, the need for qualified labor and modern high-cost equipmentare factors that hinder the use of electrodeposited pure gold in everyday clinical practice. The aim of thisstudy is to perform a literature review to compare the quality of the marginal fit, longevity,biocompatibility, and esthetic of restorations whose copings were obtained by the electrodeposition technique using conventional metal-ceramics and ceramic systems

PRNP/prion protein regulates the secretion of exosomes modulating CAV1/caveolin-1-suppressed autophagy

<p>Prion protein modulates many cellular functions including the secretion of trophic factors by astrocytes. Some of these factors are found in exosomes, which are formed within multivesicular bodies (MVBs) and secreted into the extracellular space to modulate cell-cell communication. The mechanisms underlying exosome biogenesis were not completely deciphered. Here, we demonstrate that primary cultures of astrocytes and fibroblasts from prnp-null mice secreted lower levels of exosomes than wild-type cells. Furthermore, prnp-null astrocytes exhibited reduced MVB formation and increased autophagosome formation. The reconstitution of PRNP expression at the cell membrane restored exosome secretion in PRNP-deficient astrocytes, whereas macroautophagy/autophagy inhibition via BECN1 depletion reestablished exosome release in these cells. Moreover, the PRNP octapeptide repeat domain was necessary to promote exosome secretion and to impair the formation of the CAV1-dependent ATG12–ATG5 cytoplasmic complex that drives autophagosome formation. Accordingly, higher levels of CAV1 were found in lipid raft domains instead of in the cytoplasm in prnp-null cells. Collectively, these findings demonstrate that PRNP supports CAV1-suppressed autophagy to protect MVBs from sequestration into phagophores, thus facilitating exosome secretion.</p

The unconventional secretion of stress-inducible protein 1 by a heterogeneous population of extracellular vesicles

The co-chaperone stress-inducible protein 1 (STI1) is released by astrocytes, and has important neurotrophic properties upon binding to prion protein (PrPC). However, STI1 lacks a signal peptide and pharmacological approaches pointed that it does not follow a classical secretion mechanism. Ultracentrifugation, size exclusion chromatography, electron microscopy, vesicle labeling, and particle tracking analysis were used to identify three major types of extracellular vesicles (EVs) released from astrocytes with sizes ranging from 20–50, 100–200, and 300–400 nm. These EVs carry STI1 and present many exosomal markers, even though only a subpopulation had the typical exosomal morphology. The only protein, from those evaluated here, present exclusively in vesicles that have exosomal morphology was PrPC. STI1 partially co-localized with Rab5 and Rab7 in endosomal compartments, and a dominant-negative for vacuolar protein sorting 4A (VPS4A), required for formation of multivesicular bodies (MVBs), impaired EV and STI1 release. Flow cytometry and PK digestion demonstrated that STI1 localized to the outer leaflet of EVs, and its association with EVs greatly increased STI1 activity upon PrPC-dependent neuronal signaling. These results indicate that astrocytes secrete a diverse population of EVs derived from MVBs that contain STI1 and suggest that the interaction between EVs and neuronal surface components enhances STI1–PrPC signalingFAPESP, 2009/14027-2FAPESP, 2012/04370-4PrioNet-Canada, Canadian Institutes of Health Research (CIHR)Canadian Foundation for Innovation and Ontario Research FundCNPqFAPER

Retrovirus infection strongly enhances scrapie infectivity release in cell culture

Prion diseases are neurodegenerative disorders associated in most cases with the accumulation in the central nervous system of PrP(Sc) (conformationally altered isoform of cellular prion protein (PrP(C)); Sc for scrapie), a partially protease-resistant isoform of the PrP(C). PrP(Sc) is thought to be the causative agent of transmissible spongiform encephalopathies. The mechanisms involved in the intercellular transfer of PrP(Sc) are still enigmatic. Recently, small cellular vesicles of endosomal origin called exosomes have been proposed to contribute to the spread of prions in cell culture models. Retroviruses such as murine leukemia virus (MuLV) or human immunodeficiency virus type 1 (HIV-1) have been shown to assemble and bud into detergent-resistant microdomains and into intracellular compartments such as late endosomes/multivesicular bodies. Here we report that moloney murine leukemia virus (MoMuLV) infection strongly enhances the release of scrapie infectivity in the supernatant of coinfected cells. Under these conditions, we found that PrP(C), PrP(Sc) and scrapie infectivity are recruited by both MuLV virions and exosomes. We propose that retroviruses can be important cofactors involved in the spread of the pathological prion agent