6 research outputs found
Identification of LAT4, a novel amino acid transporter with system L activity
System L amino acid transporters mediate the movement of bulky neutral amino acids across cell membranes. Until now three proteins that induce system L activity have been identified: LAT1, LAT2, and LAT3. The former two proteins belong to the solute carrier family 7 (SLC7), whereas the latter belongs to SLC43. In the present study we present a new cDNA, designated LAT4, which also mediates system L activity when expressed in Xenopus laevis oocytes. Human LAT4 exhibits 57% identity to human LAT3. Like LAT3, the amino acid transport activity induced by LAT4 is sodium-, chloride- and pH-independent, is not trans-stimulated, and shows two kinetic components. The low affinity component of LAT4 induced activity is sensitive to the sulfhydryl-specific reagent N-ethylmaleimide but not that with high affinity. Mutation in LAT4 of the SLC43 conserved serine 297 to alanine abolishes sensitivity to N-ethylmaleimide. LAT4 activity is detected at the basolateral membrane of PCT kidney cells. In situ hybridization experiments show that LAT4 mRNA is restricted to the epithelial cells of the distal tubule and the collecting duct in the kidney. In the intestine, LAT4 is mainly present in the cells of the crypt
Extracellular vesicles in parasitic diseases
Parasitic diseases affect billions of people and are considered a major public health issue. Close to 400 species are estimated to parasitize humans, of which around 90 are responsible for great clinical burden and mortality rates. Unfortunately, they are largely neglected as they are mainly endemic to poor regions. Of relevance to this review, there is accumulating evidence of the release of extracellular vesicles (EVs) in parasitic diseases, acting both in parasite–parasite inter-communication as well as in parasite–host interactions. EVs participate in the dissemination of the pathogen and play a role in the regulation of the host immune systems. Production of EVs from parasites or parasitized cells has been described for a number of parasitic infections. In this review, we provide the most relevant findings of the involvement of EVs in intercellular communication, modulation of immune responses, involvement in pathology, and their potential as new diagnostic tools and therapeutic agents in some of the major human parasitic pathogens
Spleen rupture in a case of untreated Plasmodium vivax infection
We report the unique case of a 19-yearold nonimmune patient with Plasmodium vivax monoinfection, confirmed by PCR in the peripheral blood and in the spleen section, who was splenectomized due to spleen rupture two days prior to the diagnosis and treatment of the malarial infection. Microscopic analyses evidenced white pulp expansion and a diffuse hypercellularity in the splenic red pulp, with intense proliferating plasmablasts in the subcapsular and perivascular compartments as well as large numbers of intact P. vivax-infected reticulocytes in the cords, in the absence of other concomitant infectious diseases. To our knowledge, this is the first full detailed immunohistopathological characterization of a nontreated P. vivax-infected spleen
Spleen-Dependent Immune Protection Elicited by CpG Adjuvanted Reticulocyte-Derived Exosomes from Malaria Infection Is Associated with Changes in T cell Subsets' Distribution
Added corrigendum published in 2017-01-17 https://doi.org/10.3389/fcell.2016.00153Reticulocyte-derived exosomes (rex) are 30-100 nm membrane vesicles of endocytic origin released during the maturation of reticulocytes to erythrocytes upon fusion of multivesicular bodies with the plasma membrane. Combination of CpG-ODN with rex obtained from BALB/c mice infected with the reticulocyte-prone non-lethal P. yoelii 17X malaria strain (rexPy), had been shown to induce survival and long lasting protection. Here, we show that splenectomized mice are not protected upon rexPy+CpG inmunizations and that protection is restored upon passive transfer of splenocytes obtained from animals immunized with rexPy+CpG. Notably, rexPy immunization of mice induced changes in PD1- memory T cells with effector phenotype. Proteomics analysis of rexPy confirmed their reticulocyte origin and demonstrated the presence of parasite antigens. Our studies thus prove, for what we believe is the first time, that rex from reticulocyte-prone malarial infections are associated with splenic long-lasting memory responses. To try extrapolating these data to human infections, in vitro experiments with spleen cells of human transplantation donors were performed.
Plasma-derived exosomes from vivax malaria patients (exPv) were actively uptaken by human splenocytes and stimulated spleen cells leading to changes in T cell subsets
Plasmodium vivax spleen-dependent genes encode antigens associated with cytoadhesion and clinical protection.
The most widely distributed human malaria parasite, causes severe
clinical syndromes despite low peripheral blood parasitemia.
This conundrum is further complicated as cytoadherence in the
microvasculature is still a matter of investigations. Previous
reports in " - ", another parasite species shown to infect
humans, demonstrated that variant genes involved in
cytoadherence were dependent on the spleen for their expression.
Hence, using a global transcriptional analysis of parasites
obtained from spleen-intact and splenectomized monkeys, we
identified 67 " - " genes whose expression was spleen dependent.
To determine their role in cytoadherence, two " - " transgenic
lines expressing two variant proteins pertaining to VIR and
Pv-FAM-D multigene families were used. Cytoadherence assays
demonstrated specific binding to human spleen but not lung
fibroblasts of the transgenic line expressing the VIR14 protein.
To gain more insights, we expressed five " - " spleen-dependent
genes as recombinant proteins, including members of three
different multigene families (VIR, Pv-FAM-A, Pv-FAM-D), one
membrane transporter (SECY), and one hypothetical protein
(HYP1), and determined their immunogenicity and association with
clinical protection in a prospective study of 383 children in
Papua New Guinea. Results demonstrated that spleen-dependent
antigens are immunogenic in natural infections and that
antibodies to HYP1 are associated with clinical protection.
These results suggest that the spleen plays a major role in
expression of parasite proteins involved in cytoadherence and can reveal antigens associated with clinical protection, thus
prompting a paradigm shift in " - " biology toward deeper
studies of the spleen during infection
Minimal information for studies of extracellular vesicles 2018 (MISEV2018): a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines
The last decade has seen a sharp increase in the number
of scientific publications describing physiological and
pathological functions of extracellular vesicles (EVs), a
collective term covering various subtypes of cell-released,
membranous structures, called exosomes, microvesicles,
microparticles, ectosomes, oncosomes, apoptotic bodies, and many
other names. However, specific issues arise when working with
these entities, whose size and amount often make them difficult
to obtain as relatively pure preparations, and to characterize
properly. The International Society for Extracellular Vesicles
(ISEV) proposed Minimal Information for Studies of Extracellular
Vesicles ("MISEV") guidelines for the field in 2014. We now
update these "MISEV2014" guidelines based on evolution of the
collective knowledge in the last four years. An important point
to consider is that ascribing a specific function to EVs in
general, or to subtypes of EVs, requires reporting of specific
information beyond mere description of function in a crude,
potentially contaminated, and heterogeneous preparation. For
example, claims that exosomes are endowed with exquisite and
specific activities remain difficult to support experimentally,
given our still limited knowledge of their specific molecular
machineries of biogenesis and release, as compared with other
biophysically similar EVs. The MISEV2018 guidelines include
tables and outlines of suggested protocols and steps to follow
to document specific EV-associated functional activities.
Finally, a checklist is provided with summaries of key points