Candida albicans stimulates in vivo differentiation of haematopoietic stem and progenitor cells towards macrophages by a TLR2-dependent signalling

Toll-like receptors (TLRs) are expressed by haematopoietic stem and progenitor cells (HSPCs), and may play a role in haematopoiesis in response to pathogens during infection. We have previously demonstrated that (i) inactivated yeasts of Candida albicans induce in vitro differentiation of HSPCs towards the myeloid lineage, and (ii) soluble TLR agonists induce in vivo their differentiation towards macrophages. In this work, using an in vivo model of HSPCs transplantation, we report for the first time that HSPCs sense C. albicans in vivo and subsequently are directed to produce macrophages by a TLR2-dependent signalling. Purified lineage-negative cells (Lin−) from bone marrow of C57BL/6 mice (CD45.2 alloantigen) were transplanted into B6Ly5.1 mice (CD45.1 alloantigen), which were then injected with viable or inactivated C. albicans yeasts. Transplanted cells were detected in the spleen and in the bone marrow of recipient mice, and they differentiate preferentially to macrophages, both in response to infection or in response to inactivated yeasts. The generation of macrophages was dependent on TLR2 but independent of TLR4, as transplanted Lin− cells from TLR2−/− mice did not give rise to macrophages, whereas Lin− cells from TLR4−/− mice generated macrophages similarly to control cells. Interestingly, the absence of TLR2, or in a minor extent TLR4, gives Lin− cells an advantage in transplantation assays, as increases the percentage of transplanted recovered cells. Our results indicatethat TLR-mediated recognition of C. albicans by HSPCs may help replace and/or increase cells that constitute the first line of defence against the fungus, and suggest that TLR-mediated signalling may lead to reprogramming early progenitors to rapidly replenishing the innate immune system and generate the most necessary mature cells to deal with the pathogen.

Cellular responses following retinal injuries and therapeutic approaches for neurodegenerative diseases

Retinal neurodegenerative diseases like age-related macular degeneration, glaucoma, diabetic retinopathy and retinitis pigmentosa each have a different etiology and pathogenesis. However, at the cellular and molecular level, the response to retinal injury is similar in all of them, and results in morphological and functional impairment of retinal cells. This retinal degeneration may be triggered by gene defects, increased intraocular pressure, high levels of blood glucose, other types of stress or aging, but they all frequently induce a set of cell signals that lead to well-established and similar morphological and functional changes, including controlled cell death and retinal remodeling. Interestingly, an inflammatory response, oxidative stress and activation of apoptotic pathways are common features in all these diseases. Furthermore, it is important to note the relevant role of glial cells, including astrocytes, Müller cells and microglia, because their response to injury is decisive for maintaining the health of the retina or its degeneration. Several therapeutic approaches have been developed to preserve retinal function or restore eyesight in pathological conditions. In this context, neuroprotective compounds, gene therapy, cell transplantation or artificial devices should be applied at the appropriate stage of retinal degeneration to obtain successful results. This review provides an overview of the common and distinctive features of retinal neurodegenerative diseases, including the molecular, anatomical and functional changes caused by the cellular response to damage, in order to establish appropriate treatments for these pathologies.

Expression and cellular localization of the voltage-gated calcium channel α2δ3 in the rodent retina

High-voltage-activated calcium channels are hetero-oligomeric protein complexes that mediate multiple cellular processes, including the influx of extracellular Ca2+, neurotransmitter release, gene transcription, and synaptic plasticity. These channels consist of a primary α1 pore-forming subunit, which is associated with an extracellular α2δ subunit and an intracellular β auxiliary subunit, which alter the gating properties and trafficking of the calcium channel. The cellular localization of the α2δ3 subunit in the mouse and rat retina is unknown. In this study using RT-PCR, a single band at ∼305 bp corresponding to the predicted size of the α2δ3 subunit fragment was found in mouse and rat retina and brain homogenates. Western blotting of rodent retina and brain homogenates showed a single 123-kDa band. Immunohistochemistry with an affinity-purified antibody to the α2δ3 subunit revealed immunoreactive cell bodies in the ganglion cell layer and inner nuclear layer and immunoreactive processes in the inner plexiform layer and the outer plexiform layer. α2δ3 immunoreactivity was localized to multiple cell types, including ganglion, amacrine, and bipolar cells and photoreceptors, but not horizontal cells. The expression of the α2δ3 calcium channel subunit to multiple cell types suggests that this subunit participates widely in Ca-channel-mediated signaling in the retina.

Sub-Cellular Localization and Complex Formation by Aminoacyl-tRNA Synthetases in Cyanobacteria: Evidence for Interaction of Membrane-Anchored ValRS with ATP Synthase

tRNAs are charged with cognate amino acids by aminoacyl-tRNA synthetases (aaRSs) and subsequently delivered to the ribosome to be used as substrates for gene translation. Whether aminoacyl-tRNAs are channeled to the ribosome by transit within translational complexes that avoid their diffusion in the cytoplasm is a matter of intense investigation in organisms of the three domains of life. In the cyanobacterium Anabaena sp. PCC 7120, the valyl-tRNA synthetase (ValRS) is anchored to thylakoid membranes by means of the CAAD domain. We have investigated whether in this organism ValRS could act as a hub for the nucleation of a translational complex by attracting other aaRSs to the membranes. Out of the 20 aaRSs, only ValRS was found to localize in thylakoid membranes whereas the other enzymes occupied the soluble portion of the cytoplasm. To investigate the basis for this asymmetric distribution of aaRSs, a global search for proteins interacting with the 20 aaRSs was conducted. The interaction between ValRS and the FoF1 ATP synthase complex here reported is of utmost interest and suggests a functional link between elements of the gene translation and energy production machineries.