A novel mechanosensitive channel controls osmoregulation, differentiation, and infectivity in Trypanosoma cruzi

Anti-inflammatory and immunomodulatory effects of mesenchymal stem cell therapy on parasitic drug resistance

INTRODUCTION

The emergence of antiparasitic drug resistance poses a concerning threat to animals and humans. Mesenchymal Stem Cells (MSCs) have been widely used to treat infections in humans, pets, and livestock. Although this is an emerging field of study, the current review outlines possible mechanisms and examines potential synergism in combination therapies and the possible harmful effects of such an approach.

AREAS COVERED

The present study delved into the latest pre-clinical research on utilizing MSCs to treat parasitic infections. As per investigations, the introduction of MSCs to patients grappling with parasitic diseases like schistosomiasis, malaria, cystic echinococcosis, toxoplasmosis, leishmaniasis, and trypanosomiasis has shown a reduction in parasite prevalence. This intervention also alters the levels of both pro- and anti-inflammatory cytokines. Furthermore, the combined administration of MSCs and antiparasitic drugs has demonstrated enhanced efficacy in combating parasites and modulating the immune response.

EXPERT OPINION

Mesenchymal stem cells are a potential solution for addressing parasitic drug resistance. This is mainly because of their remarkable immunomodulatory abilities, which can potentially help combat parasites' resistance to drugs.

Advances in the cellular biology, biochemistry, and molecular biology of acidocalcisomes

SUMMARYAcidocalcisomes are organelles conserved during evolution and closely related to the so-called volutin granules of bacteria and archaea, to the acidocalcisome-like vacuoles of yeasts, and to the lysosome-related organelles of animal species. All these organelles have in common their acidity and high content of polyphosphate and calcium. They are characterized by a variety of functions from storage of phosphorus and calcium to roles in Ca2+ signaling, osmoregulation, blood coagulation, and inflammation. They interact with other organelles through membrane contact sites or by fusion, and have several enzymes, pumps, transporters, and channels.

A sticky situation: When trypanosomatids attach to insect tissues

Transmission of trypanosomatids to their mammalian hosts requires a complex series of developmental transitions in their insect vectors, including stable attachment to an insect tissue. While there are many ultrastructural descriptions of attached cells, we know little about the signaling events and molecular mechanisms involved in this process. Each trypanosomatid species attaches to a specific tissue in the insect at a particular stage of its life cycle. Attachment is mediated by the flagellum, which is modified to accommodate a filament-rich plaque within an expanded region of the flagellar membrane. Attachment immediately precedes differentiation to the mammal-infectious stage and in some cases a direct mechanistic link has been demonstrated. In this review, we summarize the current state of knowledge of trypanosomatid attachment in insects, including structure, function, signaling, candidate molecules, and changes in gene expression. We also highlight remaining questions about this process and how the field is poised to address them through modern approaches.

Gene editing of putative cAMP and Ca2+ -regulated proteins using an efficient cloning-free CRISPR/Cas9 system in Trypanosoma cruzi

Trypanosoma cruzi, the agent of Chagas disease, must adapt to a diversity of environmental conditions that it faces during its life cycle. The adaptation to these changes is mediated by signaling pathways that coordinate the cellular responses to the new environmental settings. Cyclic AMP (cAMP) and Calcium (Ca2+ ) signaling pathways regulate critical cellular processes in this parasite, such as differentiation, osmoregulation, host cell invasion and cell bioenergetics. Although the use of CRISPR/Cas9 technology prompted reverse genetics approaches for functional analysis in T. cruzi, it is still necessary to expand the toolbox for genome editing in this parasite, as for example to perform multigene analysis. Here we used an efficient T7RNAP/Cas9 strategy to tag and delete three genes predicted to be involved in cAMP and Ca2+ signaling pathways: a putative Ca2+ /calmodulin-dependent protein kinase (CAMK), Flagellar Member 6 (FLAM6) and Cyclic nucleotide-binding domain/C2 domain-containing protein (CC2CP). We endogenously tagged these three genes and determined the subcellular localization of the tagged proteins. Furthermore, the strategy used to knockout these genes allows us to presume that TcCC2CP is an essential gene in T. cruzi epimastigotes. Our results will open new venues for future research on the role of these proteins in T. cruzi.

Mechanoresponses mediated by the TRP11 channel in cilia of Chlamydomonas reinhardtii

Cilia are organelles involved in motility and sensory transduction, but how these two functions coexist has not been elucidated in depth. Here, the involvement of the ciliary transient receptor potential (TRP) channel TRP11 in mechanoresponses is studied in Chlamydomonas reinhardtii using a TRP11-knockout mutant. The mutant has defects in the conversion of the bending mode of the cilium from forward to reverse when tapped with a glass rod, the detachment of cilia when shear is applied, the increase in ciliary beat frequency upon application of mechanical agitation by vortex mixing, and the initiation of gliding while both cilia are attached in opposite directions to a glass surface. These observations indicate that TRP11 can perceive mechanical stimuli with distinct intensities and durations and induce various types of ciliary responses.

Dual localization of receptor-type adenylate cyclases and cAMP response protein 3 unveils the presence of two putative signaling microdomains in Trypanosoma cruzi

Trypanosoma cruzi is the etiologic agent of Chagas disease, a leading cause of disability and premature death in the Americas. This parasite spends its life between a triatomine insect and a mammalian host, transitioning between developmental stages in response to microenvironmental changes. Among the second messengers driving differentiation in T. cruzi, cAMP has been shown to mediate metacyclogenesis and response to osmotic stress, but this signaling pathway remains largely unexplored in this parasite. Adenylate cyclases (ACs) catalyze the conversion of ATP to cAMP. They comprise a multigene family encoding putative receptor-type ACs in T. cruzi. Using protein sequence alignment, we classified them into five groups and chose a representative member from each group to study their localization (TcAC1-TcAC5). We expressed an HA-tagged version of each protein in T. cruzi and performed immunofluorescence analysis. A peculiar dual localization of TcAC1 and TcAC2 was observed in the flagellar distal domain and in the contractile vacuole complex (CVC), and their enzymatic activity was confirmed by gene complementation in yeast. Furthermore, TcAC1 overexpressing parasites showed an increased metacyclogenesis, a defect in host cell invasion, and a reduced intracellular replication, highlighting the importance of this protein throughout T. cruzi life cycle. These mutants were more tolerant to hypoosmotic stress and showed a higher adhesion capacity during in vitro metacyclogenesis, whereas the wild-type phenotype was restored after disrupting TcAC1 localization. Finally, TcAC1 was found to interact with cAMP response protein 3 (TcCARP3), co-localizing with this protein in the flagellar tip and CVC. IMPORTANCE We identified three components of the cAMP signaling pathway (TcAC1, TcAC2, and TcCARP3) with dual localization in Trypanosoma cruzi: the flagellar distal domain and the CVC, structures involved in cell adhesion and osmoregulation, respectively. We found evidence on the role of TcAC1 in both cellular processes, as well as in metacyclogenesis. Our data suggest that TcACs act as signal sensors and transducers through cAMP synthesis in membrane microdomains. We propose a model in which TcACs sense the harsh conditions in the triatomine hindgut (nutrient deprivation, acidic pH, osmotic stress, ionic composition, hydrophobic interactions) and become active. Synthesis of cAMP then triggers cell adhesion prior completion of metacyclogenesis, while mediating a response to osmotic stress in the parasite. These results shed light into the mechanisms driving cAMP-mediated cell differentiation in T. cruzi, while raising new questions on the activation of TcACs and the role of downstream components of this pathway.

"Force-From-Lipids" Dependence of the MscCG Mechanosensitive Channel Gating on Anionic Membranes

Mechanosensory transduction in Corynebacterium glutamicum plays a major role in glutamate efflux for industrial MSG, whose production depends on the activation of MscCG-type mechanosensitive channels. Dependence of the MscCG channel activation by membrane tension on the membrane lipid content has to date not been functionally characterized. Here, we report the MscCG channel patch clamp recording from liposomes fused with C. glutamicum membrane vesicles as well as from proteoliposomes containing the purified MscCG protein. Our recordings demonstrate that mechanosensitivity of MscCG channels depends significantly on the presence of negatively charged lipids in the proteoliposomes. MscCG channels in liposome preparations fused with native membrane vesicles exhibited the activation threshold similar to the channels recorded from C. glutamicum giant spheroplasts. In comparison, the activation threshold of the MscCG channels reconstituted into azolectin liposomes was higher than the activation threshold of E. coli MscL, which is gated by membrane tension close to the bilayer lytic tension. The spheroplast-like activation threshold was restored when the MscCG channels were reconstituted into liposomes made of E. coli polar lipid extract. In liposomes made of polar lipids mixed with synthetic phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin, the activation threshold of MscCG was significantly reduced compared to the activation threshold recorded in azolectin liposomes, which suggests the importance of anionic lipids for the channel mechanosensitivity. Moreover, the micropipette aspiration technique combined with patch fluorometry demonstrated that membranes containing anionic phosphatidylglycerol are softer than membranes containing only polar non-anionic phosphatidylcholine and phosphatidylethanolamine. The difference in mechanosensitivity between C. glutamicum MscCG and canonical MscS of E. coli observed in proteoliposomes explains the evolutionary tuning of the force from lipids sensing in various bacterial membrane environments.

CRISPR Genome Editing and the Study of Chagas Disease

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, is an illness that affects 6-8 million people worldwide and is responsible for approximately 50,000 deaths per year. Despite intense research efforts on Chagas disease and its causative agent, there is still a lack of effective treatments or strategies for disease control. Although significant progress has been made toward the elucidation of molecular mechanisms involved in host-parasite interactions, particularly immune evasion mechanisms, a deeper understanding of these processes has been hindered by a lack of efficient genetic manipulation protocols. One major challenge is the fact that several parasite virulence factors are encoded by multigene families, which constitute a distinctive feature of the T. cruzi genome. The recent advent of the CRISPR/Cas9 technology represented an enormous breakthrough in the studies involving T. cruzi genetic manipulation compared to previous protocols that are poorly efficient and required a long generation time to develop parasite mutants. Since the first publication of CRISPR gene editing in T. cruzi, in 2014, different groups have used distinct protocols to generated knockout mutants, parasites overexpressing a protein or expressing proteins with sequence tags inserted in the endogenous gene. Importantly, CRISPR gene editing allowed generation of parasite mutants with gene disruption in multi-copy gene families. We described four main strategies used to edit the T. cruzi genome and summarized a large list of studies performed by different groups in the past 7 years that are addressing several mechanisms involved with parasite proliferation, differentiation, and survival strategies within its different hosts.

Down the membrane hole: Ion channels in protozoan parasites

Parasitic diseases caused by protozoans are highly prevalent around the world, disproportionally affecting developing countries, where coinfection with other microorganisms is common. Control and treatment of parasitic infections are constrained by the lack of specific and effective drugs, plus the rapid emergence of resistance. Ion channels are main drug targets for numerous diseases, but their potential against protozoan parasites is still untapped. Ion channels are membrane proteins expressed in all types of cells, allowing for the flow of ions between compartments, and regulating cellular functions such as membrane potential, excitability, volume, signaling, and death. Channels and transporters reside at the interface between parasites and their hosts, controlling nutrient uptake, viability, replication, and infectivity. To understand how ion channels control protozoan parasites fate and to evaluate their suitability for therapeutics, we must deepen our knowledge of their structure, function, and modulation. However, methodological approaches commonly used in mammalian cells have proven difficult to apply in protozoans. This review focuses on ion channels described in protozoan parasites of clinical relevance, mainly apicomplexans and trypanosomatids, highlighting proteins for which molecular and functional evidence has been correlated with their physiological functions.

New insights into the role of acidocalcisomes in trypanosomatids

Acidocalcisomes are electron-dense organelles rich in polyphosphate and inorganic and organic cations that are acidified by proton pumps, and possess several channels, pumps, and transporters. They are present in bacteria and eukaryotes and have been studied in greater detail in trypanosomatids. Biogenesis studies of trypanosomatid acidocalcisomes found that they share properties with lysosome-related organelles of animal cells. In addition to their described roles in autophagy, cation and phosphorus storage, osmoregulation, pH homeostasis, and pathogenesis, recent studies have defined the role of these organelles in phosphate utilization, calcium ion (Ca2+ ) signaling, and bioenergetics, and will be the main subject of this review.

The old and the new about the contractile vacuole of Trypanosoma cruzi

Osmoregulation is a conserved cellular process required for the survival of all organisms. In protists, the need for robust compensatory mechanisms that can maintain cell volume and tonicity within physiological range is even more relevant, as their life cycles are often completed in different environments. Trypanosoma cruzi, the protozoan pathogen responsible for Chagas disease, is transmitted by an insect vector to multiple types of mammalian hosts. The contractile vacuole complex (CVC) is an organelle that senses and compensates osmotic changes in the parasites, ensuring their survival upon ionic and osmotic challenges. Recent work shows that the contractile vacuole is also a key component of the secretory and endocytic pathways, regulating the selective targeting of surface proteins during differentiation. Here we summarize our current knowledge of the mechanisms involved in the osmoregulatory processes that take place in the vacuole, and we explore the new and exciting functions of this organelle in cell trafficking and signaling.

The Kinetoplastid-Specific Protein TcCAL1 Plays Different Roles During In Vitro Differentiation and Host-Cell Invasion in Trypanosoma cruzi

In the pathogen Typanosoma cruzi, the calcium ion (Ca2+) regulates key processes for parasite survival. However, the mechanisms decoding Ca2+ signals are not fully identified or understood. Here, we investigate the role of a hypothetical Ca2+-binding protein named TcCAL1 in the in vitro life cycle of T. cruzi. Results showed that the overexpression of TcCAL1 fused to a 6X histidine tag (TcCAL1-6xHis) impaired the differentiation of epimastigotes into metacyclic trypomastigotes, significantly decreasing metacyclogenesis rates. When the virulence of transgenic metacyclic trypomastigotes was explored in mammalian cell invasion assays, we found that the percentage of infection was significantly higher in Vero cells incubated with TcCAL1-6xHis-overexpressing parasites than in controls, as well as the number of intracellular amastigotes. Additionally, the percentage of Vero cells with adhered metacyclic trypomastigotes significantly increased in samples incubated with TcCAL1-6xHis-overexpressing parasites compared with controls. In contrast, the differentiation rates from metacyclic trypomastigotes to axenic amastigotes or the epimastigote proliferation in the exponential phase of growth have not been affected by TcCAL1-6xHis overexpression. Based on our findings, we speculate that TcCAL1 exerts its function by sequestering intracellular Ca2+ by its EF-hand motifs (impairing metacyclogenesis) and/or due to an unknown activity which could be amplified by the ion binding (promoting cell invasion). This work underpins the importance of studying the kinetoplastid-specific proteins with unknown functions in pathogen parasites.

Interaction With the Extracellular Matrix Triggers Calcium Signaling in Trypanosoma cruzi Prior to Cell Invasion

Trypanosoma cruzi, the etiological agent of Chagas disease in humans, infects a wide variety of vertebrates. Trypomastigotes, the parasite infective forms, invade mammalian cells by a still poorly understood mechanism. Adhesion of tissue culture- derived trypomastigotes to the extracellular matrix (ECM) prior to cell invasion has been shown to be a relevant part of the process. Changes in phosphorylation, S-nitrosylation, and nitration levels of proteins, in the late phase of the interaction (2 h), leading to the reprogramming of both trypomastigotes metabolism and the DNA binding profile of modified histones, were described by our group. Here, the involvement of calcium signaling at a very early phase of parasite interaction with ECM is described. Increments in the intracellular calcium concentrations during trypomastigotes-ECM interaction depends on the Ca²⁺ uptake from the extracellular medium, since it is inhibited by EGTA or Nifedipine, an inhibitor of the L-type voltage gated Ca²⁺ channels and sphingosine-dependent plasma membrane Ca²⁺ channel, but not by Vanadate, an inhibitor of the plasma membrane Ca²⁺-ATPase. Furthermore, Nifedipine inhibits the invasion of host cells by tissue culture- derived trypomastigotes in a dose-dependent manner, reaching 95% inhibition at 100 µM Nifedipine. These data indicate the importance of both Ca²⁺ uptake from the medium and parasite-ECM interaction for host-cell invasion. Previous treatment of ECM with protease abolishes the Ca²⁺ uptake, further reinforcing the possibility that these events may be connected. The mitochondrion plays a relevant role in Ca²⁺ homeostasis in trypomastigotes during their interaction with ECM, as shown by the increment of the intracellular Ca²⁺ concentration in the presence of Antimycin A, in contrast to other calcium homeostasis disruptors, such as Cyclopiazonic acid for endoplasmic reticulum and Bafilomycin A for acidocalcisome. Total phosphatase activity in the parasite decreases in the presence of Nifedipine, EGTA, and Okadaic acid, implying a role of calcium in the phosphorylation level of proteins that are interacting with the ECM in tissue culture- derived trypomastigotes. In summary, we describe here the increment of Ca²⁺ at an early phase of the trypomastigotes interaction with ECM, implicating both nifedipine-sensitive Ca²⁺ channels in the influx of Ca²⁺ and the mitochondrion as the relevant organelle in Ca²⁺ homeostasis. The data unravel a complex sequence of events prior to host cell invasion itself.