Postnatal maturation of cardiomyocytes is characterized by a metabolic switch from glycolysis to fatty acid oxidation, chromatin reconfiguration and exit from the cell cycle, instating a barrier for adult heart regeneration ^1,2 . Here, to explore whether metabolic reprogramming can overcome this barrier and enable heart regeneration, we abrogate fatty acid oxidation in cardiomyocytes by inactivation of Cpt1b . We find that disablement of fatty acid oxidation in cardiomyocytes improves resistance to hypoxia and stimulates cardiomyocyte proliferation, allowing heart regeneration after ischaemia–reperfusion injury. Metabolic studies reveal profound changes in energy metabolism and accumulation of α-ketoglutarate in Cpt1b -mutant cardiomyocytes, leading to activation of the α-ketoglutarate-dependent lysine demethylase KDM5 (ref. ³ ). Activated KDM5 demethylates broad H3K4me3 domains in genes that drive cardiomyocyte maturation, lowering their transcription levels and shifting cardiomyocytes into a less mature state, thereby promoting proliferation. We conclude that metabolic maturation shapes the epigenetic landscape of cardiomyocytes, creating a roadblock for further cell divisions. Reversal of this process allows repair of damaged hearts.

In this review, we summarize the current knowledge concerning the eukaryotic protozoan parasite Leishmania tarentolae, with a main focus on its potential for biotechnological applications. We will also discuss the genus, subgenus, and species-level classification of this parasite, its life cycle and geographical distribution, and similarities and differences to human-pathogenic species, as these aspects are relevant for the evaluation of biosafety aspects of L. tarentolae as host for recombinant DNA/protein applications. Studies indicate that strain LEM-125 but not strain TARII/UC of L. tarentolae might also be capable of infecting mammals, at least transiently. This could raise the question of whether the current biosafety level of this strain should be reevaluated. In addition, we will summarize the current state of biotechnological research involving L. tarentolae and explain why this eukaryotic parasite is an advantageous and promising human recombinant protein expression host. This summary includes overall biotechnological applications, insights into its protein expression machinery (especially on glycoprotein and antibody fragment expression), available expression vectors, cell culture conditions, and its potential as an immunotherapy agent for human leishmaniasis treatment. Furthermore, we will highlight useful online tools and, finally, discuss possible future applications such as the humanization of the glycosylation profile of L. tarentolae or the expression of mammalian recombinant proteins in amastigote-like cells of this species or in amastigotes of avirulent human-pathogenic Leishmania species. Recent studies indicate that the classification of Leishmania species into one of the four currently recognized subgenera (L. [Leishmania], L. [Sauroleishmania], L. [Viannia], and L. [Mundinia]), or even the related genera, can be a challenging task. A monotonous morphology of this group is coupled with a high genetic variability in nature, a multitude of clinical manifestations, and a propensity for rapid evolution in culture. As some geographic regions have not been adequately sampled, the known biodiversity of this group may be an underestimate of its true dimensions. Therefore, the taxonomic classification of the genus Leishmania and its close relatives is not definitively settled. In this review, we will focus on biotechnological applications of L. tarentolae, a protozoan parasite of geckos. As this species belongs to the genus Leishmania and subgenus L. (Sauroleishmania), and because many Leishmania are human-pathogenic, the taxonomic status and phylogenetic position of L. tarentolae are relevant for biosafety and also discussed herein. The subgenus of L. (Sauroleishmania) mostly contains species that are infectious to reptiles, but some species and strains, such as L. adleri and L. tarentolae strain LEM-125, were also shown to be (transiently) infectious to humans. However, most strains of L. tarentolae are nonpathogenic to humans and can be easily handled as laboratory culture. Therefore, this species has been a successful model system for representing other Leishmania in basic research. It has also been of great interest for the scientific community, as it represents a promising host for the expression of human recombinant proteins (including glycoproteins and its future application for the expression of full-length antibodies) and immunotherapy agent for human leishmaniasis treatment. These two topics will also be discussed.

Competition between viruses andWolbachiafor host lipids is a proposed mechanism ofWolbachia-mediated virus blocking in insects. Yet, the metabolomic interaction between virus and symbiont within the mosquito has not been clearly defined. We compare the lipid profiles ofAedes aegyptimosquitoes bearing mono- or dual-infections of theWolbachia wMel strain and dengue virus serotype 3 (DENV3). We found metabolic signatures of infection-induced intracellular events but little evidence to support direct competition betweenWolbachiaand virus for host lipids. Lipid profiles of dual-infected mosquitoes resemble those of DENV3 mono-infected mosquitoes, suggesting virus-driven modulation dominates over that ofWolbachia. Interestingly, knockdown of key metabolic enzymes suggests cardiolipins are host factors for DENV3 andWolbachiareplication. These findings define theWolbachia-DENV3 metabolic interaction as indirectly antagonistic, rather than directly competitive, and reveal new research avenues with respect to mosquito × virus interactions at the molecular level.

Secretory signal peptides (SPs) are well-known sequence motifs targeting proteins for translocation across the endoplasmic reticulum membrane. After passing through the secretory pathway, most proteins are secreted to the environment. Here, we describe the modification of an expression vector containing the SP from secreted acid phosphatase 1 (SAP1) of Leishmania mexicana for optimized protein expression-secretion in the eukaryotic parasite Leishmania tarentolae with regard to recombinant antibody fragments. For experimental design the online tool SignalP was used, which predicts the presence and location of SPs and their cleavage sites in polypeptides. To evaluate the signal peptide cleavage site as well as changes of expression, SPs were N-terminally linked to single-chain Fragment variables (scFv’s). The ability of L. tarentolae to express complex eukaryotic proteins with highly diverse post-translational modifications and its easy bacteria-like handling, makes the parasite a promising expression system for secretory proteins.

Plaques that characterize Alzheimer’s disease accumulate over 20 years as a result of decreased clearance of amyloid-β peptides. Such long-lived peptides are subjected to multiple post-translational modifications, in particular isomerization. Using liquid chromatography ion mobility separations mass spectrometry, we characterized the most common isomerized amyloid-β peptides present in the temporal cortex of sporadic Alzheimer’s disease brains. Quantitative assessment of amyloid-β N-terminus revealed that > 80% of aspartates (Asp-1 and Asp-7) in the N-terminus was isomerized, making isomerization the most dominant post-translational modification of amyloid-β in Alzheimer’s disease brain. Total amyloid-β_1–15 was ∼85% isomerized at Asp-1 and/or Asp-7 residues, with only 15% unmodified amyloid-β_1–15 left in Alzheimer’s disease. While amyloid-β_4–15 the next most abundant N-terminus found in Alzheimer’s disease brain, was only ∼50% isomerized at Asp-7 in Alzheimer’s disease. Further investigations into different biochemically defined amyloid-β-pools indicated a distinct pattern of accumulation of extensively isomerized amyloid-β in the insoluble fibrillar plaque and membrane-associated pools, while the extent of isomerization was lower in peripheral membrane/vesicular and soluble pools. This pattern correlated with the accumulation of aggregation-prone amyloid-β₄₂ in Alzheimer’s disease brains. Isomerization significantly alters the structure of the amyloid-β peptide, which not only has implications for its degradation, but also for oligomer assembly, and the binding of therapeutic antibodies that directly target the N-terminus, where these modifications are located.

Characterisation and diagnosis of idiopathic Parkinson’s disease (iPD) is a current challenge that hampers both clinical assessment and clinical trial development with the potential inclusion of non-PD cases. Here, we used a targeted mass spectrometry approach to quantify 38 metabolites extracted from the serum of 231 individuals. This cohort is currently one of the largest metabolomic studies including iPD patients, drug-naïve iPD, healthy controls and patients with Alzheimer’s disease as a disease-specific control group. We identified six metabolites (3-hydroxykynurenine, aspartate, beta-alanine, homoserine, ornithine (Orn) and tyrosine) that are significantly altered between iPD patients and control participants. A multivariate model to predict iPD from controls had an area under the curve (AUC) of 0.905, with an accuracy of 86.2%. This panel of metabolites may serve as a potential prognostic or diagnostic assay for clinical trial prescreening, or for aiding in diagnosing pathological disease in the clinic.