Molecular characterization and tissue-specific expression of a murine putative G-protein-coupled receptor

New Insights into the LANCL2- Binding Mode towards the Evaluation of New LANCL Agonists

The lanthionine synthetase C-like (LANCL) proteins include LANCL2, which is expressed in the central nervous system (CNS) and in peripheral tissues. LANCL2 exhibits glutathionylation activity and is involved in the neutralization of reactive electrophiles. Several studies explored LANCL2 activation as a validated pharmacological target for diabetes and inflammatory bowel disease. In this context, LANCL2 was found to bind the natural product abscisic acid (ABA), whose pre-clinical effectiveness in different inflammatory diseases was reported in the literature. More recently, LANCL2 attracted more attention as a valuable resource in the field of neurodegenerative disorders. ABA was found to regulate neuro-inflammation and synaptic plasticity to enhance learning and memory, exhibiting promising neuroprotective effects. Up until now, a limited number of LANCL2 ligands are known; among them, BT-11 is the only compound patented and investigated for its anti-inflammatory properties. To guide the design of novel putative LANCL2 agonists, a computational study including molecular docking and long molecular dynamic (MD) simulations of both ABA and BT-11 was carried out. The results pointed out the main LANCL2 ligand chemical features towards the following virtual screening of a novel putative LANCL2 agonist (AR-42). Biochemical assays on rat H9c2 cardiomyocytes showed a similar, LANCL2-mediated stimulation by BT-11 and by AR-42 of the mitochondrial proton gradient and of the transcriptional activation of the AMPK/PGC-1α/Sirt1 axis, the master regulator of mitochondrial function, effects that are previously observed with ABA. These results may allow the development of LANCL2 agonists for the treatment of mitochondrial dysfunction, a common feature of chronic and degenerative diseases.

Single-Cell RNAseq Resolve the Potential Effects of LanCL1 Gene in the Mouse Testis

Infertility affects lots of couples, half of which are caused by male factors. The LanCL1 gene is highly expressed in testis specifically, which might affect the development of sperms. In order to understand the potential functions of the LanCL1 gene in the testis, this study was conducted with constructed transgenic LanCL1 knockout mice. The mouse breeding experiment, semen analysis and single-cell RNAseq of testicular tissue were performed. Results suggested that the LanCL1 gene would significantly influence the reproduction ability and sperm motility of male mice. Single-cell RNAseq also confirmed the high expression of the LanCL1 gene in the spermatocytes and spermatids. Downregulating the LanCL1 gene expression could promote M2 macrophage polarity to maintain testicular homeostasis. Moreover, the LanCL1 gene could affect both the germ cells and stromal cells through various pathways such as the P53 signaling and the PPAR signaling pathway to disturb the normal process of spermatogenesis. However, no effects of the LanCL1 gene in testosterone synthesis and serum testosterone level were shown. Further studies are needed to discuss the mechanisms of the LanCL1 gene in the various cells of the testis independently.

Abscisic Acid Improves Insulin Action on Glycemia in Insulin-Deficient Mouse Models of Type 1 Diabetes

Abscisic acid (ABA), a plant hormone, has recently been shown to play a role in glycemia regulation in mammals, by stimulating insulin-independent glucose uptake and metabolism in skeletal muscle. The aim of this study was to test whether ABA could improve glycemic control in a murine model of type 1 diabetes (T1D). Mice were rendered diabetic with streptozotocin and the effect of ABA administration, alone or with insulin, was tested on glycemia. Diabetic mice treated with a single oral dose of ABA and low-dose subcutaneous insulin showed a significantly reduced glycemia profile compared with controls treated with insulin alone. In diabetic mice treated for four weeks with ABA, the effect of low-dose insulin on the glycemia profile after glucose load was significantly improved, and transcription both of the insulin receptor, and of glycolytic enzymes in muscle, was increased. Moreover, a significantly increased transcription and protein expression of AMPK, PGC1-α, and GLUT4 was observed in the skeletal muscle from diabetic mice treated with ABA, compared with untreated controls. ABA supplementation in conjunction with insulin holds the promise of reducing the dose of insulin required in T1D, reducing the risk of hypoglycemia, and improving muscle insulin sensitivity and glucose consumption.

At the intersection of sulfur redox chemistry, cellular signal transduction and proteostasis: A useful perspective from which to understand and treat neurodegeneration

Although we can thoroughly describe individual neurodegenerative diseases from the molecular level through cell biology to histology and clinical presentation, our understanding of them and hence treatment gains have been depressingly limited, partly due to difficulty conceptualizing different diseases as variations within the same overarching pathological rubric. This review endeavors to create such rubric by knitting together the seemingly disparate phenomena of oxidative stress, dysregulated proteostasis, and neuroinflammation into a cohesive triad that highlights mechanistic connectivities. We begin by considering that brain metabolic demands necessitate careful control of oxidative homeostasis, largely through sulfur redox chemistry and glutathione (GSH). GSH is essential for brain antioxidant defense, but also for redox signaling and thus neuroinflammation. Delicate regulation of neuroinflammatory pathways (NFκB, MAPK-p38, and NLRP3 particularly) occurs through S-glutathionylation of protein phosphatases but also through redox-sensing elements like ASK1; the 26S proteasome and cysteine deubiquitinases (DUBs). The relationship amongst triad elements is underscored by our discovery that LanCL1 (lanthionine synthetase-like protein-1) protects against oxidant toxicity; mediates GSH-dependent reactivation of oxidized DUBs; and antagonizes the pro-inflammatory cytokine, tumor necrosis factor-α (TNFα). We highlight currently promising pharmacological efforts to modulate key triad elements and suggest nexus points that might be exploited to further clinical advantage.

The Endogenous Alterations of the Gut Microbiota and Feces Metabolites Alleviate Oxidative Damage in the Brain of LanCL1 Knockout Mice

Altered composition of the gut microbiota has been observed in many neurodegenerative diseases. LanCL1 has been proven to protect neurons and reduce oxidative stress. The present study was designed to investigate alterations of the gut microbiota in LanCL1 knockout mice and to study the interactions between gut bacteria and the brain. Wild-type and LanCL1 knockout mice on a normal chow diet were evaluated at 4 and 8-9 weeks of age. 16s rRNA sequence and untargeted metabolomics analyses were performed to investigate changes in the gut microbiota and feces metabolites. Real-time polymerase chain reaction analysis, AB-PAS staining, and a TUNEL assay were performed to detect alterations in the gut and brain of knockout mice. The serum cytokines of 9-week-old knockout mice, which were detected by a multiplex cytokine assay, were significantly increased. In the central nervous system, there was no increase of antioxidant defense genes even though there was only low activity of glutathione S-transferase in the brain of 8-week-old knockout mice. Interestingly, the gut tight junctions, zonula occludens-1 and occludin, also displayed a downregulated expression level in 8-week-old knockout mice. On the contrary, the production of mucus increased in 8-week-old knockout mice. Moreover, the compositions of the gut microbiota and feces metabolites markedly changed in 8-week-old knockout mice but not in 4-week-old mice. Linear discriminant analysis and t-tests identified Akkermansia as a specific abundant bacteria in knockout mice. Quite a few feces metabolites that have protective effects on the brain were reduced in 8-week-old knockout mice. However, N-acetylsphingosine was the most significant downregulated feces metabolite, which may cause the postponement of neuronal apoptosis. To further investigate the effect of the gut microbiota, antibiotics treatment was given to both types of mice from 5 to 11 weeks of age. After treatment, a significant increase of oxidative damage in the brain of knockout mice was observed, which may have been alleviated by the gut microbiota before. In conclusion, alterations of the gut microbiota and feces metabolites alleviated oxidative damage to the brain of LanCL1 knockout mice, revealing that an endogenous feedback loop mechanism of the microbiota-gut-brain axis maintains systemic homeostasis.

Abscisic acid transport in human erythrocytes

Abscisic acid (ABA) is a plant hormone involved in the response to environmental stress. Recently, ABA has been shown to be present and active also in mammals, where it stimulates the functional activity of innate immune cells, of mesenchymal and hemopoietic stem cells, and insulin-releasing pancreatic β-cells. LANCL2, the ABA receptor in mammalian cells, is a peripheral membrane protein that localizes at the intracellular side of the plasma membrane. Here we investigated the mechanism enabling ABA transport across the plasmamembrane of human red blood cells (RBC). Both influx and efflux of [(3)H]ABA occur across intact RBC, as detected by radiometric and chromatographic methods. ABA binds specifically to Band 3 (the RBC anion transporter), as determined by labeling of RBC membranes with biotinylated ABA. Proteoliposomes reconstituted with human purified Band 3 transport [(3)H]ABA and [(35)S]sulfate, and ABA transport is sensitive to the specific Band 3 inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. Once inside RBC, ABA stimulates ATP release through the LANCL2-mediated activation of adenylate cyclase. As ATP released from RBC is known to exert a vasodilator response, these results suggest a role for plasma ABA in the regulation of vascular tone.

Structure of human lanthionine synthetase C-like protein 1 and its interaction with Eps8 and glutathione

Eukaryotic lanthionine synthetase C-like protein 1 (LanCL1) is homologous to prokaryotic lanthionine cyclases, yet its biochemical functions remain elusive. We report the crystal structures of human LanCL1, both free of and complexed with glutathione, revealing glutathione binding to a zinc ion at the putative active site formed by conserved GxxG motifs. We also demonstrate by in vitro affinity analysis that LanCL1 binds specifically to the SH3 domain of a signaling protein, Eps8. Importantly, expression of LanCL1 mutants defective in Eps8 interaction inhibits nerve growth factor (NGF)-induced neurite outgrowth, providing evidence for the biological significance of this novel interaction in cellular signaling and differentiation.

GCR2 is a new member of the eukaryotic lanthionine synthetase component C-like protein family

GCR2 was recently proposed to represent a G-protein-coupled receptor (GPCR) for the plant hormone, abscisic acid (ABA). We and others provided evidence that GCR2 is unlikely to be a bona fide GPCR because it is not clearly predicted to contain seven transmembrane domains, a structural hallmark for classical GPCRs. Instead, GCR2 shows significant sequence similarity to homologs of bacterial lanthionine synthetase component C (LanC). Here, we provide additional analysis of GCR2 and LanC-like (LANCL) proteins in plants, and propose that GCR2 is a new member of the eukaryotic LANCL protein family.

LANCL1, an erythrocyte protein recruited to the Maurer's clefts during Plasmodium falciparum development

As the malarial parasite Plasmodium falciparum develops inside the erythrocyte, parasite-derived membrane structures, referred to as Maurer's clefts, play an important role in parasite development by delivering parasite proteins to the host cell surface, and participating in the assembly of the cytoadherence complex, essential for the pathogenesis of cerebral malaria. PfSBP1 is an integral membrane protein of the clefts, interacting with an erythrocyte cytosolic protein, identified here as the human Lantibiotic synthetase component C-like protein LANCL1. LANCL1 is specifically recruited to the surface of Maurer's clefts in P. falciparum mature blood stages. We propose that the interaction between PfSBP1 and LANCL1 is central for late steps of the parasite development to prevent premature rupture of the red blood cell membrane.

Molecular cloning, characterization, and tissue-specific expression of human LANCL2, a novel member of the LanC-like protein family

We identified and characterized the cDNA coding for human LANCL2, a new member of the eukaryotic LanC-like protein family which is related to the bacterial lanthionine synthetase components C (LanC). The composite nucleotide sequence revealed a coding region of 1353 bp, a 5'-UTR of 186 bp and a 3'-UTR of 2421 bp. The deduced sequence of 450 amino acids showed 57.9% identity (74.7% similarity) when compared with the human LANCL1 homologue. In contrast to LANCL1, a unique ATP/GTP-binding site motif A was found in LANCL2. Northern blot analysis revealed the presence of two major transcripts in the brain, 4.7 kb and 4.1 kb in size, and a major 1.8 kb transcript in testis. Accordingly, expression array analysis showed prominent signals in these tissues. Because of the structural similarity to LanC, we postulate that LANCL2 may play a role as a component of a peptide-modifying complex.

Characterization of rat LANCL1, a novel member of the lanthionine synthetase C-like protein family, highly expressed in testis and brain

We isolated and characterized the cDNA coding for rat LANCL1, a new member of the eukaryotic LanC-like protein family which is related to the bacterial lanthionine synthetase components C (LanC). LanC is involved in the synthesis of antimicrobial peptides. Rat LANCL1 showed 91.5% and 96% identity when compared with the previously characterized human and mouse orthologs, respectively. Northern blot analysis revealed the presence of two major transcripts, at 1.5 kb and 5 kb, probably arising from the usage of two different polyadenylation signals. The 1.5 kb mRNA is massively expressed in testis, whereas the 5 kb transcript is most abundant in brain. The high level of expression of rat LANCL1 in these tissues was confirmed by Western blotting. In situ hybridization analyses of various rat tissues revealed a strong signal in the germinal cells of the seminiferous tubules in testis, in the neurons of the cerebellum, in liver hepatocytes, and in cardiac myocytes. The clear relationship between LANCL1 and bacterial LanC proteins suggests similar functions as peptide-modifying enzymes synthesizing antimicrobial peptides. In particular, the high expression of LANCL1 in testis and brain, organs separated by blood-tissue barriers, may hint at a role in the immune surveillance of these organs.

Characterization of p40/GPR69A as a peripheral membrane protein related to the lantibiotic synthetase component C

The 40 kDa erythrocyte membrane protein p40/GPR69A, previously assigned to the G-protein-coupled receptor superfamily, was now identified by peptide-antibodies and characterized as a loosely associated peripheral membrane protein. This result is in striking contrast to the proposed seven-transmembrane protein structure and function and therefore we wish to correct our previous proposal. p40 is located at the cytoplasmic side of the membrane and is neither associated with the cytoskeleton nor lipid rafts. Refined sequence analysis revealed that p40 is related to the LanC family of bacterial membrane-associated proteins which are involved in the biosynthesis of antimicrobial peptides. Therefore, we rename p40 to LanC-like protein 1 (LANCL1) and suggest that it may play a similar role as a peptide-modifying enzyme component in eukaryotic cells.