Glio- and neuroprotection by prosaposin is mediated by orphan G-protein coupled receptors GPR37L1 and GPR37

This is the author accepted manuscript. Available on open access from Wiley via the DOI in this recordDiscovery of neuroprotective pathways is one of the major priorities for neuroscience. Astrocytes are the natural neuroprotectors and it is likely that brain resilience can be enhanced by mobilising their protective potential. Among G-protein coupled receptors expressed by astrocytes, two highly related receptors, GPR37L1 and GPR37, are of particular interest. Previous studies suggested that these receptors are activated by a peptide Saposin C and its neuroactive fragments (such as prosaptide TX14), which were demonstrated to be neuroprotective in various animal models by several groups. However, pairing of Saposin C or prosaptides with GPR37L1/GPR37 has been challenged and presently GPR37L1/GPR37 have regained their orphan status. Here we demonstrate that in their natural habitat, astrocytes, these receptors mediate a range of effects of TX14, including protection from oxidative stress. The Saposin C/GPR37L1/GPR37 pathway is also involved in the neuroprotective effect of astrocytes on neurons subjected to oxidative stress. The action of TX14 is at least partially mediated by Gi-proteins and the cAMP-PKA axis. On the other hand, when recombinant GPR37L1 or GPR37 are expressed in HEK293 cells, they are not functional and do not respond to TX14, which explains unsuccessful attempts to confirm the ligand-receptor pairing. Therefore this study identifies GPR37L1/GPR37 as the receptors for TX14, and, by extension of Saposin C, and paves the way for the development of neuroprotective therapeutics acting via these receptors.Biotechnology and Biological Sciences Research CouncilMedical Research Council (MRC

The Baum-Connes Conjecture via Localisation of Categories

We redefine the Baum-Connes assembly map using simplicial approximation in the equivariant Kasparov category. This new interpretation is ideal for studying functorial properties and gives analogues of the assembly maps for all equivariant homology theories, not just for the K-theory of the crossed product. We extend many of the known techniques for proving the Baum-Connes conjecture to this more general setting

Groupoids and an index theorem for conical pseudo-manifolds

We define an analytical index map and a topological index map for conical pseudomanifolds. These constructions generalize the analogous constructions used by Atiyah and Singer in the proof of their topological index theorem for a smooth, compact manifold $M$. A main ingredient is a non-commutative algebra that plays in our setting the role of $C_0(T^*M)$. We prove a Thom isomorphism between non-commutative algebras which gives a new example of wrong way functoriality in $K$-theory. We then give a new proof of the Atiyah-Singer index theorem using deformation groupoids and show how it generalizes to conical pseudomanifolds. We thus prove a topological index theorem for conical pseudomanifolds

Expression of Microbial Enzymes in Mammalian Astrocytes to Modulate Lactate Release

This is the final version. Available on open access from MDPI via the DOI in this recordData Availability Statement: Data reported in this study are available upon request. Clones are available via addgene.org (accessed date 6 August 2021).Astrocytes support and modulate neuronal activity through the release of L-lactate. The suggested roles of astrocytic lactate in the brain encompass an expanding range of vital functions, including central control of respiration and cardiovascular performance, learning, memory, executive behaviour and regulation of mood. Studying the effects of astrocytic lactate requires tools that limit the release of lactate selectively from astrocytes. Here, we report the validation in vitro of novel molecular constructs derived from enzymes originally found in bacteria, that when expressed in astrocytes, interfere with lactate handling. When lactate 2-monooxygenase derived from M. smegmatis was specifically expressed in astrocytes, it reduced intracellular lactate pools as well as lactate release upon stimulation. D-lactate dehydrogenase derived from L. bulgaricus diverts pyruvate towards D-lactate production and release by astrocytes, which may affect signalling properties of lactate in the brain. Together with lactate oxidase, which we have previously described, this set of transgenic tools can be employed to better understand astrocytic lactate release and its role in the regulation of neuronal activity in different behavioural contextsBritish Heart FoundationConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Academy of Medical Science

Reducing l-lactate release from hippocampal astrocytes by intracellular oxidation increases novelty induced activity in mice

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record DATA AVAILABILITY STATEMENT: Data available on request from the authors.Astrocytes are in control of metabolic homeostasis in the brain and support and modulate neuronal function in various ways. Astrocyte-derived l-lactate (lactate) is thought to play a dual role as a metabolic and a signaling molecule in inter-cellular communication. The biological significance of lactate release from astrocytes is poorly understood, largely because the tools to manipulate lactate levels in vivo are limited. We therefore developed new viral vectors for astrocyte-specific expression of a mammalianized version of lactate oxidase (LOx) from Aerococcus viridans. LOx expression in astrocytes in vitro reduced their intracellular lactate levels as well as the release of lactate to the extracellular space. Selective expression of LOx in astrocytes of the dorsal hippocampus in mice resulted in increased locomotor activity in response to novel stimuli. Our findings suggest that a localized decreased intracellular lactate pool in hippocampal astrocytes could contribute to greater responsiveness to environmental novelty. We expect that use of this molecular tool to chronically limit astrocytic lactate release will significantly facilitate future studies into the roles and mechanisms of intercellular lactate communication in the brain.British Heart FoundationBritish Heart FoundationConselho Nacional de Desenvolvimento Científico e TecnológicoNational Institute of HealthNational Institute of HealthNational Institute of HealthNorthcott Devon Medical Trust FoundationNational Institute of Neurological Disorders and Strok

CNS distribution, signalling properties and central effects of G-protein coupled receptor 4

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordInformation on the distribution and biology of the G-protein coupled receptor 4 (GPR4) in the brain is limited. It is currently thought that GPR4 couples to Gs proteins and may mediate central respiratory sensitivity to CO2. Using a knock-in mouse model, abundant GPR4 expression was detected in the cerebrovascular endothelium and neurones of dorsal raphe, retro-trapezoidal nucleus locus coeruleus and lateral septum. A similar distribution was confirmed using RNAscope in situ hybridisation. In HEK293 cells, overexpressing GPR4, it was highly constitutively active at neutral pH with little further increase in cAMP towards acidic pH. The GPR4 antagonist NE 52-QQ57 effectively blocked GPR4-mediated cAMP accumulation (IC50 26.8 nM in HEK293 cells). In HUVEC which natively express GPR4, physiological acidification (pH 7.4-7.0) resulted in a cAMP increase by ∼55% which was completely prevented by 1 μM NE 52-QQ57. The main extracellular organic acid, l-lactic acid (LL; 1-10 mM), suppressed pH dependent activation of GPR4 in HEK293 and HUVEC cells, suggesting allosteric negative modulation. In unanaesthetised mice and rats, NE 52-QQ57 (20 mg kg-1) reduced ventilatory response to 5 and 10% CO2. In anaesthetised rats, systemic administration of NE 52-QQ57 (up to 20 mg kg-1) had no effect on hemodynamics, cerebral blood flow and blood oxygen level dependent responses. Central administration of NE 52-QQ57 (1 mM) in vagotomised anaesthetised rats did not affect CO2-induced respiratory responses. Our results indicate that GPR4 is expressed by multiple neuronal populations and endothelium and that its pH sensitivity is affected by level of expression and LL. NE 52-QQ57 blunts hypercapnic response to CO2 but this effect is absent under anaesthesia, possibly due to the inhibitory effect of LL on GPR4.Biotechnology and Biological Sciences Research Council (BBSRC)Medical Research Council (MRC)Wellcome Trus

CNS distribution, signalling properties and central effects of G-protein coupled receptor 4

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordInformation on the distribution and biology of the G-protein coupled receptor 4 (GPR4) in the brain is limited. It is currently thought that GPR4 couples to Gs proteins and may mediate central respiratory sensitivity to CO2. Using a knock-in mouse model, abundant GPR4 expression was detected in the cerebrovascular endothelium and neurones of dorsal raphe, retro-trapezoidal nucleus locus coeruleus and lateral septum. A similar distribution was confirmed using RNAscope in situ hybridisation. In HEK293 cells, overexpressing GPR4, it was highly constitutively active at neutral pH with little further increase in cAMP towards acidic pH. The GPR4 antagonist NE 52-QQ57 effectively blocked GPR4-mediated cAMP accumulation (IC50 26.8 nM in HEK293 cells). In HUVEC which natively express GPR4, physiological acidification (pH 7.4-7.0) resulted in a cAMP increase by ∼55% which was completely prevented by 1 μM NE 52-QQ57. The main extracellular organic acid, l-lactic acid (LL; 1-10 mM), suppressed pH dependent activation of GPR4 in HEK293 and HUVEC cells, suggesting allosteric negative modulation. In unanaesthetised mice and rats, NE 52-QQ57 (20 mg kg-1) reduced ventilatory response to 5 and 10% CO2. In anaesthetised rats, systemic administration of NE 52-QQ57 (up to 20 mg kg-1) had no effect on hemodynamics, cerebral blood flow and blood oxygen level dependent responses. Central administration of NE 52-QQ57 (1 mM) in vagotomised anaesthetised rats did not affect CO2-induced respiratory responses. Our results indicate that GPR4 is expressed by multiple neuronal populations and endothelium and that its pH sensitivity is affected by level of expression and LL. NE 52-QQ57 blunts hypercapnic response to CO2 but this effect is absent under anaesthesia, possibly due to the inhibitory effect of LL on GPR4.Biotechnology and Biological Sciences Research Council (BBSRC)Medical Research Council (MRC)Wellcome Trus

Characteristics of neutrophilic granulocytes of peripheral blood in patients with mechanical jaundice caused by cholangiocarcinoma

Obstructive jaundice caused by cholangiocarcinoma takes a special place among malignant disorders and surgical pathology in Russia. Involvement of nonspecific immunity and the role of neutrophils in carcinogenesis are ambiguously evaluated. The aim of this study was to study functional activity of peripheral blood neutrophilic granulocytes and their phenotype in obstructive jaundice caused by cholangiocarcinoma. The study included 56 patients with obstructive jaundice associated with cholangiocarcinoma at the T2- 3N0- 1M0 stage (clinical stages II-III), and 90 apparently healthy volunteers of similar age group. Neutrophilic granulocytes were isolated from peripheral blood by means of double-density Ficoll-Urografin gradient.Venous blood was collected in patients into vacutainers with heparin upon admission to the hospital, before the surgery was performed. Spontaneous cytokine production (IL-8, IFNá) was determined by enzyme-linked immunosorbent assay using Vector-Best diagnostic kits. To assess phagocytic activity of neutrophilic granulocytes, the phagocytic index (according to Hamburger), number of phagocytes (according to Wright) and the index of completed phagocytosis (according to Rudik, 2006) were calculated. Immunophenotyping of neutrophilic granulocytes was carried out using an FC500 flow cytometer (Beckman Coulter, USA) with monoclonal antibodies to CD11b+, CD16+, CD95+. The results were statistically analyzed using the Statistica v.12.0 software (StatSoft Inc., USA). To assess intergroup differences, the nonparametric Kruskal-Wallis tests (for three or more comparison groups) and Mann-Whitney tests (for pairwise comparison) were used. Comparison of groups for a qualitative binary trait was carried out using the two-sided Fisher’s exact test. Data are presented as Median (25 quartile-75 quartile).The study of the functional activity of peripheral blood neutrophiles in obstructive jaundice patients caused by cholangiocarcinoma revealed an increase in their relative and absolute number, increased phagocytic index and decreased phagocytic number of neutrophilic granulocytes, increased expression of CD11b+, CD16+, CD95+ immunological markers. The changes in neutrophil secretory activity were characterized by a decrease in cytokine production (IL-2, IFNá). An increase in functional activity of neutrophilic granulocytes, along with a decrease in their cytokine production suggests that, in obstructive jaundice observed in cholangiocarcinoma at clinical stage T2-3N0-1M0, an equilibrium stage is revealed between the cells of immune system and malignant tumor

Cartan subalgebras and the UCT problem, II

We show that outer approximately represenbtable actions of a finite cyclic group on UCT Kirchberg algebras satisfy a certain quasi-freeness type property if the corresponding crossed products satisfy the UCT and absorb a suitable UHF algebra tensorially. More concretely, we prove that for such an action there exists an inverse semigroup of homogeneous partial isometries that generates the ambient C*-algebra and whose idempotent semilattice generates a Cartan subalgebra. We prove a similar result for actions of finite cyclic groups with the Rokhlin property on UCT Kirchberg algebras absorbing a suitable UHF algebra. These results rely on a new construction of Cartan subalgebras in certain inductive limits of Cartan pairs. We also provide a characterisation of the UCT problem in terms of finite order automorphisms, Cartan subalgebras and inverse semigroups of partial isometries of the Cuntz algebra $\mathcal{O}_2$. This generalizes earlier work of the authors.Comment: minor revisions; final version, accepted for publication in Math. Ann.; 26 page

The bulk-edge correspondence for the quantum Hall effect in Kasparov theory

We prove the bulk-edge correspondence in $K$-theory for the quantum Hall effect by constructing an unbounded Kasparov module from a short exact sequence that links the bulk and boundary algebras. This approach allows us to represent bulk topological invariants explicitly as a Kasparov product of boundary invariants with the extension class linking the algebras. This paper focuses on the example of the discrete integer quantum Hall effect, though our general method potentially has much wider applications.Comment: 16 pages. Minor corrections and introduction expanded. To appear in Letters in Mathematical Physic