Single-cell analysis of peptide expression and electrophysiology of right parietal neurons involved in male copulation behavior of a simultaneous hermaphrodite

Male copulation is a complex behavior that requires coordinated communication between the nervous system and the peripheral reproductive organs involved in mating. In hermaphroditic animals, such as the freshwater snail Lymnaea stagnalis, this complexity increases since the animal can behave both as male and female. The performance of the sexual role as a male is coordinated via a neuronal communication regulated by many peptidergic neurons, clustered in the cerebral and pedal ganglia and dispersed in the pleural and parietal ganglia. By combining single-cell matrix-assisted laser mass spectrometry with retrograde staining and electrophysiology, we analyzed neuropeptide expression of single neurons of the right parietal ganglion and their axonal projections into the penial nerve. Based on the neuropeptide profile of these neurons, we were able to reconstruct a chemical map of the right parietal ganglion revealing a striking correlation with the earlier electrophysiological and neuroanatomical studies. Neurons can be divided into two main groups: (i) neurons that express heptapeptides and (ii) neurons that do not. The neuronal projection of the different neurons into the penial nerve reveals a pattern where (spontaneous) activity is related to branching pattern. This heterogeneity in both neurochemical anatomy and branching pattern of the parietal neurons reflects the complexity of the peptidergic neurotransmission involved in the regulation of male mating behavior in this simultaneous hermaphrodite

Interaction proteomics reveals brain region-specific AMPA receptor complexes.

Fast excitatory synaptic transmission in the brain is mediated by glutamate acting on postsynaptic AMPA receptors. Recent studies have revealed a substantial number of AMPA receptor auxiliary proteins, which potentially contribute to the regulation of AMPA receptor trafficking, subcellular receptor localization, and receptor gating properties. Here we examined the AMPA receptor interactomes from cortex, hippocampus, and cerebellum by comprehensive interaction proteomics. The study reveals that AMPA receptor auxiliary proteins are engaged in distinct brain region-specific AMPA receptors subcomplexes, which might underlie brain region-specific differential regulation of AMPA receptor properties. Depending on the brain region, an interacting protein can be involved in an AMPA and a non-AMPA receptor complex

The macrophage CD163 surface glycoprotein is an erythroblast adhesion receptor

Erythropoiesis occurs in erythroblastic islands, where developing erythroblasts closely interact with macrophages. The adhesion molecules that govern macrophage-erythroblast contact have only been partially defined. Our previous work has implicated the rat ED2 antigen, which is highly expressed on the surface of macrophages in erythroblastic islands, in erythroblast binding. In particular, the monoclonal antibody ED2 was found to inhibit erythroblast binding to bone marrow macrophages. Here, we identify the ED2 antigen as the rat CD163 surface glycoprotein, a member of the group B scavenger receptor cysteine-rich (SRCR) family that has previously been shown to function as a receptor for hemoglobin-haptoglobin (Hb-Hp) complexes and is believed to contribute to the clearance of free hemoglobin. CD163 transfectants and recombinant protein containing the extracellular domain of CD163 supported the adhesion of erythroblastic cells. Furthermore, we identified a 13-amino acid motif (CD163p2) corresponding to a putative interaction site within the second scavenger receptor domain of CD163 that could mediate erythroblast binding. Finally, CD163p2 promoted erythroid expansion in vitro, suggesting that it enhanced erythroid proliferation and/or survival, but did not affect differentiation. These findings identify CD163 on macrophages as an adhesion receptor for erythroblasts in erythroblastic islands, and suggest a regulatory role for CD163 during erythropoiesis

The macrophage CD163 surface glycoprotein is an erythroblast adhesion receptor

Erythropoiesis occurs in erythroblastic islands, where developing erythroblasts closely interact with macrophages. The adhesion molecules that govern macrophage-erythroblast contact have only been partially defined. Our previous work has implicated the rat ED2 antigen, which is highly expressed on the surface of macrophages in erythroblastic islands, in erythroblast binding. In particular, the monoclonal antibody ED2 was found to inhibit erythroblast binding to bone marrow macrophages. Here, we identify the ED2 antigen as the rat CD163 surface glycoprotein, a member of the group B scavenger receptor cysteine-rich (SRCR) family that has previously been shown to function as a receptor for hemoglobin-haptoglobin (Hb-Hp) complexes and is believed to contribute to the clearance of free hemoglobin. CD163 transfectants and recombinant protein containing the extracellular domain of CD163 supported the adhesion of erythroblastic cells. Furthermore, we identified a 13-amino acid motif (CD163p2) corresponding to a putative interaction site within the second scavenger receptor domain of CD163 that could mediate erythroblast binding. Finally, CD163p2 promoted erythroid expansion in vitro, suggesting that it enhanced erythroid proliferation and/or survival, but did not affect differentiation. These findings identify CD163 on macrophages as an adhesion receptor for erythroblasts in erythroblastic islands, and suggest a regulatory role for CD163 during erythropoiesi

A glia-derived acetylcholine-binding protein that modulates synaptic transmission

There is accumulating evidence that glial cells actively modulate neuronal synaptic transmission. We identified a glia-derived soluble acetylcholine-binding protein (AChBP), which is a naturally occurring analogue of the ligand-binding domains of the nicotinic acetylcholine receptors (nAChRs). Like the nAChRs, it assembles into a homopentamer with ligand-binding characteristics that are typical for a nicotinic receptor; unlike the nAChRs, however, it lacks the domains to form a transmembrane ion channel. Presynaptic release of acetylcholine induces the secretion of AChBP through the glial secretory pathway. We describe a molecular and cellular mechanism by which glial cells release AChBP in the synaptic cleft, and propose a model for how they actively regulate cholinergic transmission between neurons in the central nervous system