Water‐soluble variant of human Lynx1 positively modulates synaptic plasticity and ameliorates cognitive impairment associated with α7‐nAChR dysfunction

Abstract

Lynx1 is a GPI-tethered protein colocalized with nicotinic acetylcholine receptors (nAChRs) in the brain areas important for learning and memory. Previously, we demonstrated that at low micromolar concentrations the water-soluble Lynx1 variant lacking GPI-anchor (ws-Lynx1) acts on α7-nAChRs as a positive allosteric modulator. We hypothesized that ws-Lynx1 could be used for improvement of cognitive processes dependent on nAChRs. Here we showed that 2 µM ws-Lynx1 increased the acetylcholine-evoked current at α7-nAChRs in the rat primary visual cortex L1 interneurons. At higher concentrations ws-Lynx1 inhibits α7-nAChRs expressed in Xenopus laevis oocytes with IC 50 ~ 50 µM. In mice, ws-Lynx1 penetrated the bloodbrain barrier upon intranasal administration and accumulated in the cortex, hippocampus, and cerebellum. Chronic ws-Lynx1 treatment prevented the olfactory memory and motor learning impairment induced by the α7-nAChRs inhibitor methyllycaconitine (MLA). Enhanced long-term potentiation and increased paired-pulse facilitation ratio were observed in the hippocampal slices incubated with ws-Lynx1 and in the slices from ws-Lynx1-treated mice. Long-term potentiation blockade observed in MLA-treated mice was abolished by ws-Lynx1 co-administration. To understand the mechanism of ws-Lynx1 action, we studied the interaction of ws-Lynx1 and MLA at α7-nAChRs, measured the basal concentrations of endogenous Lynx1 and the α7 nAChR subunit and their association in the mouse brain. Our findings suggest that endogenous Lynx1 limits α7-nAChRs activation in the adult brain. Ws-Lynx1 partially displaces Lynx1 causing positive modulation of α7-nAChRs and enhancement 42) for the binding to the nAChR subunits, abolishes the Aβ 1-42 cytotoxic effect in the cultured cortical neurons (Thomsen et al., 2016), and prevents the long-term potentiation (LTP) blockade caused by Aβ 1-42 (Bychkov et al., 2018). Here, we investigated the ws-Lynx1 influence on cognitive processes in vivo and on the synaptic plasticity processes ex vivo. To model cognitive impairment associated with the loss of nAChR function, C57BL/6 mice were chronically treated with of synaptic plasticity. Ws-Lynx1 and similar compounds may constitute useful hits for treatment of cognitive deficits associated with the cholinergic system dysfunction.

Structural Diversity and Dynamics of Human Three-Finger Proteins Acting on Nicotinic Acetylcholine Receptors

“…Interestingly, similar aggregation was previously observed for SLURP-2 [ 32 ], which also has a relatively high hydrophobicity index (+0.10, Table 1 ). The aggregation of Lynx2 and SLURP-2 was observed at concentrations > 0.1 mM, which are significantly higher than expected protein concentrations in the organism [ 15 ]; therefore, this aggregation, probably, has no biological consequences. One of the probable oligomerization interfaces in the Lynx2 molecule (Thr25-Val28) is located near the proposed glycosylation site (Asn23).…”

“…For example, Lynx1 is colocalized with α7- and α4β2-nAChRs in the brain [ 10 ] and modulates their function [ 11 ], in particular controlling an assembly of α4β2-nAChRs in the endoplasmic reticulum [ 12 ]. Lynx1 regulates neuronal plasticity during postnatal development [ 13 ], motor learning [ 14 ], and other cognitive functions by interaction with α7-nAChRs [ 15 ]. Similarly, Lynx2 (also known as LYPD1) is expressed in the peripheral and central nervous systems [ 16 ] and modulates α4β2-nAChRs [ 17 ], probably controlling their assembly [ 18 ].…”

Mambalgin-2 Induces Cell Cycle Arrest and Apoptosis in Glioma Cells via Interaction with ASIC1a

“…Nevertheless, a question about the permeability of the blood-brain barrier (BBB) for mambalgin-2 remains open. Recently, we showed that water-soluble domain of the nAChR modulator ws-Lynx1 crosses BBB in mice, despite the quite high molar mass of the protein (~8 kDa) [57]. We proposed that ws-Lynx1 can penetrate BBB by transcytosis via interaction with nAChRs expressed on endothelial cells [57].…”

“…Recently, we showed that water-soluble domain of the nAChR modulator ws-Lynx1 crosses BBB in mice, despite the quite high molar mass of the protein (~8 kDa) [57]. We proposed that ws-Lynx1 can penetrate BBB by transcytosis via interaction with nAChRs expressed on endothelial cells [57]. Besides nAChRs, human brain endothelial cells express ASIC1a [58], so we suppose that mambalgin-2 can also pass through BBB by transcytosis, however further investigation of this issue is required.…”

Biophysical characterization of lynx‐nicotinic receptor interactions using atomic force microscopy

“…Lynx1 has been shown to regulate plasticity in the hippocampus (20,21), alter plasticity in the adult visual and auditory cortices (20) and suppress associative learning and memory (9). More specifically, it has been shown to associate with α4β2-nAChRs and to increase the rate of receptor desensitization to acetylcholine (22).…”