The Soluble Form of LOTUS inhibits Nogo Receptor-Mediated Signaling by Interfering with the Interaction Between Nogo Receptor Type 1 and p75 Neurotrophin Receptor

Abstract

Nogo receptor type 1 (NgR1) is known to inhibit neuronal regeneration in the CNS. We have previously identified lateral olfactory tract usher substance (LOTUS) interacts with NgR1 and inhibits its function by blocking its ligand binding. Therefore, LOTUS is expected to have therapeutic potential for the promotion of neuronal regeneration. However, it remains unknown whether the soluble form of LOTUS (s-LOTUS) also has an inhibitory action on NgR1 function as a candidate for therapeutic agents. Here, we show that s-LOTUS inhibits NgR1-mediated signaling by inhibiting the molecular interaction between NgR1 and its co-receptor p75 neurotrophin receptor (p75). In contrast to the membrane-bound form of LOTUS, s-LOTUS did not block ligand binding to NgR1. However, we identified p75 as a novel LOTUS binding partner, and found that s-LOTUS suppressed the interaction between p75 and NgR1. s-LOTUS inhibited myelin-associated inhibitor (MAI)-induced RhoA activation in murine cortical neurons. Functional analyses revealed that s-LOTUS inhibited MAI-induced growth cone collapse and neurite outgrowth inhibition in chick DRG neurons. In addition, while olfactory bulb (OB) neurons of -KO mice are sensitive to MAI due to a lack of LOTUS expression, treatment with s-LOTUS inhibited MAI-induced growth cone collapse in these neurons. Finally, we observed that s-LOTUS promoted axonal regeneration in optic nerve crush injury of mice (either sex). These findings suggest that s-LOTUS inhibits NgR1-mediated signaling possibly by interfering with the interaction between NgR1 and p75 Thus, s-LOTUS may have potential as a therapeutic agent for neuronal regeneration in the damaged CNS.Nogo receptor type 1 (NgR1) is a well-known receptor to inhibit neuronal regeneration in the CNS. Because the membrane-bound form of LOTUS antagonizes NgR1 through a cis-type molecular interaction between LOTUS and NgR1, the soluble form of LOTUS (s-LOTUS) is expected to be a therapeutic agent for neuronal regeneration. In our present study, we show that s-LOTUS inhibits the interaction between NgR1 and p75, NgR1 ligand-induced RhoA activation, growth cone collapse and neurite outgrowth inhibition, and promotes axonal regeneration. Our results indicate that s-LOTUS inhibits NgR1-mediated signaling through a trans-type molecular interaction between LOTUS and NgR1, and therefore, s-LOTUS may have therapeutic potential for neuronal regeneration.

Keratan sulfate (KS)‐proteoglycans and neuronal regulation in health and disease: the importance ofKS‐glycodynamics and interactive capability with neuroregulatory ligands

“…; Kawakami et al . ,b). This converts an inhibitory environment to an attractive environment for neural growth favoring axonal elongation (Kurihara et al .…”

Regulation of Macrophage and Dendritic Cell Function by Chondroitin Sulfate in Innate to Antigen-Specific Adaptive Immunity

“…Glycosaminoglycans (GAGs) are linear polysaccharides consisting of repeating disaccharide units and modified with sulfate groups at various positions on the sugar residues. The GAG chains retain negatively charged domains due to characteristics of the sulfate groups, allowing for the absorption of water and other positively charged soluble ligands, such as chemokines (1,2), cytokines (3), growth factors (4,5), and cell surface receptors (6,7). They are classified into chondroitin sulfate/dermatan sulfate (CS/DS), heparin/heparan sulfate (HP/HS), hyaluronan (HA), and keratan sulfate (KS).…”

LOTUS as an endogenous protein converting the adult central nervous system environment from nonpermissive to permissive for axonal regrowth after brain injury

“…Interestingly, the soluble form of LOTUS (s‐LOTUS) is secreted from the membrane‐bound form of LOTUS by cutting of the C‐terminal edge of LOTUS with protease. s‐LOTUS also shows the same potent antagonism for NgR1 function induced by all five of its ligands . These findings indicate that LOTUS is an endogenous potent NgR1 antagonist.…”

“…A recent study of LOTUS‐TG rats also showed the promotion of anatomical and physiological neuronal regeneration and functional recovery after unilateral pyramidotomy . As mentioned before, s‐LOTUS shows the same antagonistic activity against NgR1 as the membrane‐bound form of LOTUS, as well as intravitreal injection of s‐LOTUS, which can be detected in the optic nerve around the injury site, promotes axonal regeneration after optic nerve crush injury in mice . In addition to purified protein administration, LOTUS overexpression due to intravitreal injection of an adeno‐associated virus (AAV) containing LOTUS also promotes axonal regrowth of retinal ganglion cells after optic nerve crush injury .…”