Differential binding of anti-Reelin monoclonal antibodies reveals the characteristics of Reelin protein under various conditions

REELIN ameliorates Alzheimer's disease, but how?

Alzheimer's disease (AD) is the most prevalent type of dementia; therefore, there is a high demand for therapeutic medication targeting it. In this context, extensive research has been conducted to identify molecular targets for drugs. AD manifests through two primary pathological signs: senile plaques and neurofibrillary tangles, caused by accumulations of amyloid-beta (Aβ) and phosphorylated tau, respectively. Thus, studies concerning the molecular mechanisms underlying AD etiology have primarily focused on Aβ generation and tau phosphorylation, with the anticipation of uncovering a signaling pathway impacting these molecular processes. Over the past two decades, studies using not only experimental model systems but also examining human brains have accumulated fragmentary evidences suggesting that REELIN signaling pathway is deeply involved in AD. Here, we explore REELIN signaling pathway and its involvement in memory function within the brain and review studies investigating molecular connections between REELIN signaling pathway and AD etiology. This review aims to understand how the manipulation (activation) of this pathway might ameliorate the disease's etiology.

Reelin regulates the migration of late-born hippocampal CA1 neurons via cofilin phosphorylation

Reelin, a large secreted glycoprotein, plays an important role in neuronal migration during brain development. The C-terminal region (CTR) of Reelin is involved in the efficient activation of downstream signaling and its loss leads to abnormal hippocampal layer formation. However, the molecular mechanism by which Reelin CTR regulates hippocampal development remains unknown. Here, we showed that the migration of late-born, but not early-born, neurons is impaired in the knock-in mice in which Reelin CTR is deleted (ΔC-KI mice). The phosphorylation of cofilin, an actin-depolymerizing protein, was remarkably decreased in the hippocampus of the ΔC-KI mice. Exogenous expression of pseudo-phosphorylated cofilin rescued the ectopic positioning of neurons in the hippocampus of ΔC-KI mice. These results suggest that Reelin CTR is required for the migration of late-born neurons in the hippocampus and that this event involves appropriate phosphorylation of cofilin.

Visualization of Reelin secretion from primary cultured neurons by bioluminescence imaging

Reelin is a secreted glycoprotein important for brain development and synaptic plasticity in the adult brain. Some reports suggest that Reelin is secreted from the nerve terminals and functions as a neurotransmitter. However, the mechanism of Reelin secretion is unknown. In this study, we visualized Reelin secretion by bioluminescence imaging using a fusion protein of Reelin and Gaussia luciferase (GLase-Reelin). GLase-Reelin expressed in HEK293T cells was correctly processed and secreted. Luminescence signals from the secreted GLase-Reelin of primary cultured neurons were visualized by bioluminescence microscopy. Reelin secretory events were observed at neurites and cell bodies. Bioluminescence imaging was also performed before and after KCl depolarization to compare the secretory events of Reelin and brain-derived neurotrophic factor (BDNF). The secretion of BDNF increased markedly shortly after depolarization. In contrast, the frequency of Reelin secretion did not change significantly by depolarization. Thus, Reelin secretion from neurites might not be regulated in a neuronal activity-dependent manner.

The hsa_circRNA_102049 mediates the sorafenib sensitivity of hepatocellular carcinoma cells by regulating Reelin gene expression

A growing body of research has illuminated that non-coding RNAs (ncRNAs) plays an important role in the development of drug resistance in hepatocellular carcinoma (HCC) cells. The expression profiles of differential expressed genes (DEGs) and ncRNAs related to the sorafenib resistance in HCC cells were analyzed according to the Gene Expression Omnibus (GEO) dataSets and The Cancer Genome Atlas (TCGA) datasets. Bioinformatics technology was used to construct the interaction network of DEGs and ncRNAs. Cell transfection, dual-luciferase reporter assay, Western blot, cell counting kit-8 (CCK-8), flow cytometry and quantitative real-time polymerase chain reaction(qRT-PCR) were used to study the mechanism of sorafenib resistance in HepG2 cells and Huh-7 cells. The expression of reelin (RELN) and secretagogin (SCGN) were the only down-regulated in sorafenib-resistant HCC cells. The results showed that RELN gene demethylation reversed the cytotoxic of sorafenib on HepG2 cells and Huh-7 cells. Hsa_circRNA_102049 over-expression promoted the sensitivity of HepG2 cells and Huh-7 cells to sorafenib, hsa_circRNA_102049 up-regulated the expression of RELN gene by sponging hsa-miR-214-3p. The resistance to sorafenib in RELN knockout HepG2 cells and Huh-7 cells could be reverted by has-circRNA_102049. These findings support targeting of hsa_circRNA_102049 and RELN in sorafenib-treated HCC cells as a novel intervention, which is expected to overcome sorafenib resistance of HCC cells.

Elevated Plasma Reelin Levels in Children With Autism

Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders involving age-dependent gene dysregulation. Reelin is a glycoprotein that varies its expression throughout lifetime and controls cortical patterning and synaptogenesis. Brain and plasma reelin levels have been reported to be low in adults with autism; as well as in children with autism, but only when compared to control adults. Therefore, reelin expression levels in children with autism are unclear. For this reason, we compared plasma reelin levels in children with autism and children without autism (non-ASD) of similar ages to evaluate reelin expression in ASD during childhood. Plasma samples from 19 non-ASD (8.9 ± 0.8 years) and 40 children with autism (7.5 ± 0.5 years) were analyzed. We found that 50% of the children with autism displayed similar plasma reelin levels to the non-ASD group. However, the remaining 50% expressed more than 30 times more reelin compared to non-ASD levels. We also show that male children with autism displayed significantly higher reelin levels than females. The clinical presentation of this subgroup could not be distinguished from that of children with autism. Epilepsy or attention-deficit/hyperactivity disorder (ADHD) was not associated to reelin levels. We conclude that the high levels of plasma reelin might be an important hallmark in a subset of children with autism, previously unnoticed. As we could not find any correlation between reelin levels and ASD clinical presentations, our results may indicate transient reelin increases in the plasma or the characterization of a group of ASD individuals with a different pathophysiology.