Mettl14 mutation restrains liver regeneration by attenuating mitogens derived from non-parenchymal liver cells.

Liver regeneration is a well-known systemic homeostatic phenomenon. The N6-methyladenosine (m6A) modification pathway has been associated with liver regeneration and hepatocellular carcinoma. m6A methyltransferases, such as methyltransferase 3 (METTL3) and methyltransferase 14 (METTL14), are involved in the hepatocyte-specific-regenerative pathway. To illustrate the role of METTL14, secreted from non-parenchymal liver cells, in the initiation phase of liver regeneration, we performed 70% partial hepatectomy (PH) in Mettl14 heterozygous (HET) and wild-type (WT) mice. Next, we analyzed the ratio of liver weight to body weight and the expression of mitogenic stimulators derived from non-parenchymal liver cells. Furthermore, we evaluated the expression of cell cycle-related genes and the hepatocyte proliferation rate via MKI67-immunostaining. During regeneration after PH, the weight ratio was lower in Mettl14 HET mice compared to WT mice. The expressions of hepatocyte growth factor (HGF) and tumor necrosis factor (TNF)-α, mitogens derived from non-parenchymal liver cells that stimulate the cell cycle, as well as the expressions of cyclin B1 and D1, which regulate the cell cycle, and the number of MKI67-positive cells, which indicate proliferative hepatocyte in the late G1-M phase, were significantly reduced in Mettl14 HET mice 72 h after PH. Our findings demonstrate that global Mettl14 mutation may interrupt the homeostasis of liver regeneration after an acute injury like PH by restraining certain mitogens, such as HGF and TNF-α, derived from sinusoidal endothelial cells, stellate cells, and Kupffer cells. These results provide new insights into the role of METTL14 in the clinical treatment strategies of liver disease. [BMB Reports 2022; 55(12): 633-638].

Correction: Tumor suppressor RARRES1 links tubulin deglutamylation to mitochondrial metabolism and cell survival.

[This corrects the article DOI: 10.18632/oncotarget.26600.].

Ibrutinib modulates Aß/tau pathology, neuroinflammation, and cognitive function in mouse models of Alzheimer's disease.

We previously demonstrated that ibrutinib modulates LPS-induced neuroinflammation in vitro and in vivo, but its effects on the pathology of Alzheimer's disease (AD) and cognitive function have not been investigated. Here, we investigated the effects of ibrutinib in two mouse models of AD. In 5xFAD mice, ibrutinib injection significantly reduced Aß plaque levels by promoting the non-amyloidogenic pathway of APP cleavage, decreased Aß-induced neuroinflammatory responses, and significantly downregulated phosphorylation of tau by reducing levels of phosphorylated cyclin-dependent kinase-5 (p-CDK5). Importantly, tau-mediated neuroinflammation and tau phosphorylation were also alleviated by ibrutinib injection in PS19 mice. In 5xFAD mice, ibrutinib improved long-term memory and dendritic spine number, whereas in PS19 mice, ibrutinib did not alter short- and long-term memory but promoted dendritic spinogenesis. Interestingly, the induction of dendritic spinogenesis by ibrutinib was dependent on the phosphorylation of phosphoinositide 3-kinase (PI3K). Overall, our results suggest that ibrutinib modulates AD-associated pathology and cognitive function and may be a potential therapy for AD.

Tumor suppressor RARRES1 links tubulin deglutamylation to mitochondrial metabolism and cell survival.

RARRES1, a retinoic acid regulated carboxypeptidase inhibitor associated with fatty acid metabolism, stem cell differentiation and tumorigenesis is among the most commonly methylated loci in multiple cancers but has no known mechanism of action. Here we show that RARRES1 interaction with cytoplasmic carboxypeptidase 2 (CCP2) inhibits tubulin deglutamylation, which in turn regulates the mitochondrial voltage dependent anion channel (VDAC1), mitochondrial membrane potential, AMPK activation, energy balance and metabolically reprograms cells and zebrafish to a more energetic and anabolic phenotype. Depletion of RARRES1 also increases expression of stem cell markers, promotes anoikis, anchorage independent growth and insensitivity to multiple apoptotic stimuli. As depletion of CCP2 or inhibition of VDAC1 reverses the effects of RARRES1 depletion on energy balance and cell survival we conclude that RARRES1 modulation of CCP2-modulated tubulin-mitochondrial VDAC1 interactions is a fundamental regulator of cancer and stem cell metabolism and survival.

Essential role of Ahnak in adipocyte differentiation leading to the transcriptional regulation of Bmpr1α expression.

The role of Ahnak in obesity has been reported previously. Loss of Ahnak leads to decreased Bmp4/Smad1 signaling, resulting in the downregulation of adipocyte differentiation. However, the biological significance of Ahnak remains largely unknown. In this study, we demonstrate that Ahnak-mediated impaired adipogenesis results in decreased Bmpr1α transcriptional expression. To confirm this, Ahnak siRNA was used to knock-down Ahnak in C3H10T1/2 and primary stromal vascular fraction cells. Ahnak siRNA transfected cells showed suppression of Bmpr1α expression and decreased BMP4/ Bmpr1α signaling. The differential adipogenesis was further confirmed by knock-down of Bmpr1α in C3H10T1/2 cells, which resulted in reduced adipogenesis. Moreover, stable Ahnak knock-out C3H10T1/2 cells stably transfected with Ahnak CRISPR/Cas9 plasmid suppressed expression of Bmpr1α and prevented differentiation into adipocytes. Furthermore, we developed immortalized pre-adipocytes from wild-type or Ahnak Knock-out mice's stromal vascular fraction (SVF) to confirm the function of Ahnak in pre-adipocyte transition. Immortalized Ahnak knock-out SVF cells showed lower level of Bmpr1α expression, evidence by their impaired BMP4/Bmpr1α signaling. Upon adipogenic induction, immortalized Ahnak knock-out SVF cells exhibited a marked decrease in adipocyte differentiation compared with immortalized wild-type pre-adipocytes. Furthermore, over-expression of Bmpr1α restored the adipogenic activity of Ahnak knock-out C3H10T1/2 cells and immortalized Ahnak knock-out SVF cells. Our data reveal the missing link in Ahnak-mediated adipose tissue remodeling and suggest that precise regulation of Ahnak in adipose tissue might have a therapeutic advantage for metabolic disease treatment.

General rules for functional microRNA targeting.

The functional rules for microRNA (miRNA) targeting remain controversial despite their biological importance because only a small fraction of distinct interactions, called site types, have been examined among an astronomical number of site types that can occur between miRNAs and their target mRNAs. To systematically discover functional site types and to evaluate the contradicting rules reported previously, we used large-scale transcriptome data and statistically examined whether each of approximately 2 billion site types is enriched in differentially downregulated mRNAs responding to overexpressed miRNAs. Accordingly, we identified seven non-canonical functional site types, most of which are novel, in addition to four canonical site types, while also removing numerous false positives reported by previous studies. Extensive experimental validation and significantly elevated 3' UTR sequence conservation indicate that these non-canonical site types may have biologically relevant roles. Our expanded catalog of functional site types suggests that the gene regulatory network controlled by miRNAs may be far more complex than currently understood.

A Mercaptoacetamide-Based Class II Histone Deacetylase Inhibitor Increases Dendritic Spine Density via RasGRF1/ERK Pathway.

BACKGROUND: The accumulation of amyloid-ß (Aß) leads to the loss of dendritic spines and synapses, which is hypothesized to cause cognitive impairments in Alzheimer's disease (AD) patients. In our previous study, we demonstrated that a novel mercaptoacetamide-based class II histone deacetylase inhibitor (HDACI), known as W2, decreased Aß levels and improved learning and memory in mice. However, the underlying mechanism of this effect is unknown. OBJECTIVE: Because dendritic spine formation is associated with cognitive performance, here we investigated whether HDACI W2 regulates dendritic spine density and its molecular mechanism of action. METHODS: To examine the effect of HDACI W2 on dendritic spine density, we conducted morphological analysis of dendritic spines using GFP transfection and Golgi staining. In addition, to determine the molecular mechanism of W2 effects on spines, we measured the levels of mRNAs and proteins involved in the Ras signaling pathway using quantitative real-time PCR, immunocytochemistry, and western analysis. RESULTS: We found that HDACI W2 altered dendritic spine density and morphology in vitro and in vivo. Additionally, W2 increased the mRNA or protein levels of Ras GRF1 and phospho-ERK. Moreover, knockdown of RasGRF1 and inhibition of ERK activity prevented the W2-mediated spinogenesis in primary hippocampal neurons. CONCLUSION: Our Class II-selective HDACI W2 promotes the formation and growth of dendritic spines in a RasGRF1 and ERK dependent manner in primary hippocampal neurons.

Hexa (ethylene glycol) derivative of benzothiazole aniline promotes dendritic spine formation through the RasGRF1-Ras dependent pathway.

Our recent study demonstrated that an amyloid-ß binding molecule, BTA-EG4, increases dendritic spine number via Ras-mediated signaling. To potentially optimize the potency of the BTA compounds, we synthesized and evaluated an amyloid-ß binding analog of BTA-EG4 with increased solubility in aqueous solution, BTA-EG6. We initially examined the effects of BTA-EG6 on dendritic spine formation and found that BTA-EG6-treated primary hippocampal neurons had significantly increased dendritic spine number compared to control treatment. In addition, BTA-EG6 significantly increased the surface level of AMPA receptors. Upon investigation into the molecular mechanism by which BTA-EG6 promotes dendritic spine formation, we found that BTA-EG6 may exert its effects on spinogenesis via RasGRF1-ERK signaling, with potential involvement of other spinogenesis-related proteins such as Cdc42 and CDK5. Taken together, our data suggest that BTA-EG6 boosts spine and synapse number, which may have a beneficial effect of enhancing neuronal and synaptic function in the normal healthy brain.

Deficiency in LRP6-mediated Wnt signaling contributes to synaptic abnormalities and amyloid pathology in Alzheimer's disease.

Alzheimer's disease (AD) is an age-related neurological disorder characterized by synaptic loss and dementia. The low-density lipoprotein receptor-related protein 6 (LRP6) is an essential coreceptor for Wnt signaling, and its genetic variants have been linked to AD risk. Here we report that neuronal LRP6-mediated Wnt signaling is critical for synaptic function and cognition. Conditional deletion of Lrp6 gene in mouse forebrain neurons leads to age-dependent deficits in synaptic integrity and memory. Neuronal LRP6 deficiency in an amyloid mouse model also leads to exacerbated amyloid pathology due to increased APP processing to amyloid-ß. In humans, LRP6 and Wnt signaling are significantly downregulated in AD brains, likely by a mechanism that depends on amyloid-ß. Our results define a critical pathway in which decreased LRP6-mediated Wnt signaling, synaptic dysfunction, and elevated Aß synergistically accelerate AD progression and suggest that restoring LRP6-mediated Wnt signaling can be explored as a viable strategy for AD therapy.

A tetra(ethylene glycol) derivative of benzothiazole aniline ameliorates dendritic spine density and cognitive function in a mouse model of Alzheimer's disease.

We recently reported that the tetra(ethylene glycol) derivative of benzothiazole aniline, BTA-EG4, acts as an amyloid-binding small molecule that promotes dendritic spine density and cognitive function in wild-type mice. This raised the possibility that BTA-EG4 may benefit the functional decline seen in Alzheimer's disease (AD). In the present study, we directly tested whether BTA-EG4 improves dendritic spine density and cognitive function in a well-established mouse model of AD carrying mutations in APP, PS1 and tau (APPswe;PS1M146V;tauP301L, 3xTg AD mice). We found that daily injections of BTA-EG4 for 2 weeks improved dendritic spine density and cognitive function of 3xTg AD mice in an age-dependent manner. Specifically, BTA-EG4 promoted both dendritic spine density and morphology alterations in cortical layers II/III and in the hippocampus at 6-10 months of age compared to vehicle-injected mice. However, at 13-16 months of age, only cortical spine density was improved without changes in spine morphology. The changes in dendritic spine density correlated with Ras activity, such that 6-10 month old BTA-EG4 injected 3xTg AD mice had increased Ras activity in the cortex and hippocampus, while 13-16 month old mice only trended toward an increase in Ras activity in the cortex. Finally, BTA-EG4 injected 3xTg AD mice at 6-10 months of age showed improved learning and memory; however, only minimal improvement was observed at 13-16 months of age. This behavioral improvement corresponds to a decrease in soluble Aß 40 levels. Taken together, these findings suggest that BTA-EG4 may be beneficial in ameliorating the synaptic loss seen in early AD.