Dual specificity phosphatase 15 regulates Erk activation in Schwann cells

LEM Domain Containing 1 Acts as a Novel Oncogene and Therapeutic Target for Triple-Negative Breast Cancer

Breast cancer is the most common deadly malignancy in women worldwide. In particular, triple-negative breast cancer (TNBC) exhibits the worst prognosis among four subtypes of breast cancer due to limited treatment options. Exploring novel therapeutic targets holds promise for developing effective treatments for TNBC. Here, we demonstrated for the first time that LEMD1 (LEM domain containing 1) is highly expressed in TNBC and contributes to reduced survival in TNBC patients, through analysis of both bioinformatic databases and collected patient samples. Furthermore, LEMD1 silencing not only inhibited the proliferation and migration of TNBC cells in vitro, but also abolished tumor formation of TNBC cells in vivo. Knockdown of LEMD1 enhanced the sensitivity of TNBC cells to paclitaxel. Mechanistically, LEMD1 promoted the progress of TNBC by activating the ERK signaling pathway. In summary, our study revealed that LEMD1 may act as a novel oncogene in TNBC, and targeting LEMD1 may be exploited as a promising therapeutic approach to enhance the efficacy of chemotherapy against TNBC.

HSP90 inhibition in the mouse spinal cord enhances opioid signaling by suppressing an AMPK-mediated negative feedback loop

Opioids and other agonists of the μ-opioid receptor are effective at managing acute pain, but their chronic use can lead to tolerance that limits their efficacy. We previously reported that inhibiting the chaperone protein HSP90 in the spinal cords of mice promotes the antinociceptive effects of opioids in a manner that involved increased activation of the kinase ERK. Here, we found that the underlying mechanism involves the relief of a negative feedback loop mediated by the kinase AMPK. Intrathecal treatment of male and female mice with the HSP90 inhibitor 17-AAG decreased the abundance of the β1 subunit of AMPK in the spinal cord. The antinociceptive effects of 17-AAG with morphine were suppressed by intrathecal administration of AMPK activators and enhanced by an AMPK inhibitor. Opioid treatment increased the abundance of phosphorylated AMPK in the dorsal horn of the spinal cord, where it colocalized with a neuronal marker and the neuropeptide CGRP. Knocking down AMPK in CGRP-positive neurons enhanced the antinociceptive effects of morphine and demonstrated that AMPK mediated the signal transduction between HSP90 inhibition and ERK activation. These data suggest that AMPK mediates an opioid-induced negative feedback loop in CGRP neurons of the spinal cord and that this loop can be disabled by HSP90 inhibition to enhance the efficacy of opioids.

Electroceutical approach ameliorates intracellular PMP22 aggregation and promotes pro-myelinating pathways in a CMT1A in vitro model

Charcot-Marie-Tooth disease subtype 1A (CMT1A) is one of the most prevalent demyelinating peripheral neuropathies worldwide, caused by duplication of the peripheral myelin protein 22 (PMP22) gene, which is expressed primarily in Schwann cells (SCs). PMP22 overexpression in SCs leads to intracellular aggregation of the protein, which eventually results in demyelination. Unfortunately, previous biochemical approaches have not resulted in an approved treatment for CMT1A disease, compelling the pursuit for a biophysical approach such as electrical stimulation (ES). However, the effects of ES on CMT1A SCs have remained unexplored. In this study, we established PMP22-overexpressed Schwannoma cells as a CMT1A in vitro model, and investigated the biomolecular changes upon applying ES via a custom-made high-throughput ES platform, screening for the condition that delivers optimal therapeutic effects. While PMP22-overexpressed Schwannoma exhibited intracellular PMP22 aggregation, ES at 20 Hz for 1 h improved this phenomenon, bringing PMP22 distribution closer to healthy condition. ES at this condition also enhanced the expression of the genes encoding myelin basic protein (MBP) and myelin-associated glycoprotein (MAG), which are essential for assembling myelin sheath. Furthermore, ES altered the gene expression for myelination-regulating transcription factors Krox-20, Oct-6, c-Jun and Sox10, inducing pro-myelinating effects in PMP22-overexpressed Schwannoma. While electroceuticals has previously been applied in the peripheral nervous system towards acquired peripheral neuropathies such as pain and nerve injury, this study demonstrates its effectiveness towards ameliorating biomolecular abnormalities in an in vitro model of CMT1A, an inherited peripheral neuropathy. These findings will facilitate the clinical translation of an electroceutical treatment for CMT1A.

Dissecting 16p11.2 hemi-deletion to study sex-specific striatal phenotypes of neurodevelopmental disorders

Neurodevelopmental disorders (NDDs) are polygenic in nature and copy number variants (CNVs) are ideal candidates to study the nature of this polygenic risk. The disruption of striatal circuits is considered a central mechanism in NDDs. The 16p11.2 hemi-deletion (16p11.2 del) is one of the most common CNVs associated with NDD, and 16p11.2 del/+ mice show sex-specific striatum-related behavioral phenotypes. However, the critical genes among the 27 genes in the 16p11.2 region that underlie these phenotypes remain unknown. Previously, we applied a novel strategy to identify candidate genes associated with the sex-specific phenotypes of 16p11.2 del/+ mice and identified 3 genes of particular importance within the deleted region: thousand and one amino acid protein kinase 2 (Taok2), seizure-related 6 homolog-like 2 (Sez6l2), and major vault protein (Mvp). Using the CRISPR/Cas9 technique, we generated 3 gene hemi-deletion (3g del/+) mice carrying null mutations in Taok2, Sez6l2, and Mvp. We assessed striatum-dependent phenotypes of these 3g del/+ mice in behavioral, molecular, and imaging studies. Hemi-deletion of Taok2, Sez6l2, and Mvp induces sex-specific behavioral alterations in striatum-dependent behavioral tasks, specifically male-specific hyperactivity and impaired motivation for reward seeking, resembling behavioral phenotypes of 16p11.2 del/+ mice. Moreover, RNAseq analysis revealed that 3g del/+ mice exhibit gene expression changes in the striatum similar to 16p11.2 del/+ mice, but only in males. Pathway analysis identified ribosomal dysfunction and translation dysregulation as molecular mechanisms underlying male-specific, striatum-dependent behavioral alterations. Together, the mutation of 3 genes within the 16p11.2 region phenocopies striatal sex-specific phenotypes of 16p11.2 del/+ mice, unlike single gene mutation studies. These results support the importance of a polygenic approach to study NDDs and our novel strategy to identify genes of interest using gene expression patterns in brain regions, such as the striatum, which are impacted in these disorders.

Dissecting 16p11.2 hemi-deletion to study sex-specific striatal phenotypes of neurodevelopmental disorders

Neurodevelopmental disorders (NDDs) are polygenic in nature and copy number variants (CNVs) are ideal candidates to study the nature of this polygenic risk. The disruption of striatal circuits is considered a central mechanism in NDDs. The 16p11.2 hemi-deletion (16p11.2 del) is one of the most common CNVs associated with NDD, and 16p11.2 del/+ mice show sex-specific striatum-related behavioral phenotypes. However, the critical genes among the 27 genes in the 16p11.2 region that underlie these phenotypes remain unknown. Previously, we applied a novel strategy to identify candidate genes associated with the sex-specific phenotypes of 16p11.2 del/+ mice and identified 3 genes of particular importance within the deleted region: thousand and one amino acid protein kinase 2 ( Taok2 ), seizure-related 6 homolog-like 2 ( Sez6l2 ), and major vault protein ( Mvp ). Using the CRISPR/Cas9 technique, we generated 3 gene hemi-deletion (3g del/+) mice carrying null mutations in Taok2, Sez6l2 , and Mvp . We assessed striatum-dependent phenotypes of these 3g del/+ mice in behavioral, molecular, and imaging studies. Hemi-deletion of Taok2, Sez6l2 , and Mvp induces sex-specific behavioral alterations in striatum-dependent behavioral tasks, specifically male-specific hyperactivity and impaired motivation for reward seeking, resembling behavioral phenotypes of 16p11.2 del/+ mice. Moreover, RNAseq analysis revealed that 3g del/+ mice exhibit gene expression changes in the striatum similar to 16p11.2 del/+ mice, but only in males. Pathway analysis identified ribosomal dysfunction and translation dysregulation as molecular mechanisms underlying male-specific, striatum-dependent behavioral alterations. Together, the mutation of 3 genes within the 16p11.2 region phenocopies striatal sex-specific phenotypes of 16p11.2 del/+ mice, unlike single gene mutation studies. These results support the importance of a polygenic approach to study NDDs and our novel strategy to identify genes of interest using gene expression patterns in brain regions, such as the striatum, which are impacted in these disorders.

DUSP15 expression is reduced in the hippocampus of Myrf knock-out mice but attention and object recognition memory remain intact

The atypical protein tyrosine phosphatase enzyme, dual-specificity phosphate 15 (DUSP15) is thought to be activated by myelin regulatory factor (MyRF) and to have a role in oligodendrocyte differentiation. Here, we assess whether Dusp15 is reduced in the hippocampus of mice with conditional knock-out of Myrf in oligodendrocyte precursor cells. Using quantitative polymerase chain reaction (qPCR) we found that Dusp15 expression was indeed lower in these mice. Alterations in myelin have been associated with Alzheimer's disease (AD), autism spectrum disorder (ASD) and attention deficit/hyperactivity disorder (ADHD). Symptoms of these disorders can include impairments of object recognition and attention. We, therefore tested the mice in the object recognition task (ORT) and 5-choice serial reaction time task (5CSRTT). However, we did not find behavioural impairments indicating that attentional abilities and object recognition are not impacted by reduced oligodendrogenesis and hippocampal Dusp15 expression. Gaining insight into the role of newly formed oligodendrocytes and Dusp15 expression is helpful for the development of well targeted treatments for myelin dysregulation.

Association between Genetic Variants in DUSP15, CNTNAP2, and PCDHA Genes and Risk of Childhood Autism Spectrum Disorder

Objective

Genetic factors play an important role in the development of autism spectrum disorder (ASD). This case-control study was to determine the association between childhood ASD and single nucleotide polymorphisms (SNPs) rs3746599 in the DUSP15 gene, rs7794745 in the CNTNAP2 gene, and rs251379 in the PCDHA gene in a Chinese Han population.

Methods

Genotypes of SNPs were examined in DNA extracted from blood cells from 201 children with ASD and 200 healthy controls. The Children Autism Rating Scale (CARS) was applied to evaluate the severity of the disease and language impairment. The relationship between SNPs and the risk of ASD or the severity of the disease was determined by logistic regression and one-way ANOVA.

Results

The genotype G/G of rs3746599 in the DUSP15 gene was significantly associated with a decreased risk of ASD (odds ratio (OR) = 0.65, 95% confidence interval (CI): 0.42-0.99, P = 0.0449). The T allele of rs7794745 in the CNTNAP2 gene was associated with an increased risk of ASD (OR = 1.34, 95% CI: 1.01-1.77, P = 0.0435). The SNP rs251379 was not associated with ASD. Though none of the SNPs examined were associated with ASD severity, rs7794745 was associated with severity of language impairment.

Conclusions

Our findings suggest that both rs3746599 in the DUSP15 gene and rs7794745 in the CNTNAP2 gene are associated with risk of childhood ASD, and rs7794745 is also related to the severity of language impairment in autistic children from a Chinese Han population.

Dual-Specificity Phosphatase 15 (DUSP15) Modulates Notch Signaling by Enhancing the Stability of Notch Protein

Dual-specificity phosphatases (DUSPs) comprise a unique group of enzymes that dephosphorylate signaling proteins at both phospho-serine/threonine and phospho-tyrosine residues. Since Notch signaling is an essential pathway for neuronal cell fate determination and development that is also upregulated in Alzheimer's disease tissues, we sought to explore whether and how DUSPs may impact Notch processing. Our results show that overexpression of DUSP15 concomitantly and dose-dependently increased the steady-state levels of recombinant Notch (extracellular domain-truncated Notch, NotchΔE) protein and its cleaved product, Notch intracellular domain (NICD). The overall ratio of NotchΔE to NICD was unchanged by overexpression of DUSP15, suggesting that the effect is independent of γ-secretase. Interestingly, overexpression of DUSP15 also dose-dependently increased phosphorylated ERK1/2. Phosphorylated ERK1/2 is known to be positively correlated with Notch protein level, and we found that DUSP15-mediated regulation of Notch was dependent on ERK1/2 activity. Together, our findings reveal the existence of a previously unidentified DUSP15-ERK1/2-Notch signaling axis, which could potentially play a role in neuronal differentiation and neurological disease.

Fibulin 5, a human Wharton's jelly-derived mesenchymal stem cells-secreted paracrine factor, attenuates peripheral nervous system myelination defects through the Integrin-RAC1 signaling axis

In the peripheral nervous system (PNS), proper development of Schwann cells (SCs) contributing to axonal myelination is critical for neuronal function. Impairments of SCs or neuronal axons give rise to several myelin-related disorders, including dysmyelinating and demyelinating diseases. Pathological mechanisms, however, have been understood at the elementary level and targeted therapeutics has remained undeveloped. Here, we identify Fibulin 5 (FBLN5), an extracellular matrix (ECM) protein, as a key paracrine factor of human Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs) to control the development of SCs. We show that co-culture with WJ-MSCs or treatment of recombinant FBLN5 promotes the proliferation of SCs through ERK activation, whereas FBLN5-depleted WJ-MSCs do not. We further reveal that during myelination of SCs, FBLN5 binds to Integrin and modulates actin remodeling, such as the formation of lamellipodia and filopodia, through RAC1 activity. Finally, we show that FBLN5 effectively restores the myelination defects of SCs in the zebrafish model of Charcot-Marie-Tooth (CMT) type 1, a representative demyelinating disease. Overall, our data propose human WJ-MSCs or FBLN5 protein as a potential treatment for myelin-related diseases, including CMT.

Modelling the role of dual specificity phosphatases in herceptin resistant breast cancer cell lines

BACKGROUND

Breast cancer remains the most lethal type of cancer for women. A significant proportion of breast cancer cases are characterised by overexpression of the human epidermal growth factor receptor 2 protein (HER2). These cancers are commonly treated by Herceptin (Trastuzumab), but resistance to drug treatment frequently develops in tumour cells. Dual-specificity phosphatases (DUSPs) are thought to play a role in the mechanism of resistance, since some of them were reported to be overexpressed in tumours resistant to Herceptin.

RESULTS

We used a systems biology approach to investigate how DUSP overexpression could favour cell proliferation and to predict how this mechanism could be reversed by targeted inhibition of selected DUSPs. We measured the expression of 20 DUSP genes in two breast cancer cell lines following long-term (6 months) exposure to Herceptin, after confirming that these cells had become resistant to the drug. We constructed several Boolean models including specific substrates of each DUSP, and showed that our models correctly account for resistance when overexpressed DUSPs were kept activated. We then simulated inhibition of both individual and combinations of DUSPs, and determined conditions under which the resistance could be reversed.

CONCLUSIONS

These results show how a combination of experimental analysis and modelling help to understand cell survival mechanisms in breast cancer tumours, and crucially enable us to generate testable predictions potentially leading to new treatments of resistant tumours.

Molecular Mechanisms Involved in Schwann Cell Plasticity

Schwann cell incredible plasticity is a hallmark of the utmost importance following nerve damage or in demyelinating neuropathies. After injury, Schwann cells undergo dedifferentiation before redifferentiating to promote nerve regeneration and complete functional recovery. This review updates and discusses the molecular mechanisms involved in the negative regulation of myelination as well as in the reprogramming of Schwann cells taking place early following nerve lesion to support repair. Significant advance has been made on signaling pathways and molecular components that regulate SC regenerative properties. These include for instance transcriptional regulators such as c-Jun or Notch, the MAPK and the Nrg1/ErbB2/3 pathways. This comprehensive overview ends with some therapeutical applications targeting factors that control Schwann cell plasticity and highlights the need to carefully modulate and balance this capacity to drive nerve repair.