Molecular pathology of NEU1 gene in sialidosis

Clinical and Structural Characteristics of NEU1 Variants Causing Sialidosis Type 1

OBJECTIVE

Sialidosis type 2 has variants that are both catalytically inactive (severe), while sialidosis type 1 has at least one catalytically active (mild) variant. This study aimed to discuss the structural changes associated with these variants in a newly reported family carrying N-acetyl-α-neuraminidase-1 (NEU1) variants and explore the clinical characteristics of different combinations of variants in sialidosis type 1.

METHODS

First, whole-exome sequencing and detailed clinical examinations were performed on the family. Second, structural analyses, including assessments of energy, flexibility and polar contacts, were conducted for several NEU1 variants, and a sialidase activity assay was performed. Third, previous NEU1 variants were systematically reviewed, and the clinical characteristics of patients in the severe-mild and mild-mild groups with sialidosis type 1 were analyzed.

RESULTS

We report a novel family with sialidosis type 1 and the compound heterozygous variants S182G and V143E. The newly identified V143E variant was predicted to be a mild variant through structural analysis and was confirmed by a sialidase activity assay. Cherry-red spots were more prevalent in the severe-mild group, and ataxia was more common in the mild-mild group. Impaired cognition was found only in the severe-mild group. Moreover, patients with cherry-red spots and abnormal electroencephalographies and visual evoked potentials had a relatively early age of onset, whereas patients with myoclonus had a late onset.

CONCLUSION

Changes in flexibility and local polar contacts may be indicators of NEU1 pathogenicity. Sialidosis type 1 can be divided into two subgroups according to the variant combinations, and patients with these two subtypes have different clinical characteristics.

Juvenile sialidosis: a rare case and review of the literature

Background

Sialidosis is a rare variety of lysosomal storage disease that results in intracellular accumulation of sialic acid containing compounds. The authors report the first case of type II sialidosis, juvenile subtype in a 30-month-old male child from Nepal.

Case presentation

Progressive hearing loss with coarse facies, hepatomegaly, kyphoscoliosis, dysostosis multiplex were the major features in a 30-month-old child born to healthy non-consanguineous parents. With the suspicion of lysosomal storage disease, urinary oligosaccharides were tested and were positive. Whole-exome sequencing revealed a mutation in the neuraminidase gene (NEU1) and established the diagnosis of sialidosis.

Clinical discussion

Sialidosis is a rare autosomal recessive type of lysosomal storage disease resulting due to mutation of the neuraminidase gene leading to intracellular accumulation of sialic acid compounds. Based on the presence of visual symptoms, sialidosis is classified into type I and II varieties. Our case is of type II juvenile sialidosis.

Conclusion

Despite rare, sialidosis is a life-threatening, and disabling disease. Exploring targeted therapy is the utmost to treat this condition.

Proteomic Analysis to Identify Prospective Biomarkers of Treatment Outcome After Microvascular Decompression for Trigeminal Neuralgia: A Preliminary Study

Trigeminal neuralgia (TN) is a severe neuropathic facial pain disorder, often caused by vascular or neuronal compression of the trigeminal nerve. In such cases, microvascular decompression (MVD) surgery can be used to treat TN, but pain relief is not guaranteed. The molecular mechanisms that affect treatment response to MVD are not well understood. In this exploratory study, we performed label-free quantitative proteomic profiling of plasma and cerebrospinal fluid samples from patients undergoing MVD for TN, then compared the proteomic profiles of patients graded as responders (n = 7) versus non-responders (n = 9). We quantified 1,090 proteins in plasma and 1,087 proteins in the cerebrospinal fluid, of which 12 were differentially regulated in the same direction in both sample types. Functional analyses of differentially regulated proteins in protein-protein interaction networks suggested pathways of the immune system, axon guidance, and cellular stress response to be associated with response to MVD. These findings suggest potential biomarkers of response to MVD, as well as possible mechanisms of variable treatment success in TN patients. PERSPECTIVE: This exploratory study evaluates proteomic profiles in plasma and cerebrospinal fluid of patients undergoing microvascular decompression surgery for trigeminal neuralgia. Differential expression of proteins between surgery responders versus non-responders may serve as biomarkers to predict surgical success and provide insight into surgical mechanisms of pain relief in trigeminal neuralgia.

Severe kidney dysfunction in sialidosis mice reveals an essential role for neuraminidase 1 in reabsorption

Sialidosis is an ultra-rare multisystemic lysosomal disease caused by mutations in the neuraminidase 1 (NEU1) gene. The severe type II form of the disease manifests with a prenatal/infantile or juvenile onset, bone abnormalities, severe neuropathology, and visceromegaly. A subset of these patients present with nephrosialidosis, characterized by abrupt onset of fulminant glomerular nephropathy. We studied the pathophysiological mechanism of the disease in 2 NEU1-deficient mouse models, a constitutive Neu1-knockout, Neu1ΔEx3, and a conditional phagocyte-specific knockout, Neu1Cx3cr1ΔEx3. Mice of both strains exhibited terminal urinary retention and severe kidney damage with elevated urinary albumin levels, loss of nephrons, renal fibrosis, presence of storage vacuoles, and dysmorphic mitochondria in the intraglomerular and tubular cells. Glycoprotein sialylation in glomeruli, proximal distal tubules, and distal tubules was drastically increased, including that of an endocytic reabsorption receptor megalin. The pool of megalin bearing O-linked glycans with terminal galactose residues, essential for protein targeting and activity, was reduced to below detection levels. Megalin levels were severely reduced, and the protein was directed to lysosomes instead of the apical membrane. Together, our results demonstrated that desialylation by NEU1 plays a crucial role in processing and cellular trafficking of megalin and that NEU1 deficiency in sialidosis impairs megalin-mediated protein reabsorption.

Sialylation: A Cloak for Tumors to Trick the Immune System in the Microenvironment

The tumor microenvironment (TME), where the tumor cells incite the surrounding normal cells to create an immune suppressive environment, reduces the effectiveness of immune responses during cancer development. Sialylation, a type of glycosylation that occurs on cell surface proteins, lipids, and glycoRNAs, is known to accumulate in tumors and acts as a "cloak" to help tumor cells evade immunological surveillance. In the last few years, the role of sialylation in tumor proliferation and metastasis has become increasingly evident. With the advent of single-cell and spatial sequencing technologies, more research is being conducted to understand the effects of sialylation on immunity regulation. This review provides updated insights into recent research on the function of sialylation in tumor biology and summarizes the latest developments in sialylation-targeted tumor therapeutics, including antibody-mediated and metabolic-based sialylation inhibition, as well as interference with sialic acid-Siglec interaction.

Sialylation of cell surface glycoconjugates modulates cytosolic galectin-mediated responses upon organelle damage : Minireview

Sialylation is an important terminal modification of glycoconjugates that mediate diverse functions in physiology and disease. In this review we focus on how altered cell surface sialylation status is sensed by cytosolic galectins when the integrity of intracellular vesicles or organelles is compromised to expose luminal glycans to the cytosolic milieu, and how this impacts galectin-mediated cellular responses. In addition, we discuss the roles of mammalian sialidases on the cell surface, in the organelle lumen and cytosol, and raise the possibility that intracellular glycan processing may be critical in controlling various galectin-mediated responses when cells encounter stress.

GNE myopathy: History, etiology, and treatment trials

GNE myopathy is an ultrarare muscle disease characterized by slowly progressive muscle weakness. Symptoms typically start in early adulthood, with weakness and atrophy in the tibialis anterior muscles and with slow progression over time, which largely spares the quadriceps muscles. Muscle biopsy shows atrophic fibers and rimmed vacuoles without inflammation. Inherited in an autosomal recessive manner, patients with GNE myopathy carry mutations in the GNE gene which affect the sialic acid synthesis pathway. Here, we look at the history and clinical aspects of GNE myopathy, as well as focus on prior treatment trials and challenges and unmet needs related to this disorder.

Neuraminidases-Key Players in the Inflammatory Response after Pathophysiological Cardiac Stress and Potential New Therapeutic Targets in Cardiac Disease

Glycoproteins and glycolipids on the cell surfaces of vertebrates and higher invertebrates contain α-keto acid sugars called sialic acids, terminally attached to their glycan structures. The actual level of sialylation, regulated through enzymatic removal of the latter ones by NEU enzymes, highly affects protein-protein, cell-matrix and cell-cell interactions. Thus, their regulatory features affect a large number of different cell types, including those of the immune system. Research regarding NEUs within heart and vessels provides new insights of their involvement in the development of cardiovascular pathologies and identifies mechanisms on how inhibiting NEU enzymes can have a beneficial effect on cardiac remodelling and on a number of different cardiac diseases including CMs and atherosclerosis. In this regard, a multitude of clinical studies demonstrated the potential of N-acetylneuraminic acid (Neu5Ac) to serve as a biomarker following cardiac diseases. Anti-influenza drugs i.e., zanamivir and oseltamivir are viral NEU inhibitors, thus, they block the enzymatic activity of NEUs. When considering the improvement in cardiac function in several different cardiac disease animal models, which results from NEU reduction, the inhibition of NEU enzymes provides a new potential therapeutic treatment strategy to treat cardiac inflammatory pathologies, and thus, administrate cardioprotection.

Alteration of the neuronal and glial cell profiles in Neu1-deficient zebrafish

Neu1 is a glycosidase that releases sialic acids from the non-reducing ends of glycoconjugates, and its enzymatic properties are conserved among vertebrates. Recently, Neu1-KO zebrafish were generated using genome editing technology, and the KO fish showed abnormal emotional behavior, such as low schooling, low aggressiveness, and excess exploratory behavior, accompanied by the downregulation of anxiety-related genes. To examine the alteration of neuronal and glial cells in Neu1-KO zebrafish, we analyzed the molecular profiles in the zebrafish brain, focusing on the midbrain and telencephalon. Using immunohistochemistry, we found that signals of Maackia amurensis (MAM) lectin that recognizes Sia α2-3 linked glycoconjugates were highly increased in Neu1-KO zebrafish brains, accompanied by an increase in Lamp1a. Neu1-KO zebrafish suppressed the gene expression of AMPA-type glutamate receptors such as gria1a, gria2a, and gria3b, and vesicular glutamate transporter 1. Additionally, Neu1-KO zebrafish induced the hyperactivation of astrocytes accompanied by an increase in Gfap and phosphorylated ERK levels, while the mRNA levels of astrocyte glutamate transporters (eaat1a, eaat1c, and eaat2) were downregulated. The mRNA levels of sypb and ho1b, which are markers of synaptic plasticity, were also suppressed by Neu1 deficiency. Abnormal activity of microglia was also revealed by IHC, and the expressions of iNOS and IL-1β, an inflammatory cytokine, were increased in Neu1-KO zebrafish. Furthermore, drastic neuronal degeneration was detected in Neu1-KO zebrafish using Fluoro-Jade B staining. Collectively, the neuronal and glial abnormalities in Neu1-KO zebrafish may be caused by changes in the excitatory neurotransmitter glutamate and involved in the emotional abnormalities.

Hematopoietic cell transplantation for sialidosis type I

We report the clinical and laboratory follow-up data of an adolescent female with Type I Sialidosis who underwent bone marrow transplant (BMT). After BMT, plasma and urine biomarkers responded concurrently with engraftment. Neuropsychiatry data showed preservation in some domains, but she did have overall decline in motor performance. Sialidosis is a very rare lysosomal condition, and we believe this to be the first report of a case of Type I Sialidosis undergoing BMT.

Neuraminidase 1 Exacerbating Aortic Dissection by Governing a Pro-Inflammatory Program in Macrophages

Inflammation plays an important role in aortic dissection (AD). Macrophages are critically involved in the inflammation after aortic injury. Neuraminidases (NEUs) are a family of enzymes that catalyze the cleavage of terminal sialic acids from glycoproteins or glycolipids, which is emerging as a regulator of macrophage-associated immune responses. However, the role of neuraminidase 1 (NEU1) in pathological vascular remodeling of AD remains largely unknown. This study sought to characterize the role and identify the potential mechanism of NEU1 in pathological aortic degeneration. After β-aminopropionitrile monofumarate (BAPN) administration, NEU1 elevated significantly in the lesion zone of the aorta. Global or macrophage-specific NEU1 knockout (NEU1 CKO) mice had no baseline aortic defects but manifested improved aorta function, and decreased mortality due to aortic rupture. Improved outcomes in NEU1 CKO mice subjected to BAPN treatment were associated with the ameliorated vascular inflammation, lowered apoptosis, decreased reactive oxygen species production, mitigated extracellular matrix degradation, and improved M2 macrophage polarization. Furthermore, macrophages sorted from the aorta of NEU1 CKO mice displayed a significant increase of M2 macrophage markers and a marked decrease of M1 macrophage markers compared with the controls. To summarize, the present study demonstrated that macrophage-derived NEU1 is critical for vascular homeostasis. NEU1 exacerbates BAPN-induced pathological vascular remodeling. NEU1 may therefore represent a potential therapeutic target for the treatment of AD.

Modeling Sialidosis with Neural Precursor Cells Derived from Patient-Derived Induced Pluripotent Stem Cells

Sialidosis, caused by a genetic deficiency of the lysosomal sialidase gene (NEU1), is a systemic disease involving various tissues and organs, including the nervous system. Understanding the neurological dysfunction and pathology associated with sialidosis remains a challenge, partially due to the lack of a human model system. In this study, we have generated two types of induced pluripotent stem cells (iPSCs) with sialidosis-specific NEU1^G227R and NEU1^V275A/R347Q mutations (sialidosis-iPSCs), and further differentiated them into neural precursor cells (iNPCs). Characterization of NEU1^G227R- and NEU1^V275A/R347Q- mutated iNPCs derived from sialidosis-iPSCs (sialidosis-iNPCs) validated that sialidosis-iNPCs faithfully recapitulate key disease-specific phenotypes, including reduced NEU1 activity and impaired lysosomal and autophagic function. In particular, these cells showed defective differentiation into oligodendrocytes and astrocytes, while their neuronal differentiation was not notably affected. Importantly, we found that the phenotypic defects of sialidosis-iNPCs, such as impaired differentiation capacity, could be effectively rescued by the induction of autophagy with rapamycin. Our results demonstrate the first use of a sialidosis-iNPC model with NEU1^G227R- and NEU1^V275A/R347Q- mutation(s) to study the neurological defects of sialidosis, particularly those related to a defective autophagy-lysosome pathway, and may help accelerate the development of new drugs and therapeutics to combat sialidosis and other LSDs.

Neuraminidase 1 and its Inhibitors from Chinese Herbal Medicines: An Emerging Role for Cardiovascular Diseases

Neuraminidase, also known as sialidase, is ubiquitous in animals and microorganisms. It is predominantly distributed in the cell membrane, cytoplasmic vesicles, and lysosomes. Neuraminidase generally recognizes the sialic acid glycosidic bonds at the ends of glycoproteins or glycolipids and enzymatically removes sialic acid. There are four types of neuraminidases, named as Neu1, Neu2, Neu3, and Neu4. Among them, Neu1 is the most abundant in mammals. Recent studies have revealed the involvement of Neu1 in several diseases, including cardiovascular diseases, diabetes, cancers, and neurological disorders. In this review, we center the attention to the role of Neu1 in cardiovascular diseases, including atherosclerosis, ischemic myocardial injury, cerebrovascular disease, congenital heart disease, and pulmonary embolism. We also summarize inhibitors from Chinese herbal medicines (CHMs) in inhibiting virus neuraminidase or human Neu1. Many Chinese herbs and Chinese herb preparations, such as Lonicerae Japonicae Flos, Scutellariae Radix, Yupingfeng San, and Huanglian Jiedu Decoction, have neuraminidase inhibitory activity. We hope to highlight the emerging role of Neu1 in humans and potentially titillate interest for further studies in this area.

Sialometabolism in Brain Health and Alzheimer's Disease

Sialic acids refer to a unique family of acidic sugars with a 9-carbon backbone that are mostly found as terminal residues in glycan structures of glycoconjugates including both glycoproteins and glycolipids. The highest levels of sialic acids are expressed in the brain where they regulate neuronal sprouting and plasticity, axon myelination and myelin stability, as well as remodeling of mature neuronal connections. Moreover, sialic acids are the sole ligands for microglial Siglecs (sialic acid-binding immunoglobulin-type lectins), and sialic acid-Siglec interactions have been indicated to play a critical role in the regulation of microglial homeostasis in a healthy brain. The recent discovery of CD33, a microglial Siglec, as a novel genetic risk factor for late-onset Alzheimer's disease (AD), highlights the potential role of sialic acids in the development of microglial dysfunction and neuroinflammation in AD. Apart from microglia, sialic acids have been found to be involved in several other major changes associated with AD. Elevated levels of serum sialic acids have been reported in AD patients. Alterations in ganglioside (major sialic acid carrier) metabolism have been demonstrated as an aggravating factor in the formation of amyloid pathology in AD. Polysialic acids are linear homopolymers of sialic acids and have been implicated to be an important regulator of neurogenesis that contributes to neuronal repair and recovery from neurodegeneration such as in AD. In summary, this article reviews current understanding of neural functions of sialic acids and alterations of sialometabolism in aging and AD brains. Furthermore, we discuss the possibility of looking at sialic acids as a promising novel therapeutic target for AD intervention.

Using Bibliometric Analysis and Machine Learning to Identify Compounds Binding to Sialidase-1

Rare diseases impact hundreds of millions of individuals worldwide. However, few therapies exist to treat the rare disease population because financial resources are limited, the number of patients affected is low, bioactivity data is often nonexistent, and very few animal models exist to support preclinical development efforts. Sialidosis is an ultrarare lysosomal storage disorder in which mutations in the NEU1 gene result in the deficiency of the lysosomal enzyme sialidase-1. This enzyme catalyzes the removal of sialic acid moieties from glycoproteins and glycolipids. Therefore, the defective or deficient protein leads to the buildup of sialylated glycoproteins as well as several characteristic symptoms of sialidosis including visual impairment, ataxia, hepatomegaly, dysostosis multiplex, and developmental delay. In this study, we used a bibliometric tool to generate links between lysosomal storage disease (LSD) targets and existing bioactivity data that could be curated in order to build machine learning models and screen compounds in silico. We focused on sialidase as an example, and we used the data curated from the literature to build a Bayesian model which was then used to score compound libraries and rank these molecules for in vitro testing. Two compounds were identified from in vitro testing using microscale thermophoresis, namely sulfameter (K d 2.15 ± 1.02 μM) and mexenone (K d 8.88 ± 4.02 μM), which validated our approach to identifying new molecules binding to this protein, which could represent possible drug candidates that can be evaluated further as potential chaperones for this ultrarare lysosomal disease for which there is currently no treatment. Combining bibliometric and machine learning approaches has the ability to assist in curating small molecule data and model building, respectively, for rare disease drug discovery. This approach also has the capability to identify new compounds that are potential drug candidates.

Compound heterozygous mutations in the neuraminidase 1 gene in type 1 sialidosis: A case report and review of literature

BACKGROUND

Type 1 sialidosis, also known as cherry-red spot-myoclonus syndrome, is a rare autosomal recessive lysosomal storage disorder presenting in the second decade of life. The most common symptoms are myoclonus, ataxia and seizure. It is rarely encountered in the Chinese mainland.

CASE SUMMARY

A 22-year-old male presented with complaints of progressive myoclonus, ataxia and slurred speech, without visual symptoms; the presenting symptoms began at the age of 15-year-old. Whole exome sequencing revealed two pathogenic heterozygous missense variants [c.239C>T (p.P80L) and c.544A>G (p.S182G) in the neuraminidase 1 (NEU1) gene], both of which have been identified previously in Asian patients with type 1 sialidosis. All three patients identified in Mainland China come from three unrelated families, but all three show the NEU1 mutations p.S182G and p.P80L pathogenic variants. Increasing sialidase activity through chaperones is a promising therapeutic target in sialidosis.

CONCLUSION

Through retrospective analysis and summarizing the clinical and genetic characteristics of type 1 sialidosis, we hope to raise awareness of lysosomal storage disorders among clinicians and minimize the delay in diagnosis.

Therapeutic Potential of Neu1 in Alzheimer's Disease Via the Immune System

Alzheimer's Disease (AD) is pathologically characterized by the accumulation of soluble oligomers causing extracellular beta-amyloid deposits in form of neuritic plaques and tau-containing intraneuronal neurofibrillary tangles in brain. One proposed mechanism explaining the formation of these proteins is impaired phagocytosis by microglia/macrophages resulting in defective clearance of soluble oligomers of beta-amyloid stimulating aggregation of amyloid plaques subsequently causing AD. However, research indicates that activating macrophages in M2 state may reduce toxic oligomers. NEU1 mutation is associated with a rare disease, sialidosis. NEU1 deficiency may also cause AD-like amyloidogenic process. Amyloid plaques have successfully been reduced using NEU1.Thus, NEU1 is suggested to have therapeutic potential for AD, with lysosomal exocytosis being suggested as underlying mechanism. Studies however demonstrate that NEU1 may activate macrophages in M2 state, which as noted earlier, is crucial to reducing toxic oligomers. In this review, authors discuss the potential therapeutic role of NEU1 in AD via immune system.

Sialylation acts as a checkpoint for innate immune responses in the central nervous system

Sialic acids are monosaccharides that normally terminate the glycan chains of cell surface glyco-proteins and -lipids in mammals, and are highly enriched in the central nervous tissue. Sialic acids are conjugated to proteins and lipids (termed "sialylation") by specific sialyltransferases, and are removed ("desialylation") by neuraminidases. Cell surface sialic acids are sensed by complement factor H (FH) to inhibit complement activation or by sialic acid-binding immunoglobulin-like lectin (SIGLEC) receptors to inhibit microglial activation, phagocytosis, and oxidative burst. In contrast, desialylation of cells enables binding of the opsonins C1, calreticulin, galectin-3, and collectins, stimulating phagocytosis of such cells. Hypersialylation is used by bacteria and cancers as camouflage to escape immune recognition, while polysialylation of neurons protects synapses and neurogenesis. Insufficient lysosomal cleavage of sialylated molecules can lead to lysosomal accumulation of lipids and aggregated proteins, which if excessive may be expelled into the extracellular space. On the other hand, desialylation of immune receptors can activate them or trigger removal of proteins. Loss of inhibitory SIGLECs or FH triggers reduced clearance of aggregates, oxidative brain damage and complement-mediated retinal damage. Thus, cell surface sialylation recognized by FH, SIGLEC, and other immune-related receptors acts as a major checkpoint inhibitor of innate immune responses in the central nervous system, while excessive cleavage of sialic acid residues and consequently removing this checkpoint inhibitor may trigger lipid accumulation, protein aggregation, inflammation, and neurodegeneration.

p53-R273H promotes cancer cell migration via upregulation of neuraminidase-1

Accumulating evidence indicates that hotspot p53 mutants have gain-of-function in promoting cell migration and tumor metastasis. However, the molecular mechanisms are not completely understood. Here, we show that a hotspot mutation, p53-R273H, promotes non-small cell lung cancer (NSCLC) cell migration and upregulates the mRNA and protein expression of neuraminidase-1 (NEU1), a sialidase involved in cell proliferation, cell migration and tumorigenesis. Silencing of NEU1 leads to upregulation of integrin β4 which significantly inhibits NSCLC cell migration induced by p53-R273H. Mechanistically, p53-R273H promotes NEU1 transcription via activation of AKT signaling. Importantly, NEU1 expression is upregulated in human NSCLC samples harboring mutant p53 and is associated with poor clinical outcome. Overall, this study highlights an important role of NEU1 in p53-R273H-induced NSCLC cell migration and provides a potential target for NSCLC diagnosis and treatment.

Bergmeister's papilla in a young patient with type 1 sialidosis: case report

Background

Sialidosis is a rare genetic lysosomal storage disorder caused by a deficit of neuraminidase enzyme activity. Patients with sialidosis present various neurological disorders such as: myoclonic epilepsy and hypotonia, often associated with visual impairment. A typical aspect of sialidosis is the finding of a macular cherry-red spot on ocular fundus examination. In this paper we describe a unilateral case of Bergmeister’s papilla (BP) in a young female patient suffering from type 1 sialidosis.

Case presentation

A 28-year-old young woman suffering from type 1 sialidosis, confirmed by previously described compound heterozigosity Leu91Arg and Gly328Ser on N-acetyl-alpha-neuraminidase − 1 (NEU1) gene, underwent an opthalmological examination at the Eye Clinic of the University of Campania L. Vanvitelli, for bilateral visual deterioration. The patient was suffering from myoclonic epilepsy with hypotonia and severe motor disability. Fundoscopic examination showed a typical macular cherry-red spot with retinal pigment epithelium dystrophy in the middle periphery, in both eyes. Furthermore, in the left eye (OS), a vitreous thickening was observed in the nasal sector of the optic disc, remnant of fetal vasculature on the optic disc (Bergmeister’s papilla). Optical coherence tomography (OCT) showed, in both eyes, a thickening of the ganglion cell layer (GCL) with a hyperreflective opacity as a cap on the left optic disc.

Conclusions

In our paper we have described, for the first time in literature, a case of BP in a patient with type 1 sialidosis. The detection of BP with thickening of the peripapillary vitreous by SD-OCT is useful in monitoring any vitreo-retinal change that could cause future visual deterioration.

Lipophagy and Lipolysis Status in Lipid Storage and Lipid Metabolism Diseases

This review discusses how lipophagy and cytosolic lipolysis degrade cellular lipids, as well as how these pathway ys communicate, how they affect lipid metabolism and energy homeostasis in cells and how their dysfunction affects the pathogenesis of lipid storage and lipid metabolism diseases. Answers to these questions will likely uncover novel strategies for the treatment of aforementioned human diseases, but, above all, will avoid destructive effects of high concentrations of lipids-referred to as lipotoxicity-resulting in cellular dysfunction and cell death.

Diagnosis and Management of Type 1 Sialidosis: Clinical Insights from Long-Term Care of Four Unrelated Patients

Background: Sialidosis is a rare autosomal recessive disease caused by NEU1 mutations, leading to neuraminidase deficiency and accumulation of sialic acid-containing oligosaccharides and glycopeptides into the tissues. Sialidosis is divided into two clinical entities, depending on residual enzyme activity, and can be distinguished according to age of onset, clinical features, and progression. Type 1 sialidosis is the milder, late-onset form, also known as non-dysmorphic sialidosis. It is commonly characterized by progressive myoclonus, ataxia, and a macular cherry-red spot. As a rare condition, the diagnosis is often only made after few years from onset, and the clinical management might prove difficult. Furthermore, the information in the literature on the long-term course is scarce. Case presentations: We describe a comprehensive clinical, neuroradiological, ophthalmological, and electrophysiological history of four unrelated patients affected by type 1 sialidosis. The long-term care and novel clinical and neuroradiological insights are discussed. Discussion and conclusions: We report the longest follow-up (up to 30 years) ever described in patients with type 1 sialidosis. During the course, we observed a high degree of motor and speech disability with preserved cognitive functions. Among the newest antiseizure medication, perampanel (PER) was proven to be effective in controlling myoclonus and tonic–clonic seizures, confirming it is a valid therapeutic option for these patients. Brain magnetic resonance imaging (MRI) disclosed new findings, including bilateral gliosis of cerebellar folia and of the occipital white matter. In addition, a newly reported variant (c.914G > A) is described.

Sialylation and Galectin-3 in Microglia-Mediated Neuroinflammation and Neurodegeneration

Microglia are brain macrophages that mediate neuroinflammation and contribute to and protect against neurodegeneration. The terminal sugar residue of all glycoproteins and glycolipids on the surface of mammalian cells is normally sialic acid, and addition of this negatively charged residue is known as “sialylation,” whereas removal by sialidases is known as “desialylation.” High sialylation of the neuronal cell surface inhibits microglial phagocytosis of such neurons, via: (i) activating sialic acid receptors (Siglecs) on microglia that inhibit phagocytosis and (ii) inhibiting binding of opsonins C1q, C3, and galectin-3. Microglial sialylation inhibits inflammatory activation of microglia via: (i) activating Siglec receptors CD22 and CD33 on microglia that inhibit phagocytosis and (ii) inhibiting Toll-like receptor 4 (TLR4), complement receptor 3 (CR3), and other microglial receptors. When activated, microglia release a sialidase activity that desialylates both microglia and neurons, activating the microglia and rendering the neurons susceptible to phagocytosis. Activated microglia also release galectin-3 (Gal-3), which: (i) further activates microglia via binding to TLR4 and TREM2, (ii) binds to desialylated neurons opsonizing them for phagocytosis via Mer tyrosine kinase, and (iii) promotes Aβ aggregation and toxicity in vivo. Gal-3 and desialylation may increase in a variety of brain pathologies. Thus, Gal-3 and sialidases are potential treatment targets to prevent neuroinflammation and neurodegeneration.

Clinical and genetic characteristics of type I sialidosis patients in mainland China

Objective

Type I sialidosis (ST‐1) is a rare autosomal recessive inherited disorder. To date, there has been no study on ST‐1 patients in mainland China.

Methods

We reported in detail the cases of five Chinese ST‐1 patients from two centers, and summarized all worldwide cases. Then, we compared the differences between Chinese and foreign patients.

Results

A total of 77 genetically confirmed ST‐1 patients were identified: 12 from mainland China, 23 from Taiwan, 10 from other Asian regions, and 32 from European and American regions. The mean age of onset was 16.0 ± 6.7 years; the most common symptoms were myoclonus seizures (96.0%), followed by ataxia (94.3%), and blurred vision (67.2%). Compared to other groups, the onset age of patients from mainland China was much younger (10.8 ± 2.7 years). The incidence of visual impairment was lower in patients from other Asian regions than in patients from mainland China and Taiwan (28.6% vs. 81.8%–100%). Cherry‐red spots were less frequent in the Taiwanese patients than in patients from other regions (27.3% vs. 55.2%–90.0%). Furthermore, 48 different mutation types were identified. Chinese mainland and Taiwanese patients were more likely to carry the c.544A > G mutation (75% and 100%, respectively) than the patients from other regions (only 0%–10.0%). Approximately 50% of Chinese mainland patients carried the c.239C > T mutation, a much higher proportion than that found in the other populations. In addition, although the brain MRI of most patients was normal, ¹⁸F‐FDG‐PET analysis could reveal cerebellar and occipital lobe hypometabolism.

Interpretation

ST‐1 patients in different regions are likely to have different mutation types; environmental factors may influence clinical manifestations. Larger studies enrolling more patients are required.

Drug Treatment of Progressive Myoclonic Epilepsy

The progressive myoclonic epilepsies (PMEs) represent a rare but devastating group of syndromes characterized by epileptic myoclonus, typically action-induced seizures, neurological regression, medically refractory epilepsy, and a variety of other signs and symptoms depending on the specific syndrome. Most of the PMEs begin in children who are developing as expected, with the onset of the disorder heralded by myoclonic and other seizure types. The conditions are considerably heterogenous, but medical intractability to epilepsy, particularly myoclonic seizures, is a core feature. With the increasing use of molecular genetic techniques, mutations and their abnormal protein products are being delineated, providing a basis for disease-based therapy. However, genetic and enzyme replacement or substrate removal are in the nascent stage, and the primary therapy is through antiepileptic drugs. Epilepsy in children with progressive myoclonic seizures is notoriously difficult to treat. The disorder is rare, so few double-blinded, placebo-controlled trials have been conducted in PME, and drugs are chosen based on small open-label trials or extrapolation of data from drug trials of other syndromes with myoclonic seizures. This review discusses the major PME syndromes and their neurogenetic basis, pathophysiological underpinning, electroencephalographic features, and currently available treatments.

Type I sialidosis, a normosomatic lysosomal disease, in the differential diagnosis of late-onset ataxia and myoclonus: An overview

Lysosomal storage diseases (LSDs) are rare to extremely rare monogenic disorders. Their incidence, however, has probably been underestimated owing to their complex clinical manifestations. Sialidosis is a prototypical LSD inherited as an autosomal recessive trait and caused by mutations in the NEU1 gene that result in a deficiency of alpha-N-acetyl neuraminidase 1 (NEU1). Two basic forms of this disease, type I and type II, are known. The dysmorphic type II form features LSD symptoms including congenital hydrops, dysmorphogenetic traits, hepato-splenomegaly and severe intellectual disability. The diagnosis is more challenging in the normosomatic type I forms, whose clinical findings at onset include ocular defects, ataxia and generalized myoclonus. Here we report the clinical, biochemical and molecular analysis of five patients with sialidosis type I. Two patients presented novel NEU1 mutations. One of these patients was compound heterozygous for two novel NEU1 missense mutations: c.530A>T (p.Asp177Val) and c.1010A>G (p.His337Arg), whereas a second patient was compound heterozygous for a known mutation and a novel c.839G>A (p.Arg280Gln) mutation. We discuss the impact of these new mutations on the structural properties of NEU1. We also review available clinical reports of patients with sialidosis type I, with the aim of identifying the most frequent initial clinical manifestations and achieving more focused diagnoses.

Diversity of sialidases found in the human body - A review

Sialidases are enzymes essential for numerous organisms including humans. Hydrolytic sialidases (EC 3.2.1.18), trans-sialidases and anhydrosialidases (intramolecular trans-sialidases, EC 4.2.2.15) are glycoside hydrolase enzymes that cleave the glycosidic linkage and release sialic acid residues from sialyl substrates. The paper summarizes diverse sialidases present in the human body and their potential impact on development of antiviral compounds - inhibitors of viral neuraminidases. It includes a brief overview of catalytic mechanisms of action of sialidases and describes the origin of sialidases in the human body. This is followed by description of the structure and function of sialidase families with a special focus on the GH33 and GH34 families. Various effects of sialidases on human body are also briefly described. Modulation of sialidase activity may be considered a useful tool for effective treatment of various diseases. In some cases, it is desired to completely suppress the activity of sialidases by suitable inhibitors. Specific sialidase inhibitors are useful for the treatment of influenza, epilepsy, Alzheimer's disease, diabetes, different types of cancer, or heart defects. Challenges and future directions are shortly depicted in the final part of the paper.

Glycosphingolipids and lysosomal storage disorders as illustrated by gaucher disease

Glycosphingolipids are important building blocks of the outer leaflet of the cell membrane. They are continuously recycled, involving fragmentation inside lysosomes by glycosidases. Inherited defects in degradation cause lysosomal glycosphingolipid storage disorders. The relatively common glycosphingolipidosis Gaucher disease is highlighted here to discuss new insights in the molecular basis and pathophysiology of glycosphingolipidoses reached by fundamental research increasingly using chemical biology tools. We discuss improvements in the detection of glycosphingolipid metabolites by mass spectrometry and review new developments in laboratory diagnosis and disease monitoring as well as therapeutic interventions.

Infantile sialidosis: natural history in a preterm infant with two new pathogenic mutations and new ocular findings

Sialidosis is a rare lysosomal storage disease caused by an α-N-acetyl neuraminidase-1 deficiency due to mutations of the NEU1 gene (6p21). Disease severity varies among patients and is linked to the level of residual neuraminidase activity in vivo. At least 40 disease-causing mutations in the NEU1 gene have been reported. Sialidosis occurs in two main clinical variants: type I, the milder form of the disease, and type II, which is subdivided into congenital, infantile, and juvenile forms. We report the clinical, biochemical, and molecular characterization of a patient with infantile sialidosis type II. The abnormal urinary oligosaccharide profile is described for the first time. The genetic characterization of the patient showed two previously unreported missense mutations in the NEU1 gene: p.R78C (c.232C>T) and p.R290Q (c.869G>A).

Exploration of the Sialic Acid World

Sialic acids are cytoprotectors, mainly localized on the surface of cell membranes with multiple and outstanding cell biological functions. The history of their structural analysis, occurrence, and functions is fascinating and described in this review. Reports from different researchers on apparently similar substances from a variety of biological materials led to the identification of a 9-carbon monosaccharide, which in 1957 was designated "sialic acid." The most frequently occurring member of the sialic acid family is N-acetylneuraminic acid, followed by N-glycolylneuraminic acid and O-acetylated derivatives, and up to now over about 80 neuraminic acid derivatives have been described. They appeared first in the animal kingdom, ranging from echinoderms up to higher animals, in many microorganisms, and are also expressed in insects, but are absent in higher plants. Sialic acids are masks and ligands and play as such dual roles in biology. Their involvement in immunology and tumor biology, as well as in hereditary diseases, cannot be underestimated. N-Glycolylneuraminic acid is very special, as this sugar cannot be expressed by humans, but is a xenoantigen with pathogenetic potential. Sialidases (neuraminidases), which liberate sialic acids from cellular compounds, had been known from very early on from studies with influenza viruses. Sialyltransferases, which are responsible for the sialylation of glycans and elongation of polysialic acids, are studied because of their significance in development and, for instance, in cancer. As more information about the functions in health and disease is acquired, the use of sialic acids in the treatment of diseases is also envisaged.

Presence of aberrant epididymal tubules revealing undifferentiated epithelial cells and absence of spermatozoa in a combined neuraminidase-3 and -4 deficient adult mouse model

Mammalian neuraminidases are responsible for the removal of sialic acids from glycoproteins and glycolipids and function in a variety of biological phenomena such as lysosomal catabolism and control of cell differentiation and growth. Disruption of Neu3 and Neu4 genes has led to the generation of a mouse model revealing severe neurological disorders. In this study a morphological analysis was performed on the epididymis of 3 month-old neu3^-/-neu4^-/- mice as compared with wild type animals. In neu3^-/-neu4^-/- mice the majority of tubules of the main epididymal duct were large and lined by differentiated epithelial cells, but revealing lysosomal abnormalities in principal and basally located cells. Of particular note was the presence of aberrant epididymal tubules (ATs) juxtaposed next to the main tubules. ATs were small and of different shapes. Layers of myoid cells encased ATs, which they shared with those of the main tubules, but no interstitial space existed between the two. While some ATs were a dense mass of cells, others revealed a distinct lumen devoid of spermatozoa. The latter revealed an undifferentiated epithelium consisting of cuboidal cells and basal cells, with junctional complexes evident at the luminal front. The absence of spermatozoa from the lumen of the ATs suggests that they were not in contact with the main duct, as also implied by the undifferentiated appearance of the epithelium suggesting lack of lumicrine factors. Despite the presence of ATs, the main duct contained ample spermatozoa, as the neu3^-/-neu4^-/- mice were fertile. Taken together the data suggest that absence of Neu3 and Neu4 leads to defects in cell adhesion and differentiation of epithelial cells resulting in aberrant tubular offshoots that fail to remain connected with the main duct. Hence Neu3 and Neu 4 play an essential role in the guidance of epithelial cells during early embryonic formation.

Type 1 sialidosis presenting with ataxia, seizures and myoclonus with no visual involvement

Sialidosis is an autosomal recessive lysosomal storage disease caused by pathogenic variants in NEU1 which encodes lysosomal sialidase (neuraminidase 1). Lysosomal neuraminidase catalyzes the removal of terminal sialic acid molecules from glycolipids, glycoproteins and oligosaccharides. Sialidosis is classified into two types, based on phenotype and age of onset. Patients with the milder type 1 typically present late, usually in the second or third decade, with myoclonus, ataxia and visual defects. Type 2 is more severe and presents earlier with coarse facial features, developmental delay, hepatosplenomegaly and dysostosis multiplex. Presentation and severity of the disease are related to whether lysosomal sialidase is inactive or there is some residual activity. Diagnosis is suspected based on clinical features and increased urinary bound sialic acid excretion and confirmed by genetic testing showing pathogenic variants in NEU1. We report a patient with type 1 sialidosis who presented mainly with ataxia and both generalized and myoclonic seizures but no visual involvement. Whole exome sequencing of the proband detected compound heterozygous likely pathogenic variants (S182G and G227R) in NEU1.

Selective Inhibitors of Human Neuraminidase 3

Human neuraminidases (NEU) are associated with human diseases including cancer, atherosclerosis, and diabetes. To obtain small molecule inhibitors as research tools for the study of their biological functions, we designed a library of 2-deoxy-2,3-didehydro- N-acetylneuraminic acid (DANA) analogues with modifications at C4 and C9 positions. This library allowed us to discover selective inhibitors targeting the human NEU3 isoenzyme. Our most selective inhibitor for NEU3 has a K_i of 320 ± 40 nM and a 15-fold selectivity over other human neuraminidase isoenzymes. This inhibitor blocks glycolipid processing by NEU3 in vitro. To improve their pharmacokinetic properties, various esters of the best inhibitors were synthesized and evaluated. Finally, we confirmed that our best compounds exhibited selective inhibition of NEU orthologues from murine brain.

Cortical damage in the posterior visual pathway in patients with sialidosis type 1

In order to identify the cortical changes in patients with Sialidosis type 1, diffusion tensor imaging and resting state fMRI were acquired from 11 patients and 11 sex/age matched normal controls after clinical evaluations. The neuroimages from each participant were normalized and parcellated according to the Automatic Anatomical Labeling. Both the mean diffusivity and the corresponding functional connectivity were calculated from each cortical region. The white matter tract integrity was examined. The difference between patients and controls was examined using Student's t-test and between patients with either homozygous or heterozygous mutations by Mann-Whitney U test, both at a threshold of 0.05. Increased mean diffusivity throughout the brain can be noticed in the patients, together with a compromised white matter tracts integrity. The most severely affected cortical regions are in the occipital lobe. Decreased functional connectivity was from the temporal and occipital lobes to the hippocampus and parahippocampus. In contrast, connectivity from thalamus was enhanced. Diffused cortical atrophy with posterior focal lesions was noticed. We concluded that MRI observed functional changes in the posterior cortical pathways in the patients with Sialidosis. The observation might be related to the cortical blindness due to an altered neural network and a compromised visual pathway in the patients.

Abnormal Sphingolipid World in Inflammation Specific for Lysosomal Storage Diseases and Skin Disorders

Research in recent years has shown that sphingolipids are essential signalling molecules for the proper biological and structural functioning of cells. Long-term studies on the metabolism of sphingolipids have provided evidence for their role in the pathogenesis of a number of diseases. As many inflammatory diseases, such as lysosomal storage disorders and some dermatologic diseases, including psoriasis, atopic dermatitis and ichthyoses, are associated with the altered composition and metabolism of sphingolipids, more studies precisely determining the responsibilities of these compounds for disease states are required to develop novel pharmacological treatment opportunities. It is worth emphasizing that knowledge from the study of inflammatory metabolic diseases and especially the possibility of their treatment may lead to insight into related metabolic pathways, including those involved in the formation of the epidermal barrier and providing new approaches towards workable therapies.

Biochemical, Cellular, Physiological, and Pathological Consequences of Human Loss of N-Glycolylneuraminic Acid

About 2-3 million years ago, Alu-mediated deletion of a critical exon in the CMAH gene became fixed in the hominin lineage ancestral to humans, possibly through a stepwise process of selection by pathogen targeting of the CMAH product (the sialic acid Neu5Gc), followed by reproductive isolation through female anti-Neu5Gc antibodies. Loss of CMAH has occurred independently in some other lineages, but is functionally intact in Old World primates, including our closest relatives, the chimpanzee. Although the biophysical and biochemical ramifications of losing tens of millions of Neu5Gc hydroxy groups at most cell surfaces remains poorly understood, we do know that there are multiscale effects functionally relevant to both sides of the host-pathogen interface. Hominin CMAH loss might also contribute to understanding human evolution, at the time when our ancestors were starting to use stone tools, increasing their consumption of meat, and possibly hunting. Comparisons with chimpanzees within ethical and practical limitations have revealed some consequences of human CMAH loss, but more has been learned by using a mouse model with a human-like Cmah inactivation. For example, such mice can develop antibodies against Neu5Gc that could affect inflammatory processes like cancer progression in the face of Neu5Gc metabolic incorporation from red meats, display a hyper-reactive immune system, a human-like tendency for delayed wound healing, late-onset hearing loss, insulin resistance, susceptibility to muscular dystrophy pathologies, and increased sensitivity to multiple human-adapted pathogens involving sialic acids. Further studies in such mice could provide a model for other human-specific processes and pathologies involving sialic acid biology that have yet to be explored.

Sialidosis Type 1 with a Novel Mutation in the Neuraminidase-1 (NEU1) Gene

A patient with Sialidosis type 1 with a novel variation in neuraminidase-1 (NEU1) is described. The patient developed ataxia and myoclonus at 9 y of age. He was born to a second degree consanguineous marriage couple. On examination child had cerebellar signs and bilateral macular cherry-red spots. MRI of the brain and electroencephalogram were normal. The enzyme analysis revealed deficiency of neuraminidase. Genetic analysis identified novel homozygous missense mutation c.742G > T (p.G248C) in exon 4 of NEU1 gene. At 13 y of age, the ataxia and had myoclonus progressed.

Optical coherence tomography features in a case of Type I sialidosis

A 15-year-old boy presented with progressive myoclonic epilepsy and unbalance gaits for 4 years. Slit lamp examination showed a punctate cataract and funduscopic examination revealed bilateral macular cherry-red spots. Macular scan of spectral domain optical coherence tomography (SD-OCT) showed hyperreflectivity of the inner retinal layer and apparent hyperreflectivity of the photoreceptor layers in the foveal region. The clinical presentations were consistent with a Type I sialidosis which led to genetic analysis and revealed NEU1 mutation in this patient. He was under regular follow-up by ophthalmologist and neurologist. Sialidosis is a rare lysosomal storage disease resulting from a deficiency of alpha-N-acetyl neuraminidase caused by a mutation in the NEU1 gene. This results in abnormal intracellular accumulation of sialyloligosaccharides in brain neurons and ganglion cells of the retina. SD-OCT is a useful tool in detecting macular cherry-red spot and has a role in evaluating the extent of ganglion cell damage. It can aid in the differential diagnosis and long-term follow-up of the neurological metabolic disorders.

Carbohydrate-Processing Enzymes of the Lysosome: Diseases Caused by Misfolded Mutants and Sugar Mimetics as Correcting Pharmacological Chaperones

Lysosomal storage diseases are hereditary disorders caused by mutations on genes encoding for one of the more than fifty lysosomal enzymes involved in the highly ordered degradation cascades of glycans, glycoconjugates, and other complex biomolecules in the lysosome. Several of these metabolic disorders are associated with the absence or the lack of activity of carbohydrate-processing enzymes in this cell compartment. In a recently introduced therapy concept, for susceptible mutants, small substrate-related molecules (so-called pharmacological chaperones), such as reversible inhibitors of these enzymes, may serve as templates for the correct folding and transport of the respective protein mutant, thus improving its concentration and, consequently, its enzymatic activity in the lysosome. Carbohydrate-processing enzymes in the lysosome, related lysosomal diseases, and the scope and limitations of reported reversible inhibitors as pharmacological chaperones are discussed with a view to possibly extending and improving research efforts in this area of orphan diseases.

A Novel Potent and Highly Specific Inhibitor against Influenza Viral N1-N9 Neuraminidases: Insight into Neuraminidase-Inhibitor Interactions

People throughout the world continue to be at risk for death from influenza A virus, which is always creating a new variant. Here we present a new effective and specific anti-influenza viral neuraminidase (viNA) inhibitor, 9-cyclopropylcarbonylamino-4-guanidino-Neu5Ac2en (cPro-GUN). Like zanamivir, it is highly effective against N1-N9 avian and N1-N2 human viNAs, including H274Y oseltamivir-resistant N1 viNA, due to its C-6 portion still being anchored in the active site, different from the disruption of oseltamivir's C-6 anchoring by H274Y mutation. Unlike zanamivir, no sialidase inhibitory activity has been observed for cPro-GUN against huNeu1-huNeu4 enzymes. Broad efficacy of cPro-GUN against avian and human influenza viruses in cell cultures comparable to its sialidase inhibitory activities makes cPro-GUN ideal for further development for safe therapeutic or prophylactic use against both seasonal and pandemic influenza.

Fundus autofluorescence and optical coherence tomography of a macular cherry-red spot in a case report of sialidosis

Background

Sialidosis is a rare lysosomal storage disorder characterized by deficiency of alpha-N-acetyl neuraminidase. The macular cherry-red spot, which could be important for diagnosis, is a distinctive feature of its ocular manifestation. We evaluated the fundus autofluorescence (FAF) and optical coherence tomography (OCT) images of a juvenile patient who presented with vision decrease and was later confirmed with genetic sialidosis.

Case presentation

A 13-year-old Chinese male presented with bilateral decreased vision over the past 2 years before his initial visit. Funduscopic examination revealed a macular cherry-red bilateral spot. FAF showed hyperreflective areas surrounding a central hyporeflective fovea in both eyes. OCT revealed increased reflectivity in the ganglion cell layer in both maculae without a definite boundary between the hyperreflective and normal areas. These findings suggested that lipofuscin had accumulated in the retinal ganglion cells, which is a distinctive ocular feature in metabolic central nervous system (CNS) disorders. He was later confirmed with genetic sialidosis.

Conclusions

FAF and OCT images are very sensitive and useful techniques for diagnosing lysosomal storage disease of the CNS, and are helpful in evaluating the extent of damage in retinal ganglion cells.

Effects of sialidase NEU1 siRNA on proliferation, apoptosis, and invasion in human ovarian cancer

Ovarian cancer is one of the most common malignancies encountered in the world. In ovarian cancer tissues of patients, NEU1 was expressed in a higher level than that in adjacent normal tissues. In this research, we aimed to elucidate the role of NEU1 siRNA on proliferation, apoptosis, and invasion of OVCAR3 and SKOV3 cells which expressed NEU1 notably. By cell viability assay and flow cytometry method, we found that NEU1 siRNA effectively inhibited the cancer proliferation, arrested cells cycle at G0/G1 phase, and induced apoptosis when compared to the Mock group. Result of transwell assay showed that invasion of cells in OVCAR3 and SKOV3 treated with NEU1 siRNA were suppressed significantly. Gene set enrichment analysis showed that lysosome and oxidative phosphorylation related signal pathway were associated with the NEU1 expression. In addition, Western blot revealed that expressions of Cln3 and Cln5 were depressed, and ATP5B and ATP5J expressions were also reduced. In conclusion, NEU1 siRNA can effectively inhibit proliferation, apoptosis, and invasion of human ovarian cancer cells by targeting lysosome and oxidative phosphorylation signaling, which can serve as a new target ovarian cancer treatment.