LncRNA DGUOK-AS1 Promotes Cell Progression in Lung Squamous Cell Carcinoma by Regulation of miR-653-5p/SLC6A15 Axis

Long noncoding RNA (lncRNA) plays a key role in regulating cancer development. LncRNA deoxyguanosine kinase antisense RNA 1 (DGUOK-AS1) has been reported as a promoter in tumor. The work was designed to further investigate the mechanism of action of DGUOK-AS1 in lung squamous cell carcinoma (LUSC). DGUOK-AS1 level in LUSC cells was measured using RT-qPCR. Counting Kit-8 assays and colony forming assays were performed to evaluate LUSC cell viability and proliferation. Transwell assays were performed to detect cell migration and invasion. Luciferase reporter and RNA pulldown assays were used to verify the binding capacity of DGUOK-AS1 and miR-653-5p. RNA immunoprecipitation assays were performed to verify the relationship of DGUOK-AS1, miR-653-5p, and SLC6A15. DGUOK-AS1 was highly expressed in LUSC cells. DGUOK-AS1 knockdown suppressed LUSC cell proliferation, migration, and invasion. SLC6A15 was demonstrated to be targeted by miR-653-5p, and DGUOK-AS1 interacted with miR-653-5p to modulate SLC6A15 level in LUSC cells. Overexpression of SLC6A15 reversed the suppressive effects of DGUOK-AS1 knockdown on LUSC cell processes. In conclusion, DGUOK-AS1 promotes malignant behaviors of LUSC cells by upregulating SLC6A15 level through interaction with miR-653-5p.

SLC6A15 acts as a tumor suppressor to inhibit migration and invasion in human papillary thyroid cancer

Solute Carrier Family 6 Member 15 (SLC6A15), a sodium-dependent neutral amino acid transporter, has been found with dysregulated expression in several kinds of cancers. However, the expression pattern and the biological functions of SLC6A15 in papillary thyroid cancer (PTC) remain unknown. In this study, we found that SLC6A15 was downregulated in PTC, which was related to N classification. Ectopic overexpression of SLC6A15 impaired migratory and invasive abilities of PTC cell in vitro. In addition, we identified intercellular adhesion molecule-1, a vital oncogene in thyroid cancer progression, was involved in the effects of SLC6A15 on PTC cell. These results indicate that SLC6A15 acts as a tumor suppressor and might be a potential therapeutic target in the treatment of PTC.

Loss of the psychiatric risk factor SLC6A15 is associated with increased metabolic functions in primary hippocampal neurons

Major depressive disorder (MDD) is one of the most severe global health problems with millions of people affected, however, the mechanisms underlying this disorder is still poorly understood. Genome-wide association studies have highlighted a link between the neutral amino acid transporter SLC6A15 and MDD. Additionally, a number of preclinical studies support the function of this transporter in modulating levels of brain neurotransmitters, stress system regulation and behavioural phenotypes related to MDD. However, the molecular and functional mechanisms involved in this interaction are still unresolved. Therefore, to investigate the effects of the SLC6A15 transporter, we used hippocampal tissue from Slc6a15-KO and wild-type mice, together with several in-vitro assays in primary hippocampal neurons. Utilizing a proteomics approach we identified differentially regulated proteins that formed a regulatory network and pathway analysis indicated significantly affected cellular domains, including metabolic, mitochondrial and structural functions. Furthermore, we observed reduced release probability at glutamatergic synapses, increased mitochondrial function, higher GSH/GSSG redox ratio and an improved neurite outgrowth in primary neurons lacking SLC6A15. In summary, we hypothesize that by controlling the intracellular concentrations of neutral amino acids, SLC6A15 affects mitochondrial activity, which could lead to alterations in neuronal structure and activity. These data provide further indication that a pharmacological or genetic reduction of SLC6A15 activity may indeed be a promising approach for antidepressant therapy.

A Combined Study of SLC6A15 Gene Polymorphism and the Resting-State Functional Magnetic Resonance Imaging in First-Episode Drug-Naive Major Depressive Disorder

AIMS

The SLC6A15 gene has been identified as a novel candidate gene for major depressive disorder (MDD). However, the mechanism underlying the effects of how the SLC6A15 gene affects functional brain activity of patients with MDD remains unknown.

METHODS

In the present study, we investigated the effect of the SLC6A15 gene polymorphism, rs1545843, on resting-state brain function in MDD with the imaging genomic technology and the regional homogeneity (ReHo) method. Sixty-seven MDD patients and 44 healthy controls underwent functional magnetic resonance imaging scans and genotyping. The differences in ReHo between genotypes were initially tested using the student's t test. We then performed a 2 × 2 (genotypes × disease status) analysis of variance to identify the main effects of genotypes, disease status, and their interactions in MDD.

RESULTS

MDD patients with A+ genotypes showed decreased ReHo in the medial cingulum compared with MDD patients with the GG genotype. This was in contrast to normal controls with A+ genotypes who showed increased ReHo in the posterior cingulum and the frontal, temporal, and parietal lobes and decreased ReHo in the left corpus callosum, compared with controls with the GG genotypes. The main effect of disease was found in the frontal, parietal, and temporal lobes. The main effect of genotypes was found in the left corpus callosum and the frontal lobe. There was no interaction between rs1545843 genotypes and disease status. We found that the left corpus callosum ReHo was positively correlated with total scores of the Hamilton Depression Scale (HAMD) (p = 0.021), so as was the left inferior parietal gyrus ReHo with cognitive disorder (p = 0.02). In addition, the right middle temporal gyrus had a negative correlation with retardation (p = 0.049).

CONCLUSION

We observed an association between the SLC6A15 rs1545843 and resting-state brain function of the corpus callosum, cingulum and the frontal, parietal, and temporal lobes in MDD patients, which may be involved in the pathogenesis of MDD.

SLC6A15, a novel stress vulnerability candidate, modulates anxiety and depressive-like behavior: involvement of the glutamatergic system

Major depression is a multifactorial disease, involving both environmental and genetic risk factors. Recently, SLC6A15 - a neutral amino acid transporter mainly expressed in neurons - was proposed as a new candidate gene for major depression and stress vulnerability. Risk allele carriers for a single nucleotide polymorphism (SNP) in a SLC6A15 regulatory region display altered hippocampal volume, glutamate levels, and hypothalamus-pituitary-adrenal axis activity, all markers associated with major depression. Despite this genetic link between SLC6A15 and depression, its functional role with regard to the development and maintenance of depressive disorder is still unclear. The aim of the current study was therefore to characterize the role of mouse slc6a15 in modulating brain function and behavior, especially in relation to stress as a key risk factor for the development of mood disorders. We investigated the effects of slc6a15 manipulation using two mouse models, a conventional slc6a15 knock-out mouse line (SLC-KO) and a virus-mediated hippocampal slc6a15 overexpression (SLC-OE) model. Mice were tested under basal conditions and following chronic social stress. We found that SLC-KO animals displayed a similar behavioral profile to wild-type littermates (SLC-WT) under basal conditions. Interestingly, following chronic social stress SLC-KO animals showed lower levels of anxiety- and depressive-like behavior compared to stressed WT littermates. In support of these findings, SLC-OE animals displayed increased anxiety-like behavior already under basal condition. We also provide evidence that GluR1 expression in the dentate gyrus, but not GluR2 or NR1, are regulated by slc6a15 expression, and may contribute to the difference in stress responsiveness observed between SLC-KO and SLC-WT animals. Taken together, our data demonstrate that slc6a15 plays a role in modulating emotional behavior, possibly mediated by its impact on glutamatergic neurotransmission.