PGM3 regulates beta-catenin activity to promote colorectal cancer cell progression

Intron retention as an excellent marker for diagnosing depression and for discovering new potential pathways for drug intervention

Background

Peripheral inflammation is often associated with depressive disorders, and immunological biomarkers of depression remain a focus of investigation.

Methods

We performed RNA-seq analysis of RNA transcripts of human peripheral blood mononuclear cells from a case-control study including subjects with self-reported depression in the pre-symptomatic state of major depressive disorder and analyzed differentially expressed genes (DEGs) and the frequency of intron retention (IR) using rMATS.

Results

Among the statistically significant DEGs identified, the 651 upregulated DEGs were particularly enriched in the term "bacterial infection and phagocytosis", whereas the 820 downregulated DEGs were enriched in the terms "antigen presentation" and "T-cell proliferation and maturation". We also analyzed 158 genes for which the IR was increased (IncIR) and 211 genes for which the IR was decreased (DecIR) in the depressed subjects. Although the Gene Ontology terms associated with IncIR and DecIR were very similar to those of the up- and downregulated genes, respectively, IR genes appeared to be particularly enriched in genes with sensor functions, with a preponderance of the term "ciliary assembly and function". The observation that IR genes specifically interact with innate immunity genes suggests that immune-related genes, as well as cilia-related genes, may be excellent markers of depression. Re-analysis of previously published RNA-seq data from patients with MDD showed that common IR genes, particularly our predicted immune- and cilia-related genes, are commonly detected in populations with different levels of depression, providing validity for using IR to detect depression.

Conclusion

Depression was found to be associated with activation of the innate immune response and relative inactivation of T-cell signaling. The DEGs we identified reflect physiological demands that are controlled at the transcriptional level, whereas the IR results reflect a more direct mechanism for monitoring protein homeostasis. Accordingly, an alteration in IR, namely IncIR or DecIR, is a stress response, and intron-retained transcripts are sensors of the physiological state of the cytoplasm. The results demonstrate the potential of relative IR as a biomarker for the immunological stratification of depressed patients and the utility of IR for the discovery of novel pathways involved in recovery from depression.

Kaempferol regulates apoptosis and migration of neural stem cells to attenuate cerebral infarction by O-GlcNAcylation of β-catenin

Ischemic stroke remains a major cause of disability and death. Kaempferol (Kae) is a neuroprotective flavonoid compound. Thus, this study aimed to explore the impact of Kae on cerebral infarction. We generated the middle cerebral artery occlusion (MCAO) mouse model to study the effects of Kae on infarction volume and neurological function. The oxygen and glucose deprivation (OGD)/reoxygenation (R) model of neural stem cells (NSCs) was established to study the effects of Kae on cell viability, migration, and apoptosis. Cell processes were assessed by cell counting kit-8, Transwell assay, flow cytometry, and TUNEL analysis. The molecular mechanism was assessed using the Western blot. The results indicated that Kae attenuated MCAO-induced cerebral infarction and neurological injury. Besides, Kae promoted cell viability and migration and inhibited apoptosis of OGD/R-treated NSCs. Moreover, OGD/R suppressed total O-GlcNAcylation level and O-GlcNAcylation of β-catenin, thereby suppressing the Wnt/β-catenin pathway, whereas Kae reversed the suppression. Inactivation of the Wnt/β-catenin pathway abrogated the biological functions of NSCs mediated by Kae. In conclusion, Kae suppressed cerebral infarction by facilitating NSC viability, migration, and inhibiting apoptosis. Mechanically, Kae promoted O-GlcNAcylation of β-catenin to activate the Wnt/β-catenin pathway. Kae may have a lessening effect on ischemic stroke.

TRIM28 suppresses cancer stem-like characteristics in gastric cancer cells through Wnt/β-catenin signaling pathways

The influences of TRIM28 on the gastric tumorigenesis together with potential molecular mechanisms remain to be studied. We aimed at exploring the important effects of TRIM28 on gastric cancer (GC) and uncovering underling molecular mechanisms. Through immunohistochemistry analysis of 20 pairs of GC and the peritumoral tissues, the expression level of TRIM28 was determined. A variety of assays were applied to explore the important roles of TRIM28 in GC. Western blotting and qRT-PCR analyses were used to analyze the association between TRIM28 and the Wnt/β-catenin signaling pathway. TRIM28 was highly expressed in GC tissues than peritumoral tissues. And high expression level of TRIM28 in GC was associated with good prognostic effects. In vitro functional assays suggested TRIM28 knockdown enhanced the proliferation and clone formation of GC cell. Moreover, TRIM28 knockdown enhanced the expression level of stemness markers, strengthened sphere-forming and drug-resistance properties of GC cells, suggesting important effect on GC cell stemness. Besides, our analysis showed that the Wnt/β-catenin signaling was involved in the effect of TRIM28 on GC cell stemness property, and blocking Wnt/β-catenin signaling pathway obviously rescued the promotion influence of TRIM28 knockdown. Overall, TRIM28 has an important influence on regulating the stem-like property of GC cell via Wnt/β-catenin signaling, suggesting TRIM28 a promising drug target and a potential predictor of prognosis.

On a sugar high: Role of O-GlcNAcylation in cancer

Recent advances in the understanding of the molecular mechanisms underlying cancer progression have led to the development of novel therapeutic targeting strategies. Aberrant glycosylation patterns and their implication in cancer have gained increasing attention as potential targets due to the critical role of glycosylation in regulating tumor-specific pathways that contribute to cancer cell survival, proliferation, and progression. A special type of glycosylation that has been gaining momentum in cancer research is the modification of nuclear, cytoplasmic, and mitochondrial proteins, termed O-GlcNAcylation. This protein modification is catalyzed by an enzyme called O-GlcNAc transferase (OGT), which uses the final product of the Hexosamine Biosynthetic Pathway (HBP) to connect altered nutrient availability to changes in cellular signaling that contribute to multiple aspects of tumor progression. Both O-GlcNAc and its enzyme OGT are highly elevated in cancer and fulfill the crucial role in regulating many hallmarks of cancer. In this review, we present and discuss the latest findings elucidating the involvement of OGT and O-GlcNAc in cancer.

The Hexosamine Biosynthesis Pathway: Regulation and Function

The hexosamine biosynthesis pathway (HBP) produces uridine diphosphate-N-acetyl glucosamine, UDP-GlcNAc, which is a key metabolite that is used for N- or O-linked glycosylation, a co- or post-translational modification, respectively, that modulates protein activity and expression. The production of hexosamines can occur via de novo or salvage mechanisms that are catalyzed by metabolic enzymes. Nutrients including glutamine, glucose, acetyl-CoA, and UTP are utilized by the HBP. Together with availability of these nutrients, signaling molecules that respond to environmental signals, such as mTOR, AMPK, and stress-regulated transcription factors, modulate the HBP. This review discusses the regulation of GFAT, the key enzyme of the de novo HBP, as well as other metabolic enzymes that catalyze the reactions to produce UDP-GlcNAc. We also examine the contribution of the salvage mechanisms in the HBP and how dietary supplementation of the salvage metabolites glucosamine and N-acetylglucosamine could reprogram metabolism and have therapeutic potential. We elaborate on how UDP-GlcNAc is utilized for N-glycosylation of membrane and secretory proteins and how the HBP is reprogrammed during nutrient fluctuations to maintain proteostasis. We also consider how O-GlcNAcylation is coupled to nutrient availability and how this modification modulates cell signaling. We summarize how deregulation of protein N-glycosylation and O-GlcNAcylation can lead to diseases including cancer, diabetes, immunodeficiencies, and congenital disorders of glycosylation. We review the current pharmacological strategies to inhibit GFAT and other enzymes involved in the HBP or glycosylation and how engineered prodrugs could have better therapeutic efficacy for the treatment of diseases related to HBP deregulation.