Intron retention decreases METTL3 expression by inhibiting mRNA export to the cytoplasm.

Methyltransferase-like 3 (METTL3), a key component of the m6A methyltransferase complex, regulates the splicing, nuclear transport, stability, and translation of its target genes. However, the mechanism underlying the regulation of METTL3 expression by alternative splicing (AS) remains unknown. We analyzed the expression pattern of METTL3 after AS in human tissues and confirmed the expression of an isoform retaining introns 8 and 9 (METTL3-IR). We confirmed the different intracellular localizations of METTL3-IR and METTL3 proteins using immunofluorescence microscopy. Furthermore, the endogenous expression of METTL3-IR at the protein level was different from that at the mRNA level. We found that 3'-UTR generation by intron retention (IR) inhibited the export of METTL3-IR mRNA to the cytoplasm, which in turn suppressed protein expression. To the best of our knowledge, this is the first study to confirm the regulation of METTL3 gene expression by AS, providing evidence that the suppression of METTL3 protein expression by IR is an integral part of the mechanism by which 3'-UTR generation regulates protein expression via inhibition of RNA export to the cytoplasm. [BMB Reports 2023; 56(9): 514-519].

Bioactive peptides in the pancreatin-hydrolysates of whey protein support cell proliferation and scavenge reactive oxygen species.

Whey protein (WP) in milk shows physiologically active functions such as cholesterol control and immune system strengthening. In this study, we performed hydrolysis and peptide polarity fractionation to enhance the efficacy and diversity of its physiological activities, using the digesting enzyme, pancreatin. Our results indicate that hydrolysis significantly increased the cell proliferation of the WP fractions, with the lower-polarity fractions showing greater efficacy in this regard. Our results indicate that hydrolysis significantly increases cell proliferation of the WP fractions. Additionally, we confirmed differences in the antioxidant activity of the WP fractions as a function of polarity was confirmed via scavenging 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay in vitro. WP itself did not show anti-inflammatory efficacy. However, all the hydrolyzed fractions downregulated the mRNA expression levels of inflammatory cytokines in all treated cell lines and, based on a senescence-associated (SA)-ß-galactosidase assay, the fraction with the lowest polarity (F6) inhibited cellular senescence to the greatest extent. Furthermore, we identified the peptide sequences with various physiological activities from whey protein hydrolysates through mass spectrometry. Taken together, our results indicate that the fractionation of WP via hydrolysis generates novel functions including promoting cellular cell proliferation, anti-inflammatory effects, and enhancing antioxidant and anti-cellular senescence.

Melittin-derived peptides exhibit variations in cytotoxicity and antioxidant, anti-inflammatory and allergenic activities.

Melittin is a major component of bee venom; it is widely used in traditional medicine because of its therapeutic effects, such as anti-inflammatory effects. However, melittin has limited medical applications owing to its adverse effects, such as high cytotoxicity. In this study, we investigated the physiological activities of various hydrolyzed melittin-derived peptides to eliminate the cytotoxicity of melittin and enhance its efficacy. The 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assay confirmed that melittin-derived peptides showed antioxidant activity comparable to that of melittin. Moreover, unlike melittin, which showed high cytotoxicity in the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt (MTS) assay, the melittin-derived peptides showed negligible cytotoxicity. Among the melittin-derived peptides, the peptide composed of sequence TTGLPALISWIKRKRQQ (P1) showed inhibitory effects on the mRNA expression of inflammatory cytokines and phosphorylation of IκBα, similar to the effects of melittin in RAW 264.7 cells. Degranulation of RBL-2H3 cells was analyzed using a ß-hexosaminidase release assay to confirm the allergenic activity of melittin and P1, which showed remarkably reduced allergenicity of P1 compared to that of melittin. These results indicate that P1 maintained the anti-inflammatory effects of melittin while reducing its cytotoxicity and allergic reactions. In conclusion, the melittin-derived peptide P1 efficiently decreased the adverse effects while maintaining the beneficial effects of melittin, making it suitable for therapeutic applications.

Mangifera Indica leaf extracts promote hair growth via activation of Wnt signaling pathway in human dermal papilla cells.

The crosstalk between androgens and Wnt signaling pathways is critical in the hair growth cycle. Therefore, natural products that target these two pathways for the inhibition of hair loss are sought after. In this study, we investigated the effect of water extracts of Mangifera indica leaves (WEML) on hair growth. WEML treatment significantly reduced the expression levels of both dickkopf-1 (DKK1) and type 2 5α-reductase (SRD5A2) involved in Wnt signal suppression activity and dihydrotestosterone (DHT) synthesis, respectively, in human follicle dermal papilla cells (HFDP). In addition, WEML treatment effectively upregulated Wnt target genes and downregulated DKK1 expression that was increased by DHT treatment. Degranulation analysis in rat basophilic leukemia mast cell line (RBL-2H3) using ß-hexosaminidase release assay confirmed that WEML did not exhibit allergenic activity. Furthermore, hair growth was significantly enhanced in in vivo mice model treated with WEML. These results suggest that M. indica leave extract contains bioactive materials that can be used to treat hair loss.