Post-translational modifications of the apelin receptor regulate its functional expression.

Post-translational modifications (PTMs) are protein modifications that occur after protein biosynthesis, playing a crucial role in regulating protein function. They are involved in the functional expression of G-protein-coupled receptors (GPCRs), as well as intracellular and secretory protein signaling. Here, we aimed to investigate the PTMs of the apelin receptor (APLNR), a GPCR and their potential influence on the receptor's function. In an in vitro experiment using HEK cells, we only observed glycosylation as a PTM of the APLNR and ineffective receptor signaling by the agonist, (Pyr1)-apelin-13. In contrast, when analyzing mouse spinal cord, we detected glycosylation and other PTMs, excluding isopeptidation. This suggests that additional PTMs are involved in the functional expression of the APLNR in vitro. In summary, these findings suggest that the APLNR in vivo requires multiple PTMs for functional expression. To comprehensively understand the pharmacological effects of the APLNR, it is essential to establish an in vitro system that adequately replicates the receptor's PTM profile. Nonetheless, it is crucial to overcome the challenge of heat-sensitive proteolysis in APLNR studies. By elucidating the regulation of PTMs, further research has the potential to advance the analysis and pharmacological studies of both the apelin/APLNR system and GPCR signal modulation.

Effects of aliphatic aldehydes on the growth and patulin production of Penicillium expansum in apple juice.

The effects of 16 aliphatic aldehydes with 3-10 carbons on the growth and patulin production of Penicillium expansum were examined. When P. expansum spores were inoculated into apple juice broth, some alkenals, including 2-propenal, (E)-2-butenal, (E)-2-pentenal, and (E)-2-hexenal, inhibited fungal growth and patulin production. Their minimal inhibitory concentrations were 5, 50, 80, and 80 µg/mL respectively. Vital staining indicated that these alkenals killed mycelia within 4 h. Treatment of the spores with these aldehydes also resulted in rapid loss of germination ability, within 0.5-2 d. On the other hand, aliphatic aldehydes with 8-10 carbons significantly enhanced patulin production without affecting fungal growth: 300 µg/mL of octanal and 100 µg/mL of (E)-2-octenal increased the patulin concentrations in the culture broth by as much as 8.6- and 7.8-fold as compared to that of the control culture respectively. The expression of the genes involved in patulin biosynthesis in P. expansum was investigated in mycelia cultured in apple juice broth containing 300 µg/mL of octanal for 3.5, 5, and 7 d. Transcription of the msas gene, encoding 6-methylsalicylic acid synthase, which catalyzed the first step in the patulin biosynthetic pathway was remarkably high in the 3.5-d and 5-d-old cultures as compared with the control. However, octanal did not any increase the transcription of the msas in the 7-d-old culture or that of the other two genes, IDH and the peab1, in culture. Thus the enhanced patulin accumulation with supplementation with these aldehydes is attributable to the increased amount of the msas transcript.

[Multiresidue method for pesticides and veterinary drugs in bovine milk using GC/MS and LC/MS/MS].

A simple, sensitive and selective method with gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS) has been developed to detect 342 pesticides and veterinary drugs contaminating bovine milk at the maximum residue limits (MRLs) defined in the "positive list system". Sample preparation was performed by extracting the analytes with acetonitrile, followed by salting-out with sodium chloride. For some pesticides, the extract was further cleaned up by n-hexane partitioning and PSA cartridge column chromatography. GC/MS-EI or -NCI was used to determine pesticide residues, while LC/MS/MS-ESI was applicable to the determination of pesticide and veterinary drug residues. The variation of the recoveries of these drugs at MRL was relatively wide; however the relative standard deviations of the recovery of each drug were within 28%, suggesting that the present method is good enough for use as a screening test for contaminants at the MRLs. These results show that this method is useful for multiresidue analysis of numerous pesticides and veterinary drugs in bovine milk.