Towards the in vivo identification of protein-protein interactions.

Protein-protein interactions (PPIs) play crucial roles in biological processes. The conventional methods based on affinity purification of a protein of interest (POI) have been widely used to identify unknown PPIs. Recently, proximity-dependent biotin identification (BioID) has been used increasingly to investigate PPIs. BioID utilizes the proximity-dependent biotinylation, in the presence of biotin, of endogenous proteins that are located within a certain distance of POI-fused biotin ligase, which enables us to reveal the more physiologically relevant PPIs in vivo compared to the conventional methods. However, there is little information on an appropriate way to administer biotin in vivo. Recent studies reported some biotin supplementations for in vivo BioID. In this commentary, we review the BioID technique as a tool to examine PPIs, and we introduce a potential method to achieve efficient proximity labelling for in vivo BioID.

Midkine regulation of the renin-angiotensin system.

Hypertension and chronic kidney disease are often associated. The pathogenesis of these diseases involves the renin-angiotensin system. We have recently reported that the growth factor midkine is a novel regulator of the renin-angiotensin system. Midkine is a heparin-binding growth factor so far implicated in neuronal differentiation, neuroprotection, cardioprotection, inflammation, and cancer development. In a mouse model of chronic kidney disease induced by 5/6 nephrectomy, midkine is produced in the lung and in turn upregulates angiotensin-converting enzyme expression. Hypertension associated with 5/6 nephrectomy is not observed in midkine-deficient mice. Conversely, supplemental administration of midkine to the deficient mice induces hypertension. This review describes the molecular characteristics of midkine and its significance in the renin-angiotensin system and the kidney-lung interaction.

Ginger ingredients reduce viability of gastric cancer cells via distinct mechanisms.

Ginger has been used throughout the world as spice, food and traditional herb. We found that 6-gingerol, a phenolic alkanone isolated from ginger, enhanced the TRAIL-induced viability reduction of gastric cancer cells while 6-gingerol alone affected viability only slightly. 6-Gingerol facilitated TRAIL-induced apoptosis by increasing TRAIL-induced caspase-3/7 activation. 6-Gingerol was shown to down-regulate the expression of cIAP1, which suppresses caspase-3/7 activity, by inhibiting TRAIL-induced NF-kappaB activation. As 6-shogaol has a chemical structure similar to 6-gingerol, we also assessed the effect of 6-shogaol on the viability of gastric cancer cells. Unlike 6-gingerol, 6-shogaol alone reduced the viability of gastric cancer cells. 6-Shogaol was shown to damage microtubules and induce mitotic arrest. These findings indicate for the first time that in gastric cancer cells, 6-gingerol enhances TRAIL-induced viability reduction by inhibiting TRAIL-induced NF-kappaB activation while 6-shogaol alone reduces viability by damaging microtubules.

Paeonol attenuates TNBS-induced colitis by inhibiting NF-kappaB and STAT1 transactivation.

Paeonol, a major phenolic component of Moutan Cortex, is known to have anti-inflammatory activity. However, the effect of Paeonol on colitis has not been evaluated and the molecular mechanism of its anti-inflammatory action remains unknown. The aim of this study was to determine if Paeonol enema attenuates trinitrobenzene sulfonic acid (TNBS)-induced colitis in mice. We also investigated the effects of Paeonol in colon cancer-derived CW-2 cells and T cell leukemia-derived Jurkat cells treated with tumor necrosis factor alpha (TNFalpha) and/or interferon gamma (IFNgamma), which play critical roles in TNBS-induced colitis. Paeonol enema attenuated TNBS-induced colitis judging by body weigh reduction, colon length and histological score. Myeloperoxidase activity and inducible nitric oxide synthase (iNOS) production in the colon were also reduced with Paeonol enema. In CW-2 cells, Paeonol inhibited iNOS protein and mRNA expression induced by costimulation of TNFalpha and IFNgamma. Furthermore, Paeonol reduced TNFalpha-induced NF-kappaB transactivation and IFNgamma-induced STAT1 transactivation in CW-2 cells and also in Jurkat cells. These findings suggest that Paeonol enema may be useful for the treatment of colitis.

Basigin expression and hormonal regulation in mouse uterus during the peri-implantation period.

Basigin, a transmembrane glycoprotein belonging to the immunoglobulin superfamily, has been shown to be essential for fertilization and implantation. The aim of this study was to determine the expression and hormonal regulation of basigin gene in mouse uterus during the peri-implantation period. Basigin immunostaining and mRNA were strongly localized in luminal and glandular epithelium on day 1 of pregnancy and gradually decreased to a basal level from day 2-4 of pregnancy. Basigin mRNA expression in the sub-luminal stroma was first detected on day 3 of pregnancy and increased on day 4 of pregnancy. On day 5 of pregnancy, the expression of basigin protein and mRNA was only detected in the implanting embryos, and the luminal epithelium and sub-luminal stroma surrounding the embryos. A similar expression pattern of basigin was also induced in the delayed-implantation uterus which was activated by estrogen injection. On day 6-8 of pregnancy, although a basal level of basigin protein was detected in the secondary decidual zone, basigin mRNA expression was strongly seen in this location. Basigin mRNA was also highly expressed in the decidualized cells under artificial decidualization. Estrogen significantly stimulated basigin expression in the ovariectomized mouse uterus. A high level of basigin immunostaining and mRNA was also seen in proestrus and estrus uteri. These results suggest that basigin expression is closely related to mouse implantation and up-regulated by estrogen.