Stress granule (SG) assembly is a conserved cellular strategy that copes with stress-related damage and promotes cell survival. SGs form through a process of liquid–liquid phase separation. Cellular ...signaling also appears to employ SG assembly as a mechanism for controlling cell survival and cell death by spatial compartmentalization of signal-transducing factors. While several lines of evidence highlight the importance of SGs as signaling hubs, where protein components of signaling pathways can be temporarily sequestered, shielded from the cytoplasm, the regulation and physiological significance of SGs in this aspect remain largely obscure. A recent study of the heat-shock response in the fission yeast
Schizosaaccharomyces pombe
provides an unexpected answer to this question. Recently, we demonstrated that the PKC orthologue Pck2 in fission yeast translocates into SGs through phase separation in a PKC kinase activity-dependent manner upon high-heat stress (HHS). Importantly, the downstream MAPK Pmk1 promotes Pck2 recruitment into SGs, which intercepts MAPK hyperactivation and cell death, thus posing SGs as a negative feedback circuit in controlling MAPK signaling. Intriguingly, HHS, but not modest-heat stress targets Pck2 to SGs, independent of canonical SG machinery. Finally, cells fail to activate MAPK signaling when Pck2 is sequestrated into SGs. In this review, we will discuss how SGs have a role as signaling hubs beyond serving as a repository for non-translated mRNAs during acute stress.
The RAF/MEK/ERK signaling pathway regulates diverse cellular processes as exemplified by cell proliferation, differentiation, motility, and survival. Activation of ERK1/2 generally promotes cell ...proliferation, and its deregulated activity is a hallmark of many cancers. Therefore, components and regulators of the ERK pathway are considered potential therapeutic targets for cancer, and inhibitors of this pathway, including some MEK and BRAF inhibitors, are already being used in the clinic. Notably, ERK1/2 kinases also have pro-apoptotic functions under certain conditions and enhanced ERK1/2 signaling can cause tumor cell death. Although the repertoire of the compounds which mediate ERK activation and apoptosis is expanding, and various anti-cancer compounds induce ERK activation while exerting their anti-proliferative effects, the mechanisms underlying ERK1/2-mediated cell death are still vague. Recent studies highlight the importance of dual-specificity phosphatases (DUSPs) in determining the pro- versus anti-apoptotic function of ERK in cancer. In this review, we will summarize the recent major findings in understanding the role of ERK in apoptosis, focusing on the major compounds mediating ERK-dependent apoptosis. Studies that further define the molecular targets of these compounds relevant to cell death will be essential to harnessing these compounds for developing effective cancer treatments.
Fingolimod hydrochloride (FTY720) is a first-in-class of sphingosine-1-phosphate (S1P) receptor modulator approved to treat multiple sclerosis by its phosphorylated form (FTY720-P). Recently, a novel ...role of FTY720 as a potential anticancer drug has emerged. One of the anticancer mechanisms of FTY720 involves the induction of reactive oxygen species (ROS) and subsequent apoptosis, which is largely independent of its property as an S1P modulator. ROS have been considered as a double-edged sword in tumor initiation/progression. Intriguingly, prooxidant therapies have attracted much attention due to its efficacy in cancer treatment. These strategies include diverse chemotherapeutic agents and molecular targeted drugs such as sulfasalazine which inhibits the CD44v-xCT (cystine transporter) axis. In this review, we introduce our recent discoveries using a chemical genomics approach to uncover a signaling network relevant to FTY720-mediated ROS signaling and apoptosis, thereby proposing new potential targets for combination therapy as a means to enhance the antitumor efficacy of FTY720 as a ROS generator. We extend our knowledge by summarizing various measures targeting the vulnerability of cancer cells’ defense mechanisms against oxidative stress. Future directions that may lead to the best use of FTY720 and ROS-targeted strategies as a promising cancer treatment are also discussed.
Phosphatidylinositol-4-phosphate 5-kinase (PI4P5K) is a highly conserved enzyme that generates phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) by phosphorylating phosphatidylinositol 4-phosphate ...(PI(4)P). Schizosaccharomyces pombe (S. pombe) its3-1 is a loss-of-function mutation in the essential its3+ gene that encodes a PI4P5K. Its3 regulates cell proliferation, cytokinesis, cell integrity, and membrane trafficking, but little is known about the regulatory mechanisms of Its3. To identify regulators of Its3, we performed a genetic screening utilizing the high-temperature sensitivity (TS) of its3-1 and identified puf3+ and puf4+, encoding Pumilio/PUF family RNA-binding proteins as multicopy suppressors of its3-1 cells. The deletions of the PUF domains in the puf3+ and puf4+ genes resulted in the reduced ability to suppress its3-1, suggesting that the suppression by Puf3 and Puf4 may involve their RNA-binding activities. The gene knockout of Puf4, but not that of Puf3, exacerbated the TS of its3-1. Interestingly, mutant Its3 expression levels both at mRNA and protein levels were lower than those of the wild-type (WT) Its3. Consistently, the overexpression of the mutant its3-1 gene suppressed the its3-1 phenotypes. Notably, Puf3 and Puf4 overexpression increased the mRNA and protein expression levels of both Its3 and Its3-1. Collectively, our genetic screening revealed a functional relationship between the Pumilio/PUF family RNA-binding proteins and PI4P5K.
HER1-and HER2-targeted drugs are effective in cancer therapy, especially against lung, breast and colon malignancies; however, resistance of cancer cells to HER1-and HER2-targeted therapies is ...becoming a serious problem. The avidity/affinity constant (KA) and growth inhibitory effect of anti-HER3 rat monoclonal antibodies (mAb, Ab1∼Ab6) in the presence of therapeutic mAb or low-molecular-weight inhibitors against HER family proteins were analyzed by flow cytometry-based Scatchard plots (Splot) and cell proliferation assay. The KA of Ab3 and Ab6, but not Ab1 or Ab4, split into dual (high and low) modes of KA, and Ab6 exhibited greater anti-proliferative effects against LS-174T colon cancer cells in the presence of Pertuzumab (anti-HER2 mAb). A high KA by Ab6 and Ab6-mediated increased growth inhibition were observed against NCI–H1838 lung or BT474 breast cancer cells, respectively, in the presence of Panitumumab (anti-HER1 mAb) or Perutuzumab. A high KA by Ab6 and Ab6-mediated increased anti-proliferative effects against NCI–H1838 or BT474 were also respectively observed in the presence of Erlotinib (HER1 inhibitor) or Lapatinib (HER1/HER2 inhibitor). In HER1-knockout (KO) NCI–H1838, the reactivity and KA of Ab4 increased compared with in parent NCI–H1838. In HER1-KO or HER3-KO SW1116 colon cancer cells, dual modes of KA with Pertuzumab were noted, and the combination Ab6 and Pertuzumab promoted growth inhibition of HER1-KO, but not of parent SW1116.
•Anti-proliferative effects of anti-HER3 mAb were evaluated in the presence of HER1-or HER2-targeted drugs.•Avidity constants (KA) of mAb were determined by flow cytometry (FCM)-based Scatchard plot (Splot) analysis.•High KA rather than total binding is important for the anti-proliferative capacity of mAb in combination.•Analysis of binding avidity (KA) will contribute to evaluate additional mAb aiming at therapeutic improvement over preceding anti-cancer drugs.
Aim: The aim of this study was to identify the age and sex-specific reference ranges for the non-high-density lipoprotein cholesterol (non-HDLC) levels in Japanese children. Methods: The subjects ...included 441,431 schoolchildren (207,015 boys, 234,416 girls) 9-16 years of age who participated in a screening and care program for lifestyle-related diseases from 2006 to 2011. The serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and triglyceride (TG) levels were measured, and the non-HDL-C levels were calculated. The serum lipid levels were analyzed according to age and sex. Results: The overall mean non-HDL-C level was 105.7±24.0 mg/dL, with a sex difference: boys= 103.0±24.0 mg/dL and girls=108.2±23.8 mg/dL. In boys, the median non-HDL-C level decreased gradually from 104 mg/dL in the 9-year-old age group to 96 mg/dL in the 15-year-old age group. The 75th percentile level was approximately 120 mg/dL in the 9- to 11-year-old groups and decreased at approximately 113 mg/dL in the 12- to 15-year-old groups, whereas the 95th percentile level was approximately 150 mg/dL in the 9- to 11-year-old groups and decreased at approximately 140 mg/dL in the 13- to 15-year-old groups. In girls, the median non-HDL-C level remained unchanged at approximately 105 mg/dL, with 75th and 95th percentile levels of approximately 122 and 150 mg/dL, respectively. Conclusions: The non-HDL-C levels vary by age and sex. The age- and sex-specific reference ranges for the non-HDL-C levels may be a valuable tool for management with respect to preventing the development of atherosclerosis in childhood.
PDF
