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CLP1 plays an essential role in the protein complex involved in mRNA 3′-end formation and polyadenylation as well as in the tRNA splicing endonuclease (TSEN) complex involved in the splicing of precursor tRNAs. NOL9 localizes in the nucleolus of cells and plays an essential role in ribosomal RNA maturation. Both CLP1 and NOL9 are RNA kinases that phosphorylate the 5′ end of RNAs. From the evidence that phosphorylation of the 5′ end of a siRNA is essential for its efficient RNA cleavage, it was expected that CLP1 and NOL9 would be corresponding molecules. However, there had been no direct evidence that this is the case. In this study, murine NOL9 showed no apparent RNA kinase activity in cells or even in an RNA kinase assay using recombinant murine NOL9 protein. Although siRNA efficiency was decreased in CLP1 kinase-dead (Clp1 K/K ) cells, it was not influenced by NOL9 overexpression. These findings indicate that in mouse cells it is CLP1 that mainly acts to phosphorylate the 5′ end of RNAs in the siRNA pathway, with no apparent involvement of NOL9. • RNA kinase activity was not detected in CLP1 kinase-dead mice. • Overexpression of murine NOL9 did not augment RNA kinase activity in cells. • Recombinant murine NOL9 showed no apparent RNA kinase activity. • CLP1, not NOL9, has an important role in the siRNA pathway. [ABSTRACT FROM AUTHOR]

Mammalian cyclin A-CDK (cyclin-dependent kinase) activity during mitotic exit is regulated by two redundant pathways, cyclin degradation and CDK inhibitors (CKIs). Ectopic expression of a destruction box-truncated (thereby stabilized) mutant of cyclin A in the mouse embryonic fibroblasts nullizygous for three CKIs (p21, p27, and p107) results in constitutive activation ("hyperactivation") of cyclin A-CDK and induces rapid tetraploidization, suggesting loss of the two redundant pathways causes genomic instability. To elucidate the mechanism underlying teraploidization by hyperactive cyclin A-CDK, we first examined if the induction of tetraploidization depends on specific cell cycle stage(s). Arresting the cell cycle at either S phase or M phase blocked the induction of tetraploidization, which was restored by subsequent release from the arrest. These results suggest that both S- and M-phase progressions are necessary for the tetraploidization by hyperactive cyclin A-CDK and that the tetraploidization is not caused by chromosome endoreduplication but by mitotic failure. We also observed that the induction of tetraploidization is associated with excessive duplication of centrosomes , which was suppressed by S-phase but not M-phase block, suggesting that hyperactive cyclin A-CDK promotes centrosome overduplication during S phase. Time-lapse microscopy revealed that hyperactive cyclin A-CDK can lead cells to bypass cell division and enter pseudo-G1 state. These observations implicate that hyperactive cyclin A-CDK causes centrosome overduplication, which leads to mitotic slippage and subsequent tetraploidization. • Many cancers show overexpression of cyclin A and low expression of CDK inhibitors. • Loss of both cyclin degradation and CDK inhibitors hyperactivates cyclin A-CDK. • Hyperactive cyclin A-CDK induces overduplication of centrosomes in S phase. • Centrosome overduplication leads cells to bypass cell division (mitotic slippage), resulting in tetraploidy • Hyperactivation of cyclin A-CDK could contribute to polyploidy in tumorigenesis. [ABSTRACT FROM AUTHOR]

When SRPC was applied to mice, chromium is absorbed by passive diffusion and then binds to the iron-transport protein in the blood. Transferrin delivers chromium to the tissues where it binds to a low-molecular-weight organic species that is cleared from the tissues. A proposed mechanism for the activation of insulin receptor (IR) kinase activity by chromodulin in response to insulin as depicted in the above figure. The inactive form of the IR is converted to the active form by binding insulin. This triggers the movement of Cr from transferrin into the insulin dependent cells and the binding of Cr to apochromodulin. The holochromodulin containing 4 mol Cr/mol chromodulin then binds to the IR further activating IR kinase activity. In this study, we used molecular docking to predict the binding patterns of Cr and IR. SRPC-treatment improved glucose metabolism via an activation of the IR/IRS-2/PI3K/PKB/GSK-3β glycogen synthesis-related signaling pathway and enhanced glucose transport through insulin signalling cascade-induced GLUT4 translocation. • A novel sulfated polysaccharides-chromium (III) complex (SRPC) was synthesized and characterized. • Hypoglycemic effect in T2DM by SRPC is reported for the first time. • SRPC improved glucose metabolism via an activation of the PKB/GSK-3β glycogen synthesis-related signaling pathway. • Activation of PKB/GLUT4 pathway caused glucose uptake in skeletal muscle by SRPC. • SRPC is a stable and significant functional factor for T2DM therapy. The sulfated rhamnose polysaccharides found in Enteromorpha prolifera belong to a class of unique polyanionic polysaccharides with high chelation capacity. In this study, a complex of sulfated rhamnose polysaccharides with chromium(III) (SRPC) was synthesized, and its effect on type 2 diabetes mellitus (T2DM) in mice fed a high-fat, high-sucrose diet was investigated. The molecular weight of SRPC is 4.57 kDa, and its chromium content is 28 μg/mg. Results indicated that mice treated by oral administration of SRPC (10 mg/kg and 30 mg/kg body mass per day) for 11 weeks showed significantly improved oral glucose tolerance, decreased body mass gain, reduced serum insulin levels, and increased tissue glycogen content relative to T2DM mice (p < 0.01). SRPC treatment improved glucose metabolism via activation of the IR/IRS-2/PI3K/PKB/GSK-3β signaling pathway (which is related to glycogen synthesis) and enhanced glucose transport through insulin signaling cascade–induced GLUT4 translocation. Because of its effectiveness and stability, SRPC could be used as a therapeutic agent for blood glucose control and a promising nutraceutical for T2DM treatment. [ABSTRACT FROM AUTHOR]

Abstract: Oocyte maturation invokes complex signaling pathways to achieve cytoplasmic and nuclear competencies for fertilization and development. The Src-family kinases FYN, YES and SRC are expressed in mammalian oocytes but their function during oocyte maturation remains an open question. Using chemical inhibitor, siRNA knockdown, and gene deletion strategies the function of Src-family kinases was evaluated in mouse oocytes during maturation under in vivo and in vitro conditions. Suppression of Src-family as a group with SKI606 greatly reduced meiotic cell cycle progression to metaphase-II. Knockdown of FYN kinase expression after injection of FYN siRNA resulted in an approximately 50% reduction in progression to metaphase-II similar to what was observed in oocytes isolated from FYN (−/−) mice matured in vitro. Meiotic cell cycle impairment due to a Fyn kinase deficiency was also evident during oocyte maturation in vivo since ovulated cumulus oocyte complexes collected from FYN (−/−) mice included immature metaphase-I oocytes (18%). Commonalities in meiotic spindle and chromosome alignment defects under these experimental conditions demonstrate a significant role for Fyn kinase activity in meiotic maturation. [Copyright &y& Elsevier]

Abstract: α2-HS glycoprotein (AHSG), also known as fetuin-A, inhibits insulin receptor autophosphorylation and tyrosine kinase activity in vitro and in vivo. Earlier we have shown that fetuin-null (KO) mice demonstrate improved insulin sensitivity and resistance to diet-induced obesity. Since aging is associated with insulin resistance and impaired glucose handling, we tested the hypothesis that fetuin-null (KO) mice are resilient to changes in insulin sensitivity associated with aging. Aged (80-week-old) fetuin-null mice were leaner and demonstrated significantly lower body weights compared to age- and sex-matched wild-type (WT) littermates. Leanness in aged fetuin KO mice was accompanied by a significant increase in dark-onset energy expenditure, without marked alteration of respiratory quotient. In comparison to WT mice, fetuin KO mice demonstrated a lower fasting insulin resistance index, and significantly lower blood glucose and insulin levels, following a 4h fast. Interestingly, despite significantly decreased insulin levels during a glucose tolerance test, aged fetuin-null mice demonstrated a similar glucose excursion as WT mice, indicative of improved insulin sensitivity. Analysis of aldehyde–fuchsin stained pancreas from aged fetuin KO mice indicated no difference in islet β-cell size or number. An insulin tolerance test confirmed the increased insulin sensitivity of aged fetuin KO mice. Further, compared to WT mice, aged fetuin-null mice demonstrated increased skeletal muscle and liver IR autophosphorylation and TK activity. Taken together, this study suggests that the absence of fetuin may contribute to the improvement of insulin sensitivity associated with aging. [Copyright &y& Elsevier]

Tumor progression locus 2 (Tpl2, gene name MAP3K8), a mitogen-activated protein kinase, is widely expressed in immune and non-immune cells to integrate tumor necrosis factor (TNF), toll-like receptors (TLRs), and interleukin-1 (IL1) receptor signaling to regulate inflammatory response. Given its central role in inflammatory response, Tpl2 is an attractive small molecule drug target. However, the role of Tpl2 as an oncogene or tumor suppressor gene remains controversial, and its function outside immune cells is not understood. We therefore utilized a Tpl2 kinase dead (Tpl2-KD) mouse model in an 18-month aging study to further elucidate Tpl2 effects on lifespan and chronic disease. Histopathological studies revealed the incidence and severity of spontaneous tumors and non-neoplastic lesions were comparable between wild type and Tpl2-KD mice. The only finding was that male Tpl2-KD mice had higher bodyweight and an increased incidence of liver steatosis, suggesting a sex-specific role for Tpl2 in hepatic lipid metabolism. In conclusion, loss of Tpl2 kinase activity did not lead to increased tumorigenesis over aging in mice but affected likely alterations in lipid metabolism in male animals. [Display omitted] • Comparable aging related tumor incidence observed in Tpl2-KD and WT mice. • Tumor incidence suggests lack of Tpl2 activity has no impact on tumorigenesis. • Tpl2 inhibitor did not cause cell hyperproliferation in vitro. • Aged male Tpl2-KD mice had increased bodyweight and liver steatosis compared to WT. • All other non-neoplastic age-related changes in Tpl2-KD and WT mice were comparable. [ABSTRACT FROM AUTHOR]