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Activating Kinase (activating + kinase)
Selected AbstractsRegulation of oocyte maturation in fishDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 2008Yoshitaka Nagahama A period of oocyte growth is followed by a process called oocyte maturation (the resumption of meiosis) which occurs prior to ovulation and is a prerequisite for successful fertilization. Our studies using fish models have revealed that oocyte maturation is a three-step induction process involving gonadotropin (LH), maturation-inducing hormone (MIH), and maturation-promoting factor (MPF). LH acts on the ovarian follicle layer to produce MIH (17,, 20,-dihydroxy-4-pregnen-3-one, 17,, 20,-DP, in most fishes). The interaction of ovarian thecal and granulosa cell layers (two-cell type model), is required for the synthesis of 17,,20,-DP. The dramatic increase in the capacity of postvitellogenic follicles to produce 17,,20,-DP in response to LH is correlated with decreases in P450c17 (P450c17-I) and P450 aromatase (oP450arom) mRNA and increases in the novel form of P450c17 (P450c17-II) and 20,-hydroxysteroid dehydrogenase (20,-HSD) mRNA. Transcription factors such as Ad4BP/SF-1, Foxl2, and CREB may be involved in the regulation of expression of these steroidogenic enzymes. A distinct family of G-protein-coupled membrane-bound MIH receptors has been shown to mediate non-genomic actions of 17,, 20,-DP. The MIH signal induces the de novo synthesis of cyclin B from the stored mRNA, which activates a preexisting 35 kDa cdc2 kinase via phosphorylation of its threonine 161 by cyclin-dependent kinase activating kinase, thus producing the 34 kDa active cdc2 (active MPF). Upon egg activation, MPF is inactivated by degradation of cyclin B. This process is initiated by the 26S proteasome through the first cut in its NH2 terminus at lysine 57. [source] Reactive oxygen species control senescence-associated matrix metalloproteinase-1 through c-Jun-N-terminal kinase,JOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2010Jaya Dasgupta The lifetime exposure of organisms to oxidative stress influences many aging processes which involve the turnover of the extracellular matrix. In this study, we identify the redox-responsive molecular signals that drive senescence-associated (SA) matrix metalloproteinase-1 (MMP-1) expression. Precise biochemical monitoring revealed that senescent fibroblasts increase steady-state (H2O2) 3.5-fold (13.7,48.6,pM) relative to young cells. Restricting H2O2 production through low O2 exposure or by antioxidant treatments prevented SA increases in MMP-1 expression. The H2O2 -dependent control of SA MMP-1 is attributed to sustained JNK activation and c-jun recruitment to the MMP-1 promoter. SA JNK activation corresponds to increases and decreases in the levels of its activating kinase (MKK-4) and inhibitory phosphatase (MKP-1), respectively. Enforced MKP-1 expression negates SA increases in JNK phosphorylation and MMP-1 production. Overall, these studies define redox-sensitive signaling networks regulating SA MMP-1 expression and link the free radical theory of aging to initiation of aberrant matrix turnover. J. Cell. Physiol. 225: 52,62, 2010. © 2010 Wiley-Liss, Inc. [source] Human glioma PKC-, and PKC-,II phosphorylate cyclin-dependent kinase activating kinase during the cell cycleCELL PROLIFERATION, Issue 1 2002M. Acevedo-Duncan Cell cycle phase transition is regulated in part by the trimeric enzyme, cyclin-dependent kinase activating kinase (CAK) which phosphorylates and activates cyclin-dependent kinases (cdks). Protein kinase C (PKC) inhibitors prevent cell cycle phase transition, suggesting a fundamental role for PKCs in cell cycle regulation. We report that in glioma cells, CAK (cdk7) is constitutively associated with PKC-,. In vitro phosphorylation, co-immunoprecipitation, and analysis of phosphorylated proteins by autoradiography indicate that CAK (cdk7) is a substrate for PKC-, and PKC-,II hyperphosphorylation. These results establish a role for PKC-, and PKC-,II in the activation of CAK during the glioma cell cycle. [source] | ||||||||||