Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.22 (cdc2)
 8,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) is a well-known activator of both protein kinase C (PKC) and mitogen activated protein kinase (MAPK) signal cascade triggering a lot of effects in many non-tumor and tumor cells. We have reported activation of PKCalpha isozyme was specifically required for TPA-induced ERK (MAPK) signaling that mediated gene expressions of the CDK inhibitors p15(INK4b) and p16 (INK4a) leading to growth inhibition of hepatoma cell HepG2. We further investigated the upstream signal molecule linking PKCalpha to ERK. In the Ras activation assay, HepG2 cell exhibited substantial amount of Ras activity. Treatment of the cell with 50nM TPA for 10min slightly inhibited Ras activity by about 10-20%. Pretreatment of the cell with 10microM manumycin A, which abolish basal Ras activity, did not prevent TPA-triggered ERK phosphorylation. Immunoprecipitation coupled with kinase assay demonstrated that MEK-1 activity was strongly induced by treatment of TPA for 5-30min in HepG2. In contrast, c-Raf activity was not significantly induced by TPA within 5-15min. Consistently, Western blot of Phospho(ser-218/222)-MEK demonstrated that phosphorylation of MEK-1 was greatly induced by 50nM TPA, which can be prevented by the PKC inhibitor Bisindolylmaleimides II. Moreover, pretreatment of the MEK1/2 inhibitor, but not c-Raf inhibitor prevented the TPA-induced ERK phosphorylation, gene expression of p15(INK4b) and p16 (INK4a) and growth inhibition of HepG2. In addition, transient expression of a dominant negative Raf mutant in HepG2 did not prevent these effects of TPA. Constitutive expression of an active PKCalpha mutant in HepG2 enhanced phosphorylation of both MEK and ERK accompanied with induction of gene expression of p16(INK4a) and growth inhibition of HepG2. In contrast, Ras and Raf activity were not increased by expression of active PKCalpha. Taken together, we conclude that PKCalpha may activate MEK, independently of Raf and Ras, to trigger sustained ERK (MAPK) signaling and cell cycle arrest of HepG2 induced by TPA.
 ...
PMID:Protein kinase C alpha trigger Ras and Raf-independent MEK/ERK activation for TPA-induced growth inhibition of human hepatoma cell HepG2. 1616 61

Among normal organs and tissues, the MAPKK-like mitotic protein kinase TOPK is expressed exclusively in the testis. We analyzed the expression and phosphorylation of TOPK to address the functional role of this kinase during spermatogenesis. TOPK protein is expressed mainly in the cytosol of spermatocytes and spermatids, but not in spermatids and spermatogonia in situ. TOPK-Thr-9, a cdk1/cyclin B target residue, was specifically phosphorylated during mitotic and meiotic phases, while TOPK-Thr-198, a key amino acid for the ATP pocket, was constantly phosphorylated irrespective of the cell cycle. These data indicate that spermatogenic germ cells with vital proliferation activity express TOPK. As TOPK-Thr-9 was phosphorylated during both mitosis and meiosis, TOPK was indicted to play a role in cytokinesis and/or chromosomal segregation but not in DNA replication.
 ...
PMID:Expression and phosphorylation of TOPK during spermatogenesis. 1631 8

The actin-binding protein caldesmon (CaD) exists both in smooth muscle (the heavy isoform, h-CaD) and non-muscle cells (the light isoform, l-CaD). In smooth muscles h-CaD binds to myosin and actin simultaneously and modulates the actomyosin interaction. In non-muscle cells l-CaD binds to actin and stabilizes the actin stress fibers; it may also mediate the interaction between actin and non-muscle myosins. Both h- and l-CaD are phosphorylated in vivo upon stimulation. The major phosphorylation sites of h-CaD when activated by phorbol ester are the Erk-specific sites, modification of which is attenuated by the MEK inhibitor PD98059. The same sites in l-CaD are also phosphorylated when cells are stimulated to migrate, whereas in dividing cells l-CaD is phosphorylated more extensively, presumably by cdc2 kinase. Both Erk and cdc2 are members of the MAPK family. Thus it appears that CaD is a downstream effector of the Ras signaling pathways. Significantly, the phosphorylatable serine residues shared by both CaD isoforms are in the C-terminal region that also contains the actin-binding sites. Biochemical and structural studies indicated that phosphorylation of CaD at the Erk sites is accompanied by a conformational change that partially dissociates CaD from actin. Such a structural change in h-CaD exposes the myosin-binding sites on the actin surface and allows actomyosin interactions in smooth muscles. In the case of non-muscle cells, the change in l-CaD weakens the stability of the actin filament and facilitates its disassembly. Indeed, the level of l-CaD modification correlates very well in a reciprocal manner with the level of actin stress fibers. Since both cell migration and cell division require dynamic remodeling of actin cytoskeleton that leads to cell shape changes, phosphorylation of CaD may therefore serve as a plausible means to regulate these processes. Thus CaD not only links the smooth muscle contractility and non-muscle motility, but also provides a common mechanism for the regulation of cell migration and cell proliferation.
 ...
PMID:Phosphorylation of caldesmon during smooth muscle contraction and cell migration or proliferation. 1645 76

Caldesmon is an actin-binding protein that is capable of stabilizing actin filaments against actin-severing proteins, inhibiting actomyosin ATPase activity, and inhibiting Arp2/3-mediated actin polymerization in vitro. Caldesmon is a substrate of cdc2 kinase and Erk1/2 MAPK, and phosphorylation by either of these kinases reverses the inhibitory effects of caldesmon. Cdc2-mediated caldesmon phosphorylation and the resulting dissociation of caldesmon from actin filaments are essential for M-phase progression during mitosis. Cells overexpressing the actin-binding carboxyterminal fragment of caldesmon fail to release the fragment completely from actin filaments during mitosis, resulting in a higher frequency of multinucleated cells. PKC-mediated MEK/Erk/caldesmon phosphorylation is an important signaling cascade in the regulation of smooth muscle contraction. Furthermore, PKC activation has been shown to remodel actin stress fibers into F-actin-enriched podosome columns in cultured vascular smooth muscle cells. Podosomes are cytoskeletal adhesion structures associated with the release of metalloproteases and degradation of extracellular matrix during cell invasion. Interestingly, caldesmon is one of the few actin-binding proteins that is associated with podosomes but excluded from focal adhesions. Caldesmon also inhibits the function of gelsolin and Arp2/3 complex that are essential for the formation of podosomes. Thus, caldesmon appears to be well positioned for playing a modulatory role in the formation of podosomes. Defining the roles of actin filament-stabilizing proteins such as caldesmon and tropomyosin in the formation of podosomes should provide a more complete understanding of molecular systems that regulate the remodeling of the actin cytoskeleton in cell transformation and invasion.
 ...
PMID:Caldesmon phosphorylation in actin cytoskeletal remodeling. 1654 74

The reported studies on the metabolism in chicken hepatocytes in comparison with those of mammals are quite different. Therefore, this study examined the effect of EGF on DNA synthesis along with its related signal cascades in primary cultured chicken hepatocytes. EGF stimulated DNA synthesis in a dose (> or =10 ng/ml)-dependent manner, which correlated with the increase in CDK-2 and CDK-4 expression. The EGF-induced increase in [3H]-thymidine incorporation was blocked by AG 1478 (an EGF receptor tyrosine kinase antagonist), genistein, and herbimycin A (tyrosine kinase inhibitors), suggesting a role in the activation and tyrosine phosphorylation of the EGF receptor. In addition, the EGF-induced stimulation of [3H]-thymidine incorporation was prevented by staurosporine, H-7, or bisindolylmaleimide I (protein kinase C inhibitors), suggesting a role of PKC. In addition, PD 98059 (a MEK inhibitor), SB 203580 (a p38 MAPK inhibitor), and SP 600125 (a JNK inhibitor) blocked the EGF-induced stimulation of [3H]-thymidine incorporation and CDK-2/4 expression. Indeed, EGF increased the translocation of PKC from the cytosol to the membrane fraction, and increased the activation of p44/42 MAPK, p38 MAPK, and JNK. Moreover, EGF increased the CDK-2, CDK-4, cyclin D1, and cyclin E expression levels but decreased the p21 and p27 expression levels. These EGF-induced increases were blocked by an EGF receptor antagonist, tyrosine kinase inhibitors, PKC inhibitors, and MAPKs inhibitors. In conclusion, EGF stimulates DNA synthesis of primary cultured chicken hepatocytes via Ca2+/PKC and the MAPKs signaling pathways.
 ...
PMID:Effect of EGF on [3H]-thymidine incorporation and cell cycle regulatory proteins in primary cultured chicken hepatocytes: Involvement of Ca2+/PKC and MAPKs. 1682 72

Cyclin D1 overexpression is a frequent change in hepatocellular carcinomas (HCCs). Our present study demonstrated that cyclin D1 overexpression with abundant cyclin E, cdk4, cdk2, and p27Kip1 (p27) occurred in neoplastic hepatocytes from the early stage of mouse hepatocarcinogenesis. While cyclin D1 expression was mainly found in the cytoplasm of the tumor cells, it shifted to the nucleus in association with cell proliferation after the animals were subjected to a partial hepatectomy (PH), and then returned once more to the cytoplasm when the cells became quiescent. Inhibition of PI3 kinase (PI3K) by Ly294002 in mouse HCC cells in vitro suppressed the nuclear shift of cyclin D1 as well as cell proliferation, while PI3K activation by PTEN suppression failed to induce nuclear shift of cyclin D1, suggesting that PI3K activation is essential but not sufficient for the cyclin D1 nuclear shift. While MEK-ERK1/2 inhibition by PD98059 and mTOR inhibition by rapamycin affected the cyclin D1 nuclear shift and cell proliferation to a lesser extent, both these inhibitors reduced cyclin D1 levels. Finally, although p27, cdk4 and calmodulin (CaM) were detected in the cyclin D1 immunoprecipitates from both quiescent and proliferating HCC cells, Hsc70 and SSeCKS were detected only in the immunoprecipitate from quiescent cells, and p21Waf1/Cip1 (p21) was detected only in that from proliferating cells, suggesting that the cyclin D1 complex is different in quiescent and proliferating cells. These observations indicate that the nuclear/cytoplasmic localization of cyclin D1 plays an important role in the proliferation/quiescence of neoplastic hepatocytes.
 ...
PMID:Neoplastic hepatocyte growth associated with cyclin D1 redistribution from the cytoplasm to the nucleus in mouse hepatocarcinogenesis. 1701 36

In matured rat oocytes, spontaneous activation from the metaphase-II (MII) stage occurred after collection from the oviducts. It is well known that the mitogen-activated protein kinase (MAPK) pathway and p34(cdc2) kinase play an important role in the arrest at MII in other species. However, there is no information about the difference in these factors among strains of rats. In the present study, in spontaneously activated oocytes from the Wistar rat, the Mos protein level and the activity of MAPK kinase (MEK)/MAPK were decreased at 120 min (13.8, 25.7, and 19.3, respectively, P<0.05), whereas Sprague-Dawley (SD) oocytes, which were not spontaneously activated, had a high level of Mos protein and MEK/MAPK activity (75.9, 76.2, and 87.9, respectively, P<0.05). Phosphorylation of MAPK in the SD oocytes was significantly suppressed by MEK inhibitor, U0126 at 60 min; this treatment decreased p34(cdc2) kinase activity via cyclin B1 degradation in a time-dependent manner. The treatment with proteasome inhibitor, MG132 or Ca2+-chelator, BAPTA-AM, overcame the spontaneous degradation of both Mos and cyclin B1 in a dose-dependent manner in Wistar oocytes. More than 90% of Wistar oocytes treated with BAPTA-AM were arrested at MII until 120 min. In conclusion, SD oocytes carrying Mos/MEK/MAPK, maintained a high activity of p34(cdc2) kinase by stabilizing cyclin B1, thus involved in their meiotic arrest. In contrast, Wistar oocytes had a relatively low cytostatic factor activity; rapid decrease of Mos/MEK/MAPK failed to stabilize both cyclin B1 and Mos, and these oocytes were likely to spontaneously activate.
 ...
PMID:Involvement of Ca2+-dependent proteasome in the degradation of both cyclin B1 and Mos during spontaneous activation of matured rat oocytes. 1702 76

The effect of growth factors on the cell cycle progression, except G1/S transition, is poorly understood. Herein, we examined the effect of hepatocyte growth factor (HGF) treated at S phase on the cell cycle progression of HeLa cells. Interestingly, the treatment resulted in G2 delay, evidenced by flow cytometric and mitotic index analyses. The delay corresponded with the delay of degradation of cyclin A and cyclin B, and the delay of decrease of Cdk1/cyclin B and Cdk2/cyclin A kinase activities. As for the signaling responsible, sustained activation of ERK, but neither of p38MAPK nor of JNK, was observed after HGF treatment at S phase. Furthermore, U0126, an inhibitor of MEK1, and DN-MEK partially abrogated the G2 delay, indicating that activation of MEK-ERK pathway is involved. Taken together, HGF treatment of HeLa cells at S phase induces G2 delay partially through sustained activation of ERK signaling.
 ...
PMID:Hepatocyte growth factor at S phase induces G2 delay through sustained ERK activation. 1734 75

A MAPKK-like mitotic kinase, TOPK, implies the formation of mitotic spindles and spindle midzone and accomplishing cytokinesis, however, its underlying mechanism remains unclear. A microtubule bundling protein, PRC1, plays a pivotal role in the formation of mitotic spindles and spindle midzone. Because of their functional resemblance, we attempted to clarify the links between these two molecules. TOPK supported mitotic advance via the cdk1/cyclin B1-dependent phosphorylation of PRC1. TOPK induced the phosphorylation of PRC1 at T481 in vivo, however, TOPK did not phosphorylate PRC1 in vitro. TOPK induced the phosphorylation of PRC1 at T481 only when the cdk1/cyclin B1 existed simultaneously in vitro. Both the enzymatic activity of TOPK and association competence of TOPK with PRC1 were mandatory for this phosphorylation. TOPK binds to cdk1/cyclin B1, microtubules and PRC1 via its unique region near the C terminus. TOPK co-localized closely with cdk1 throughout the cell cycle in vivo. Collectively, these data indicate that TOPK, which makes a kinase-substrate complex with cdk1/cyclin B1 and PRC1 on microtubules during mitosis, enhances the cdk1/cyclin B1-dependent phosphorylation of PRC1 and thereby strongly promotes cytokinesis.
 ...
PMID:A mitotic kinase TOPK enhances Cdk1/cyclin B1-dependent phosphorylation of PRC1 and promotes cytokinesis. 1751 44

In mammals, matured oocytes are arrested at the MII stage until fertilization, which is regulated by cytostaticfactor (CSF) activity. Maturation-promoting factor (MPF) and the mitogen-activated protein kinase (MAPK) pathway are known as candidates for CSF. Despite of the results that nuclear and perinuclear materials were dispensable for activation of MPF and MAPK in other species, our previous study in rats demonstrated that MPF activity was rapidly decreased after enucleation. We showed here for the first time that nuclear and perinuclear materials were indispensable for CSF activity in matured rat oocytes. In both cytoplasm-removed and enucleated oocytes, high activity of p34(cdc2) kinase was observed immediately after manipulation, but the activity of enucleated oocytes was dramatically reduced within 1 h. Cyclin B level was also decreased, corresponding with inactivation of p34(cdc2) kinase. In enucleated oocytes, the Mos level was dramatically decreased, and both MEK and MAPK dephosphorylation were also induced. A combined treatment with a proteasome inhibitor, MG132, and a protein phosphatase inhibitor, okadaic acid, dramatically improved both levels of p-MAPK and cyclin B in these enucleated oocytes. These data suggest that nuclear and perinuclear materials of matured rat oocytes suppress proteasome and protein phosphatase activation, which is indispensable for stability of CSF.
 ...
PMID:Effect of enucleation on inactivation of cytostatic factor activity in matured rat oocytes. 1757 58


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>