In clinic, we examined the expression of protein kinase C (PKC)‐α and Dicer in the samples of bladder cancer patients, and found that the two proteins have a line correlation. Our study confirmed this correlation existing by clearing the decreasing expression of Dicer after the PKC‐α knockdown. Treatment of bladder cancer cell lines (T24, 5637) with the PKC‐α or Dicer knockdown and the PKC inhibitors (Calphostin C and Gö 6976) can promote the apoptosis. Inhibition of PKC can increase the activities of caspase‐3 and PARP, however, decrease the expression of Dicer. And knockdown of the PKC‐α or Dicer can also activate the caspase‐3 or the PARP. Considering the reduction of PKC‐α can induce the Dicer down‐regulation, we make the conclusion that the reduction of PKC‐α can promote the apoptosis via the down‐regulation of Dicer in bladder cancer. 相似文献
Diacylglycerol kinase (DGK) terminates diacylglycerol (DAG) signaling by phosphorylating DAG to produce phosphatidic acid, which also has signaling properties. Thus, precise control of DGK activity is essential for proper signal transduction. We demonstrated previously that a peptide corresponding to the myristoylated alanine-rich C kinase substrate (MARCKS) phosphorylation site domain (PSD) in DGK zeta was phosphorylated in vitro by an active fragment of protein kinase C (PKC). In the present study, we tested full-length DGK zeta and found that PKC alpha phosphorylated DGK zeta on serines within the MARCKS PSD in vitro and in vivo. DGK zeta also coimmunoprecipitated with PKC alpha, suggesting that they reside in a regulated signaling complex. We then tested whether phosphorylation affected DAG kinase activity. We found that a mutant (DGK zeta S/D) in which serines within the MARCKS PSD were altered to aspartates (to mimic phosphorylation) had lower activity compared with wild-type DGK zeta or a control mutant (DGK zeta S/N) in which the same serines were changed to asparagines. Furthermore, activation of PKC alpha by phorbol 12-myristate 13-acetate inhibited the activity of wild-type DGK zeta, but not DGK zeta S/D, in human embryonic kidney 293 cells. These results suggest that by phosphorylating the MARCKS PSD, PKC alpha attenuates DGK zeta activity. Supporting this, we found that cells expressing DGK zeta S/D had higher DAG levels and grew more rapidly compared with cells expressing DGK zeta S/N that could not be phosphorylated. Taken together, these results indicate that PKC alpha phosphorylates DGK zeta in cells, and this phosphorylation inhibits its kinase activity to remove cellular DAG, thereby affecting cell growth. 相似文献
Astrocytic tumors are the most common form of primary brain tumor. Astrocytic tumor cells infiltrate the surrounding CNS tissue, allowing them to evade removal upon surgical resection of the primary tumor. Dynamic changes to the actin cytoskeleton are crucial to cancer cell invasion, but the specific mechanisms that underlie the particularly invasive phenotype of astrocytic tumor cells are unclear. Protein interacting with C kinase 1 (PICK1) is a PDZ and BAR domain–containing protein that inhibits actin-related protein 2/3 (Arp2/3)-dependent actin polymerization and is involved in regulating the trafficking of a number of cell-surface receptors. Here we report that, in contrast to other cancers, PICK1 expression is down-regulated in grade IV astrocytic tumor cell lines and also in clinical cases of the disease in which grade IV tumors have progressed from lower-grade tumors. Exogenous expression of PICK1 in the grade IV astrocytic cell line U251 reduces their capacity for anchorage-independent growth, two-dimensional migration, and invasion through a three-dimensional matrix, strongly suggesting that low PICK1 expression plays an important role in astrocytic tumorigenesis. We propose that PICK1 negatively regulates neoplastic infiltration of astrocytic tumors and that manipulation of PICK1 is an attractive possibility for therapeutic intervention. 相似文献
PKC comprises a large family of serine/threonine kinases that share a requirement for allosteric activation by lipids. While PKC isoforms have significant homology, functional divergence is evident among subfamilies and between individual PKC isoforms within a subfamily. Here, we highlight these differences by comparing the regulation and function of representative PKC isoforms from the conventional (PKCα) and novel (PKCδ) subfamilies. We discuss how unique structural features of PKCα and PKCδ underlie differences in activation and highlight the similar, divergent, and even opposing biological functions of these kinases. We also consider how PKCα and PKCδ can contribute to pathophysiological conditions and discuss challenges to targeting these kinases therapeutically. 相似文献
c-Jun N-terminal kinases (JNKs) are important regulators of cell proliferation and apoptosis that have been implicated in
tumorigenesis. We investigated the role of JNKs in apoptotic responses in Ishikawa and HEC-50 cells, models of type I and
type II endometrial cancer, respectively. Etoposide treatment or UV irradiation resulted in sustained activation of JNK, correlating
with the induction of apoptosis. Inhibition of JNK, or MAP kinase kinase 4 (MKK4), selectively suppressed apoptotic responses
in both Ishikawa and HEC-50 cells. Knockdown of protein kinase C δ (PKCδ) also attenuated apoptosis in endometrial cancer
cells and inhibited the sustained, UV-mediated JNK activation in HEC-50, but not Ishikawa cells. Etoposide-induced JNK phosphorylation
was unaffected by PKCδ knockdown, implying that JNK can regulate apoptosis by PKCδ-dependent and independent pathways, according
to stimulus and cell type. Thus, expression and activity of JNK and PKCδ in endometrial cancer cells modulate apoptosis and
sensitivity to chemotherapeutic agents and may function as tumor suppressors in the endometrium.
Elaine M. Reno and James M. Haughian are first authors. 相似文献
About 70% of human breast cancers express and are dependent for growth on estrogen receptor α (ERα), and therefore are sensitive to antiestrogen therapies. However, progression to an advanced, more aggressive phenotype is associated with acquisition of resistance to antiestrogens and/or invasive potential. In this study, we highlight the role of the serine/threonine‐protein kinase D1 (PKD1) in ERα‐positive breast cancers. Growth of ERα‐positive MCF‐7 and MDA‐MB‐415 human breast cancer cells was assayed in adherent or anchorage‐independent conditions in cells overexpressing or depleted for PKD1. PKD1 induces cell growth through both an ERα‐dependent manner, by increasing ERα expression and cell sensitivity to 17β‐estradiol, and an ERα‐independent manner, by reducing cell dependence to estrogens and conferring partial resistance to antiestrogen ICI 182,780. PKD1 knockdown in MDA‐MB‐415 cells strongly reduced estrogen‐dependent and independent invasion. Quantification of PKD1 mRNA levels in 38 cancerous and non‐cancerous breast cell lines and in 152 ERα‐positive breast tumours from patients treated with adjuvant tamoxifen showed an association between PKD1 and ERα expression in 76.3% (29/38) of the breast cell lines tested and a strong correlation between PKD1 expression and invasiveness (P < 0.0001). In tamoxifen‐treated patients, tumours with high PKD1 mRNA levels (n = 77, 50.66%) were significantly associated with less metastasis‐free survival than tumours with low PKD1 mRNA expression (n = 75, 49.34%; P = 0.031). Moreover, PKD1 mRNA levels are strongly positively associated with EGFR and vimentin levels (P < 0.0000001). Thus, our study defines PKD1 as a novel attractive prognostic factor and a potential therapeutic target in breast cancer. 相似文献
Protein kinase C alpha (PKC alpha) is a serine/threonine kinase and a member of the conventional (classical) PKCs (cPKCs), which have four conserved (C1 to C4) regions. This ubiquitously expressed PKC isotype is activated in response to many different kinds of stimuli and translocates from cytosol to the specialized cellular compartments (nucleus, focal adhesion, caveolae, etc.) where it is presumed to work. Therefore, PKC alpha has been implicated in a variety of cellular functions including proliferation, apoptosis, differentiation, motility, and inflammation. However, the responses induced by activation or overexpression of PKC alpha vary depending on the types, and sometimes conditions, of cells. For example, in some types of cells, PKC alpha is implicated in cell growth. In contrast, it may play a role in cell cycle arrest and differentiation in other types of cells. Therefore, alterations of cell responses induced by PKC alpha are not an intrinsic property of this isoform. The responses are modulated by dynamic interactions with cell-type specific factors: substrates, modulators and anchoring proteins. 相似文献
The WWC1 gene has been genetically associated with human episodic memory performance, and its product KIdney/BRAin protein (KIBRA) has been shown to interact with the atypical protein kinase protein kinase M ζ (PKMζ). Although recently challenged, PKMζ remains a candidate postsynaptic regulator of memory maintenance. Here, we show that PKMζ is subject to rapid proteasomal degradation and that KIBRA is both necessary and sufficient to counteract this process, thus stabilizing the kinase and maintaining its function for a prolonged time. We define the binding sequence on KIBRA, a short amino acid motif near the C‐terminus. Both hippocampal knock‐down of KIBRA in rats and KIBRA knock‐out in mice result in decreased learning and memory performance in spatial memory tasks supporting the notion that KIBRA is a player in episodic memory. Interestingly, decreased memory performance is accompanied by decreased PKMζ protein levels. We speculate that the stabilization of synaptic PKMζ protein levels by KIBRA may be one mechanism by which KIBRA acts in memory maintenance.
Integrins alpha v beta 3 and alpha v beta 5 both mediate cell adhesion to vitronectin yet trigger different postligand binding events. Integrin alpha v beta 3 is able to induce cell spreading, migration, angiogenesis, and tumor metastasis without additional stimulators, whereas alpha v beta 5 requires exogenous activation of protein kinase C (PKC) to mediate these processes. To investigate this difference, the ability of beta 3 or beta 5 to induce colocalization of intracellular proteins was assessed by immunofluorescence in hamster CS-1 melanoma cells. We found that alpha v beta 5 induced colocalization of talin, alpha-actinin, tensin, and actin very weakly relative to alpha v beta 3. alpha v beta 5 was able to efficiently induce colocalization of focal adhesion kinase (FAK); however, it was unable to increase phosphorylation of FAK on tyrosine. Activation of PKC by adding phorbol ester to alpha v beta 5-expressing cells induced spreading, increased colocalization of alpha-actinin, tensin, vinculin, p130cas and actin, and triggered tyrosine phosphorylation of FAK. Unexpectedly, talin colocalization remained low even after activation of PKC. Treatment of cells with the PKC inhibitor calphostin C inhibited spreading and the colocalization of talin, alpha-actinin, tensin, and actin for both alpha v beta 3 and alpha v beta 5. We conclude that PKC regulates localization of cytoskeletal proteins and phosphorylation of FAK induced by alpha v beta 5. Our results also show that FAK can be localized independent of its phosphorylation and that cells can spread and induce localization of other focal adhesion proteins in the absence of detectable talin. 相似文献
We have demonstrated that IFN-γ, a potent peptide mediator in inflammatory responses, operates via the protein kinase C dependent transduction pathway in the induction of class II MHC antigens on rat microvascular endothelial cells. Stimulators of protein kinase C, like PMA, replaced IFN-γ in the induction of MHC class II on endothelial cells in a dose-dependent manner. Selective enzyme inhibitors of protein kinase C, H-7 as well as sphingosine down-regulated the IFN-γ induced class II expression in a dose-dependent manner. Addition of cAMP or cGMP in the culture, had no effect on the class II expression on the endothelial cells. Transient rise of cytosolic Ca2+ by calcium ionophore A23187, or a calmodulin antagonist W-7, had no effect on the IFN-γ induced class II expression. 相似文献
We studied the effects of protein kinase C (PKC) activation onendothelial cell surface expression and function of the proteolytically activated thrombin receptor 1 (PAR-1). Cell surface PAR-1 expression was assessed by immunofluorescence (using anti-PAR-1 monoclonal antibody), and receptor activation was assessed by measuring increases in cytosolic Ca2+ concentration inhuman dermal microvascular endothelial cells (HMEC) exposed to-thrombin or phorbol ester,12-O-tetradecanoylphorbol-13-acetate (TPA).Immunofluorescence showed that thrombin and TPA reduced the cellsurface expression of PAR-1. Prior exposure of HMEC to thrombin for 5 min desensitized the cells to thrombin, indicating homologous PAR-1desensitization. In contrast, prior activation of PKC with TPA produceddesensitization to thrombin and histamine, indicatingheterologous PAR-1 desensitization. Treatment of cells withstaurosporine, a PKC inhibitor, fully prevented heterologous desensitization, whereas thrombin-induced homologous desensitization persisted. Depletion of PKC isozymes(PKCI andPKCII) by transducing cellswith antisense cDNA of PKCIprevented the TPA-induced decrease in cell surface PAR-1 expression andrestored ~60% of the cytosolic Ca2+ signal in response tothrombin. In contrast, depletion of PKC isozymes did not affect theloss of cell surface PAR-1 and induction of homologous PAR-1desensitization by thrombin. Therefore, homologous PAR-1desensitization by thrombin occurs independently of PKC isozymes,whereas the PKC-activated pathway is important in signaling heterologous PAR-1 desensitization in endothelial cells. 相似文献