Molecular and cellular pharmacology最新文献

Homeodomain-interacting protein kinases including HIPK1, HIPK2 and HIPK3 are serine/threonine kinases that form a family of highly conserved kinases. HIPKs are involved in diverse cellular functions including regulation cell death, survival, proliferation and differentiation. Here we report the characterization of a human HIPK4 that we identified in a proteomic screen during our efforts to unravel novel markers linked to cell death and survival. Human HIPK4 protein is composed of 616 residues with predicted molecular mass of 69.425 kDa and harbors a serine/threonine protein kinase catalytic domain at its N-terminal end. In the in vitro kinase assay, HIPK4 exhibits kinase activity and mutation of the conserved lysine 40 or aspartic acid 136 residue in its catalytic domain inactivates its kinase function. Human HIPK4 harbors multiple putative serine/threonine- and tyrosine-specific phsophorylation sites and also contains four high probability sumoylation sites, findings that suggest its function to be modulated by post-translational modifications. HIPK4 has been so named in the database because of its sequence homology to HIPK1, 2 and 3 predominantly within its catalytic domain. However, HIPK4 is smaller in size than the known HIPKs and has additional distinct features suggesting it to be a unique member of the HIPK family. Further functional characterization of HIPK4 is needed and will prove valuable to ascertain whether it performs distinct functions or share overlapping functions with other HIPKs.

Fibroblast growth factor 2 (basic FGF or FGF2) has been shown to affect growth and differentiation in some tissues and to be required for cardiac hypertrophy in vivo. FGF2 has been shown in vitro to signal through the mitogen-activated protein kinase (MAPK) to affect cell survival and growth. To ascertain the role of FGF2 in cardiac hypertrophy, wildtype, Fgf2 knockout, non-transgenic, and FGF2 transgenic mice were treated with isoproterenol or saline via subcutaneous mini-osmotic pump implants to induce a hypertrophic response to β-adrenergic stimulation. Fgf2 knockout hearts are protected from isoproterenol-induced cardiac hypertrophy; whereas, FGF2 transgenic hearts show exacerbated cardiac hypertrophy as assessed by heart weight-to-body weight ratios and myocyte cross-sectional area. Echocardiography reveals significantly decreased fractional shortening in isoproterenol-treated FGF2 transgenic mice but not in Fgf2 knockout mice suggesting that FGF2 mediates the maladaptive cardiac dysfunction seen in cardiac hypertrophy induced by isoproterenol. Western blot analysis also reveals alterations in MAPK signaling in Fgf2 knockout and FGF2 transgenic hearts subjected to isoproterenol treatment, suggesting that this cascade mediates FGF2's pro-hypertrophic effect. Pharmacologic inhibition of extracellular signal-regulated kinase (ERK) signaling results in an attenuated hypertrophic response in isoproterenol-treated FGF2 transgenic mice, but this response is not seen with p38 mitogen-activated protein kinase (p38) pathway inhibition, suggesting that FGF2 activation of ERK but not p38 is necessary for FGF2's role in the mediation of cardiac hypertrophy.

G protein-coupled receptors (GPRs) constitute one of the largest families of membrane proteins encoded by the human genome. Upon binding to various ligands, these seven-transmembrane receptors play an essential role in many physiological processes, including neurotransmission, immunity, inflammation, regulation of mood and behavior. In view of their important functions, aberrant expression and activity of GPRs have been implicated in a wide spectrum of diseases, including tumorigenesis. GPR87, a cell surface GPR related to the LPA receptor family, is overexpressed in diverse carcinomas and plays an essential role in tumor cell survival. In our recent work, we uncovered that GPR87 expression is regulated by the tumor suppressor p53 and by DNA damage in a p53-dependent manner. Moreover, we found that a lack of GPR87 triggers an increase in p53, concomitant with a decrease in Akt, which results in the sensitization of tumor cells to DNA damage-induced apoptosis and growth suppression. Altogether, we uncovered an essential function for GPR87 in p53-dependent cell survival in response to stress signals. Due to their unique structure, localization and ligand binding ability, GPRs have been extensively used for drug development and are the most common targets of commercial drugs. Although studies are required to determine GPR87 natural ligand(s) and signaling pathways, GPR87 is undoubtedly a very promising novel target for cancer prevention and treatment.

Tremendous progress has been made during the last few years in identification of novel tumor-associated microRNAs and experimental validation of their cancer relevant gene targets. Indeed, these small non-coding RNAs are now known to modulate many biological pathways related to cancer progression, metastasis and therapy-resistance. Therefore, modulating miRNA functions may provide novel therapeutic opportunities for cancer treatment. This article reviews recent literature on the role of miRNAs in cancer with an emphasis on their potential as cancer therapeutics.

Ataxia Telangiectasia (AT) cells exhibit suboptimal activation of radiation-induced cell cycle checkpoints despite having a wild type p53 genotype. Reducing or eliminating this delay could restore p53 function and reinstate normal cellular response to genotoxic stress. Here we show that the levels of Nuclephosmin (NPM), NPM phosphorylated at Serine 125, p53, p53 phosphorylated at Serine 15 and Serine 392 and the levels of Nucleolin (NCL) are high in AT fibroblasts compared to normal cells. Transfection of a functional ATM into AT fibroblasts reduced p53, phospo-p53, phospho-NPM and NCL levels to wild type fibroblasts levels. Our data indicate that ATM regulates phospho-NPM and NCL indirectly through the Protein Phosphatase 1 (PP1). Both, NPM and NCL interact with p53 and hinder its phosphorylation at Serine 15 in response to bleomycin. Moreover, NPM and NCL are phosphorylated by several of the same kinases targeting p53 and could potentially compete with p53 for phosphorylation in AT cells. In addition, our data indicate that down regulation of NCL and to a lesser extent NPM increase the number of AT cells arrested in G2/M in response to bleomycin. Together this data indicate that the lack of PP1 activation in AT cells result in increased NPM and NCL protein levels which prevents p53 phosphorylation in response to bleomycin and contributes to a defective G2/M checkpoint.

Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used medications for the treatment of both acute and chronic pain. Selective cyclooxygenase-2 (COX-2) inhibitors, such as celecoxib (Celebrex(®)), rofecoxib (Vioxx(®)), and diclofenac, have been among the most widely prescribed NSAIDs because they prevent the generation of prostaglandins involved in inflammation and pain, but avoid some of the gastrointestinal complications associated with less selective COX-1/COX-2 inhibitors. In 2004, rofecoxib (Vioxx(®)) was voluntarily withdrawn from the market because of adverse cardiovascular side effects. This led to an explosion of research into the cardiovascular effects of the 'coxibs', which revealed differential cardiovascular risk profiles among the members of this drug class. The differential risk profiles may relate to the tendency of some of the drugs to elevate blood pressure (BP). An important component of BP regulation is dependent on the contractile state of vascular smooth muscle cells (VSMCs), which is controlled to a large extent by the activities of KCNQ (Kv7 family) potassium channels and L-type calcium channels. Our recently published data indicate that celecoxib, but not rofecoxib or diclofenac, at therapeutically relevant concentrations, acts as a Kv7 potassium channel activator and a calcium channel blocker, causing relaxation of VSMCs and decreasing vascular tone. These vasorelaxant ion channel effects may account for the differential cardiovascular risk profiles among the different COX-2 inhibitors. We further speculate that these properties may be exploited for therapeutic benefit in the treatment of cardiovascular diseases or other medical conditions.

Both cell culture and clinical studies show that the androgen receptor (AR) plays a key role in the growth and survival of castration-resistant prostate cancer (CRPC), a lethal form of the disease in the clinic, suggesting that AR remains to be a major target for the treatment of CRPC. Taxol chemotherapy is one of the few therapeutic options for patients with CRPC albeit the underlying mechanism is not fully understood. We have demonstrated recently that Taxol (paclitaxel and its semisynthetic analogue docetaxel) treatment of 22Rv1, a CRPC cell line that expresses the tumor suppressor gene PTEN, inhibits AR transcriptional activity. In contrast, paclitaxel failed to inhibit AR activity in the PTEN-deficient C4-2 CRPC cells. Docetaxel treatment of 22Rv1 xenografts in mice induced mitotic arrest and a decrease in expression of the AR target gene prostate-specific antigen (PSA) mainly in tumor cells adjacent to vascular vessels. Further studies demonstrated that Taxol inhibition of the AR is mediated, at least in part, by Taxol-induced nuclear accumulation of FOXO1, a key downstream effector protein of PTEN and increased association of FOXO1 with the AR. These studies suggest that the status of the functional PTEN/FOXO pathway and the drug bioavailability may be the two key determinants for Taxol chemoresistance of CRPC in the clinic.

The biochemistry, physiology and behavior of nearly all organisms are influenced by an inherent circadian (24 hr) clock timing mechanism. For mammals, the linchpin of this biological timing process is located in the suprachiasmatic nuclei (SCN) of the hypothalamus. One key feature of the SCN clock is that it is tightly entrained to lighting cues, thus ensuring that the clock is synchronized to the ever-changing seasonal light cycle. Within the field of circadian biology, there has been intense interest in understanding the intracellular signaling events that drive this process. To this end, our recent studies have revealed a role for an evolutionarily conserved translational control kinase, the mammalian target of rapamycin (mTOR), in the SCN clock entrainment process. Here we provide an overview of mechanisms of inducible mTOR activation in the SCN, and describe the effects of mTOR on clock protein synthesis and behavioral rhythmicity. Given that dysregulation of SCN timing has been associated with an array of clinical conditions (e.g., hypertension, obesity, diabetes, depression), new insights into the molecular mechanisms that regulate clock timing may provide new therapeutic treatments for circadian rhythm-associated disorders.

Doxorubicin (DOX) is a broad spectrum antineoplastic drug widely used in the treatment of several hematogenous and solid human malignancies. Despite its excellent clinical efficacy as a chemotherapeutic agent, its therapeutic usage has been restricted due to its cardiotoxicity. Phosphodiesterase-5 (PDE-5) inhibitors or erectile dysfunction drugs including sildenafil, have been shown to have powerful cardioprotective effect against injuries under a variety of experimental situations including ischemia/reperfusion injury, myocardial infarction and DOX-induced cardiomyopathy. We studied the effect of - tadalafil, a long acting PDE-5 inhibitor in preventing damage in the heart with DOX treatment. Our results showed that tadalafil improved left ventricular function and survival by attenuating DOX-induced apoptosis and cardiac oxidative stress without interfering with the anti-tumor efficacy of DOX in both in vitro and in vivo tumor models. Herein, we present an overview of our study, and consider the potential mechanisms by which tadalafil, at therapeutically relevant concentrations mediate beneficial cardioprotective effects in DOX cardiotoxicity. Based on our current and previously published studies, we propose that the class of PDE-5 inhibitors can represent a novel approach which can be exploited for achieving therapeutic benefit in the treatment of DOX-induced cardiotoxicity in patients.

Breast tumors expressing estrogen receptor alpha (ER) respond well to therapeutic strategies using SERMs (selective estrogen receptor modulators) such as tamoxifen. However, about thirty percent of invasive breast cancers are hormone independent because they lack ER expression due to hypermethylation of ER promoter. Treatment of ER-negative breast cancer cells with demethylating agents and histone deacetylase inhibitors leads to expression of ER mRNA and functional protein. Additionally, growth factor signaling pathways have also been implicated in ER silencing in ER-negative tumor phenotype. Recently, important role of components of ubiquitin-proteasome pathway has been shown in mediating downregulation of ER. In this article, we will review various mechanisms underlying the silencing of ER in ER negative tumor phenotype and discuss diverse strategies to combat it. Ongoing studies may provide the mechanistic insight to design therapeutic strategies directed towards epigenetic and non-epigenetic mechanisms in the prevention or treatment of ER-negative breast cancer.