Aim: To investigate the effect of aldosterone and its antagonists on cell behavior and gene modulation in human endothelial cells.
Food is a requirement of life. Unicellular and multicellular organisms have therefore developed mechanisms to detect, react to and, if necessary, survive the lack of it. In mammals, responses to lack of nutrients in blood are coordinated at the organismal level by hormonal cues. However, individual cells also sense and respond to nutrient deprivation, which occurs under physiological or pathological situations such as fasting, ischemia or solid tumor development. Frequently cells try and survive nutrient deprivation by reducing their energy and carbon requirements and by recycling structural components. However, under certain conditions, the cell reacts to nutrient deprivation by engaging the mitochondrial pathway of apoptosis. Indeed, the metabolic state of the cell can regulate pro- and antiapoptotic Bcl-2 family proteins such as PUMA, Bad, Bim or Mcl-1, thus altering the response to pro-apoptotic stimuli. Severe energetic stress can also kill cells by a form of death with necrotic phenotype. Metabolic pathways are currently receiving enormous attention from cell biologists, due to the fact that tumors have a special metabolism which makes them more susceptible to lack of specific nutrients, particularly glucose and glutamine. For this reason, targeting tumor metabolism opens new therapeutic avenues. We will discuss how nutrient deprivation engages cell death pathways, and how cell metabolism interferes with the apoptotic machinery by regulating apoptotic proteins. We will also re-examine the hypothesis that ATP levels determine whether a cell dies by apoptosis or necrosis. Finally, we will discuss how and why metabolic stress can lead to either cell adaptation and survival or cell death.
Tumour necrosis factor (TNF) is the founding member of a cytokine family with important roles in both, physiology and pathological conditions. The two seemingly opposing cellular responses to stimulation by TNF itself are death and induction of pro-inflammatory signalling. TNF and other TNF superfamily (SF) members signal by crosslinking their cognate receptors. These form part of the TNF receptor SF (TNFRSF). Members of this family have between two and six characteristic cysteine-rich repeats in their extracellular domain. These repeats are crucial for receptor-ligand interaction. Members of the TNFRSF come in three flavours: as type I transmembrane proteins, attached to the plasma membrane by a glycosylphosphatidylinositol (GPI) anchor, or as secreted soluble proteins. The latter receptors act as decoys for their respective ligands. To date 30 members of the TNFRSF are known. Six of them form part of the subfamily of the death receptors. Death receptors are characterised by the presence of an intracellular death domain (DD). Amongst the death receptors there are again at least two subclasses, the ones which recruit the Fas-Associated Death Domain (FADD) and the ones that recruit the TNFR-Associated Death Domain (TRADD) protein. The primary function of FADD-recruiting receptors is to induce apoptosis whilst the primary function of the TRADD recruiters is to activate pro-inflammatory signalling (Fig. 1). However, from a second platform both systems are also capable of triggering the respective other signalling outcome.
Ever since the discovery that the founding member of the Bcl-2 family of proteins contributes to tumour development by inhibiting cell survival rather than encouraging proliferation [1], interest (and controversy) in these functionally diverse homologues has raged. The Bcl-2 family of proteins participate in multiple protein-protein interactions that govern whether a cell dies in response to toxic stress. This review summarises the current knowledge of how a death stimulus culminates in the activation of Bax and Bak, the pivotal effectors of the apoptotic program, and how these critical proteins cause damage to mitochondria and the consequent demise of a cell.
Morphogens, as intercellular signalling proteins, provide a non-cell-autonomous mechanism to impart positional information to cells and govern essential cellular processes such as apoptosis. Individual morphogen pathways utilise diverse strategies to regulate the assembly and activity of the pro-apoptotic multi-protein complexes – namely the apoptosome and the death-inducing signalling complex (DISC). This review aims to highlight the apoptotic regulatory mechanisms utilised by the Hedgehog (HH) morphogen pathway – with particular emphasis on a novel Caspase-9 activating complex and the utilisation of a pro-apoptotic autocrine-signalling loop.
Whether a virus is coded for by RNA, single-stranded DNA or double-stranded DNA (dsDNA), the ultimate goal of the virus is to hijack the host’s biosynthetic machinery to replicate and spread. Like spies fomenting revolt behind enemy lines, viruses have evolved to invade cells and then use stealth and deception to avoid or disrupt the cell’s defences [1]. Cells are not without defences, however, and have evolved a number of ways to detect the presence of viral invaders and prevent their replication. In particular, cells may choose the ‘scorched earth’ policy and kill themselves by activating an apoptotic program to prevent the virus from replicating. Multicellular organisms have evolved to accept a small-scale cellular loss for the greater good, i.e., to prevent the defeat of the entire organism. However, while viruses must evade the cellular apoptosis response in order to replicate and therefore mostly counteract apoptosis, some viruses even manage to subvert this protective response to destroy their hosts at a late stage of infection in order to facilitate release of mature viral particles.
It has long been known that many cell types are dependent on specific cytokines that signal proliferation, regulate differentiation and suppress apoptosis. A detailed picture of the structure of several cytokine receptors has added to our understanding of the molecular mechanism of receptor activation. An explosion of knowledge of apoptosis pathways and the ways in which the Bcl-2 family of proteins function has deepened the understanding of the effector arm of the programmed cell death pathway. The challenge is to uncover the molecular links between these two pathways. In this article, we will try to examine what is known of the intersections between cytokine signalling pathways and apoptosis pathways, with particular reference to receptor signalling by the haematopoietic cytokines Interleukin-3 (IL-3) and Granulocyte-Macrophage-Colony Stimulating Factor (GM-CSF).
Many of the key molecules in cell cycle progression (e.g. pRB, cyclin complexes) and their basic interactions are oncogene or tumor suppressor genes, which are well characterized in the clinical and experimental analysis. However, there are still unknown mechanisms for the cell cycle regulation, which is critical step for the progression of the cancer development. Especially it is not fully understood how the cells move to G1 phase from quiescent G0 phase in the mammalian cells. To find out the new gene networks associated with the two transition of the mammalian cell cycle (G0 to G1 and G1 to S phase), we analyzed the linkages between 39 representative oncogene or tumor suppressor genes, which related to the cell cycle regulation, with gene expression sets obtained from the publicly opened microarray data for mouse embryonic fibroblasts that synchronized by the serum starvation or hydroxyurea treatment. Analyses with a qualitative algorithm based on Bayesian networks that assume a log-linear relationship between genes have applied, and newly found networks were validated. Results highlighted the importance of two master genes, Cdk7 and Cdkna2 for the re-entry to G1 from G0, and suggested a new network connection from Cdk7 to downstream molecules, including the EGF receptor and N-myc. Introduction of a recombinant Cdk7 with retrovirus decreased endogenous EGFR and N-myc protein levels. The results supported the computational prediction of the Cdk7 network. Taken together, these result showed the existence of new regulating pathway from Cdk7 to Egfr and N-myc, suggesting this analytical approach provides an assessment of regulatory networks in complex mammalian cells, and the process of the carcinogenesis.
Altered signal transduction can be considered a hallmark of many solid tumors. In thyroid cancers the receptor tyrosine kinase (rtk) genes NTRK1 (Online Mendelian Inheritance in Man = OMIM *191315, also known as 'TRKA'), RET ('Rearranged during Transfection protooncogene', OMIM *164761) and MET (OMIM *164860) have been reported as activated, rearranged or overexpressed. In many cases, a combination of cytogenetic and molecular techniques allows elucidation of cellular changes that initiate tumor development and progression. While the mechanisms leading to overexpression of the rtk MET gene remain largely unknown, a variety of chromosomal rearrangements of the RET or NTKR1 gene could be demonstrated in thyroid cancer. Abnormal expressions in these tumors seem to follow a similar pattern: the rearrangement translocates the 3'- end of the rtk gene including the entire catalytic domain to an expressed gene leading to a chimeric RNA and protein with kinase activity. Our research was prompted by an increasing number of reports describing translocations involving ret and previously unknown translocation partners.We developed a high resolution technique based on fluorescence in situ hybridization (FISH) to allow rapid screening for cytogenetic rearrangements which complements conventional chromosome banding analysis. Our technique applies simultaneous hybridization of numerous probes labeled with different reporter molecules which are distributed along the target chromosome allowing the detection of cytogenetic changes at near megabasepair (Mbp) resolution. Here, we report our results using a probe set specific for human chromosome 10, which is altered in a significant portion of human thyroid cancers (TC's). While rendering accurate information about the cytogenetic location of rearranged elements, our multi-locus, multi-color analysis was developed primarily to overcome limitations of whole chromosome painting (WCP) and chromosome banding techniques for fine mapping of breakpoints in papillary thyroid cancer (PTC).
Mob proteins from distantly related eukaryotic species share very high sequence similarity and they are characteristic of a conserved Mob domain with around 180 amino-acid residues in length.However, the evolutionary relationship of mob family genes has not been extensively investigated.Through a phylogenetic approach, we have conducted a comprehensive evolutionary analysis of the mob gene family.Here we show that over 270 mob family members from protists to animals can be organized in four distinct groups.This classification is strongly supported by the analysis of mob exon-intron structures.Moreover, the conservation and divergence patterns of different groups of Mob proteins have been elucidated.Structural information and the identification of fixed amino acid substitutions provide evidence about the putative significance of specific residues in the structural integrity and/or molecular functions of Mob proteins.Thus, this study reveals the evolutionary history of mob gene family and provides a basis for functional studies of Mob proteins.
