Two distinct steps of Bak regulation during apoptotic stress signaling: different roles of MEKK1 and JNK1

Stress-activated protein (SAP) kinases and the mitochondrial pro-apoptotic Bcl-2 protein Bak are important regulators of apoptosis. Reduced expression of Bak increases cellular resistance to the anticancer agent cisplatin, and we report here that mouse embryo fibroblasts deficient in the SAP kinase jnk1 are highly resistant to apoptosis induced by cisplatin. When human melanoma cells were treated with cisplatin, Bak function was found to be regulated in two distinct steps by two SAP kinases, MEKK1 and JNK1. The first of these steps involves MEKK1-controlled conformational activation of Bak. The second step leads to formation of 80-170 kDa Bak complexes correlating with apoptosis, and is controlled by JNK1. Inhibition of MEKK1 blocked the initial Bak conformational activation but did not block JNK1 activation, and deficiency in, or inhibition of, JNK1 did not prevent conformational activation of Bak. Furthermore, inducible expression of a constitutively active form of MEKK1 led to Bak conformational activation, but not to 80-170 kDa complexes. Consequently, apoptosis was delayed unless JNK was exogenously stimulated, indicating that Bak conformational activation is not necessarily an apoptotic marker. The two-step regulation of Bak revealed here may be important for tight control of mitochondrial factor release and apoptosis.     

Using an evolutionary algorithm to determine the parameters of a biologically inspired model of head direction cells

A biologically inspired model of head direction cells is presented and tested on a small mobile robot. Head direction cells (discovered in the brain of rats in 1984) encode the head orientation of their host irrespective of the host’s location in the environment. The head direction system thus acts as a biological compass (though not a magnetic one) for its host. Head direction cells are influenced in different ways by idiothetic (host-centred) and allothetic (not host-centred) cues. The model presented here uses the visual, vestibular and kinesthetic inputs that are simulated by robot sensors. Real robot-sensor data has been used in order to train the model’s artificial neural network connections. The main contribution of this paper lies in the use of an evolutionary algorithm in order to determine the values of parameters that determine the behaviour of the model. More importantly, the objective function of the evolutionary strategy used takes into consideration quantitative biological observations reported in the literature.     

Clinical significance of FAK expression in human neoplasia

Focal Adhesion Kinase is a 119-121 kDa nonreceptor protein kinase widely expressed in various tissues and cell types. Several studies showed that FAK plays an important role in integrin signaling. Once activated by integrin and non-integrin stimuli, it binds and activates several other molecules, such as Src, p130Cas, Grb2, PI3K and paxillin, thus promoting signaling transduction. In normal cells FAK activity is under constant regulation by mechanisms such as gene amplification, alternative splicing and action of phosphatases. On the contrary, in vitro studies showed that in transformed cells unopposed FAK signaling promoted cancer cells' malignant characteristics. FAK was held responsible for cancer cells' uninhibited proliferation, protection from apoptosis, invasion, migration, adhesion and spreading, as well as tumor angiogenesis. Several in vivo studies supported the above observations and further correlated FAK expression with various clinicopathological parameters of several types of human malignancies. The purpose of this article is a comprehensive review of the existing data on FAK expression and signaling and their clinical significance in human malignancy.     

Recovery of active ribosomal complexes from cellulose nitrate membranes

The ternary Ac-[3H]Phe-tRNA-poly(U)-ribosome complex (complex C) [D. L. Kalpaxis, D.A. Theocharis, and C. Coutsogeorgopoulos (1986) Eur. J. Biochem. 154, 267-271] was used in model experiments aiming at the purification of this complex via adsorption on cellulose nitrate membranes and then desorbing the complex back into solution. The desorption was carried out at pH 7.2 in the presence of the nonionic detergent Zwittergent (ZW). The activity status of complex C was assessed with the aid of the puromycin reaction which characterizes ribosomal peptidyltransferase as part of complex C. The optimal conditions for desorbing complex C were 5 degrees C and a buffered solution containing 0.1% ZW. The kinetic constants of peptidyltransferase in the adsorbed state were kcat = 2.0 min-1, Ks = 0.4 mM. In the desorbed state, in solution, kcat = 3.4 min-1 and Ks = 0.3 mM. The method promises to be suitable for the rapid purification of ribosomal complexes containing mRNA and aminoacyl-tRNA.     

The role of heparins and nano-heparins as therapeutic tool in breast cancer

Glycosaminoglycans are integral part of the dynamic extracellular matrix (ECM) network that control crucial biochemical and biomechanical signals required for tissue morphogenesis, differentiation, homeostasis and cancer development. Breast cancer cells communicate with stromal ones to modulate ECM mainly through release of soluble effectors during cancer progression. The intracellular cross-talk between cell surface receptors and estrogen receptors is important for the regulation of breast cancer cell properties and production of ECM molecules. In turn, reorganized ECM-cell surface interface modulates signaling cascades, which regulate almost all aspects of breast cell behavior. Heparan sulfate chains present on cell surface and matrix proteoglycans are involved in regulation of breast cancer functions since they are capable of binding numerous matrix molecules, growth factors and inflammatory mediators thus modulating their signaling. In addition to its anticoagulant activity, there is accumulating evidence highlighting various anticancer activities of heparin and nano-heparin derivatives in numerous types of cancer. Importantly, heparin derivatives significantly reduce breast cancer cell proliferation and metastasis in vitro and in vivo models as well as regulates the expression profile of major ECM macromolecules, providing strong evidence for therapeutic targeting. Nano-formulations of the glycosaminoglycan heparin are possibly novel tools for targeting tumor microenvironment. In this review, the role of heparan sulfate/heparin and its nano-formulations in breast cancer biology are presented and discussed in terms of future pharmacological targeting.     

A comparison of root architecture and shoot morphology between naturally regenerated and container-grown seedlings of Quercus ilex

We explored the different mechanisms developed by naturally regenerated seedlings of Quercus ilex L. (Holm oak) under Mediterranean conditions compared to container-seedlings commonly used in plantations. We examined the differences in root architecture (including topology and morphology) and shoot parameters. The results showed that there are many differences in the architecture of the root system as well as in the shoot morphology between the two types of seedlings. The naturally regenerated seedlings were smaller with regard to most of the shoot and root parameters, but they developed a longer taproot, only first order lateral roots, and presented a more herringbone-like root system compared to the container seedlings. Conversely, all types of container seedlings, were larger and had a more extended root system with many orders of lateral roots, while their taproot length was restricted within the container’s depth. The quotient log (α)/ log (μ) for all seedlings, showed a tendency to decrease with plant size. A strict herringbone root system with an elongated taproot may be the optimal root architecture for Quercus ilex L. seedlings in order to survive under Mediterranean conditions.     

The neuroprotective role of l-cysteine towards the effects of short-term exposure to lanthanum on the adult rat brain antioxidant status and the activities of acetylcholinesterase, (Na+,K+)- and Mg2+-ATPase

Lanthanum (La) is a rare earth element that is widely used for industrial, medical and agricultural purposes. Its neurotoxic effects are linked to its physical and chemical properties and its interaction with certain trace elements and membrane-bound enzymes. The aim of this study was to investigate the effects of short-term La-administration (as LaCl₃, 53 mg/kg) on the adult rat whole brain total antioxidant status (TAS) and the activities of acetylcholinesterase (AChE), Na⁺,K⁺-ATPase and Mg²⁺-ATPase, as well as the potential effect of the co-administration of the antioxidant l-cysteine (Cys, 7 mg/kg) on the above parameters. Twenty-eight male Wistar rats were divided into four groups: A (saline-treated control), B (La), C (Cys),and D (La and Cys). All rats were treated once daily with intraperitoneal injections of the tested compounds, for 1-week. Rats were sacrificed by decapitation and the above mentioned parameters were measured spectrophotometrically. Rats treated with La exhibited a significant reduction in brain TAS (−36%, P < 0.001, BvsA), that was partially limited by the co-administration of Cys (−13%, P < 0.01, DvsA), while Cys (group C) had no effect on TAS. The rat brain AChE activity was found significantly increased by both La (+23%, P < 0.001, BvsA) and Cys (+59%, P < 0.001, CvsA), while it was adjusted to control levels by the co-administration of La and Cys. The activity of rat brain Na⁺,K⁺-ATPase was significantly decreased by La-administration (−28%, P < 0.001, BvsA), while Cys supplementation could not reverse this decrease. The activity of Mg²⁺-ATPase exhibited a slight but statistically significant reduction due to La (−8%, P < 0.01, BvsA), that was further reduced by Cys co-administration (−25%, P < 0.001, DvsA). The above findings suggest that La short-term in vivo administration causes a statistically significant decrease in the rat brain TAS and an increase in AChE activity. Both effects can be, partially or totally, reversed into control levels by Cys co-administration, which could thus be considered for future applications as a neuroprotective agent against chronic exposure to La. The activities of Na⁺,K⁺- and Mg²⁺-ATPase that were inhibited by La, could not be reversed by Cys co-administration. A role for the already reported concentration-dependent interaction of La with Ca-binding sites (such as Ca²⁺-ATPase) might be considered for certain of the above phenomena.