The lipophilicity of phorbol esters as a critical factor in determining the pattern of translocation of protein kinase C delta fused to green fluorescent protein

Our previous study showed differential subcellular localization of protein kinase C (PKC) delta by phorbol esters and related ligands, using a green fluorescent protein-tagged construct in living cells. Here we compared the abilities of a series of symmetrically substituted phorbol 12,13-diesters to translocate PKC delta. In vitro, the derivatives bound to PKC with similar potencies but differed in rate of equilibration. In vivo, the phorbol diesters with short, intermediate, and long chain fatty acids induced distinct patterns of translocation. Phorbol 12,13-dioctanoate and phorbol 12,13-nonanoate, the intermediate derivatives and most potent tumor promoters, showed patterns of translocation typical of phorbol 12-myristate 13-acetate, with plasma membrane and subsequent nuclear membrane translocation. The more hydrophilic compounds (phorbol 12,13-dibutyrate and phorbol 12,13-dihexanoate) induced a patchy distribution in the cytoplasm, more prominent nuclear membrane translocation, and little plasma membrane localization at all concentrations examined (100 nM to 10 microM). The highly lipophilic derivatives, phorbol 12,13-didecanoate and phorbol 12, 13-diundecanoate, at 1 microM caused either plasma membrane translocation only or no translocation at incubation times up to 60 min. Our results indicate that lipophilicity of phorbol esters is a critical factor contributing to differential PKC delta localization and thereby potentially to their different biological activities.     

Losing the desire: selection can promote obligate asexuality

Whilst parthenogenesis has evolved multiple times from sexual invertebrate and vertebrate lineages, the drivers and consequences of the sex-asex transition remain mostly uncertain. A model by Stouthamer et al. recently published in BMC Evolutionary Biology shows a pathway by which obligate asexuality could be selected for following endosymbiont infection.     

The development and reproduction of cybocephalid beetles on various foods

Cybocephalus nigriceps nigriceps (J. Sahlberg),C. micans Reitter,C. aegyptiacus Endrody-Younga, andC. binotatus Grouvelle were able to develop and reproduce while feeding on the California red scale,Aonidiella aurantii (Maskell), or on the Florida red scale,Chrysomphalus aonidum (L.). The ivy scale,Aspidiotus hederae (Vallot), was not suitable as a diet for the reproduction, developmen and survival of any of the 4Cybocephalus species. However, the suitability to the prey as a diet varied among the 4 species, being greatest withC. n. nigriceps and least withC. micans. Pollen ofCarpobrotus, eggs of some moths, and non-armoured scales, as well as various stages of a whitefly, an aphid, and a red spider mite, did not enable development or reproduction ofC. micans.     

Alpha-substituted N-(4-tert-butylbenzyl)-N'-[4-(methylsulfonylamino)benzyl]thiourea analogues as potent and stereospecific TRPV1 antagonists

A series of alpha-substituted N-(4-tert-butylbenzyl)-N'-[4-(methylsulfonylamino)benzyl]thiourea analogues have been investigated as TRPV1 receptor antagonists. alpha-Methyl substituted analogues showed potent and stereospecific antagonism to the action of capsaicin on rat TRPV1 heterologously expressed in Chinese hamster ovary cells. In particular, compounds 14 and 18, which possess the R-configuration, exhibited excellent potencies (respectively, K(i)=41 and 39.2 nM and K(i(ant))=4.5 and 37 nM).     

Geographic distribution and migration pathways of Pistacia – present,past and future

The global distribution of Pistacia is correlated to its adaptability to environmental conditions and mechanisms that had driven the genus to the current unique narrow latitudinal belt in between 10° North and 45° North. The current geostatisitcal distribution maps of the genus are shown and the derived probability maps over a period between 121 Kyr before present and the year 2100 were calculated. The tolerance of Pistacia trees to harsh climate conditions was related to leaf phenology, evergreeness vs deciduousness, which has led to geographic classification of the genus in two corresponding sections that corroborate recent molecular genetic studies. The deciduous trees are more tolerant to extreme climate conditions (?26°C to 46°C) than the evergreen species (?8°C to 41°C), except Pistacia lentiscus, which occurs at a max. temperature of 45°C. The close spatial distribution of the later species and the deciduous ones may have been conducive in further evolution of the genus. Based on the long evolution of Pistacia (approx. 84 Ma), we suggested that the genus may have originated in the boreal forest and its migration pathways might have been evoked in relation to climate change, shifting the species distribution to evolving suitable environmental conditions. The fact that most of the genera in the family of Anacardiaceae and the whole genus Pistacia are dioecious raised questions about plausible relationships between the geographic distribution, environmental conditions and evolution of dioecy. The genus Pistacia was shown to be a good candidate for research about the relationships between environmental conditions, adaptation traits and geographic distribution.     

Minireview: PPARγ as the target of obesogens

The peroxisome proliferator-activated receptor gamma (PPARγ) is a key regulator of adipogenesis and is medically important for its connections to obesity and the treatment of type II diabetes. Activation of this receptor by certain natural or xenobiotic compounds has been shown to stimulate adipogenesis in vitro and in vivo. Obesogens are chemicals that ultimately increase obesity through a variety of potential mechanisms, including activation of PPARγ. The first obesogen for which a definitive mechanism of action has been elucidated is the PPARγ and RXR activator tributyltin; however, not all chemicals that activate PPARγ are adipogenic or correlated with obesity in humans. There are multiple mechanisms through which obesogens can target PPARγ that may not involve direct activation of the receptor. Ligand-independent mechanisms could act through obesogen-mediated post-translational modification of PPARγ which cause receptor de-repression or activation. PPARγ is active in multipotent stem cells committing to the adipocyte fate during fat cell development. By modifying chromatin structure early in development, obesogens have the opportunity to influence the promoter activity of PPARγ, or the ability of PPARγ to bind to its target genes, ultimately biasing the progenitor pool towards the fat lineage. Obesogens that act by directly or indirectly activating PPARγ, by increasing the levels of PPARγ protein, or enhancing its recruitment to promoters of key genes in the adipogenic pathway may ultimately play an important role in adipogenesis and obesity.     

Receptor activity and conformational analysis of 5'-halogenated resiniferatoxin analogs as TRPV1 ligands

A series of 5′-halogenated resiniferatoxin analogs have been investigated in order to examine the effect of halogenation in the A-region on their binding and the functional pattern of agonism/antagonism for rat TRPV1 heterologously expressed in Chinese hamster ovary cells. Halogenation at the 5-position in the A-region of RTX and of 4-amino RTX shifted the agonism of parent compounds toward antagonism. The extent of antagonism was greater as the size of the halogen increased (I > Br > Cl > F) while the binding affinities were similar, as previously observed for our potent agonists. In this series, 5-bromo-4-amino RTX (39) showed very potent antagonism with K_i (ant) = 2.81 nM, which was thus 4.5-fold more potent than 5′-iodo RTX, previously reported as a potent TRPV1 antagonist. Molecular modeling analyses with selected agonists and the corresponding halogenated antagonists revealed a striking conformational difference. The 3-methoxy of the A-region in the agonists remained free to interact with the receptor whereas in the case of the antagonists, the compounds assumed a bent conformation, permitting the 3-methoxy to instead form an internal hydrogen bond with the C4-hydroxyl of the diterpene.     

Different vanilloid agonists cause different patterns of calcium response in CHO cells heterologously expressing rat TRPV1

The vanilloid receptor subtype 1 (TRPV1 or VR1) is expressed in nociceptive primary afferents of the C-fiber 'pain' pathway and has attracted considerable attention as a therapeutic target. Here, using rat TRPV1 heterologously expressed in Chinese hamster ovary cells, we show that different agonists show different patterns of modulation of the intracellular Ca2+ concentration, monitored in individual cells by fura-2 Ca2+ imaging. We identified 5 parameters (potency, maximal response, latency of response, variability of latency of response among individual cells, and desensitization) which behaved differently for different compounds. The potencies of the compounds examined ranged from EC50 values of 80 pM to 9 microM. Peak levels of induced [Ca2+]i were observed either higher (RTX) or lower (anandamide) than for capsaicin. Significant latencies of response were observed for some (e.g. RTX) but not other derivatives, with great variation among individual cells in this latency. Marked desensitization after stimulation was detected in some cases (e.g. anandamide, capsaicin); for others, no desensitization was observed. We conclude that structurally diverse vanilloid agonists induce marked diversity in the patterns of Ca2+ response. This diversity of response may provide opportunities for pharmacological exploitation.