Conversion of delta-, kappa- and mu-receptor selective opioid peptide agonists into delta-, kappa- and mu-selective antagonists

2',6'-Dimethyl substitution of the Tyr(1) residue of opioid agonist peptides and deletion of the positively charged N-terminal amino group or its replacement with a methyl group has recently been shown to represent a general structural modification to convert opioid peptide agonists into antagonists. This conversion requires the syntheses of opioid peptide analogues containing either 3-(2,6-dimethyl-4-hydroxyphenyl)propanoic acid (Dhp) or (2S)-2-methyl-3-(2,6-dimethyl-4-hydroxyphenyl)propanoic acid [(2S)-Mdp] in place of Tyr(1). Using this approach, delta-, kappa- and mu-selective opioid peptide agonist peptides were successfully converted into corresponding delta-, kappa- and mu-selective antagonists, whereby receptor selectivity was often maintained or even improved. Thus, two (2S)-Mdp(1)-analogues of the delta-selective cyclic enkephalin analogue H-Tyr-c[D-Pen-Gly-Phe(pF)-Pen]-Phe-OH turned out to be potent and selective delta antagonists. Most successful was the development of kappa antagonists derived from dynorphin A (Dyn A), including the highly potent and selective kappa-antagonist [(2S)-Mdp(1)]Dyn A(1-11)-NH(2) (dynantin) and the enzymatically stable octapeptide analogue [(2S)-Mdp(1),MeArg(7),D-Leu(8)]Dyn A(1-8)-NH(2). The (2S)-Mdp(1)-analogues of dynorphin B and alpha-neoendorphin also were kappa antagonists and may be useful as pharmacological tools in studies of kappa receptor subtypes. Finally, the Dhp(1)-analogues of the mu-selective cyclic enkephalin analogue H-Tyr-c[N(epsilon ),N(beta)-carbonyl-D-Lys(2),Dap(5)]enkephalinamide and of endomorphin-2 were moderately potent mu opioid antagonists.     

Interaction of maize (Zea mays) protein phosphatase 2A with tubulin

Immunological and biochemical evidence has been obtained for an interaction of maize protein phosphatase 2A (PP2A) holoenzyme with tubulin. Tubulin co-purifies with maize seedling PP2A. Affinity chromatography of the maize PP2A preparation on immobilized tubulin revealed two peaks of phosphorylase alpha phosphatase activity. In one of the peaks, the catalytic (C) and constant regulatory (A) subunits of PP2A were identified by Western blotting. The subunits (C and A) of PP2A were co-immunoprecipitated from maize seedlings homogenate by an anti-alpha-tubulin antibody. The interaction of plant PP2A with tubulin indicates a possible role of reversible protein phosphorylation in the dynamic structure of plant cytoskeleton.     

Energy metabolism and the evolution of reproductive suppression in the human female

Reproduction places severe demands on the energy metabolism in human females. When physical work entails higher energy expenditure, not enough energy will be left for the support of the reproductive processes and temporal suppression of the reproductive function is expected. While energy needed for reproduction may be obtained by increases in energy intake, utilization of fat reserves, or reallocation of energy from basal metabolism, several environmental or physiological constraints render such solutions unlikely. For human ancestors increases in energy intake were limited by availability of food, by labor of food preparation and by metabolic ceilings to energy assimilation. Energy stored as fat may support only a fraction of the requirements for reproduction (especially lactation). Effects of intense physical activity on basal metabolism may also interfere with fat accumulation during pregnancy. Finally, the female physiology may experience demands on increasing the basal metabolism as a consequence of physical activity and, at the same time, on decreasing the basal metabolism, when energy to support the ongoing pregnancy or lactation is inadequate. The resulting metabolic dilemmas could constitute a plausible cause for the occurrence of reproductive suppression in response to physical activity. It is, therefore, likely that allocating enough energy to the reproductive processes during periods when energy expenditure rises may be difficult due to physiological and bioenergetic constraints. Females attempting pregnancy in such conditions may compromise their lifetime reproductive output. A reproductive suppression occurring in low energy availability situations may thus represent an adaptive rather then a pathological response.     

Spread and survival of promiscuous IncP-1 plasmids

Plasmids classified to the IncP-1 incompatibility group belong to the most stably maintained mobile elements among low copy number plasmids known to date. The remarkable persistence is achieved by various tightly controlled stability mechanisms like active partitioning, efficient conjugative transfer system, killing of plasmid-free segregants and multimer resolution. The unique feature of IncP-1 plasmids is the central control operon coding for global regulators which control the expression of genes involved in vegetative replication, stable maintenance and conjugative transfer. The multivalent regulatory network provides means for coordinated expression of all plasmid functions. The current state of knowledge about two fully sequenced plasmids RK2 and R751, representatives of the IncP-1alpha and IncP-1beta subgroups, is presented.     

Cryptic MBP epitope 1-20 is inducing autoimmune anterior uveitis without EAE in Lewis rats

Lewis rats immunized with myelin basic protein (MBP) developed experimental autoimmune encephalomyelitis (EAE) and associated anterior uveitis (AU). Although several cryptic epitopes of MBP have strong encephalitogenic and uveitogenic properties, the peptide corresponding to the MBP residues 1-20 was uniquely capable of inducing AU without EAE. In this study, we showed that acetylation of the N-terminal amino acid did not produce encephalitogenicity, did not enhance uveitogenicity, and did not improve T cell proliferation in Lewis rats. The cytokine production profile induced by MBP(1-20) immunization was consistent with a Th1 response. In MBP-injected rats and in peptide-injected rats, the frequency of the IFN-gamma-secreting cells in MBP(69-89)-stimulated T cells was significantly higher than the frequency of IFN-gamma-secreting cells in MBP(1-20)-stimulated T cells. However, similar numbers of IFN-gamma-producing specific cells were found in the eyes of MBP(69-89) and MBP(1-20) immunized rats. In these rats, the iris-infiltrating cells consisted of a much higher percentage of CD4(+) T cells expressing L-selectin (CD62L) than did those cells found in the spinal cord. The results demonstrate that MBP(1-20) is immunogenic and uveitogenic, although it induced only weak proliferation and weak Th1 reaction. The fact that T cells with the same specificity have different effects on target organs suggested that, in the eye and spinal cord, a distinct mechanism might mediate the recruitment of cells to these organs.     

Conjugative transfer of glycopeptide and macrolide resistant genes among Enterococci and from Enterococcus faecalis to Staphylococcus aureus

The resistance determinants were transferred from clinical strains of enterococci to Staphylococcus aureus strains. As recipients methicillin-resistant and methicillin-susceptible strains were used and the filter-mating procedure was performed. The transconjugants resistant to erythromycin were obtained in the case of all recipients, in one case the vanA determinant conferring the resistance to vancomycin was transferred together with erythromycin resistance. However the resistance was very unstable and the level was not as high as in the case of Enterococcus faecalis donor strain. The vanA determinant was easily transferred between enterococcal strains by the conjugation and a transfer occurred of vanA alone or together with erythromycin resistance.     

Human immune cells express ppMCH mRNA and functional MCHR1 receptor

The ubiquitously expressed Na(+)/H(+) exchanger (NHE1) plays an important role in the regulation of the intracellular pH. Induction of NHE activity by phorbol esters and inhibition of growth factor-mediated stimulation of the NHE by protein kinase C (PKC) inhibitors suggest an implication of PKCs in the regulation of the NHE. Expression of PKC isotype-specific dominant negative and constitutively active mutants or downregulation of PKC by isotype-specific antisense oligonucleotides revealed that stimulation by epidermal growth factor (EGF) or phorbol ester of the NHE in NIH3T3 cells is a PKC(alpha)-specific effect. Elevation of cytoplasmic calcium by a Ca(2+) ionophore or thapsigargin causes a growth factor-independent stimulation of the NHE predominantly mediated by calcium/calmodulin kinase II. It is concluded that in NIH3T3 cells overexpressing the EGF receptor (EGFR6 cells), EGF requires cPKC(alpha) for the activation of the NHE, while calcium/calmodulin-dependent kinases are essential in thapsigargin induced stimulation of the NHE.