Serum stability of selected decapeptide agonists of KISS1R using pseudopeptides

Metastin/kisspeptin, a 54-amino acid peptide, is the ligand of the G-protein-coupled receptor KISS1R which plays a key role in pathways that regulate reproduction and cell migration in many endocrine and gonadal tissues. The N-terminally truncated decapeptide, metastin(45–54), has 3–10 times higher receptor affinity and intracellular calcium ion-mobilizing activity but is rapidly inactivated in serum. In this study we designed and synthesized stable KISS1R agonistic decapeptide analogs with selected substitutions at positions 47, 50, and 51. Replacement of glycine with azaglycine (azaGly) in which the α-carbon is replaced with a nitrogen atom at position 51 improved the stability of amide bonds between Phe⁵⁰-Gly⁵¹ and Gly⁵¹-Leu⁵² as determined by in vitro mouse serum stability studies. Substitution for tryptophan at position 47 with other amino acids such as serine, threonine, β-(3-pyridyl)alanine, and d-tryptophan (d-Trp), produced analogs that were highly stable in mouse serum. d-Trp⁴⁷ analog 13 showed not only high metabolic stability but also excellent KISS1R agonistic activity. Other labile peptides may have increased serum stability using amino acid substitution.     

The Distribution of Henipaviruses in Southeast Asia and Australasia: Is Wallace’s Line a Barrier to Nipah Virus?

Nipah virus (NiV) (Genus Henipavirus) is a recently emerged zoonotic virus that causes severe disease in humans and has been found in bats of the genus Pteropus. Whilst NiV has not been detected in Australia, evidence for NiV-infection has been found in pteropid bats in some of Australia’s closest neighbours. The aim of this study was to determine the occurrence of henipaviruses in fruit bat (Family Pteropodidae) populations to the north of Australia. In particular we tested the hypothesis that Nipah virus is restricted to west of Wallace’s Line. Fruit bats from Australia, Papua New Guinea, East Timor and Indonesia were tested for the presence of antibodies to Hendra virus (HeV) and Nipah virus, and tested for the presence of HeV, NiV or henipavirus RNA by PCR. Evidence was found for the presence of Nipah virus in both Pteropus vampyrus and Rousettus amplexicaudatus populations from East Timor. Serology and PCR also suggested the presence of a henipavirus that was neither HeV nor NiV in Pteropus alecto and Acerodon celebensis. The results demonstrate the presence of NiV in the fruit bat populations on the eastern side of Wallace’s Line and within 500 km of Australia. They indicate the presence of non-NiV, non-HeV henipaviruses in fruit bat populations of Sulawesi and Sumba and possibly in Papua New Guinea. It appears that NiV is present where P. vampyrus occurs, such as in the fruit bat populations of Timor, but where this bat species is absent other henipaviruses may be present, as on Sulawesi and Sumba. Evidence was obtained for the presence henipaviruses in the non-Pteropid species R. amplexicaudatus and in A. celebensis. The findings of this work fill some gaps in knowledge in geographical and species distribution of henipaviruses in Australasia which will contribute to planning of risk management and surveillance activities.     

Temporal rules in vocal exchanges of phees and trills in common marmosets (Callithrix jacchus)

Marmosets exchange two types of calls: phees and trills. We played back phees and trills to investigate the temporal rules of vocal exchanges using ten captive common marmosets (Callithrix jacchus). The marmosets usually emitted the same type of vocalizations just after the stimulus playbacks, and similar regularities were observed in the temporal intervals of phees and in trills. They vocalized with shorter intervals when they responded with trills rather than phees, and, after the first call, they repeatedly vocalized trills with shorter intervals than phees. These results suggest that the temporal rules between phees and trills are qualitatively similar but quantitatively different. These results might be owing to the different distances over which these contact calls are used. Am. J. Primatol. 71:617–622, 2009. © 2009 Wiley‐Liss, Inc.     

Arabidopsis dynamin-related proteins DRP3A and DRP3B are functionally redundant in mitochondrial fission, but have distinct roles in peroxisomal fission

Two similar Arabidopsis dynamin-related proteins, DRP3A and DRP3B, are thought to be key factors in both mitochondrial and peroxisomal fission. However, the functional and genetic relationships between DRP3A and DRP3B have not been fully investigated. In a yeast two-hybrid assay, DRP3A and DRP3B interacted with themselves and with each other. DRP3A and DRP3B localized to mitochondria and peroxisomes, and co-localized with each other in leaf epidermal cells. In two T-DNA insertion mutants, drp3a and drp3b , the mitochondria are a little longer and fewer in number than those in the wild-type cells. In the double mutant, drp3a/drp3b , mitochondria are connected to each other, resulting in massive elongation. Overexpression of either DRP3A or DRP3B in drp3a/drp3b restored the particle shape of mitochondria, suggesting that DRP3A and DRP3B are functionally redundant in mitochondrial fission. In the case of peroxisomal fission, DRP3A and DRP3B appear to have different functions: peroxisomes in drp3a were larger and fewer in number than those in the wild type, whereas peroxisomes in drp3b were as large and as numerous as those in the wild type, and peroxisomes in drp3a/drp3b were as large and as numerous as those in drp3a . Although overexpression of DRP3A in drp3a/drp3b restored the shape and number of peroxisomes, overexpression of DRP3B did not restore the phenotypes, and often caused elongation instead. These results suggest that DRP3B and DRP3A have redundant molecular functions in mitochondrial fission, whereas DRP3B has a minor role in peroxisomal fission that is distinct from that of DRP3A.     

Synergistic pore formation by type III toxin translocators of Pseudomonas aeruginosa

Type III secretion/translocation systems are essential actors in the pathogenicity of Gram-negative bacteria. The injection of bacterial toxins across the host cell plasma membranes is presumably accomplished by a proteinaceous structure, the translocon. In vitro, Pseudomonas aeruginosa translocators PopB and PopD form ringlike structures observed by electron microscopy. We demonstrate here that PopB and PopD are functionally active and sufficient to form pores in lipid vesicles. Furthermore, the two translocators act in synergy to promote membrane permeabilization. The size-based selectivity observed for the passage of solutes indicates that the membrane permeabilization is due to the formation of size-defined pores. Our results provide also new insights into the mechanism of translocon pore formation that may occur during the passage of toxins from the bacterium into the cell. While proteins bind to lipid vesicles equally at any pH, the kinetics of membrane permeabilization accelerate progressively with decreasing pH values. Electrostatic interactions and the presence of anionic lipids were found to be crucial for pore formation whereas cholesterol did not appear to play a significant role in functional translocon formation.