Activities of natural methyl farnesoids on pupariation and metamorphosis of Drosophila melanogaster

Methyl farnesoate (MF) and juvenile hormone (JH III), which bind with high affinity to the receptors USP and MET, respectively, and bisepoxy JH III (bisJH III) were assessed for several activities during Drosophila larval development, and during prepupal development to eclosed adults. Dietary MF and JH III were similarly active, and more active than bisJH III, in lengthening larval development prior to pupariation. However, the order of activity was changed (JH III > bisJH III > MF) with respect to preventing prepupae from eclosing as normal adults, whether administered in the larval diet or as topically applied at the white puparium stage. If endogenous production of all three larval methyl farnesoids was suppressed by a strongly driven RNAi against HMGCR in the corpora allata cells, most larvae did not attain pupariation. Farnesol (which has no demonstrated life-necessary function in larval life except in corpora allata cells as a precursor to methyl farnesoid biosynthesis) when incorporated into the diet rescued attainment of pupariation in a dose-dependent manner, presumably by rescuing endogenous production of all three hormones. A more mild suppression of endogenous methyl farnesoid production enabled larval attainment of pupariation. However, in this background dietary MF had increased activity in preventing puparia from attaining normal adult eclosion. The physiological relevance of using exogenous methyl farnesoids to block prepupal development to normally eclosed adults was tested by, instead, protecting in prepupae the endogenous titer of methyl farnesoids. JH esterase normally increases during the mid-late prepupal stage, presumably to clear endogenous methyl farnesoids. When JH esterase was inhibited with an RNAi, it prevented attainment of adult eclosion. Cultured adult corpora allata from male and female Aedes aegypti released both MF and JH III, and the A. aegypti nuclear receptor USP bound MF with nanomolar affinity. These A. aegypti data support the use of Drosophila as a model for mosquitoes of the binding of secreted MF to USP.     

Synthesis of octahydropyrano[3,2-b]pyrrole-2-carboxylic acid derivatives from D-mannose

Bicyclic amino acids are useful building blocks in synthesizing biologically active molecules and peptidomimetics. 2-Carboxy-6-hydroxyloctahydroindole (Choi) is a novel bicyclic amino acid found in the marine natural products aeruginosins. Many compounds in the aeruginosin family exhibit inhibition activities toward serine proteases including thrombin and trypsin. The unique Choi structure is the common feature of this family of oligopeptides and this motif is important for their observed biological activities. To better understand the influence of the stereochemistry of the Choi core structure on the inhibition activities, we have previously synthesized ring-oxygenated variants from glucose. The preparation of octahydro-pyrano[3,2-b]pyrrole 2-carboxylic acids from d-mannose is reported here. These novel bicyclic amino acids can be used in the preparation of aeruginosin analogs, as well as conformationally constrained peptidomimetics or other biologically active molecules.     

Targeted expression of tetanus toxin reveals sets of neurons involved in larval locomotion in Drosophila

The Drosophila larva is widely used for studies of neuronal development and function, yet little is known about the neuronal basis of locomotion in this model organism. Drosophila larvae crawl over a plain substrate by performing repetitive waves of forward peristalsis alternated by brief episodes of head swinging and turning. To identify sets of central and peripheral neurons required for the spatial or temporal pattern of larval locomotion, we blocked neurotransmitter release from defined populations of neurons by targeted expression of tetanus toxin light chain (TeTxLC) with the GAL4/UAS system. One hundred fifty GAL4 lines were crossed to a UAS-TeTxLC strain and a motion-analysis system was used to identify larvae with abnormal movement patterns. Five lines were selected that show discrete locomotor defects (i.e., increased turning and pausing) and these defects are correlated with diverse sets of central neurons. One line, 4C-GAL4, caused an unusual circling behavior that is correlated with approximately 200 neurons, including dopaminergic and peptidergic interneurons. Expression of TeTxLC in all dopaminergic and serotonergic but not in peptidergic neurons, caused turning deficits that are similar to those of 4C-GAL4/TeTxLC larvae. The results presented here provide a basis for future genetic studies of motor control in the Drosophila larva.     

Helix-coil stability constants for the naturally occuring amino acids in water. XIV. Methionine parameters from random poly(hydroxypropylglutamine,L-Methionine)

Water-soluble, random copolymers containing L -methionine and N⁵-(3-hydroxypropyl)-L -glutamine have been prepared, fractionated, and characterized. The thermally induced helix-coil transitions of these copolymers in water have been investigated, and it has been found that incorporation of L-methionine increases the helix content of the polymers at all temperatures in the range of 0–60°C. The Zimm-Bragg parameters σ and s for the helix-coil transition in poly(L -methionine) in water were deduced from an analysis of the melting curves of the copolymers using the methods described in earlier papers.