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A 220-kDa activator complex of the 26 S proteasome in insects and humans. A role in type II programmed insect muscle cell death and cross-activation of proteasomes from different species.

The S10b (SUG2) ATPase cDNA has been cloned by reverse transcription-polymerase chain reaction/rapid amplification of cDNA ends from mRNA of intersegmental muscles of the tobacco horn moth (Manduca sexta). The S10b ATPase is a component of the 26 S proteasome, and its concentration and that of its mRNA increase dramatically during development in a manner similar to other ATPases of the 19 S regulator of the 26 S proteasome. The S10b and S6' (TBP1) ATPases are also present in a complex of approximately 220 kDa in intersegmental muscles. The 220-kDa complex markedly activates (2-10-fold) the 26 S proteasome, even when bound to anti-S10b antibodies immobilized on Sepharose, and increases in concentration approximately 5-fold like the 26 S proteasome in the intersegmental muscles in preparation for the programmed death of the muscle cells. A similar activator complex is present in human brain and placenta. Free activator complexes cross-activate: the Manduca complex activates rat skeletal muscle 26 S proteasomes, and the placental complex activates Manduca 26 S proteasomes. The placental activator complex contains S10b and S6', but not p27. This 220-kDa activator complex has been evolutionarily conserved between species from insect to man and may have a fundamental role in proteasome regulation.

Adenosine Triphosphatases↗

Expression of a membrane-bound form of Trypanosoma cruzi trans-sialidase in baculovirus-infected insect cells: a potential tool for sialylation of glycoproteins produced in the baculovirus-insect cells system.

A chimeric protein containing the catalytic domain of Trypanosoma cruzi trans-sialidase, the transmembrane domain of the major envelope glycoprotein of the baculovirus (gp67), and the signal peptide of ecdysteroid glucosyltransferase of the baculovirus was expressed under the control of the very late promoter p10 in baculovirus-infected lepidopteran cells. The recombinant protein was found to be enzymatically active. Three days after infection, equal amounts of activity were found associated to the plasma membrane and in the infection medium, both forms having the same apparent molecular weight and being N-glycosylated. When exogenous galactosylated acceptors (lactose or asialo-alpha1-acid glycoprotein) were added in the culture medium of cells infected with the recombinant baculovirus in the presence of a sialylated donor, a sialylation could be observed. Therefore, we propose the use of trans-sialidase as a potential tool for sialylation of glycoconjugates in the baculovirus-insect cells system.

Animals↗

Molecular analysis of Neorickettsia risticii in adult aquatic insects in Pennsylvania, in horses infected by ingestion of insects, and isolated in cell culture.

Upon ingestion of adult aquatic insects, horses developed clinical signs of Potomac horse fever, and Neorickettsia risticii was isolated from the blood. 16S rRNA and 51-kDa antigen gene sequences from blood, isolates, and caddis flies fed to the horses were identical, proving oral transmission of N. risticii from caddis flies to horses.

Animals↗

Investigations on insects. XI. Carotenoids in some cave-dwelling insects.

The presence of carotenoids in Catopus tritis infernus Szymanowski 1957 and Choleva lederiana gracilenta Szymanowski 1957 from a cave was studies, using columnar and thin-layer chromatography. Qualitative and quantitative differences in the carotenoid content of these insect species were found.

Animals↗

Insect cardioactive neuropeptides: peptidergic modulation of the intrinsic rhythm of an insect heart is mediated by inositol 1,4,5-trisphosphate.

The beat frequency of the myogenic heart of the tobacco hawkmoth, Manduca sexta, markedly increases at adult emergence in response to 2 blood-borne peptide neurohormones, known as the cardioacceleratory peptides (CAP1 and CAP2). Three independent lines of evidence are presented supporting the hypothesis that the CAPs exert their cardiostimulatory effects on the insect myocardium through a change in the intracellular levels of inositol 1,4,5-trisphosphate (InsP3). I show that (1) InsP3 levels increase in response to CAP2 in a timely fashion, (2) exogenous application of InsP3 mimics the effects of CAP2 application, and (3) a blocker of InsP3 metabolism inhibits the effect of CAP2. These results provide strong support for the hypothesis that InsP3 is likely to be the second messenger in the regulation of heart beat activity by CAP2. Besides establishing the nature of the signaling system between CAP2 and the heart, these data also identify a novel role for InsP3, namely, the control of contraction frequency in a myogenic muscle. Given the widespread distribution of cellular systems employing InsP3 as a second messenger, it is suggested that InsP3 may also be involved in the long-term regulation of rhythmic activity in other spontaneously contractile muscles and endogenously active cells.

Animals↗