Calcium release from aortic sarcoplasmic reticulum

The ability of inositol 1,4,5-trisphosphate (IP3) and other inositol phosphates to induce calcium release from canine aortic sarcoplasmic reticulum vesicles was examined. Using the calcium indicator chlorotetracycline or antipyrylazo III, aortic vesicles were shown to accumulate calcium in the presence of ATP, and then release ~25% of the intravesicular calcium upon addition of 7 μM IP3. Inositol 2-phosphate, inositol 1,4-bisphosphate, and inositol 1,3,4,5-tetrakisphosphate did not induce calcium release from these vesicles, and GTP[γ-S] did not affect the IP3-induced calcium release. Aortic IP3-induced calcium release was not affected by ruthenium red, but was inhibited by Mg2+ and Ca2+, and thus differs from the Mg2+-insensitive IP3-induced calcium release in platelets and the ruthenium red-sensitive IP3-induced calcium pathway in skeletal muscle sarcoplasmic reticulum. Stopped-flow analyses showed that aortic IP3-induced calcium release was much slower than the caffeine-induced calcium release from skeletal muscle sarcoplasmic reticulum. Moreover, the aortic IP3-induced calcium release was biphasic, suggestive of heterogeneity of the putative calcium channels

DNA aptamers detecting generic amyloid epitopes

Amyloids are fibrillar protein aggregates resulting from non-covalent autocatalytic polymerization of various structurally and functionally unrelated proteins. Previously we have selected DNA aptamers, which bind specifically to the in vitro assembled amyloid fibrils of the yeast prionogenic protein Sup35. Here we show that such DNA aptamers can be used to detect SDS-insoluble amyloid aggregates of the Sup35 protein, and of some other amyloidogenic proteins, including mouse PrP, formed in yeast cells. The obtained data suggest that these aggregates and the Sup35 amyloid fibrils assembled in vitro possess common conformational epitopes recognizable by aptamers. The described DNA aptamers may be used for detection of various amyloid aggregates in yeast and, presumably, other organisms