Positive regulation of mu-calpain action by polyphosphoinositides

Autor: T C, Saido, M, Shibata, T, Takenawa, H, Murofushi, K, Suzuki
Rok vydání: 1992
Předmět:
Zdroj: The Journal of biological chemistry. 267(34)
ISSN: 0021-9258
Popis: Whether calcium is the only major intracellular activator of calpain has not yet been established. Here we demonstrate that polyphosphoinositides may play critical roles in the activation process of mu-calpain. Experiments with purified enzyme, substrate (fodrin), and phospholipids show that only polyphosphoinositides but not other lipids significantly promote calpain action in the physiological intracellular calcium range of 10(-7) to 10(-6) M. The effect of polyphosphoinositide is exerted through both a reduction in the calcium concentration required for calpain autolysis and an increase in the Vmax of the proteolytic reaction. Neomycin, a polyphosphoinositide-binding antibiotic, inhibits both polyphosphoinositide-assisted proteolysis in test tubes and calcium-induced calpain activation coupled with substrate proteolysis in intact cells. This implies that the presence of polyphosphoinositides may actually be a prerequisite for calpain activation inside cells.
Databáze: OpenAIRE