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Calpain abolishes the effect of filamin on the actomyosin system in platelets
Abstract:
Platelet filamin was shown to cross-link F-actin and inhibit actomyosin ATPase activity. Filamin was also shown to be degraded by calpain (calcium-activated neutral proteinase; CANP) when the platelet was activated. The consequences of the proteolysis of filamin on the actomyosin system have been investigated. When degraded by calpain in the presence of Ca2+, filamin loses its ability to cross-link F-actin. Under the same conditions, its inhibitory effects on the superprecipitation and ATPase activity of actomyosin are abolished. The result suggests that the degradation of filamin is favorable for contraction of the activated platelets.
Insights
Platelet activation involves calpain (calcium-activated neutral proteinase; CANP) degrading filamin. This degradation enhances platelet contraction by releasing inhibition on the actomyosin system.
Area of Science:
- Biochemistry
- Cell Biology
- Platelet Physiology
Background:
- Platelet filamin cross-links F-actin and inhibits actomyosin ATPase activity.
- Platelet activation triggers calpain (calcium-activated neutral proteinase; CANP) to degrade filamin.
Purpose of the Study:
- To investigate the consequences of filamin proteolysis on the platelet actomyosin system.
- To understand the role of filamin degradation in activated platelet contraction.
Main Methods:
- Investigated the effects of calpain-mediated filamin degradation on F-actin cross-linking.
- Assessed the impact of filamin proteolysis on actomyosin superprecipitation and ATPase activity in the presence of Ca2+.
Main Results:
- Degraded filamin loses its F-actin cross-linking ability.
- Calpain-mediated filamin degradation abolishes its inhibitory effects on actomyosin superprecipitation and ATPase activity.
- Proteolysis of filamin by calpain in Ca2+-containing conditions leads to loss of F-actin binding.
Conclusions:
- Filamin degradation by calpain is a key event in platelet activation.
- The loss of filamin's inhibitory function facilitates platelet contraction.
- Proteolysis of filamin by calpain is favorable for activated platelet contraction.