Calpain-mediated regulation of platelet signaling pathways.
OBJECTIVE
There is considerable interest in understanding the function and mechanism of calpains in platelet aggregation, spreading, and granular secretion pathways. Recent insights from the calpain-1 knockout platelets suggest a pivotal role of these cysteine proteases in the regulation of outside-in signaling, aggregation, and clot retraction.


RESULTS
The calpain-1 knockout mouse provided direct evidence for the role of calpain-1 in platelet aggregation and clot retraction. Reduced tyrosine phosphorylation of platelet proteins correlated with reduced platelet aggregation and clot retraction. Future investigations of the mechanism of platelet defects in calpain-1 null mice may unveil the physiological functions of this important and elusive protease in mammalian cells.


CONCLUSIONS
This review focuses on the role of calpains in platelets with a particular emphasis on recent findings in calpain-1 null platelets. Previous studies used synthetic inhibitors to study the role of calpains in platelet function yielding useful information about the identification of calpain substrates. The development of calpain-1 null mice demonstrated that calpain-1 plays an important function in the regulation of platelet aggregation and clot retraction. Since the combined deletion of calpain-1 and calpain-2 genes results in embryonic lethality, the calpain-1 null mouse remains the only experimental model available to study the physiological role of calpains in mammalian cells.
Kuchay
Shafi M
SM
Department of Pharmacology, University of Illinois College of Medicine, Chicago, IL 60612, USA.
Chishti
Athar H
AH
D000818:Animals; D001792:Blood Platelets / Q000378:metabolism / Q000502:physiology*; D002154:Calpain / Q000502:physiology*; D051379:Mice; D015398:Signal Transduction
D002154:Calpain; C112682:Capn1 protein, mouse