Summary
Time course change of the platelet cytoskeletal protein component in the Triton X-100
insoluble fraction after stimulation was analyzed in Hermansky-Pudlak syndrome and
thrombasthenia.
In Hermansky-Pudlak syndrome (HPS), a 31 kDa protein, myosin, actin, and a 100 kDa
protein assembled as in the normal platelets at the shape change and release reaction
phases after ADP or collagen stimulation, suggesting that, the deficient dense granule
content do not lead to an abnormal platelet cytoskeletal protein assembly. In thrombasthenia
(Type I), myosin increased at the shape change and release reaction phases as it does
in normal platelets, but actin and the 100 kDa protein increased only at the initial
activation phase, and then subsequently decreased to the level of the resting phase.
The actin-binding protein (ABP) and the 31 kDa protein increased a little following
stimulation. Similar cytoskeletal protein change after stimulation were found in normal
platelets which were prevented from the aggregation process by chelating the external
Ca2+ or by using synthetic decapeptide of fibrinogen γ-chain of carboxyl terminus. The
decreased platelet cytoskeletal protein assembly in thrombasthenia or in platelets
stimulated without aggregation, was derived from a loss of the platelet aggregation
process due to the defect of GP Ilb-IIIa complex or an interaction failure between
GP IIb-IIIa complex and fibrinogen. The interaction between platelets and either fibrinogen
or fibrin can induce a more stable platelet cytoskeletal protein assembly, however,
agonistic stimulation without these interactions cannot do it directly.
Keywords
Hermansky-Pudlak Sydrome - Thrombasthenia - Platelet cytoskeleton - Intercation of
platelet and fibrinogen
