Annexin V relocates to the periphery of activated platelets following thrombin activation: an ultrastructural immunohistochemical approach.
We have previously shown biochemically that the physiological agonist thrombin can cause translocation of endogenous annexin V to a fraction containing all platelet membranes. This paper reports ultrastructural immunohistochemical data revealing that annexin V molecules localize with plasma membranes of blood platelets following thrombin activation. When ultrathin sections of resting platelets were examined by immunogold staining, annexin V was found to be cytosolic, having a generalized distribution throughout the platelet. After thrombin activation, annexin V became peripheral in location and plasmalemma association increased. Morphometric analysis of gold particles shows that annexin V relocates specifically to the plasma membrane and its underlying cytoskeleton following treatment with thrombin. In control platelets 6.1% +/- 0.78 of annexin V is present at the plasma membrane and 15.0% +/- 0.82 in the region corresponding to the membrane cytoskeleton (10-80 nm); after stimulation with 0.5 unit/ml thrombin for 2 min this increased to 16.7% +/- 0.22 and 40.4% +/- 0.53, respectively.
Tzima
E
E
School of Biochemistry and Molecular Biology, University of Leeds, UK.
Poujol
C
C
Nurden
P
P
Nurden
A T
AT
Orchard
M A
MA
Walker
J H
JH
D017304:Annexin A5 / Q000502:physiology* / Q000648:ultrastructure; D001692:Biological Transport; D001792:Blood Platelets / Q000502:physiology* / Q000648:ultrastructure*; D006801:Humans; D016253:Microscopy, Immunoelectron; D015539:Platelet Activation; D013917:Thrombin / Q000502:physiology*
D017304:Annexin A5; D013917:Thrombin