Summary
A large body of biochemical and morphological evidence suggests that actin polymerizes
in response to various stimuli which activate platelets. Previous work has shown the
presence in platelets of gelsolin, a Ca2+-dependent regulator of actin filament length. This present work demonstrates that
human platelets contain scinderin, another Ca2+-dependent actin filament-severing protein recently discovered in our laboratory.
Extracts prepared from platelets were subjected to DNase-I-Sepharose 4B affinity chromatography.
EGTA eluates from the affinity columns contained scinderin as demonstrated by mono
and two-dimensional polyacrylamide gel electrophoresis and immunoblotting with scinderin
antibodies. The concentration of scinderin in platelets was 75 fmol/mg total protein.
This might represent 11% of the total actin filament-severing activity if both proteins
are equally potent, on a molar basis, in severing actin filaments. Double staining
immunocytochemical studies with antibodies against scinderin and rhodamine phalloidin,
a probe for F-actin, also demonstrated the presence of scinderin in platelets. These
findings suggest that scinderin may participate in the regulation of platelet actin
networks.