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Cap Z, a calcium insensitive capping protein in resting and activated platelets
Author(s) -
Nachmias Vivianne T.,
Golla Rajasree,
Casella James F.,
Barron-Casella Emily
Publication year - 1996
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)01474-8
Subject(s) - egta , gelsolin , platelet , biophysics , platelet activation , chemistry , actin , calcium , cytoskeleton , thrombin , protein filament , gtp' , biochemistry , biology , cell , enzyme , immunology , organic chemistry
Capping of the barbed‐ends of actin filaments is an important mechanism for control of the cytoskeleton. In platelets, a valuable model system, it has been thought that gelsolin was the major capping protein. We now report that platelets contain 2 μM Cap Z, a calcium insensitive heterodimeric capping protein; two major and additional minor isoforms of both α and β subunits are present. In lysates from resting platelets 75–80% of the Cap Z sediments with the high speed pellet, but if the platelets are activated with thrombin for 10 s, about 15% of the Cap Z leaves the pellet fraction and is found in the high speed supernatant where it is not bound to actin. This translocation of Cap Z to the supernatant is also observed when resting platelets are lysed into buffer containing 50–100 μM GTPγS and 10 mM EGTA. Our results suggest that release of Cap Z from some actin filaments could generate free filament barbed‐ends. An increase in free barbed‐ends has been reported in platelet lysates prepared shortly after thrombin activation.