TY - JOUR
T1 - SNAP-23 is a target for calpain cleavage in activated platelets
AU - Rutledge, Tara W.
AU - Whiteheart, S. W.
PY - 2002/10/4
Y1 - 2002/10/4
N2 - The role of calpain in platelet function is generally associated with aggregation and clot retraction. In this report, data are presented to show that one component of the platelet secretory machinery, SNAP-23, is specifically cleaved by calpain in activated cells. Other proteins of the membrane fusion machinery, e.g. syntaxins 2 and 4 and α-SNAP, are not affected. In vitro studies, using permeabilized platelets, demonstrate that cleavage is time- and calcium-dependent. Analysis of SNAP-23 cleavage products suggests that the calpain cleavage site(s) is in the C-terminal third of the molecule potentially between the cysteine-rich acyl attachment sites and the C-terminal coiled-coil domain. The time course of cleavage is most consistent with late calpain-mediated events such as pp60c-src cleavage, but not early events such as protein-tyrosine phosphatase-1B activation. SNAP-23 cleavage is inhibited by calpeptin, calpastatin, calpain inhibitor IV, and E-64d, but not by caspase 3 inhibitor III or cathepsin inhibitor I. When tested for their effect on secretion, none of the calpain-specific inhibitors significantly affected release of soluble components from any of the three platelet granule storage pools. These results indicate that SNAP-23 cleavage occurs after granule release and therefore may play a role in affecting granule membrane exteriorization. This is consistent with the ultrastructural morphology of calpeptin-treated platelets after activation.
AB - The role of calpain in platelet function is generally associated with aggregation and clot retraction. In this report, data are presented to show that one component of the platelet secretory machinery, SNAP-23, is specifically cleaved by calpain in activated cells. Other proteins of the membrane fusion machinery, e.g. syntaxins 2 and 4 and α-SNAP, are not affected. In vitro studies, using permeabilized platelets, demonstrate that cleavage is time- and calcium-dependent. Analysis of SNAP-23 cleavage products suggests that the calpain cleavage site(s) is in the C-terminal third of the molecule potentially between the cysteine-rich acyl attachment sites and the C-terminal coiled-coil domain. The time course of cleavage is most consistent with late calpain-mediated events such as pp60c-src cleavage, but not early events such as protein-tyrosine phosphatase-1B activation. SNAP-23 cleavage is inhibited by calpeptin, calpastatin, calpain inhibitor IV, and E-64d, but not by caspase 3 inhibitor III or cathepsin inhibitor I. When tested for their effect on secretion, none of the calpain-specific inhibitors significantly affected release of soluble components from any of the three platelet granule storage pools. These results indicate that SNAP-23 cleavage occurs after granule release and therefore may play a role in affecting granule membrane exteriorization. This is consistent with the ultrastructural morphology of calpeptin-treated platelets after activation.
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U2 - 10.1074/jbc.M204526200
DO - 10.1074/jbc.M204526200
M3 - Article
C2 - 12121992
AN - SCOPUS:0037020150
SN - 0021-9258
VL - 277
SP - 37009
EP - 37015
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 40
ER -