Concanavalin A induces interactions between surface glycoproteins and the platelet cytoskeleton.

Abstract

We have measured the association of platelet surface membrane proteins with Triton X-100 (Triton) -insoluble residues in platelets surface labeled with ' 25 1 . In both concanavalin A (Con A)-stimulated and resting platelets, this fraction is composed largely of polypeptides with apparent molecular weights of 45,000, 200,000, and 250,000 which comigrate with authenic actin, myosin heavy chain, and actin binding protein, respectively, as judged by PAGE in SDS. Less than 10% of the two major ' 25 1-labeled surface glycoproteins, GPllb and GPIII, were associated with the Triton residue in resting platelets. Within 45 s after Con A addition, 80-95% of these two glycoproteins became associated with the Triton residue and the amount of sedimentable actin doubled . No cosedimentation of GPllb and III with the cytoskeletal protein-containing Triton residue was seen when Con A was added to a Triton extract of resting cells, indicating that the sedimentation of GPllb and III seen in Con A-stimulated platelets was not due to precipitation of the glycoproteins by Con A after detergent lysis. Treatment of Triton extracts of Con A-stimulated platelets with DNase I (deoxyribonucleate 5'-oligonucleotididohydrolase [EC 3.1 .4 .5]) inhibited the sedimentation of actin and the two surface glycoproteins in a dose-dependent manner . This inhibition of cosedimentation was not due to an effect of DNase I on Con A-glycoprotein interactions since these two glycoproteins could be quantitatively recovered by Con A-Sepharose affinity absorption in the presence of DNase I . When the Con A bound to the Triton residue was localized ultrastructurally, it was associated with cellsized structures containing filamentous material . In intact cells, there was simultaneous immunofluorescent cored istribution of surface-bound Con A and myosin under conditions which induced a redistribution of platelet myosin . These data suggest that Con A can, in the intact platelet, induce physical interactions between certain surface glycoproteins and the internal cytoskeleton .There is a considerable immunohistochemical and some biochemical evidence suggesting that cell surface proteins and glycoproteins interact in a transmembrane manner with the cell cytoskeleton, especially after surface proteins have been aggregated by multivalent ligands (1,2,5,6,(21)(22)(23)32) .Elucidation of the molecular architecture of this complex of surface proteins and the cytoskeleton requires cells in which the cytoskeleton with associated surface proteins can be isolated in bulk and in a relatively pure and intact state . The human platelet appears to meet these criteria. In addition, the glycoprotein composition of the platelet surface has been wellcharacterized (4,19,(26)(27)(28) . Phillips and his co-workers (29) have recently shown that two major surface glycoproteins, designated GPIlb and GPIII, become associated with platelet THE JOURNAL OF CELL BIOLOGY " VOLUME 92 FEBRUARY 1982 565-573©The Rockefeller University Press -0021-9525/82/02/0565/09 $1 .00 cytoskeletons i...

Association of phosphatidylinositol kinase and phosphatidylinositol 4‐phosphate kinase activities with the cytoskeleton in human platelets

“…It appears therefore that Ptdlns and Ptdlns(4)P kinases might be present at anchoring points of the cytoskeleton in the plasma membrane (and possibly other organelles). Such an association of the cytoskeleton with membrane enzymes has already been described even for intrinsic proteins such as glycoproteins lib/Ilia, Ib or Ia [29][30][31][32].…”

Early tissue transglutaminase–mediated response underlies K562(S)-cell gliadin-dependent agglutination

“…Next, we addressed whether such an early Ca 2+ -dependent TG2 activation, occurring in K562(S) cells upon gliadin exposure, could also regulate the rearrangement of cytoskeleton that is pivotal in cell agglutination (23,24). Blocking TG2 activation, a central player of these cell surface events (14), by means of the Ca 2+ chelator BAPTA-AM or the anti-TG2 antibody CUB 7402 prevented the early rearrangement of the actin fibers occurring after a few minutes of gliadin challenge (Figure 4a).…”

Synthesis by cultured human umbilical vein endothelial cells of two proteins structurally and immunologically related to platelet membrane glycoproteins IIb and IIIa.

“…Central to the role of platelet-subendothelial and platelet-platelet interactions is a plasma membrane calcium-dependent heterodimer protein complex composed of glycoproteins (GPs) 1 Ilb and HIa. These two glycoproteins comprise the fibrinogen receptor that mediates platelet aggregation (1,2,26), haqebeen found to associate with the cytoskeleton after platelet activation (25,27), bind von W'fllebrand factor in the absence of competing fibrinogen (29,30), and also carry several alloantigenic determinants that are the target of both allo-and auto-immune immunologic disorders (B, 24, 35). Although GPHb-IlIa has been thought to be platelet-specific, recent work in several laboratories indicates that structurally similar, antigenically cross-reactive proteins may be found 1.…”