Phosphorylation Of Platelet Proteins In Response To Activation By Phorbol 12-Myristate 13-Acetate

1981 ◽  
Author(s):  
Roger C Carroll ◽  
Jonathan M Gerrard
Keyword(s):  
Molecular Weight ◽  
Light Chain ◽  
Time Course ◽  
Myosin Light Chain ◽  
Binding Protein ◽  
Sodium Dodecyl ◽  
Actin Binding ◽  
Actin Binding Protein ◽  
Activated Platelets ◽  
Platelet Proteins

We have investigated the 32P-1abelling of platelet proteins in response to 5uM to l0uM phorbol 12-myristate 13- acetate (PMA) which triggers pseudopod formation and aggregation but an atypical release without granule centralization by a contractile gel. Total platelet protein samples resolved on polyacrylamide-sodium dodecyl sulfate gels showed greater than 3 fold increases sustained over a 15 minute time course in the 32p-abelling of 260,000; 40,000; and 20,000 apparent molecular weight peptides. While similar increases in 32p-labelling are observed with other activators, such as thrombin, arachidonate, and A23187, peak phosphorylation routinely occurs between 30 to 60 seconds followed by an aggregation dependent dephosphorylation to less than 50% of peak levels between 3 to 5 minutes. The cytoskeletal cores which remain after 1% Triton X-100 extraction of platelets activated by typical stimuli contain mostly actin, myosin, and actin-binding protein. The presence in this cytoskeletal core most of the 32p-label associated with the 260,000 and 20,000 molecular weight peptides suggests that these phosphopeptide are the 260,000 molecular weight actin binding protein, and the 20,000 molecular weight myosin light chain subunits. Cytoskeletal cores prepared from PMA activated platelets still contain greater than 90% of the 32p-labelled 260,000 molecular weight peptide but less than 20% of the 32p-labelled 20,000 molecular weight peptide, most of which is found in the solubilized fraction. These results suggest that the lack of granule centralization by a contractile gel is due to a disruption of actin-myosin interaction even though the myosin light chain is phosphorylated. This effect seems to be specific in that actin-binding protein - actin interaction believed to be responsible for pseudopod formation is still present in PMA activated platelets.

Phosphorylation Of Platelet Actin-Binding Protein During Platelet Activation

1981 ◽  
Author(s):  
Roger C Carroll ◽  
Jonathan M Gerrard
Keyword(s):  
Molecular Weight ◽  
Platelet Activation ◽  
Time Course ◽  
Binding Protein ◽  
Sodium Dodecyl ◽  
Apparent Molecular Weight ◽  
Actin Binding ◽  
Actin Binding Protein ◽  
Platelet Protein ◽  
External Calcium

We have followed the 32P-labelling of actin-binding protein as a function of platelet activation. Utilizing polyacrylamide sodium dodecyl sulfate gel electrophoresis to resolve total platelet protein samples we found 2 to 3 fold labelling increases in actin-binding protein 30 to 60 seconds after thrombin stimulation. Somewhat larger increases were observed for 40,000 and 20,000 apparent molecular weight peptides. The actin-binding protein was identified on the gels by coelectrophoresis of purified actin-binding protein as well as cytoskeletal cores prepared by detergent extraction of activated 32p-iabelled platelets. In addition, these cytoskeletal cores indicated that the 32P-labelled actin-binding protein was closely associated with the activated platelet's cytoskeleton. Following the 32P-labelling of actin-binding protein over an 8 minute time course revealed that in aggregating platelet samples rapid desphosphorylation to almost initial levels occurred between 3 and 5 minutes. A similar curve was obtained for the 20,000 apparent molecular weight peptide. This rapid dephosphorylation was shown to be dependent on platelet aggregation in the absence of external calcium or in thrombastenic platelets lacking the aggregation response to activation. These results suggest that phosphorylation of actin-binding protein initiates its association with the platelet cytoskeleton during activation.

scholarly journals Phosphorylation of platelet actin-binding protein during platelet activation

Blood ◽  
1982 ◽  
Vol 59 (3) ◽  
pp. 466-471 ◽  
Author(s):  
RC Carroll ◽  
JM Gerrard
Keyword(s):  
Molecular Weight ◽  
Platelet Activation ◽  
Time Course ◽  
Binding Protein ◽  
Sodium Dodecyl ◽  
Apparent Molecular Weight ◽  
Actin Binding ◽  
Cell Contact ◽  
Actin Binding Protein ◽  
Platelet Protein

Abstract In this study we have followed the 32P-labeling of actin-binding protein as a function of platelet activation. Utilizing polyacrylamide- sodium dodecyl sulfate gel electrophoresis to resolve total platelet protein samples, we found 2--3-fold labeling increases in actin-binding protein 30--60 sec after thrombin stimulation. Somewhat larger increases were observed for 40,000 and 20,000 apparent molecular weight peptides. The actin-binding protein was identified on the gels by coelectrophoresis with purified actin-binding protein, its presence in cytoskeletal cores prepared by detergent extraction of activated 32P- labeled platelets, and by direct immunoprecipitation with antibodies against guinea pig vas deferens filamin (actin-binding protein). In addition, these cytoskeletal cores indicated that the 32P-labeled actin- binding protein was closely associated with the activated platelet's cytoskeleton. Following the 32P-labeling of actin-binding protein over an 8-min time course revealed that in aggregating platelet samples rapid dephosphorylation to almost initial levels occurred between 3 and 5 min. A similar curve was obtained for the 20,000 apparent molecular weight peptide. However, rapid dephosphorylation was not observed if platelet aggregation was prevented by chelating external calcium or by using thrombasthenic platelets lacking the aggregation response. Thus, cell-cell contact would seem to be crucial in initiating the rapid dephosphorylation response.

scholarly journals Phosphorylation of platelet actin-binding protein during platelet activation

Blood ◽  
1982 ◽  
Vol 59 (3) ◽  
pp. 466-471 ◽  
Author(s):  
RC Carroll ◽  
JM Gerrard
Keyword(s):  
Molecular Weight ◽  
Platelet Activation ◽  
Time Course ◽  
Binding Protein ◽  
Sodium Dodecyl ◽  
Apparent Molecular Weight ◽  
Actin Binding ◽  
Cell Contact ◽  
Actin Binding Protein ◽  
Platelet Protein

In this study we have followed the 32P-labeling of actin-binding protein as a function of platelet activation. Utilizing polyacrylamide- sodium dodecyl sulfate gel electrophoresis to resolve total platelet protein samples, we found 2--3-fold labeling increases in actin-binding protein 30--60 sec after thrombin stimulation. Somewhat larger increases were observed for 40,000 and 20,000 apparent molecular weight peptides. The actin-binding protein was identified on the gels by coelectrophoresis with purified actin-binding protein, its presence in cytoskeletal cores prepared by detergent extraction of activated 32P- labeled platelets, and by direct immunoprecipitation with antibodies against guinea pig vas deferens filamin (actin-binding protein). In addition, these cytoskeletal cores indicated that the 32P-labeled actin- binding protein was closely associated with the activated platelet's cytoskeleton. Following the 32P-labeling of actin-binding protein over an 8-min time course revealed that in aggregating platelet samples rapid dephosphorylation to almost initial levels occurred between 3 and 5 min. A similar curve was obtained for the 20,000 apparent molecular weight peptide. However, rapid dephosphorylation was not observed if platelet aggregation was prevented by chelating external calcium or by using thrombasthenic platelets lacking the aggregation response. Thus, cell-cell contact would seem to be crucial in initiating the rapid dephosphorylation response.

scholarly journals Recycling of platelet phosphorylation and cytoskeletal assembly.

1984 ◽  
Vol 98 (1) ◽  
pp. 8-15 ◽  
Author(s):  
A C Cox ◽  
R C Carroll ◽  
J G White ◽  
G H Rao
Keyword(s):  
Protein Phosphorylation ◽  
Myosin Light Chain ◽  
Shape Change ◽  
Binding Protein ◽  
Actin Binding ◽  
Dibutyryl Camp ◽  
Actin Binding Protein ◽  
Fibrinogen Binding ◽  
Triton X ◽  
Subsequent Addition

The shape change and aggregation of washed platelets induced by 10 microM arachidonic acid (AA) can be reversed by 20 ng/ml prostacyclin (PGI2), but these platelets can be reactivated by treatment with 30 microM epinephrine and subsequent addition of 10 microM AA mixture. These events may be modulated by cAMP since 2 mM dibutyryl cAMP also reversed activation without reactivation by epinephrine and AA. We examined protein phosphorylation and formation of cytoskeletal cores resistant to 1% Triton X-100 extraction of these platelets and correlated these processes with aggregation, fibrinogen binding, and changes in ultrastructure. Unactivated platelet cores contained less than 15% of the total actin and no detectable myosin or actin-binding protein. AA-induced cytoskeletal cores, which contained 60-80% of the total actin, myosin, and actin-binding protein as the major components, were disassembled back to unactivated levels by PGI2 and then fully reassembled by epinephrine and AA. Phosphorylation of myosin light chain and a 40,000-dalton protein triggered by AA (two- to fivefold) was reversed to basal levels by PGI2 but was completely restored to peak levels upon addition of the epinephrine and AA mixture. The reversibility of actin-binding protein phosphorylation could not be established clearly because both PGI2 and dibutyryl cAMP caused its phosphorylation independent of activation. With this possible exception, cytoskeletal assembly with associated protein phosphorylation, aggregation, fibrinogen binding, and changes in ultrastructure triggered by activation are readily and concertedly recyclable.

scholarly journals Identification of membrane proteins mediating the interaction of human platelets

1980 ◽  
Vol 86 (1) ◽  
pp. 77-86 ◽  
Author(s):  
D Phillips ◽  
L Jennings ◽  
H Edwards
Keyword(s):  
Actin Filaments ◽  
Binding Protein ◽  
Membrane Surface ◽  
Direct Interaction ◽  
Cytoskeletal Proteins ◽  
Actin Binding ◽  
Insoluble Residue ◽  
Membrane Glycoproteins ◽  
Actin Binding Protein ◽  
Activated Platelets

Membrane glycoproteins that mediate platelet-platelet interactions were investigated by identifying those associated with the cytoskeletal structures from aggregated platelets. The cytoskeletal structures from washed platelets, thrombin-activated platelets (platelets incubated with thrombin in the presence of mM EDTA to prevent aggregation) and thrombin- aggregated platelets (platelets activated in the presence of mM Ca(++) were prepared by first treating platelet suspensions with 1 percent Triton X-100 and 5 mM EGTA and then isolating the insoluble residue by centrifugation. The readily identifiable structures in electron micrographs of the residue from washed platelets had the shape and dimensions of actin filaments. Analysis of this residue from washed platelets had the shape and dimensions of actin filaments. Analysis of this residue by SDS gel electrophoresis showed that it consisted primarily of three proteins: actin (mol wt = 43,000), myosin (mol wt = 200,000) and a high molecular weight polypeptide (mol wt = 255,000) which had properties indentical to actin-binding protein (filamin). When platelets are activated with thrombin in the presence of EDTA to prevent aggregation, there was a marked increase in the amount of insoluble precipitate in the subsequent Triton extraction. Transmission electron microscopy showed that this residue not only contained the random array of actin filaments as seen above, but also organized structures from individual platelets which appeared as balls of electron-dense filamentous material approximately 1mum in diameter. SDS polyacrylamide gel analysis of the Triton residue of activated platelets showed that this preparation contained more actin, myosin and actin-binding protein than that from washed platelets plus polypeptides with mol wt of 56,000 and 90,000 and other minor polypeptides. Thus, thrombin activation appeared to increase polymerization of actin in association with other cytoskeletal proteins into structures that are observable after Triton extraction. The cytoskeletal structures from thrombin-aggregated platelets were similar to those from thrombin-activated platelets, except that the structural elements from individual platelets remained aggregated rather than randomly dispersed in the actin filaments. This suggested that the membrane components that mediate the direct interaction of platelets were in Triton residue from aggregated platelets. Only a small percentage of the membrane surface proteins and glycoproteins were found in the cytoskeletal structures from either washed platelets or thrombin-activated platelets. In contrast, the aggregated cytoskeletal structures from thrombin-aggregated platelets contained membrane glycoproteins IIb (26 percent of the total in pre-extracted platelets) and III (14 percent), suggesting that one or both of these glycoproteins participate in the direct interaction of platelets during aggregation.

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