Platelet-activating factor- and thrombin-induced stimulation of p34cdc2-cyclin histone H1 kinase activity in platelets.
Numerous studies of cell cycle control in dividing cells have pointed to the central role of a 34-kDa histone H1 kinase (p34cdc2) complexed with regulatory subunits known as cyclins. We now report that p34cdc2-cyclin may also participate in signal transduction in nonproliferating, terminally differentiated cells, in this instance during sheep platelet activation. Immunological evidence for the presence of a p34cdc2 cognant in sheep platelet cytosol was obtained with antipeptide antibodies raised against peptide sequences in the conserved PSTAIRE and C-terminus regions of murine cdc2. The immunoreactive 32-kDa protein was adsorbed onto p13suc1-Sepharose, which selectively binds p34cdc2. A 58-kDa protein that also bound to p13suc1-Sepharose was identified as cyclin A on the basis of its size and immunoreactivity with two different anticyclin peptide antibodies. The p34cdc2-cyclin A complex was regulated during platelet activation. Its histone H1 phosphorylating activity was stimulated 2-fold in p13suc1-Sepharose extracts from platelets that had been exposed to platelet-activating factor or thrombin for 1 min prior to harvesting. Our findings imply that the p34cdc2-cyclin complex may serve alternative functions besides control of cell division.
Samiei
M
M
Biomedical Research Centre, University of British Columbia, Vancouver, Canada.
Daya-Makin
M
M
Clark-Lewis
I
I
Pelech
S L
SL
D000595:Amino Acid Sequence; D000818:Animals; D001792:Blood Platelets / Q000201:enzymology*; D015153:Blotting, Western; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D002853:Chromatography, Liquid; D004789:Enzyme Activation; D006801:Humans; D008969:Molecular Sequence Data; D010972:Platelet Activating Factor / Q000378:metabolism*; D015539:Platelet Activation; D012756:Sheep; D015398:Signal Transduction; D013917:Thrombin / Q000378:metabolism*
D010972:Platelet Activating Factor; D016203:CDC2 Protein Kinase; D013917:Thrombin