-transparent.png){kind=logo}
Platelets accumulate PtdIns(3,4,5)P3 and PtdIns(3,4)P2 in response to thrombin and thrombin-receptor-directed peptide in a GTP-dependent manner. These phosphoinositides are considered to be mediators of signaling events in a variety of cells. We have examined the metabolic route by which PtdIns(3,4,5)P3 and PtdIns(3,4)P2 are synthesized by briefly (10 min) incubating platelets with high activities of [32P]Pi, followed by 20 or 60 s exposure to thrombin, and analysing the relative radioactivities of the individual phosphate groups in the resulting labelled PtdIns(3,4,5)P3 and PtdIns(3,4)P2. The phosphate group possessing the highest specific activity under such non-equilibrium labelling conditions indicates the last one added in a metabolic sequence. The thrombin-stimulated rate of labelling of PtdIns(3,4)P2 was significantly slower than that of PtdIns(3,4,5)P3. Increased labelled PtdIns3P was not detected within 60 s. The measured relative radioactivities decreased in the order 3 > 5 > 4 >> 1 for PtdIns(3,4,5)P3 and 3 > 4 >> 1 for PtdIns(3,4)P2. On the basis of the results of both rate-of-labelling and specific radioactivity analyses we conclude that PtdIns(3,4,5)Pa is formed by 3-OH phosphorylation of PtdIns(4,5)P2, whereas PtdIns(3,4)P2, may be formed by 3-OH phosphorylation of PtdIns4P and/or dephosphorylation of PtdIns(3,4,5)P3. These findings point to the activation of phosphoinositide 3-kinase as a critical receptor-regulated step in thrombin-stimulated platelets.
A N Carter, and
R Huang, and
A Sorisky, and
C P Downes, and
S E Rittenhouse
November 1982,
The Journal of biological chemistry,
A N Carter, and
R Huang, and
A Sorisky, and
C P Downes, and
S E Rittenhouse
January 2009,
The Journal of biological chemistry,
A N Carter, and
R Huang, and
A Sorisky, and
C P Downes, and
S E Rittenhouse
March 2007,
Biochimica et biophysica acta,
A N Carter, and
R Huang, and
A Sorisky, and
C P Downes, and
S E Rittenhouse
August 1992,
Biochemical and biophysical research communications,
A N Carter, and
R Huang, and
A Sorisky, and
C P Downes, and
S E Rittenhouse
December 1994,
Biochimica et biophysica acta,
A N Carter, and
R Huang, and
A Sorisky, and
C P Downes, and
S E Rittenhouse
January 2009,
Molecular biology of the cell,
A N Carter, and
R Huang, and
A Sorisky, and
C P Downes, and
S E Rittenhouse
January 1989,
Methods in enzymology,
A N Carter, and
R Huang, and
A Sorisky, and
C P Downes, and
S E Rittenhouse
January 1991,
Biochemical and biophysical research communications,
A N Carter, and
R Huang, and
A Sorisky, and
C P Downes, and
S E Rittenhouse
August 1987,
The Biochemical journal,
A N Carter, and
R Huang, and
A Sorisky, and
C P Downes, and
S E Rittenhouse
November 1982,
Biochemical and biophysical research communications,
