Diglycerides play an important role in a number of agonist-induced signal transduction pathways. We have recently demonstrated that α-thrombin induces a rapid increase in the level of diglyceride mass in the nucleus and a selective increase in nuclear PKC-α [Leach, K. L., Ruff, V. A., Jarpe, M. B., Fabbro, D., Adams, L. D., & Raben, D. M. (1992) J. Biol. Chem. 267, 21816–21822]. In the present report, we examined the potential source of the induced nuclear diglycerides by examining the molecular species profiles of both the induced diglycerides and nuclear phospholipids by capillary gas chromatography. The molecular species profiles of the nuclear diglycerides generated resemble the species profiles of PC, and not PI species, at all times. In addition, while our previous data indicated that the molecular species of whole-cell phospholipids did not change in response to α-thrombin, nuclear PE was altered in a dramatic and selective manner in response to this agonist. These results demonstrate that PC hydrolysis is the predominant, if not exclusive, source of the α-thrombin-induced nuclear diglycerides in these fibroblasts.
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