Soluble Plc From Platelets

Baldassare, Joseph J.

Abstract

A number of physiologically relevant agonists of human platelets are known to activate the phosphoinositide signalling pathway(s) by stimulating PtdIns-PLC activity. We have recently shown that platelets express several of the family of PtdIns-PLC isoforms namely, PtdIns-PLC- Beta1, gamma1, gamma2, delta, and alpha for studying agonist-induced PIP2 hydrolysis in isolated platelet (HEL cell) membranes, the thromboxane A2 receptor has been shown to activate PtdIns-PLC Beta 1. Resent data from our laboratory suggests that the TXA2, thrombin and collagen receptors each activate distinct PtdIns-PLC isozymes. Preliminary studies also indicate that the G-protein coupling for these receptors to their specific PtdIns-PLC isoforms are quite dissimilar. Although PtdIns-PLC gamma1 does not reconstitute thrombin mediated PIP2 hydrolysis in the reconstitution assay, studies with intact platelets demonstrate thrombin- induced translocation of PtdIns-PLC gamma 1 to the cytoskeleton/skeleton and its association with gelsolin. The primary goals of this proposal are: 1) identification of the PtdIns-PLC isozymes that reconstitute thrombin- and collagen-stimulated PIP2 hydrolysis in platelet membranes and the characterization of their G-protein regulation. 2) cloning of the PtdIns-PLC isoform that is G-protein coupled to the thrombin receptor. 3) characterization of thrombin-induced translocation of PtdIns-PLC gamma1, its association with gelsolin and possible activation. Studies also will focused on understanding the mechanism involved in PtdIns-PLC gamma 1, translocation, association with gelsolin and possible activation. In addition, these agonist-induced changes in the subcellular distribution, associations and activation will be correlated with changes in cytoskeleton/skeleton G-actin and diacylglycerol levels. 4) examination of the role of the multiple PtdIns-PLC isoforms in PIP 2 hydrolysis by overexpression and """"""""knock out"""""""" of specific PtdIns-PLC isoforms in HEL cells. Platelets play a major role in the pathogenesis both of the vasculature and the perivasculature cells and the administration of antiplatelet treatments are efficacious in only some patients, therefore, a detailed understanding of the mechanisms of agonist-induced platelet activation may provide the basis for future therapeutic interventions.

Funding Agency

• Agency: National Institute of Health (NIH)
• Institute: National Heart, Lung, and Blood Institute (NHLBI)
• Type: Research Project (R01)
• Project #: 5R01HL040901-06
• Application #: 2219779
• Study Section: Hematology Subcommittee 2 (HEM)
• Project Start: 1990-01-01
• Project End: 1998-01-31
• Budget Start: 1995-02-01
• Budget End: 1996-01-31
• Support Year: 6
• Fiscal Year: 1995

Institution

• Name: Saint Louis University
• Department: Internal Medicine/Medicine
• Type: Schools of Medicine
• City: Saint Louis
• State: MO
• Country: United States
• Zip Code: 63103

Publications

Li, Jianjun; Hu, Weimin; Baldassare, Joseph J et al. (2003) The ethanol metabolite, linolenic acid ethyl ester, stimulates mitogen-activated protein kinase and cyclin signaling in hepatic stellate cells. Life Sci 73:1083-96

Baldassare, J J; Bi, Y; Bellone, C J (1999) The role of p38 mitogen-activated protein kinase in IL-1 beta transcription. J Immunol 162:5367-73

Cheng, J; Baldassare, J J; Raben, D M (1999) Dual coupling of the alpha-thrombin receptor to signal-transduction pathways involving phosphatidylinositol and phosphatidylcholine metabolism. Biochem J 337 ( Pt 1):97-104

Weber, J D; Cheng, J; Raben, D M et al. (1997) Ablation of Goalpha overrides G1 restriction point control through Ras/ERK/cyclin D1-CDK activities. J Biol Chem 272:17320-6

Weber, J D; Hu, W; Jefcoat Jr, S C et al. (1997) Ras-stimulated extracellular signal-related kinase 1 and RhoA activities coordinate platelet-derived growth factor-induced G1 progression through the independent regulation of cyclin D1 and p27. J Biol Chem 272:32966-71

Baldassare, J J; Jarpe, M B; Alferes, L et al. (1997) Nuclear translocation of RhoA mediates the mitogen-induced activation of phospholipase D involved in nuclear envelope signal transduction. J Biol Chem 272:4911-4

Cheng, J; Weber, J D; Baldassare, J J et al. (1997) Ablation of Go alpha-subunit results in a transformed phenotype and constitutively active phosphatidylcholine-specific phospholipase C. J Biol Chem 272:17312-9

Poulos, J E; Weber, J D; Bellezzo, J M et al. (1997) Fibronectin and cytokines increase JNK, ERK, AP-1 activity, and transin gene expression in rat hepatic stellate cells. Am J Physiol 273:G804-11

Padfield, P J; Panesar, N; Henderson, P et al. (1996) Differential effects of G-protein activators on 5-hydroxytryptamine and platelet-derived growth factor release from streptolysin-O-permeabilized human platelets. Biochem J 314 ( Pt 1):123-8

Reynolds, N J; Baldassare, J J; Henderson, P A et al. (1994) Translocation and downregulation of protein kinase C isoenzymes-alpha and -epsilon by phorbol ester and bryostatin-1 in human keratinocytes and fibroblasts. J Invest Dermatol 103:364-9