Potentiation of adenosine A1 receptor-mediated inositol phospholipid hydrolysis by tyrosine kinase inhibitors in CHO cells |
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Authors: | John M Dickenson Stephen J Hill |
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Institution: | 1.Institute of Cell Signalling and School of Biomedical Sciences, Medical School, Queen''s Medical Centre, Nottingham NG7 2UH |
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Abstract: | - The effect of protein tyrosine kinase inhibitors on human adenosine A1 receptor-mediated [3H]-inositol phosphate ([3H]-IP) accumulation has been studied in transfected Chinese hamster ovary cells (CHO-A1) cells.
- In agreement with our previous studies the selective adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) stimulated the accumulation of [3H]-IPs in CHO-A1 cells. Pre-treatment with the broad spectrum tyrosine kinase inhibitor genistein (100 μM; 30 min) potentiated the responses elicited by 1 μM (199±17% of control CPA response) and 10 μM CPA (234±15%). Similarly, tyrphostin A47 (100 μM) potentiated the accumulation of [3H]-IPs elicited by 1 μM CPA (280±32%).
- Genistein (EC50=13.7±1.2 μM) and tyrphostin A47 (EC50=10.4±3.9 μM) potentiated the [3H]-IP response to 1 μM CPA in a concentration-dependent manner.
- Pre-incubation with the inactive analogues of genistein and tyrphostin A47, daidzein (100 μM; 30 min) and tyrphostin A1 (100 μM; 30 min), respectively, had no significant effect on the accumulation of [3H]-IPs elicited by 1 μM CPA.
- Genistein (100 μM) had no significant effect on the accumulation of [3H]-IPs produced by the endogenous thrombin receptor (1 u ml−1; 100±10% of control response). In contrast, tyrphostin A47 produced a small augmentation of the thrombin [3H]-IP response (148±13%).
- Genistein (100 μM) had no effect on the [3H]-IP response produced by activation of the endogenous Gq-protein coupled CCKA receptor with the sulphated C-terminal octapeptide of cholecystokinin (1 μM CCK-8; 96±6% of control). In contrast, tyrphostin A47 (100 μM) caused a small but significant increase in the response to 1 μM CCK-8 (113±3% of control).
- The phosphatidylinositol 3-kinase inhibitor LY 294002 (30 μM) and the MAP kinase kinase inhibitor PD 98059 (50 μM) had no significant effect on the [3H]-IP responses produced by 1 μM CPA and 1 μM CCK-8.
- These observations suggest that a tyrosine kinase-dependent pathway may be involved in the regulation of human adenosine A1 receptor mediated [3H]-IP responses in CHO-A1 cells.
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Keywords: | Adenosine A1 receptor inositol phosphates tyrosine kinases genistein tyrphostin CHO cells CCKA receptors |
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