Nazih-Sanderson F, Pinchon G, Nion S, Fruchart JC, Delbart C. HDL3-signalling in HepG2 cells involves glycosyl-phosphatidylinositol-anchored proteins.
BIOCHIMICA ET BIOPHYSICA ACTA 1997;
1346:45-60. [PMID:
9187302 DOI:
10.1016/s0005-2760(97)00017-9]
[Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In [3H]phosphatidylcholine (PC) prelabelled HepG2 cells, HDL3 stimulates a biphasic increase in 1.2-diacylglycerol (DAG). The early phase is mediated in part by a phospholipase C which is inhibited by 10 microM D 609, RHC-80267 or U-73122 and less by 100 microM propranolol. A phospholipase D is more likely involved in the late phase, as the DAG peak lags behind phosphatidic acid rise and is blocked by 100 microM propranolol. Cellular preincubation with 200 microg/ml antibodies against the inositolphosphoglycan (IPG) moiety of the GPI-anchor (Ab(IPG)), or depletion in GPI-anchored proteins by cellular pretreatment with 0.5 U/ml PI-PLC, 1 mM insulin and 2 HU/ml streptolysin-O, or depletion in membrane cholesterol content by filipin (5 microg/ml), digitonin (5 microg/ml) and cholesterol oxidase (0.5 U/ml) decreases the HDL3-signal, suggesting the involvement of a lipolytic cleavage of GPI-anchored proteins. Inhibition of proteases by 1 mM leupeptin/PMSF improves the response time to HDL3, with a DAG peak at 2-3 min. In the presence of protease-inhibitors, HDL3 releases in the culture medium several proteins with a residual IPG that binds Ab(IPG) after SDS-PAGE analysis and immunoblotting. HDL3-signalling pathways comprise tyrosine kinases, as preincubation with 100 microg/ml genistein or tyrphostin inhibits the HDL3-signal. HDL3 activates PC hydrolysis through a multistep pathway involving the cleavage of GPI-anchored proteins.
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