1.P.28 Binding of apolipoprotein E-containing recombinant chylomicrons to rat liver plasma membranes is stimulated by the monomeric form of hepatic lipase

1. Synthetic lysophosphatidylcholines inhibit the glucagon-stimulated adenylate cyclase activity of rat liver plasma membranes at concentrations two to five times lower than those needed to inhibit the fluoride-stimulated activity. 2. Specific 125I-labelled glucagon binding to hormone receptors is inhibited at concentrations similar to those inhibiting the fluoride-stimulated activity. 3. At concentrations of lysophosphatidylcholines immediately below those causing inhibition, an activation of adenylate cyclase activity or hormone binding was observed. 4 These effects are essentially reversible. 5. We conclude that the increased sensitivity of glucagon-stimulated adenylate cyclase to inhibition may be due to the lysophosphatidylcholines interfering with the physical coupling between the hormone receptor and catalytic unit of adenylate cyclase. 6. We suggest that, in vivo, it is possible that lysophosphatidylcholines may modulate the activity of adenylate cyclase only when it is in the hormone-stimulated state.

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A high affinity calcium-stimulated magnesium-dependent ATPase in rat liver plasma membranes. Dependence of an endogenous protein activator distinct from calmodulin.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(19)68579-0 ◽

1981 ◽

Vol 256 (21) ◽

pp. 11209-11215 ◽

Cited By ~ 3

Author(s):

S. Lotersztajn ◽

J. Hanoune ◽

F. Pecker

Keyword(s):

Rat Liver ◽

Plasma Membranes ◽

High Affinity ◽

Dependent Atpase ◽

Protein Activator ◽

Liver Plasma Membranes ◽

Endogenous Protein ◽

Rat Liver Plasma Membranes

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The roles of phospholipase D and a GTP-binding protein in guanosine 5′-[γ-thio]triphosphate-stimulated hydrolysis of phosphatidylcholine in rat liver plasma membranes

Biochemical Journal ◽

10.1042/bj2720749 ◽

1990 ◽

Vol 272 (3) ◽

pp. 749-753 ◽

Cited By ~ 20

Author(s):

K M Hurst ◽

B P Hughes ◽

G J Barritt

Keyword(s):

Rat Liver ◽

Phospholipase D ◽

Plasma Membranes ◽

Regulatory Protein ◽

Gtp Binding ◽

Liver Plasma Membranes ◽

Low Concentrations ◽

Rat Liver Plasma Membranes ◽

Triton X ◽

Hydrolysis Of

1. Guanosine 5′-[gamma-thio]triphosphate (GTP[S]) stimulated by 50% the rate of release of [3H]choline and [3H]phosphorylcholine in rat liver plasma membranes labelled with [3H]choline. About 70% of the radioactivity released in the presence of GTP[S] was [3H]choline and 30% was [3H]phosphorylcholine. 2. The hydrolysis of phosphorylcholine to choline and the conversion of choline to phosphorylcholine did not contribute to the formation of [3H]choline and [3H]phosphorylcholine respectively. 3. The release of [3H]choline from membranes was inhibited by low concentrations of SDS or Triton X-100. Considerably higher concentrations of the detergents were required to inhibit the release of [3H]phosphorylcholine. 4. Guanosine 5′-[beta gamma-imido]triphosphate and guanosine 5′-[alpha beta-methylene]triphosphate, but not adenosine 5′-[gamma-thio]-triphosphate, stimulated [3H]choline release to the same extent as did GTP[S]. The GTP[S]-stimulated [3H]choline release was inhibited by guanosine 5′-[beta-thio]diphosphate, GDP and GTP but not by GMP. 5. It is concluded that, in rat liver plasma membranes, (a) GTP[S]-stimulated hydrolysis of phosphatidylcholine is catalysed predominantly by phospholipase D with some contribution from phospholipase C, and (b) the stimulation of phosphatidylcholine hydrolysis by GTP[s] occurs via a GTP-binding regulatory protein.

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