Selective amphipathic nature of chlorpromazine binding to plasma membrane bilayers

Abstract

Chlorpromazine (CPZ), an antipsychotic agent shown to inhibit the action of various neurophysiological receptors, also exhibits preferential association with the plasma membrane, inducing stomatocytic morphological response in red blood cells (RBC). Given the cationic nature of CPZ, fluorimetry, pH titration, and red cell morphological studies were performed to assess the associative predilection of CPZ for anionic membrane components. CPZ fluorescence intensity increased 320-370% upon addition of phosphatidylcholine (PC) small unilamellar vesicles (SUVs) to aqueous CPZ, indicating an affinity of the drug for lipidic phases. After removal of unbound drug, CPZ fluorescence increased up to 92% with increasing phosphatidylserine (PS) in the lipid phase (up to 30 mol% of total lipid), suggesting a preferential association of the drug with anionic lipids. In studies of pH titration, the pK(a) of CPZ in the presence of Triton X-100 micelles or phospholipid SUVs increased with increasing anionicity of the lipidic phase [7.8 with Triton X-100, 8.0 with PC, 8.3 with phosphatidylglycerol (PG)], lending further support to preferential drug interaction with anionic lipidic components. At 0 degrees C, CPZ-induced red cell shape change was less extensive in cells made echinocytic by adenosine triphosphate (ATP) depletion, compared to cells made echinocytic by PS treatment following vanadate preincubation. This suggests that polyphosphoinositide lipids are CPZ membrane binding sites. Since polyphosphoinositide lipids are implicated as important intermediates in a number of receptor-mediated cell signaling pathways, evidence of association with these specific lipids provides a means by which psychoactive drugs may induce neurophysiological effects through direct interaction with general membrane components.

Yeast Mon2p is a highly conserved protein that functions in the cytoplasm-to-vacuole transport pathway and is required for Golgi homeostasis

“…(C) YFP93 (⌬mon2) cells expressing the Mon2p-GFP derivatives containing the indicated domains were grown on SD-LEU plates containing 0 or 20 M CPZ for 36 hours at 25°C. membranes (Jutila et al, 2001) and interacts with negatively charged lipids (Chen et al, 2003). We previously observed that CPZ modifies internal membrane structures, making Golgi mutants such as ⌬vps1 and ⌬vps54 highly sensitive to CPZ (unpublished data).…”

Differential Interference of Chlorpromazine with the Membrane Interactions of Oncogenic K-Ras and Its Effects on Cell Growth

“…(a) Trifluoperazine, a phenothiazine closely related to CPZ, was shown to bind to phospholipid membranes and to reduce their negative potential (49). (b) CPZ was found to bind with higher affinity to biological membranes containing PI(4,5)P 2 (50), which is enriched in the inner leaflet of the plasma membrane. (c) Proteins with polybasic clusters, including K-Ras and Rac1, were shown to dissociate from the plasma membrane upon enzymatic depletion of PI(4,5)P 2 and PI(3,4,5)P 3 (19) or upon alteration of the inner surface potential during phagocytosis (21).…”

The Role of the Membrane Actions of Phenothiazines and Flavonoids as Functional Modulators

“…The exclusive location of a quaternary analogue of CPZ (9) in the outside membrane leaflet was also demonstrated by Elferink [153]. On the other hand, CPZ (9) was suggested to bind preferentially to polyphosphoinositide lipids that were present in the cytoplasmic half of the erythrocyte membrane [66]. Isomaa et al [149] pointed to the shape of amphiphile molecules as an important factor governing erythrocyte shape changes induced by different compounds.…”

“…Using a model of gramicidin A channels in planar lipid bilayers, they have demonstrated that genistein (42) could alter the channel properties (conductivity and lifetime) by changing the hydrophobic mismatch and/or bilayer mechanical properties. Gramicidin channel properties were also profoundly altered by daidzein (40) and phloretin (66), while genistin (46) showed apparently no effects.…”

“…Fluorescence spectroscopy has also been employed to study CPZ-membrane interactions. Chen et al [66] exploited CPZ (9) intrinsic fluorescence to study binding of the drug to PC liposomes. As CPZ (9) fluorescence strongly increased upon addition of PC vesicles to the aqueous drug solution, it was concluded that CPZ had significant affinity for the lipid phase.…”