Detachment of surface membrane invagination systems by cationic amphiphilic drugs

Abstract

Several cell types develop extensive plasma membrane invaginations to serve a specific physiological function. For example, the megakaryocyte demarcation membrane system (DMS) provides a membrane reserve for platelet production and muscle transverse (T) tubules facilitate excitation:contraction coupling. Using impermeant fluorescent indicators, capacitance measurements and electron microscopy, we show that multiple cationic amphiphilic drugs (CADs) cause complete separation of the DMS from the surface membrane in rat megakaryocytes. This includes the calmodulin inhibitor W-7, the phospholipase-C inhibitor U73122, and anti-psychotic phenothiazines. CADs also caused loss of T tubules in rat cardiac ventricular myocytes and the open canalicular system of human platelets. Anionic amphiphiles, U73343 (a less electrophilic U73122 analogue) and a range of kinase inhibitors were without effect on the DMS. CADs are known to accumulate in the inner leaflet of the cell membrane where they bind to anionic lipids, especially PI(4,5)P2. We therefore propose that surface detachment of membrane invaginations results from an ability of CADs to interfere with PI(4,5)P2 interactions with cytoskeletal or BAR domain proteins. This establishes a detubulating action of a large class of pharmaceutical compounds.

Imipramine as an alternative to formamide to detubulate rat ventricular cardiomyocytes

“…Similarly to what has been described with formamide(Brette et al, 2002), detubulation induced by imipramine remained 2 h after treatment (data not shown), indicating that it is not reversible(Osman et al, 2016) at least within this time frame. Using confocal microscopy, we visualized the indicator, which highlighted the cell surface on the periphery and T-tubules in the centre of control cells (Figure 1a).…”

“…Interestingly, a recent study demonstrated that high concentrations of cationic amphiphilic drugs (CADs) can produce detubulation of adult rat ventricular myocytes (ARVMs) probably by interfering with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P 2 ) interactions with cytoskeletal and Binamphiphysin-Rvs (BAR) domain-containing proteins (Osman, Taylor, Allcock, Rainbow, & Mahaut-Smith, 2016). Interestingly, a recent study demonstrated that high concentrations of cationic amphiphilic drugs (CADs) can produce detubulation of adult rat ventricular myocytes (ARVMs) probably by interfering with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P 2 ) interactions with cytoskeletal and Binamphiphysin-Rvs (BAR) domain-containing proteins (Osman, Taylor, Allcock, Rainbow, & Mahaut-Smith, 2016).…”

“…Therefore, an alternative treatment that is more efficient and less toxic would be useful for cardiac physiologists. Interestingly, a recent study demonstrated that high concentrations of cationic amphiphilic drugs (CADs) can produce detubulation of adult rat ventricular myocytes (ARVMs) probably by interfering with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P 2 ) interactions with cytoskeletal and Binamphiphysin-Rvs (BAR) domain-containing proteins (Osman, Taylor, Allcock, Rainbow, & Mahaut-Smith, 2016). However, a comparison of this detubulation method with the formamide-induced removal of T-tubules has not yet been performed and the consequences for CICR and -AR signalling of the detubulation induced by CAD binding to PI(4,5)P 2 in ventricular myocytes are unknown.…”

‘Get in Early’; Biofilm and Wax Moth (Galleria mellonella) Models Reveal New Insights into the Therapeutic Potential of Clostridium difficile Bacteriophages

“…Membranes were sterilized with the glutaraldehyde for 24 h. Confocal fluorescence imaging was conducted as previously described (Osman et al, 2016). …”

Antiviral activity of cationic amphiphilic drugs

“…Overall, deregulation of the endolysosomal pathway and lipid homeostasis mediated by CAD accumulation in the LE/Lys compartment affect several cellular activities, such as macro-and/or micro-pinocytosis, the organization of the membrane invagination systems, and the vesicular transport of material to the Lys [17,23,[25][26][27][28]. The main driving force allowing CAD accumulation inside the LE/Lys compartment is the CAD trapping mechanism.…”