Azurin interaction with the lipid raft components ganglioside GM-1 and caveolin-1 increases membrane fluidity and sensitivity to anti-cancer drugs

Abstract

Membrane lipid rafts are highly ordered microdomains and essential components of plasma membranes. In this work, we demonstrate that azurin uptake by cancer cells is, in part, mediated by caveolin-1 and GM-1, lipid rafts' markers. This recognition is mediated by a surface exposed hydrophobic core displayed by azurin since the substitution of a phenylalanine residue in position 114 facing the hydrophobic cavity by alanine impacts such interactions, debilitating the uptake of azurin by cancer cells. Treating of cancer cells with azurin leads to a sequence of events: alters the lipid raft exposure at plasma membranes, causes a decrease in the plasma membrane order as examined by Laurdan two-photon imaging and leads to a decrease in the levels of caveolin-1. Caveolae, a subset of lipid rafts characterized by the presence of caveolin-1, are gaining increasing recognition as mediators in tumor progression and resistance to standard therapies. We show that azurin inhibits growth of cancer cells expressing caveolin-1, and this inhibition is only partially observed with mutant azurin. Finally, the simultaneous administration of azurin with anticancer therapeutic drugs (paclitaxel and doxorubicin) results in an enhancement in their activity, contrary to the mutated protein.

New Insights Into Targeting Membrane Lipids for Cancer Therapy

“…These effects are dependent on the caveolin 1 and ganglioside 1-mediated uptake of azurin, leading to alteration of lipid rafts; decrease in plasma membrane stiffness and in the number of ordered domains ( Bernardes and Fialho, 2018 ). The increased sensitivity of cancer cells to chemotherapeutic agents like paclitaxel and doxorubicin in combination with azurin confirms that part of the anticancer effect of azurin occurs by altering the membrane properties and increasing the membrane permeability to anticancer drugs ( Bernardes et al, 2018 ). However, the use of these peptides in MLT, has some limitations: they require further optimization to enhance their selectivity toward cancer cells and to decrease toxicity; in few cases their use alone or in combination with chemotherapeutic agents did not show any beneficial effect in clinical trials ( Planting et al, 1993 ; Gills and Dennis, 2009 ; Cho et al, 2012 ; Gerber et al, 2018 ).…”

Impact of Plasma Membrane Domains on IgG Fc Receptor Function

“…Based on the crucial role of the plasma membrane and its organized domains for many cellular processes, drugs altering the plasma membrane lipid composition, structure or function have been developed for, e.g., malignant, metabolic, cardiovascular, or neurodegenerative disorders (218,219). One example for such a drug, the compound azurin, has recently been shown to decrease the plasma membrane order of cancer cells upon uptake thereby attenuating cell signaling and subsequently tumor cell growth (220). In addition, plasma membrane altering functions have been described for established therapeutics such as lovastatin, a cholesterol-reducing drug applied in the treatment of hypercholesterinemia (221,222), or non-steroidal anti-inflammatory drugs (NSAIDs) used to treat inflammatory disorders which were shown to cause membrane softening and re-organization of membrane associated proteins (223,224).…”

p28 Bacterial Peptide, as an Anticancer Agent

“…The cell-penetrating peptide, p28, Azurin-p28 (NSC745104), has been described as a tumor-homing peptide that preferentially enters tumor cells (21). There is evidence to suggest that p28 enters tumor and normal cells through a receptor-mediated endocytic process including caveolin-1, the Golgi complex, and ganglioside GM-1 (21,26,27). Since p28 preferentially enters tumor cells over mature normal cells, one possibility is that there are an increased number of caveolin(-like) receptors, expressed at higher levels on the surface of cancer cells than the surface of normal cells (21,43).…”