Abstract

Heavy metal contamination poses a significant threat to cellular integrity, often by disrupting membrane structure and function. This study investigates the specific effect of cadmium ions ($\text{Cd}^{2+}$) on the composition of $\Delta5$-sterols within microdomains of the vacuolar membrane (tonoplast). $\Delta5$-sterols are critical components of eukaryotic membranes, playing a key role in regulating fluidity, permeability, and the formation of specialized lipid microdomains, which are analogous to lipid rafts in the plasma membrane. Using a combination of differential centrifugation and lipid analysis techniques, we quantified the $\Delta5$-sterol content in tonoplast microdomains isolated from a model organism exposed to $100\ \mu\text{M}\ \text{Cd}^{2+}$. Our results demonstrate that $\text{Cd}^{2+}$ exposure significantly alters the sterol partitioning, leading to an enrichment of $\Delta5$-sterols in the denser, detergent-resistant microdomains and a corresponding depletion in the lighter fractions. This redistribution suggests a $\text{Cd}^{2+}$-induced change in membrane organization, potentially as a cellular defense mechanism to sequester or compartmentalize the toxic metal. These findings provide new insights into the molecular mechanisms of heavy metal toxicity and the role of sterol-rich microdomains in cellular stress response and detoxification.