In this study, we used super-resolution microscopy [fluorescence photoactivation localization microscopy (FPALM); Hess, S.T. et al. Biophysical Journal, 2006] to illuminate nanoscale biological structures and phenomena. We specifically applied FPALM to investigate the nanoscale distribution and interactions between proteins and phosphoinositides (PIPs) in live cells. Meanwhile, the Gosse lab uses FPALM as a novel toxicological tool to test molecular mechanisms by which toxicants harm immune cell signaling.

                Phosphatidylinositol 4,5-bisphosphate (PIP₂) is a critical signaling lipid in numerous cell types, but many questions about PIP₂ nanostructure and dynamics remain unanswered. The cover of the October 21 issue of Biophysical Journal is a representative result from our collaborative investigation of functional PIP₂ nanoscale clustering in an immune (mast) cell model. The cover features two mast cells in which cellular PIP₂ has been tagged and imaged at the plasma membrane by using total internal reflection fluorescence-FPALM, revealing nanoscale PIP₂ clustering. A control cell is depicted in the top figure, whereas the bottom figure shows a cell treated with the antibacterial agent cetylpyridinium chloride (CPC), which diminishes the size and alters the properties of PIP₂ clusters. CPC is found in many consumer products, and thus its toxicological properties are of current interest.

                The research shown in this article reveals the biophysics of PIP₂ nanoscale clustering and dynamics, providing insights into the role of this important lipid in immune cell signaling.  Furthermore, our results uncover a mechanism for the observed CPC inhibition of immune cell function:  disrupted nanoscale PIP₂ clustering and dynamics.  These findings may extend to other quaternary ammonium and related compounds and lend evidence to be used for chemical prediction of toxicity, for drug development, or for maintaining environmental health.

                You can learn more about our work in the Hess and Gosse labs at https://physics.umaine.edu/samuel-t-hess-3/ and https://umaine.edu/biomed/home/faculty/julie-gosse/, respectively.

• Brandon M. Aho, Dylan J. Wagner, Julie A. Gosse, and Samuel T. Hess